Atomic Energy of Canada Limited
FISSION PRODUCT DATA FOR THERMAL REACTORS
PART II - YIELDS
by
W.H. WALKER
\ \ Chalk River Nuclear Laboratories V
*- ( 1 Chalk Rivet, Ontario April 1973
' AECL-3037 FISSION PRODUCT DATA FGR THERMAL REACTORS
PART II - YIELDS
by
W. H. Walker
Chalk River Nuclear Laboratories Chalk River, Ontario
April 1973 AECL-3037 Part II FISSION PRODUCT DATA FOR THERMAL REACTORS PART II - YIELDS
by
W. H. Walker
ABSTRACT Thermal neutron cumulative fission yields from 335u, 833U, 339Pu and 241Pu are reviewed. Particular attention is given to mass spectrometric data which accounts for the greater fraction of the total yields.
A three-step treatment of spectrometric data is used: first, the concentrations of isotopes of each fission product element are determined to define the local shape of the yield vs. mass curve; second, the relative numbers of atoms of each element formed in fission are derived from isotope dilution or isobaric coupling measurements thus linking together all the isotopic concentrations of both the light or heavy mass peaks to obtain the shape over the entire mass spectrometric range; third, the mass spectrometric data are normalized using isotope dilution measurements of the number of fissions and radiometric and interpolated fields.
In general, the greatest source of uncertainty in the mass spectrometric range is the second step and appears to arise from systematic differences between the methods used in different laboratories. Manuscript prepared November 1972
Chalk River Nuclear Laboratories Chalk River, Ontario April 1973 AECL-3037 Part II Données sur les produits de fission pour les réacteurs thermiques
Partie II - Rendements
par
W.H. Walker
Résumé Les rendements cumulatifs de fission des 235 233 2 neutrons thermiques de U, U, 239pu et ^lpu sont passés en revue. Une attention particulière est accordée aux données de spectrométrie de masse qui constituent la plus grande partie des rendements totaux. Un traitement en trois étapes des données spectrométriques est employé: premièrement, les concentrations des isotopes de chaque élément de produit de fission sont déterminées pour définir la forme locale de la courbe "rendement-masse"; deuxièmement, les nombres relatifs des atomes de chaque élément formé au cours de la fission sont calculés à partir de la dilution isotopique ou des mesures de couplage isobarique, reliant ainsi ensemble toutes les concentrations Isotopiques des pics des masses lourdes et légères, afin d'obtenir la forme pour l'intervalle complet de la spectrométrie de masse; troisièmement, les données spectrométriques de masse sont normalisées au moyen d'une mesure par dilution isotopique, du nombre de fissions et des rendements radiométriques et interpolés.
En général, la plus grande source d'incer- titude dans l'intervalle de la spectrométrie de masse est la deuxième ét-ipe. Elle semble provenir de différences systématiques entre les méthodes employées dans les différents laboratoires. Manuscrit rédigé en novembre 1972 L'Energie Atomique du Canada, Limitée Laboratoires Nucléaires de Chalk River Chalk River, Ontario Avril 1973 AECL-3037 Partie II TABLE OF CONTENTS
Page 1. INTRODUCTION 2. RELATIVE ISOTOPICC ABUNDANCES 3 2.1 Krypton and Rubidium 4 2.2 Strontium and Y ":rium 6 2.3 Zirconium 7 2.4 Molybdenum 8 2.5 Ruthenium 9 2.6 Xenon 10 2.7 Cesium and Barium 12 2.8 Cerium 14 2.9 Neodymium 16 2.10 Samarium and Europium 18 3. RELATIVE ELEMENT YIELDS 21 3.1 33BU 23 3.2 333U 26 3.3 339Pu 28 3.4 341Pu 30 4. ERROR ASSIGNMENTS 32 5. COMPLETING THE YIELD DISTRIBUTIONS 35 5.1 33BU Fission 36 5.2 J33U Fission 40 5.3 aa9Pu Fission 46 5.4 341Pu Fission 47 6. SUMMARY 5l 7. ACKNOWLEDGMENTS 54 8. REFERENCES 55 TABLES Page 1. Relative Yields of Krypton and Rubidium isotopes 5 2. Relative Yields of Strontium and Yttrium isotopes 6 3. Relative Yields of Zirconium Isotopes 7 4. Relative Yields of Molybdenum Isotopes 8 5. Relative Yields of Ruthenium Isotopes 9 6. Relative Yields of Xenon Isotopes 11 7. Relative Yields of Cesium and Barium isotopes 13 8. Relative Yields of Cerium Isotopes 15 9. Relative Yields of Neodymium Isotopes Isotopes 17 10. Relative Yields of Samarium and Europium isotopes 20 11. Relative Element Yields in 33Bu Thermal Neutron 24 Fission 12. Normalized Mass Spectrometric Yields in 23Bu Thermal 25 Neutron Fission 13. Relative Element Yields in S3Cu Thermal Neutron 26 Fission 14. Normalized Mass Spectrometric Yields in a33u Thermal 27 Neutron Fission 15. Relative Element Yields in 339Pu Thermal Neutron 28 Fission 16. Normalized Mass Spectrometric Yields in 339Pu Thermal 29 Neutron Fission 17. Relative Element Yields in S41Pu Thermal Neutron 30 Fission 18. Normalized Mass Spectrometric Yields in 241Pu Thermal 31 Neutron Fission 19. Error Assignments for the Heavy Mass peak 33 20. Error Assignments for the Light Mass Peak 34 21. Yields of Light Mass Fission Products from 3BU 38 22. Yields of Heavy Mass Fission Products from a35u 39 23. Yields of Light Mass Fission Products from a33U 42 24. Yields of Heavy Mass Fission Products from a33u 43 25. Yields of Light Mass Fission Products from 339Pu 44 26. Yields of Heavy Mass Fission Products from 239Pu 45 27. Yields of Light Mass Fission Products from 341Pu 48 28. Yields of Heavy Mass Fission Products from 841Pu 49 29. Summary of Recommended Yields - Light Masses 52 30. Summary of Recommended Yields - Heavy Masses 53
FIGURES
1. Cumulative Yields vs Mass 61 2. Cumulative Yields vs Displacement from A, the mean mass g2 FISSION PRODUCT DATA FOR THERMAL REACTORS PART II - YIELDS
by
W. H. Walker 1. INTRODUCTION Fission product yield measurements have played an important part in the study of fission since its discovery. The main interest initially was the general shape of the fission fragment distribution as a function of mass, and this evolved into detailed studies of the deviations from the smooth distribution (fine structure). Recent work has been directed to precise yield measurements of specific fission products for use in the accurate determination of fuel burnup.
It is surprising that the main interest in fission yields has never been their effect on fission product absorp- tion. Most of the effort in this field has been directed to determining nuclide cross sections accurately, even though neutron absorption by most fission products is proportional to both yield and cross section, in the important case of a rapidly saturating nuclide such as 136Xe and 149Sm, neutron absorption at equilibrium concentration (saturation) is primarily dependent on the yield and nearly independent of its cross section.
In this evaluation all corrections to measured data for p-decay c>.nd neutron capture are reviewed and recalculated where necessary to provide as firm a base as possible for a set of recommended yields for th3rmal neutron fission of 33Bu, 333U, 239Pu and 341Pu. An assessment of uncertainties in these yield values is also provided so that, in future, the accuracy of fission product absorption calculations can be estimated wibh greater confidence.
1.1. Outline of Evaluation Methods The earliest yield measurements were of radioactive fission products using counting techniques. These gave absolute yields with large uncertainties or relative yields normalized to some standard such as 67-h 99Mo. Later, mass spectrometers were used to determine relative yields of tne fission product isotopes of a particular element. The intro- duction of isotope dilution techniques enabled mass spectro- metrists to determine absolute yields directly and radio- chemists to improve the accuracy of their absolute yield determinations. - 2 -
Both radiometric and mass spectre-metric yield measurements are subject to the usual chemistry difficulties, but the latter have the advantage from the evaluator's viewpoint of yiving the shape of a portion of the "yield vs mass" curve (i.e. the relative yields) to a high precision. This advantage cannot be easily exploited because mass spectrometric yields are always assigned a single error which has, as its dominant component, the un- certainty in the number of fissions.
Since all mass spectrometric yields are obtained in three steps it is the purpose of this evaluation to obtain the best set of data appropriate to each step and to determine what un- certainty each step contributes to the final uncertainty.
First the yield vs mass curve is determined for each fission product element by comparing all mass spectrometric measurements of concentrations of fission product isotopes of that element (the isotopic abundance) for the fissile nuclide of interest. These shapes are then linked together to obtain the main portion of the yield vs mass distribution. The linking is done using either isotope dilution measurements, which give the number of atoms of each element per fission, or measured isotopic abundances of two isobars, each relative to other isotopes of its own element and then completing the link using known p-decay half-lives, and irradiation and decay times. The first method is subject to errors in chemistry, and the second to errors in half-lives or elapsed time.
For thermal neutron fission of a36u several mass spectro- meter measurements have been made for each of the elements near the peak of the light and heavy mass distributions. In this case it is quite probable that an incorrect yield in one measure- ment, such as might be caused by an unidentified contamination at one mass, can be detected because the isotopic abundance at that mass differs significantly from the average.
The situation for a33U, a39Pu and a41Pu is less satisfactory because fewer measurements are available. Also, the mass range measured is usually the same as for a35U, for which many of the techniques were developed, and covers a smaller fraction of the yield for 333U, a39Pu and a41Pu. The light mass peak in a41Pu fission is most poorly covered, with less than half the total light mass peak measured mass spectrometrically compared to 88% for a3Bu.
Once the relative yields over the entire mass spectrometer range are determined they are normalized to fit radiometric and interpolated values. The accuracy of this normalization depends on the fraction of yields not covered mass spectrometrically and the amount of radiometric data. In the case of 341Pu fission radiometric coverage is poor, with only three measurements in the mass range 107-130 to help define the shape of the valley and the high mass side of the light mass peak.
The average number of fission fragment nucléons, Â (=§(A+l-v)). provides an additional constraint in selecting yields since Sy.A. should equal 2ft. The values of v, the average number of neutrèns per fission, recommended by Hanna et al. (1969) are used. - 3 -
2. RELATIVE I30T0PIC ABUNDANCES To compare isotopic abundances from different laboratories the measurements must have a common notation. The usual way to normalize isotopic abundances for this purpose is to set one value to unity - usually that of the most abundance isotope or the one requiring little or no correction for P-decay or neutron capture. This normalization can introduce systematic differences between results from different laboratories - if, for instance, there is an unidentified contaminant with the same mass. Such systematic errors can be reduced if the normalization is performed so that the sum of the isotopic abundances is unity. This is the method used here. The relative abundance of an isotope is defined as the number of atoms of that isotope divided by the number of atoms of the element (the sum of atoms of all the element's isotopes). The sum of the relative abundances is then unity except where one set of measurements includes an isotope (usually a short-lived radio- nuclide) not included in the other sets. In this case the contri- bution of such an isotope is not included in the number of atoms of the element and for the set of measurements including that isotope the sum of the isotopic abundance will exceed unity. Isotopes not included in the number of atoms of the element are marked in the following tables with an asterisk.
If an isotopic abundance is missing from one set of measure- ments the average value is assumed and is included in the table in brackets. Measured isotopic abundances from thermal neutron fission of "6B, a2aU, 339pu and a41pu are listed in this report in a single table for each fission product element. Many isotopic abundances require correction for fJ-decay or neutron capture before they cm be compared - for example, in an irradiated sample the number of atoms of 284.4-d 14*Ce and its decay product 1**Sd will depend on the duration of the irradiation and the elapsed time between the end of the irradiation and the chemical separation and mass spectro- metric analyses of the two elements. These corrections were re- calculated using FISSPROD (Lane, 1968} if the irradiation and elapsed times were provided. Even if only the original correction factor and relevant cross section or decay time is given, a new correction factor can be estimated based on an effective decay or irradiation period.
Recalculated correction factors will be referred to as re- corrections in the text. Re-corrections are noted in footnotes to the tables if they have a significant effect, and if necessary, are discussed in the associated text.
The results of Lismar. et al- (1970) are the best documented and most extensive. They include fast fission results as well as thermal neutron fission of the four nuclides covered in this report. In addition to details of the irradiation and cooling periods, many of the correction factors and the decay and capture data from which they were derived are available in the interim reports listed in their references. In addition, I have a list (Lisman, 1970) of all their correction factors and additional details of the irradiation. This permitted a complete check, using FISSPROD, of correction factors for all nuclides listed for each irradiated sample*.
* Since their flux convention differs from that used in FISSPROD it was necessary to recalculate all fluxes using the measured number or fissions. In FISSPROD the flux, », is nv0 where n is the neutron density and v0 is 2200 m/s. The reaction rate is given by aft where 6 = - 4 -
In this section I am interested in the reproducibility of isotopic abundances and this is not usually available because of the way results are quoted, as noted above. However, Lisman et al. (1970) and a few others measured fission product abundances from several irradiated samples of each fissile nuclide and list their results for each sample. In these cases the average isotope abundances for all samples of one fissile nuclide can be obtained with the standard deviation from the average. Their results are so listed in the following tables. If the standard deviation from the mean of the results from all laboratories are much larger than those for the results of Lisman et al.(1970) it probably indicates the presence of systematic sources of error.
2.1 Krypton and Rubidium (Table 1) A small re-correction has been applied to the results of Lisman et al-(1970) for extra capture in 83Kr. They used a cross section of the 180 b compared to an effective cross section of 194 b in MTR based on FISSPROD data (a thermal cross section of 187 b and a resonance integral of 150 b). The difference is negligible for short irradiations (<1 n/kb) and the average re- correction is small except for 235U fission.
In the a3Bu case Lisman et al. (1970) did not use the Kr from the irradiated samples used for all other fission products, but obtained it instead from 3 MTR fuel plates with irradiations of 0.4, 1.3 and 1.5 n/kb. Results from the two longer irradiations are in very good agreement while relative yields for the 0.4 n/kb sample differ significantly (-3% for S3Kr; + 3% for 84Kr). For this reason only data from the two longer irradiations were used. Correction factors for these irradiations were not included in the list of auxiliary data (Lisman, 1970) but can be estimated. For 83Kr the correction is about + 14% for the two longer irrad- iations, with a re-correction of about + 0.8%. This has been applied in the tabulated values. It might be argued that the 0.4 n/kb and other sample data could be used to determine both S (S3Kr) and the correct relative yields by minimizing the standard deviations of the three sets of relative yields. This procedure gives a value for § (83Kr) of about 90 b, much less than the value of Table 1: Relative Yields ol Krypton and Rubidium isotopes aKr *Kr °Kr* 6Rb Rb Petruska et al- (1955) .34521 ,6548 Wanless, Thode (1955) .1526 .2806 .0821 .5668 Lisman et al. (1970)a .15463 .2852s .3827* .5602 .3428* .6572 ±0.1% ±0.1% ±0.5% ±0.1% Average .1536 .2829 .3827 .5635 .3440 .6560 ±0.7% ±0.8% ±0.6% ±0.4% ±0.2% Fleming et al (1954) .1829 .3042 .0888 .5129 Bidinosti et al. (1961) .3552 .6448 Lisman et al. (1970) .18353 .30383 .3970* .5127 .3533* .6467 *0.3% ±0.3% ±0.3% ±0.2% ±0.3% ±0.2% Average .1832 .3040 .3970 .5128 .3542 .6458 ±0.2% ±0.1% ± 0.1% ±0.3% ±0.2% "PU Fritze et al.(1958) .1921 .3113 .3642 .4967 Fickel, Tomlinson (1959) .364B .636 Lisman et al.(1970) .19383 .31223 .3645* .4940 .3651* .6349 ±1.2% ±0.7% ±1.2% ±0.4% ±0.7% ±0.4% Average .1929 .3118 .3644 .4953 .3650 .6350 ±0.5% ±0.1% ± 0.1% ±0.3% lPu Lisman et al (1970) .1727 .3075 .3363* .5198 . 3434* .6566 ±0.1% ±0.3% ±0.1% ±0.1% ±0.1% ±0,1% The relative yield of the i isotope is n./Sn. where n is the number of atoms and the sum does not include the èontribution from this isotope, see page 3 Increased 0.7% due to change in T,(a6Kr) from 10.27 y to 10.74 y Data for one Kr sample not used. *See text Corrected for change in Ô (a3Kr) from 180 b to 194 b. For Kr the changes are - a3BU, +0.8%; a33U, +0.1%; a39Pu, +0.4%; 34IPu - negligible B4Kr relative yields are decreased by corresponding amounts Sum of 8BKr and aBRb Decreased 11%. See text - 6 - 2.2 Strontium and Yttrium (Table 2) Agreement between different measurements is satisfactory except for the results of Gorshkov and Anikina (1959) and of Anikina et al.(1958). For a8Sr, the difference from the recommended relative yields is +7.4% for aa3u and -4.7% for a39Pu. Both sets of results are omitted in obtaining average relative yields. Standard deviations from the average values indicate a systematic error contribution of about 0.4%, appearing as a consistent difference of ~1% between the 8BSr yields of Lisraan et al. (1970) and the later McMaster University results (Farrar et al., 1962: Bidinosti et al., 1961; Fickel and Tomlinson,1959) , TABLE 2 Relative Yields of Strontium and Yttrium Isotopes aSr lSr* Petruska et al. (1955) .3808 Steinberg, Glendenin (1955) .3834 Faricir et al (1962) .3831 .S052 .6391 .4450 . 55503 Lisman et al. (1970) Average .5052 .6391 .4450 .5550 Gorshkov, Anikina (1959) Bidinosti et al. (1961) .51303 Lisman et al. (1970) Average .4480 .5130 ±0.6% 'Pu Anikina et al (195f.) .6243* Fickel, Tomlinson (1959) .4868 .6050 .4122 .5878s Lisman et al. (1970) .6085 ±0.2% Average .4868 .6068 .4122 .5878 ±0.3% 'Pu Lisman et al (1970) .3845 .6155 ±0.3% ±0.2% The relative yield of the i isotope is n./Sn. where n is the number of atoms and the sum does not incluàe tÂe contribution from this isotope. See Page 3 Not used in taking averages Decreased 0.25% due to a change in T,(90Sr) from 27.7y to 28.9y Corrected for change in T,(asSr) from 51.8 to 50.8d, and in T,(91Y) from 336 339 * 58 to 58.8d - U, +0.5%f Puf -0.4% Increased 2.5% due to change in T,(89Sr) from 52.Od to 50.8d - 7 - 2.3 Zirconium (Table 31 The relative yield of 9lZr in a39pu measured by Gorshkov and Anakina (1959) exceeds the average of the other three measurements by more than 3%, or ten times the standard deviation of the latter. For this reason their measurement is not included. The 9azr relative abundance in one of the a39pu samples of Lisman et al. (1970) is 5% smaller than the average for the other two samples and has been omitted. Even with these deletions taost of the average relative abundances of the Zr isotopes have a greater percentage uncertainty than the preceding four elements. Table 3s Relative Yields of Zirconium isotopes 'Zr "Zr *Zr 5Zr* 'Zr Steinberg, Glendenin (1955) .1881 .1942 .2077 .2061 .2039 Farrar et al (1962) .19021 .1916 .2067 .2079 .20873 ,2036 Lisman et al- (1970) .2054 .2083 .2020 ±0.3% ±0.4% ±0.2% Average .1899 .1929 .2066 .2074 .2067 .2032 ±0.9% ±0,7% ±0.6% ±0.6% ±0.5% Steinberg, Glendenin (1955) .1994 .2046 .2168 .2082 Gorshkov, Anikina (1959) .17473 .2059* .2047 .2180 .2056 Bidinosti et al.(1961) .1983 .2066 .2155 .2053 Lisman et al. (1970) .1993 .2020 .2141 .2085 ±0.5% ±0.2% ±0.3% ±0. Average .1747 .1990 .2045 .2161 .2069 ±0.3% ±0.9% ±0.8% ±0.8% Fickel, Tomlinson (1959) .1342 .1617 .2046 .2310 .26055 .2685 Lisman et al. (1970) .1312 .1613e .2057 .2348 .2670 ±0.2% ±0.1% ±0.3% ±0.2% ±0.1% Average .1327 .1615 .2052 .2329 .2605 .2677 ±1.1% ±0.1% ±0.3% ±0.8% ±0.3% LPu Lisnian et al, (1970) .1245 .1526 .1984 .2280 .2965 ±0.1% ±0.3% ±0.2% ±-..0.1% ±-0.1% The relative yield of the i isotope is n./2n. where n is the number of atoms ard the sum does not include the contribution from this isotope. See Page 3 Not used in calculating average. Remaining relative yields renormalized assuming the average value at this mass increased 0.3% due to change in T,(91Y) from 58d to 58.8d Increased 0.3% due to change in T?(9EZr) from 65.8d to 65.5d Decreased 1.6% due to change in T?(9°Sr) from 29.3y to 28.9y Decreased 0.4% due to change in T|(V 9BZr) £rom 65.Od to 65.5d Increased 0.6% due to change in T?(96Zr) from 65.8d to 65.5d Relative yield from one sample not used - 8 - 2.4 Molybdenum (Table 4) The 9SMo relative yields of Steinberg and Glendenin (1955) have not been used because the re-correction for hold-up in 9BZr and 9SNb cannot be estimated. They give the 95zr half-life as 63 days compared to 65.5 d used here so that hold-up would be greater than they calculated. Thus re-correction would increase their yields and bring them into closer agreement with other measurements. Standard deviations from the average are comparable to those for Zr. Table 4: Relative Yields of Molybdenum Isotopes 3 Mo* 97 Mo 3 Mo MO Steinberg, Glendenin (1955) .3451* .3352 .3181 .3467 Farrar et al.(1962) .3353 .3180 .3467 Lisman et al. (1970) .3603 .3281 .3229 .3490 ±0.4% ±0.1% ±0.1% ±0.1% Average .3603 .3341 .3197 .347 5 ±0.9% ±0.9% ±0.4% Steinberg, Glendenin (1955) .4086* .3583 .3470 .2947 Bidinosti et al-(1961) .41151 .3620 .3430 .2950 Lisman et al. (1970) .4198 .3635 .3430 .2935 ±0.7% ±0.6% ±0.7% ±0.3% Average .4157 .3613 .3443 .2944 ±1.0% ±0.8% ±0.7% ±0.3% Pu Fickel, Tomlinson (1959) .2709 .3032 .3158 .3810 The relative yield of the i isotope is n,/Zn. where n is the number of atoms and the sum does not include the contribution from this isotope. See Page 3 Not used in taking average because no information is given on correction for hold-up in Zr and Nb Increased 0.6% due to change in T,(9EZr) from 65.Od to 65.5d - 9 - 2.5 Ruthenium (Table 5) Results for aa6u are in satisfactory agreement. For B33u the three measurements give yields which differ appreciably, with standard deviations from the average ranging from 1.6* to 2.7%. Contamination from naturally occurring Ru cannot explain the spread in values since the smallest standard deviation is for 1 yr 1066RRu. Table 5: Relative Yields of Ruthenium Isotopes l01Ru loaRu 103RU* 10*Ru 1O6RU 33Bu Steinberg,, fflendenin (1955) .4432 .3632 .1600 .0337 Lisman et al.(1970) .4405 .3664 .1593 .0338 ±0.2% ±0.1% ±0.5% ±3.2% Average .4418 .3648 .1596 .0338 ±0.3% ±0.4% ±0.3% ±0.3% aaa_u Steinberg, Glendenin (1955;) .4566 .3607 .1461 .0365 Bidinosti ist al- (1961) .4682 .3426 .1533 .0359 Lisman et ,al.(1970) .4641 .3517 .1471 .0371 ±0.6% ±0.5% *i.ox ±1.6% Average .4630 .3517 .1488 .0365 ±1.7% ±2.6% ±2.7% ±1.6% 339 Pu Fiche!, Tomlinson (1959) .2639 .2674 .27281 .2647 .2040 Lisman et al.(1970) .2673 .2737 .2718 .1872 Average .2656 .2705 ,2615a .2683 .1956 ±0.7% ±1.2% ±1.3% ±4.3% Lisman et al.(1970) .2363 .2514 .2705 .2418 The relative yield of the iu isotope is n./Sn. where n is the number î contribution from this isotope. See Page 3 Increased 7.7% over yield quoted in paper; normalized to 0.2040 for l06Ru. See text Reduced to keep the 103Ru to loeRu atom ratio unchanged - 10 - For 339Pu fission, on the other hand, the agreement is poorest for 109Ru (+4.3%) indicating the possibility of contamination by naturally occurring Ru in the Lisman et al, (1970) sample. For both a39Pu and a41Pu fission they state that some fission product Ru precipitated during dissolution of the Pu, but give no indication of how much, and provide no data indicating the absence of naturally occurring Ru. The 103Ru relative abundance of Fickel and Tomlinson (1959) was determined from a separate irradiation. The sample used had already been isotope-diluted so that the ratio to 104Ru could not be used. Instead they determined the yield of 103Ru relative to 106Ru, Simulating the irradiation and cooling history using FISSPROD (Lane, 1969) gives a relative abundance for 103Ru that is 7.7% greater than the value quoted in the original paper. In view of the spread in relative abundances noted for 333U fission, and lack of information on possible contam- ination of the 239pu samples, the two sets of relative abun- dances for the latter are simply averaged. The 103Ru abun- dance is then obtained from the average 10SRu abundance using the measured atom ratio. 2.6 Xenon (Table 6) The 131Xe yields of Lisman et al.(1970) have been re-corrected to a higher effective neutron capture cross section that takes account of the large epithermal absorption in 131Xe (resonance integral of 875 b). This increases the effective cross section from 85 b (Lisman et al. 1970) to 122 b. The measurements are in excellent agreement for 131Xe, 133Xe, and 134Xe. Lisman et al.(1970) could not correct for 13SXe absorption because of the nature of the irradiation, but do quote a value for the combined 135Cs and 13SXe yield in the case of 33sPu fission. - 11 - Table 5: Relative Yields of Xenon Isotopes 131Xs X33Xe X33Xe* 134Xe 13BXe* x36Xe* x38xe* 83*2 Wanless , Thode (1955) .1906 .2853 .5241 .4206 Lisman i3t al. (1970) .19301 .28671 .5203 ±0.2% ±0.1% Average .1918 .2860 .5222 .4206 ±0.7% ±0.3% ±0.4% Fleming et al.(1954) .2420 .3322 .4258 .4746 1 1 Lisman et al.(197G) .2448 .3332 .4220 ±0.4% ±0.5% ±0.5% Average .2434 .3327 .4239 .4746 ±0.6% ±0.2% ±0.5% 339Pu Fleming , Thode (1956) .2285 .3188 . 4187 .4527 .39083 Lisman et al. (1970) .22821 .31921 .4526 .8747a ±0.7% ±0.2% ±0.5% Average .2283 .3190 .4187 .4527 .3908 ±0.1% ±0.1% .87473 3«xPu Farrar et al.(1964) .1967 .2925 .4291 .5108 .4904 .4606 .4434* Lisman et al. (1970) .1969X .29411 .5089 Average .1968 .2933 .4291 .5099 .4904 .4606 .4434 ±0.1% ±0.3% ±0.2% The relative yield of the i isotope is n./2n. where n is the number of atoms and the sum does not include the contribution from this isotope. See Page 3 Corrected for increase in effective cross section of l31Xe from 85 b to 122 b due to significant resonance absorption - relative 13IXe yields 335 333 839 34l increased 0.2% ( U), 0.7% ( U and Pu)J 0.1% ( Pu); relative 13aXe yields decreased by an equivalent amount Decreased 3.2% to account for higher 135 to 136 yield ratio than assumed in correction for 13Bxe capture (assumed ratio , 1.0; used here, 1.09) Sum of X36Cs and 13eXe Decreased 0.8% due to change in Ti (138xe) from 14.0 to 14.2 m - 12 - 2.7 Cesium and Barium (Table 7) For Cs, standard deviations from average values are much larger than for the results of Lisman et al., indicating systematic errors of from 0.5% (335u) to 1.5% (241Pu). Contamination with naturally occurring Cs is very difficult to detect because it is monoisotopic (133Cs) . If there was such contamination the most accurate results would be those with the lowest 133Cs yields. However, differences in the detected amount of Cs element, discussed in the next section, show no correlation with 133Cs isotopic abundances that might be attributed to such contamination. - 13 - Table 7: Relative Yields of Cesium and Barium Isotopes 133Cs 136ca* 137cs l37Ba* 130Ba 139Ba* ll°Ba* I"îtruska et al. (1955b) .5194 .5052 .«Î8061 Farcar, Tomlinson (1962) .919a 1.000 .9523 .935 Larsen et al-(1966) .5167 .4833 Rider et al. (1965) .5245 .4755 Lisman et al. (1970) .5178 .4822 ±0.2% ±0.2% .5196 .5052 .4804 .919 1.000 .952 .935 ±0.7% ±0.7% Ivanov et al. (1959) .4700 .5300* Bidinosti et al. (1961) .4672 .4874 .5328 Rider et al.(1966) .4738 .5262 Lisman et al. (1970) .4674 .5326 t0.3% ±0.2% Average .4696 .4874 .5304 ±0.7% ±0.6% Wiles et al (1956) .5028 .5279E .49721 +15.% Krizhansïzii et al (1957) .3084* .733 .6916 Anikina et al (1958; .4473* .5910* .5527* Fickel, Tomlinson (1959) .5163 .5560e .48371 Rider et al (1966b) .5028 .4972 Lisman et al (1970) .51637 .4837 +.0.5% +.0.5% Average .5005 .5554° .4905 +.1.3% +.2.2% +1.3% "'PU Facrar et al. (1964) .4978 .5373 .5022 1.000 .5490 Riâer et al.(1967) .5148 .4852 Lisman et al. (1970) .5042 .4958 ±0.2% ±0.2% Average .5056 .537 3 .4944 1.000 .8490 ±1.7% ±1.7% The relative yield of the i isoLope is n./ïn. where n is the number of atoms and the sua does not include the èontribution from this isotope. See Page 3 Hot used in calculating average Corrected for change in T|(laTCs) from 26.6y to 30.2y - a360, -0.8%i a33Pu, -0.6% (Wiles et ah), -0.3% (Fickel, Tomlinson) FISSPROD gives a correction factor 35% less than their ratio of corrected to observed yields. A typographical error in the observed yield is assumed (e.g. 0.216 should be 0.316) and their corrected yi^ld is used Value recalculated by Bayly et al.(1961) Increased 0.5% to allow for an ir.ci.ease in the effective cross section of 13aCs to include resonance absorption Weighted average using the squares of the inverse of the indicated uncertainties - 14 - 2.8 Cerium (Table 8) The results of Lisman et al.(1970) quote only the sum of 144Ce and 144Nd. Since their cooling periods exceeded the 144Ce half-life the bulk of this quoted yield is due to Nd and is, therefore, sensitive to uncertainties in the relative amounts of the two elements. To obtain a relative 144Ce value the original results quoted in various project reports were used (Maeck et al, 1965, 1966; Lisman et al. 1966, 1967), after re-correcting for a 144Ce half-life of 284.4 d. In the case of 341Pu fission, the 144Ce correction factors are not available, but are large (^,18) . The l44Ce yield of Farrar et al. (1964) is, therefore, substituted. The following relative yields were not used for the reasons stated* the 144Ce yield in 335U fission of Steinberg and Glendenin (1955) includes a large decay correction, not given, based on a half-life of 282 d rather than 284.4 d; the 140Ce yield in S39Pu fission of Krizhanskii et al (1958) is 17% low; one of three 144Ce yields for 339Pu fission measured by Lisman et al.(1967) was 5.7% greater than the other two, many times greater than the standard deviations of any of their other Ce isotopic abundances. If the Steinberg and Glendenin (1955) results were omitted in the case of 236u fission the 140Ce yield would decrease 0.5% and the 143Ce yield would increase 0.5%. The standard deviations would decrease to 0.5% and 1.3% respectively, placing the Steinberg and Glendenin values 5 times and 3 times away from the averages at masses 140 and 142 respectively. The case for rejection of the Steinberg and Glendenin results appears marginal, and they have been retained. For the remaining fissile nuclides, standard deviations from the average yields are less than those assigned to the experimental values of Lisman, indicating that systematic errors are probably small. - 15 - Table 8: Relative Yields of Cerium Isotopes "Ce 'Ce* 'Ce Steinberg, Glendenin (1955) .3671 Petruska et al. (1955) .3578 Chu (1959) .3559 Farrar, Tomlinson (1962) .3599 .3301 Maeck et al. (1965, 1965) .3580 *0.4% Average .3597 .3301 ±1.2% Ivanov et al.(1959) Bidinosti et al.(1961) Maeck et al.(1965, 1966) Average 'Pu Wiles et al (1956) .3872 .3484 .26441 Krizhanakii et al (1957) .3219* .34275 . 2682ll& Anikina it al (1958) .3340* .4030* (.2630) Pickel, Tomlinson (1959) .3888 .3471 .26413 Lisman et al (1967) .3902 .3513 .2577** +0.2% +.0.2% ±0.6% Average .3890 .3480 .2630 +0.5% +0.8% +1.4% kPu Farrar et al. (1964) .3974 .3328 .3228 .2798 Lisman et al.(1970) (.2798) Average .3328 .2798 .th The relative yield of the i*"' isotope is n./Sn. where in is the number of atoms and the sum does not include the contribution from this isotope. See page 3 Not used in calculating average. Remaining relative yields renormalized assuming average v ilue at this mass Corrected for change in T,(l44Ce) from 282 d to 284.4 d - 336U, -2.0%; 339Pu, -1.0%8(Wiles ^.t alj, -1% (estimated) (Krizhanskii) Corrected for change in T,(l44Ce) from 285 d to 284.4 d - U, +0.3%; aaaU, +0.3%; 33BPu* +0.5% Corrected for change in Ti(144Ce) from 278 to 284.4 d - 339Pu, -1.7% Relative yield for one sample differed by 5.7% and was not used. Remaining relative yields for that sample renormalized assuming average value at this mass Their 144Ce/143Ce abundance ratio is quoted with a 5% error. These values are given è weight in obtaining the average - 16 - 2.9 Neodymium (Table 9) Neodymium is the fission product element most frequently measured by mass spectrometrists and 14SNd is used as a burnup monitor. For 144Nd, instead of the sum of 144Ce + 144Nd quoted by Lisman et al. (197 0), the results in their progress reports (Maeck et al- 1965, 1966; Lisman et al-1966, 1.967) were used. In the case of 144Nd, the correction factors for the 144Ce decay are much smaller than for 144Ce; the re-corrections are 0.1% or less and have been omitted. For 341Pu there is not sufficient information to separate l44Ce and 144Nd, but, since the latter is about 18 times greater, the sum can be substituted for 144Nd without introducing a significant error. The results of Steinberg and Glendenin for masses 143, 144, 145 and 146 have not been used. Their relative abundance for 143Nd is less than other measurements while that for i44Nd is greater by an equal amount, so that the sums of the two relative abundances are about equal. The magnitude of the effect is about that to be expected from neutron capture in 143Nd. Since no mention is made of a capture correction this is assumed to be the cause. There is a similar levelling effect in the sum of the 14&Nd and 146Nd values, but in this case the effect is much too large to be attributed to capture in 145Nd. When the results of Melaika et al. (1955) v/ere re-corrected for the 144Ce half-life, the yield of one sample (A) changed by 3%, the others by much less. The sample A value., which had been omitted in obtaining the average relative abundance in the original paper, then agreed with the others, and has been i ^eluded here. The re-corrections to the results of Ivanov et al.(1959) for 14r'Nd capture are 0.4% and +5% for 144Nd. The re-corrected 144Nd value was obtained by requiring that the sum of 143N<3 and 4Nd relative abundances after correcting for 143Nd capture should equal the sum before correction because there is no signi- ficant loss of 144Nd by neutron capture. This condition was not satisfied by the values in the original paper. Standard deviations from the averages in Table 10 are generally greater than those assigned to the Maeck et al.and Lisman et al.measurements, indicating the probability of systematic errors. The largest standard deviations are for 1G:"Nd - up to 3.8% for 3'Î3U. - 17 - Table 9: Relative Yields of Keodymium Isotopes l43Nd 14*Nd 1#6Nd 148Nd 147Nd* 14eNd 1B0Nd Steinberg, Glendenin(1955) .2820* .2723" .1849" . 1474* .0814 .0325 Melaika et al. (195S) .2861 .26721 .1903 .1445 .0804 .0315 Farrar, Tomlinson (1958) .2863 .2661 .1906 .1447 .1093 .oeos .0315 Chu (1959) .2897 .2607 .1912 .1448 .0817 / .0319 Rider et al. (1965) .2927 .2593 .1911 .1441 .0816 .0313 Lisman et al. (1970) .2884 .2640 .1893 .1443 .0827 .0312 ±0.4% ±0.9% ±0.6% ±0.3% ±0.5% ±0.5% Average .2885 .2635 .1905 .1445 .1093 .0814 .0316 ±0.9% ±0.9% ±0.4% ±0.2% ±1.1% ±0.8% a33U Melaika et al.(1955) .3201 .25061 .1879 .1412 .0717 .0285 Ivanov et al.(1959) ,3224s .25663 .1821 .1412 .0663* .0324" Bidinosti et al-(1961) .3197 .2503 .1881 .1408 .0720 .0291 Rider et al-(1966) .3253 .2533 .1862 .1381 .0702 .0268 Lisman et al. (1970) .3198 .2574 .1850 .1389 .0717 .0272 ±0.2% ±0.4% ±0.3% ±0.3% ±0.6% ±2.4% Average .3215 .2536 .1859 .1400 .0714 .0279 ±0.7% ±1.3% ±1.4% ±1.0% ±1.2% ±3.3% Î39PU Wiles et al. (1956) .2714 .22911 .1849 .1523 .1029 .0594 Krizhanskii ut al- (1957) .2743 .2305 .1827 .1528 .0993 .0603 Anikina et al (1958) .2654' .2393" .1837 .1544 .1005 .0591 î'ickel, Tomlinson (1959) .2703 .23073 .1852 .1522 .1014 .0603 Rider et al (1966) .2744 .2294 .1850 .1512 .1014 .0586 Lisman et al (1970) .2725 .2286 .1847 .1518 .1034 .0590 +0.3% ±0.9?4 ±0.2% ±0.2% ±0.7% ±0.4% Average .2726 .2297 .1344 .1524 .1015 .0595 ±0.7% ±0.4% ±0.5% ±0.7% ±1.5% ±1.2% 341 Pu Farrar et al. (1964) .2537 .2328 .1807 .1551 .1094 .0683* Rider et al.(1967) .2560 .2385 .1817 .1520 .1075 .0643 Lisman et al. (1970) .2556 .2356 .1819 .1528 .1077 .0664 ±0.2% ± 0.1% ±0.1% ±0.2% ±0.2% ±1.0% Average .2551 .2356 .1814 .1532 .1082 .0663 ± 0.5% ±1.2% ±0.4% ± 0.9% ±1.0% ±3.O5i . th The relative yield of the i isotope is n./Sn. where n is the number of atoms and the sum does not incluàe the contribution from this isotope. See Page 3 Not used in taking average, Remaining yields normalized assuming average value at this mass 1 Corrected for change in TJ(144Ce) from 282 to 28ft,4 d - 3' U, +0.4% (see text); a33U, +0.5%: a39Pu, +1.0% 3 corrected for change in a(143Nd) from 280 b to 325 b. See text 3 corrected for change in Tjl^Ce) from 278 d to 284.4 d - a39Pu, +1.5% 4 Results for two samples were quoted with relative 1B°Nd yields differing by 4.4%. Only the value with the smaller standard deviation LS used here - 18 - 2.10 Samarium and Europium (Table 10) The interpretation of Sm abundances is complicated by several nuclear transmutations. Neutron captures effects are especially large for the long, high flux irradiations of Lisman et al (1970). The relevant transmutations are shown as arrows in the following diagram: A fission neutron a — + yield Nd 3.6b- 1.9b- lid st 1.7h st capture (3 decay m I 140b-f24kb 1400b»- stable st. Pm 155b- 3kb- *• 2.65y -FH41dJ 5-d 53h 2.7h 28h 1 I 1 I I Sm 4b- 60kb- 114b- -13kb •37 5b- ?. -5] st st st st st 47h st Mass 147 148 149 150 151 152 153 154 Corrections for most transmutations can be made accurately. The mass 149 yield will be proportional to the sum of the 149 Sm and ISO Sm isotopic abundances because the mass 150 yield accumu- lated at 150Nd. contributions from capture at mass 148 are about equal to losses from capture in Sm. The production of 1EO Pm in fission (direct yield) is estimated to be negligible. The main sources of uncertainty, in order of decreasing importance, are (1) Separation of the 1B1Sm and 153Sm contributions to the measured isa Sm abundance (2) Capture in 153Sm (a could be >10kb). After recorrecting the Lisman et al.results the sum of the 1 5 X Sm isotopic abundances agreed with those in other experi- - 19 - ments but the ratio of the two did not. There is no simple explanation for the difference.* The sum of the two, say F, was therefore averaged for all results. Then the final values for the 161 and 1BS relative abundances (f) are given by fisi _ f. -15 1 l and fl63 = F ? (" /i = F ?A fi6i+fiBaJii- ' i i' where i refers to the results of the other experiments. The a33u data of Lisman et al. (1970) for sm isotopes is incomplete for all four irradiated samples. Because of the method used in this report to normalize relative isotopic abundances an iterative approach was therefore required in which average isotopic abundances are substituted for the missing data. The final results are shown below with the substituted values in brackets. In addition one 149Sm measurement was discrepant (marked x) and the average value was substituted here as well. Retention of this value would increase uncertainties at masses 149, 151 and 152 to greater than 2%. Sample No. 6-2-4 6-4-2 6-4-3 6-5-1 Average Relative Yields 147Sm .5618 . 5582 .5618 .5606 0.5606+0.4% 149Sm .2539 .24261 (.2540) .2542 0.2540+1.1% 161Sm (.1064) .1076 .1053 .1064 0.1064^1.8% lsaSm .0631 .0654 (.0641) .0639 0.0641+1.8% 1&4Sm .0147 (.0148) (.0148) .0149 0.0148+0.6% For a35u fission the Lisman et al. (1970) value is 17% low. The only obvious explanation, natural Sm contamination in the other three results,seems unlikely since in two cases this possibility was checked and ruled out (Melaika et al., 1955; Farrar and Tomlinson, 1962). * The I4BSm/1DOSm ratios of Lisman et al.were also anomalous. The variation was too great to be explained by changes in nexitron temperature. The most likely remaining possibility is that the fractions of the 149 and 151 decay chains held up as 149Pm and 151Pm at the end of the irradiation, were very different from their average values due to a change in flux magnitude. Detailed irradiation histories would be required to decide whether this was the cause of the differences. - 20 - Table 10: Relative Yields of Samarium and Europium Isotopes lBa 166 335, 147 Sm *Sm 21 *Sm Eu* Eu» Melaika et al.(1955) .55831 .2573 . 0646 .0175 Chu (1959) .5479 .2682 .0649 .0180 .0398 .0078 Farrar, Tomlinson .5525? .2603 .10233 .0664 .0185 .0397* (1962) e Lisman et al.(1970) .5491s .2661 .1088s'7 .0580 .0151* jO.5% +0.7%jl.0% jl.0% +2.2% . 1671+0.8%9 .0078 Average .5519 .2630 .1018 .0653 .0180 .0398 + 0.8% +.9% +2.7% iO.3% 9 Melaika et al-(1955) .6272* .2499 .10429 .0707 .0152 e Lisman et al. (1970) .55996 .2537 .10758'7 .0640 .0148 iO.4% +0.1% +1.1% +1.8% +0.6% .1732 Average .5599 .2518 .1032 .0700 .0150 +0,8% +1.3% Wiles et al (1956) .41631 .2491 .1473 .1326 .0546 Anikina et al (1958)(.4170) .2577 .1549 .1151 .0552 Fickel. Tomlinson .41701 .2521 .15577 .1185 .0567 (1959) e Lisman et al (1970) .4177* .2459 .1644e»7 .1179 .0541 +1.0% +1.5% +3.3% + 2.6% i3.4% .2766 +2.O%10 Average .4170 .2512 .1570 .1195 .0551 iO.2% +2.0% Farrar et al. (1964) .3960a .2546 .1577 ,1245 .0670 Lisman et al-(1970) ,3912B .2582 (.1577) (.1245) .0682 +0.6% +0.1% +3.7% Average .3936 .2565 .1577 .1245 .0676 +0.6% +0.7% +0.9% Yields for Eu Isotopes normalized to Sm yields Not used in taking average. Remaining relative yields calculated using average for this mass. (Also omitted in later results from same laboratory (Bidinosti et al, 1961)) Corrected for a change in Ti (147Pm) from 2.52y to 2.62y and taking account of hold-up in 11.06d 147Nd - a3BU, +2.4%; a39Pu, +7% (Wiles et al.) , +8% (Fickel, Tomlinson) Corrected for a change in T, (l47Pm) from 2.52y to 2.62y - 336u. +0 2%- + 3% Corrected for a change in Ti (lB1Sm) from 98y to 93y - a36U, + 0.5% Normalized at mass 151 using 161EU *Th .e^ Eu 153/151 ratio is increased 4 .7% due to half-life change of footnote Corrected for a change in T. (147Pm) from 2.70y to 2.62y - a36U, -2.5%; "U, -2.6%; a3dPu, -2.2%;*a41Pu, -1.9% Corrected for a change in a (1B1Sm) (see text) Corrected for1B1 Sm decay - 33Bu, +1.1%; a33U, +1.0%; a39Pu, +2% (Listnan et al.); +0.8% (Fickel, Tomlinson) (assuming cooling period of 1 year) corrected for hoii-up in 28 h 16ipm and a change in d (l81Sm) from 15 2 kb to^3 kb and m flux from 1.23 x 1013n/cmas to 1.65 x 10l3n/cmas The sm yield is decreased 1.2% and the1B3 Sm yield is increased by an equivalent amount 161 1B3 Average of sum of Sm and Sm relative yields - 21 - 3. RELATIVE ELEMENT YIELDS In this section the number of atoms of each fission product element is determined relative to zirconium or neodymium using isotope dilution and isobaric coupling data. Zirconium and neodymium are chosen because they are the elements most frequently measured in the light and heavy mass peaks respectively. Isotope dilution is the method commonly used. A measured number of atoms of a particular element, preferably enriched in a non-fission-product isotope, is added to the fission product solution and the relative yields of the isotopes of that element are then determined by mass spectrometer. The total number of atoms of the fission product isotopes of that element can be determined from their abundances relative to the added isotope(s). Isobaric coupling can be used if the isotopic abundance of a radioactive nuclide is measured in addition to that of the stable isobar into which it decays. Normally the two elements involved differ by one nuclear charge (i.e. the isobars are separated by a single p-decay). The isotopic abundance of the radioactive nuclide must, of course, be corrected for decay during the irradiation and cooling periods. A separate fissile sample is usually irradiated for this measurement, with the periods chosen to minimize the correction. If the parent (radioactive) and daughter (stable or long- lived) isobars have isotopic abundances of f and f relative to their respective elements then the relative number of atoms of the two elements are given by atoms of lower charge element (parent) _ _â f atoms of higher charge element (daughter) p This method is used occasionally in all determinations, notably to link Ce and Nd at mass 144, but has been used most extensively by Farrar et al.(1962) in their study of a3Su fission. In adopting the method for use here the average relative yield (Tables 1 - 10) of the stable or long-lived isobar is used rather than the original result of the authors, along with their measured relative yield of the radioactive isobar. To determine the shape of the light and heavy mass peaks over the range covered by mass spectrometrie measurements the yield, y, of a fission product is defined as y = f.fe. N Here f is its isotopic abundance, f is the number of atoms of its element relative to Zr or Nd and N is the absolute yield, of Zr or Nd as determined by isotope dilution. The main uncertainty in the normalizing yields, N, will be the deter- mination of the number of fissions - 22 - The main sources of uncertainty in relative element yields are systematic differences between the results of different laboratories. These can arise in several ways - by contamination of the fissile material before irradiation with the naturally occurring element; contamination of the fission product element during dissolution of the irradiated fissile sample and sub- sequent chemical separation; or by loss of some atoms of either the "spike" used in isotope dilution or the fission product element. For most elements, the isotopes and their relative abundances in the naturally occurring and fission product element are sufficiently different that contamination can readily be identified from a study of the mass spectrogram and the results corrected. Fission product cesium is particularly susceptible to the introduction of systematic errors due to contamination since 133Cs is the only isotope in the naturally occurring element and is also a fission product. Contamination can affect both the relative abundances and the determination of the number of atoms by isotope dilution. Some indication of the magnitude of systematic uncertainties in Cs isotope dilution can be obtained by comparing the results of Lisman et al. (1970), Rider et al.(1965, 1966, 1967) and those from McMaster University (Farrar and Tomlinson, 1962; Bidinosti et al., 1961; Fickel and Tomlinson, 1959; Farrar et al., 1964). The latter are of particular interest because they include a determination of the mass 135 yield and therefore provide the only mass spectrometric yield data relevant to 136Xe absorption. The Cs results are presented as ratios of ratios, and R , . , defined as element' 133Cs/fission product Cs)j R isotopic (i3aCs/fission product Cs)Lisman et al. and (Cs yield/Nd yield)i Relement (Cs yield/Nd yield)Lisman et al- where i refers to the appropriate Rider et al. or McMaster data. The element yield data are taken from Tables 11, 13, 15 and 17 which appear later in this section. The average values of both R's for the four fissile materials should be nearly unity if there is no source of systematic error. 33E a33 Fissile Nuclide u u sa9Pu 34 1 Average Ratio (not including aaBu) Rider et al. 1.013 1.013 0.974 1.021 1.003+0.025 R isotopic McMaster 1.003 0.999 1.000 0.978 0.992+0.015 Rider et al. 0.988 0.966 0.969 0.974 0.970+0.004 Relement McMaster 0.998* 0.890 0.954 0.956 0.933+0.038 * McMaster value obtained by isobaric coupling - 23 - It is apparent that with the probable exception of 3a5U there are systematic differences between isotope dilution measurements of element abundance from the different laboratories and that these are not due to naturally occurring contamination of fission product Cs since the 133Cs ratio averages close to unity. For a39Pu and 341Pu fission the Rider et al-values are in better agreement with McMaster values than either are with the results of Lisman et al. (1970) . With the exception of the low relative Cs yields in 3 33U fission obtained by Bidinosti et al- (1961) and Ivanov et al. (1959) all Cs yields are given equal weight. 3.1 335u Yields (Tables 11 and 12) The results of Steinberg and Glendenin (1955)for Cs, Ba and Ce are low by 12%, 25% and 5% respectively and are not used. Difficulties with natural element contamination, as discussed for Cs, may be the cause of the discrepancies. Relative yields of the light mass peak agree well except for Sr, where the three values have a spread of nearly 4%. For elements in the heavy mass peak agreement is less satisfactory, particularly for Sm where the spread in values is 16% and the standard deviation from the mean is over 6%. The Cs relative yields agree well as noted in the introduction but the Ba results have a spread of 4%. The values of Rider et al- (1967) are con- sistently lower than those of Lisman by an average of (3.5 +_ 0.5%) for the four fissile nuclides, indicating the likelihood of only a small statistical uncertainty, but a large systematic difference comparable to that in Cs, as discussed in the introduction to this section. Rider et al (1967) assign an error of 5% to their result which appears to indicate that their value snould be given a lower weight. However, there are much larger discrepancies in the Ba results for 339Pu and 241Pu indicating additional sources of error, so their values are here given the same weighting as others. The normalized light and heavy mass yields are listed in Table 12. Extra isobaric yields appear at masses 85, 89, 91, 95, 137, 140 and 147. The differences between isobaric yields are less than the estimated uncertainties, and the final yield is obtained by averaging, except as noted. A check between the light and heavy mass peak normaliz- ation is available. Blades et al (1956) measured the ratio of 86Kr and 134Xe yields to be 0.257 ± 0.005 by isotope dilution. The ratio from Table 12 is 0.261, with an estimated uncertainly of + 0.007. - 24 - Tciiîe 11: Relative Element Yields in Element Yields Relative to Zr Lisman et al. (1970) .1124 .1252 .3084 1.000 .5796 .3707 Farrar et al. 1 1 (1962) .2092 .3422 1.000 ±0.7% Steinberg, Glendenin (1955) .3031 Petruska et al. (1955) .1238 (.3036) Average .1124 .1245 .3036 .3422 1.000 .5824 .3682 ±0.6% ±1.5% ±0.5% ±0.7% Element Xe Cs Ba Ce Nd Sm isotopic mai-,-es 131,132 133,137 138 140,142 143-146 147,149 included in 134 144 148,150 151,152 element yield 154 Element Yields Relative to Nd Lisman et al. (1970) .7068 .6359 .3323 .860 1.000 .1338a Rider et al. (1965,1067) .6284 .3194 1.000 Farrar, Tom-- linson,(1962) .7650lj4 .63461' 6 .33191 .86211 1.000 .19791 Chu (1959) .0546 1.000 .2009 Petruska et al . 1.000 .21 tl (.1955; Steinberg, Glen- .5662* ,2627" .8178s'" 1.000 denin (1955) Average .7068 .6330 .3279 .8592 1.000 .1993 ±0.6% ±2 .3% ±0. 5% ±f,. ?."•'• From average relative .86421 yields (Tables 8,9) ±1.6% 1 Using isobaric links Not used in taking average Based on absolute yield of 10oRu determined by ft-counting. Assigned half weight in taking average Based on an isotope dilution measurement giving Rb atoms/ Sr atoms = 2.451 and assuming a Sr yield of 0.3036 •' With 147Sm reduced 2.5% (Table 10) Not used because it is based on an unpublished value of the UJXe yield for which no data on decay corrections is available From Cs yields of Pstruska et al.(1955b) using mass 137 isobars Based on mass 140 and 142 only, using average relative abundances of Table 8 - 25 - Table 12: Normalized Mass Spectrometric Yields in. 336u Thermal Neutron Fission * Mass Element Yield (%) Mass Element Yield (%) 83 Kr 0.535 131 Xe 2.766 84 Kr 0,986 132 Xe 4.123 1.333 , 133 Cs 6.709 85 Kr ,327X 1.327 f 1< Rb 134 Xe 7.529 1.963 86 Kr 135 Cs 6.524 2.532 87 Rb 136 Xe 6.065 88 Sr 3.593 137 Cs 6.204 > 175 4.755 » Ba 6.147 ' ' 83 Sr .737 4.720 < Y 138 Ba 6.689 5.818 90 Sr 139 Ba 6.368 91 Sr 6.015 , ,. 6.254 , .951 140 Ba .289 Y/Zr 5.887 f " Ce2 £.323 ' 5.980 92 Zr 141 Ce3 5.803 6.405 93 Zr 142 Ce3 5.896 6.429 94 Zr 143 Nd 5.885 95 Zr 6.470 2 5.360 , .488 144 Ce .367 Mo 6.505 ' Nd 5.375 ' 6.299 96 Zr 145 Nd 3.886 97 Mo 6.032 2.230 , 147 Nd .2303 98 Mo 5.772 Sm 2.244 ' 100 MO 6.274 148 Nd 1.661 1.069 101 RU 5.043 149 Sm 102 Ru 4.164 150 Nd 0.64 5 104 Ku 1.822 151 Sm 0.414 106 RU 0.386 152 Sm 0.265 153 Eu 0.162 154 Sm 0.0732 155 Eu 0.0317 * Normalized to yields of 31.00% for Zr and 20.40% for Nd 1 The Rb value is used because the Kr value is based on only ^0 215 of the total yield and is considered less certain 3 ce yields are based on Ce atoms/Nd atoms = 0.8617 (mean of last two values in Table 11) . 3 The Nd value is used because of the 6% uncertainty in the Sm yield - 26 - 3.2 a33U Yields (Tables 13 and 14) Lisman et al-(1970) are the source of most of the data used for elements in the light mass peak. Their element yields were calculated separately for each of the four samples, and then averaged. Results from one sample were omitted for Kr and Mo. The results of Steinberg and Glendenin (1955) and those of Bidinosti et al.(1961) for the light masses (except Mo) were normalized to early radiometric measurements and are not listed. Standard deviations from the average relative yields of the elements in the heavy mass peak range from 1.7% tc 3.3%. The Cs yields of Bidinosti et al-(1961) and Ivanov et al.(1959) are low as noted at the beginning of this section, and omitted from the averages. Table 13: Relative Element Yields in 5U Thermal Neutron Fission Kr Rb Sr Zr MO Ru Isotopic masses includedd 83,84 85,87 88,90 91,92,93 97,98 101 ,102 in element yield 86 94,96 100 104 ,106 iment yields relative to Zr Lisman et al.(1970) .16731 .1891 .3782 1.000 .4502x .2123 ±0.7% ±1.1% ±0.3% ±0.9% ±1. 5% Bidinosti et al- (196.1) 1.000 .45851 3 Gorshkov, Anikina (1959')) 0.3165 1.000 Average .1673 .1891 .3782 1.000 .4543 .2123 ±0.7% ±1.1% ±0. 3% ±0.9% ±1. 5% Xe Cs Ba Nd Tsotopic masses included 131,132 133,137 138 140,142 143,144 147,149 in element yield 134 144 145,146 151,152 148,150 154 element yields relative to Nd Lisman et al.(1970) .7969 .7130 .3277 .9830 1.000 .1688' Rider et al.(1966,1967) .6887 .3138 .9951* 1.000 1>B X Bidinosti et al- (1961) .7463 .6347 .9554 1.000 .1655 Ivanov et al (1959) .6669* .9606 1.000 Average .7969 .7 009 .3207 .9735 1.000 .1672 ±1.6% ±2.2% ±1.9% ±1.1% From relative yields (Tables 8,9) .96831 ±1. 3% Not used in taking average Using isobaric link Omitting relative element yield from one sample Not used since their relative isotopic abundances are discrepant (Table 2) With ll7Sm reduced 2.6% (Table 10) Measured ^"Ce only. Value for Ce based on an isotopic abundance of U.375 for 14Sce Nut used Eir.cc the measurement of Xe atoms/Cs atcrns was based on an isobaric link for which no data are available - 27 - The data of Bidinosti et al-(1961) do give the yield of Kr relative to Rb. Their value is 0.902, in good agreement with the value of 0.901 obtained by Lisman et al. (1970). Table 14 gives the relative yields normalized to 33.0% for Zr and 18.2% for Nd. The latter is based on the absolute yields of Lisman et al. (1970) and Rider et al.(1966), both with 18.22%. Ivanov et al.(1959) obtained 15.9% for Nd and Bidinosti et al. (1961), 19.5%. Table 14: Normalized Mass Spectrometric Yields ina33 u Thermal Neutron Fission* Ele- Yield Ele- Yield Mass ment {%) Mass ment (%) 83 Kr 1.011 131 Xe~~ 3.530 84 Kr 1.678 132 Xe 4.825 85 Kr 2.192 21()1 133 Cs 5.990 # Rb 2.2ior 134 Xe 6.148 86 Kr 2.831 135 Cs 6.217 87 Rb 4.030 136 Xe 6.883 88 Sr 5.591 137 Cs 6.766 89 Sr 6.402 138 Ba 5.836 90 Sr G-889} 6.389s 140 Ce£ 6.414 Zr 5.7651 142 Ce3 6.628 91 Zr 6.567 143 Nd 5.851 92 Zr 6.749 144 Ce3 4.627 1 93 Zr 7.131 Nd 4.616 ' 6.828 94 Zr 145 Nd 3.383 6.290. 95 Zr 261 146 Nd 2.550 Mo 6.232' " 147 Sm 1.704 96 Zr 5.726 148 Nd 1.299 97 Mo 5.417 149 Sm 0.766 98 Mo 5.162 150 Nd 0.508 100 Mo 4.414 151 Sm 0.314 101 Ru 3.244 152 Sm 0.213 102 Ru 2.464 154 Sm 0.0456 104 Ru 1.042 106 Ru 0.2 56 Normalized to yields of 33.0% for Zr and 18.20% for Nd The Rb value is used because the Kr value is based on only -^0.215 of the total yield and is considered less certain The Zr value is not used Ce yields are based on Ce atoms/Nd atoms = 0.9707 (mean of last two values in Table 13) - 28 - 3.3 33MPu (Tables 15 and 16) The yields of elements in the light mass peak are in satisfactory agreement except for Rb where the two measurements differ by 10,i. Rather than take an average the Rb yield listed is based on the Kr yield of 0.600 (Table 15) using the isobaric identity at mass 85 (Table 1). Agreement is less satisfactory for elements in the heavy mass peak. For Ba, the relative yield of Fickel and Tomlinson (1959) is 15% greater than the average of the other measurements. However, it appears to fit the adjacent yields more smoothly and is carried through for future consideration. Table 15: Relative Element Yields in2J9 Pu Thermal Neutron Fission Kr Rb Sr 3r Mo Ru Isotopic masses included 83,84 85,87 88,90 89,91 91,92, 97,98 101,102 in element yield 86 93,94 100 104,106 96 Lisraan et al-(1970) .0815 .0824 .1800 1.000 1.214 Fickel, Tomlinson (1959) .0745 .1835 .22611 1.000 0 .962 1.164 +1.7% + 2.2% Fritze et al (1958) .07868 1.000 .0800 .07993 .1818 .2261 1.000 0 .962 1.189 Average ±1.9% ±1.9% ±1.0% ±2 .1% Xe Cs Ba Ce Nd Sm Isotopic masses included 131,132 133,137 138 140,142 143,144 147,149 in element yield 134 144 145,146 151,152 148,150 154 element yields relative to Nd Lisman et al-(1970) 0.9660 0.8459 0.3282 0.8772 1.000 0.3039* Rider et al • (1966,1967) 0.8196 0.3150 0.8673b 1.000 Fickel, Tomlinson (1959) 0.8070 0.8506 0.3214 0.3691 +0.850 0.5%6 1.000 + 3.3% Fritze et al.(1958) 1.0036d ~ ' ° 1.000 Average C.9848 0.8241 0.32167 0.8650 1.000 0.3121 ±2.0% ±2.4% ±2 .1% ±1.6% ±3. 0% or 0.36918 From relative yields (Tables 8,9) 0.8727 ±1.0% l Using isobaric link Using measured lùbRu radiometric yield relative toi37 Cs and average relative yield from Table 5. Renormalized to 6.76% for 137Cs and 19.20% for zr Absolute yield relative to 19.20% for Zr From Kr elemental yield and isobaric yields of 8BKr and S5Rb (Table 1) With l47Sm reduced 2.2% (Table 10) Measures Ce only. Value for Ce based on an isotopic abundance of Û.3475 for da2 Ce ' Calculated from absolute yield ofi3l 13 1Xe relative to 16.50% for Nd Excluding value of Fickel and Tomlinson Value of Fickel and Tomlinson only - 29 - The normalized yields are given in Table 16.. All authors listed in Table 15, except Fritze et al-(1958), measured the zirconium and/or neodymiura absolute yields. These are in good agreement and are averaqed to give the normalizing values. Lisman et al.(1970) determined the sum of136 Cs and 136Xe in their samples with the latter contributing much the greater portion. The average is 2% greater than sum of the individual l3Bxe and 136' yields. To take their measurement into account the individual yields are each increased 1%. The ratio of Kr to Xe determined by Fritze et al (1958) is 7è% greater than the same ratio measured by Lisman et al.(1970). Table 16-. Normalized Mass Spectrometric Yields in 339 Pu Thermal Neutron Fission* - Yield Ele- Yield Mass ment Mass ment (%) 83 Kr 0.296 131 Xe 3.710 84 Kr 0.479 132 xe 5.183 85 Kr 0.560 U ,-,„ Rb 0.560'°'560 133 Xe 6.805 6.867 86 Kr 0.761 Cs 6.928 87 Rb 0.974 134 xe 7.358 88 Sr 1.372 135 Cs 7.552. 14.2131 . 89 Sr 135 + 136 1'699!l 744 136 Xe 6.352Ï6.4221 Y J..789'1-'44 137 Cs 6.670 90 Sr 2.118 138 Ba 5.306/6.0902 91 Y/Zr 2.552 3 140 Ce 5.577 92 Zr 3.076 3 142 Ce 4.989 93 Zr 3.940 143 Nd 4.498 94 Zr 4.472 3 144 Ce 3.771i3.78 9 5 Zr/Mo 5.002 Nd 3.790* 96 Zr 5.140 145 Nd 3.043 97 Mo 5.600 146 Nd 2.515 98 Mo 5.833 147 Sm 2.147 100 Mo 7.037 148 Nd 1.67 5 101 Ru 6.063 149 Sm 1.294 102 Ru 6.175 150 Nd 0.982 103 Ru 5.970 151 Sm 0.808 104 Ru 6.125 152 Sm 0.615 106 Ru 4.465 154 Sm 0.284 * Normalized to yields of 19.20% for Zr and 16.50% for Nd 1 Increased 1.1% to give the average value for the sum 135Cs + 13sXe s High and low alternatives for xaBBa 3 Ce yields based on Ce atoms/Nd atoms = 0.8689 (mean of last two values in Table 15) - 30 - 3.4 34tpu (Tables 17 and 18) For elements in the light mass peak the only measurements are those of Lisman et al.(1970) and these are accepted as reported except in the 10S casP of Ru, which is based on a radiometric measurement of Ru relative to :37CS. Additional Xe and Ba yields are obtained from the average Cs and Ce yields using isobaric coupling (measurements of Farrar et aL, 1964). Two routes are available. In the one, the average Cs relative yield, 0.7418, and the isobars 13DCs and 133Xe are used to obtain a Xe yield, and thence, via the isobars lû8Xe and l*BBa, a Ba yield. In the second, the average Ce relative yield, 0.8438 is used with the isobars 140Ba and 140Ce to obtain a Ba yield. From this a Xe yield is derived using the mass 138 isobars. The Ce-related Ba and Xe yields are greater by 1.9%. Since both sets of Ba and Xe yields are linked by the same mass 138 isobars the two Ba and two Xe yields are averaged. The Ba yield of Farrar et al-(1964) obtained in this way is 7.5% greater than the average of the results of Lisman et al.(1970) and Rider et al-(1967). Both are listed with the averages and will be treated separately in the next section. Table 17: Relative Element Yields in Pu Thermal Neutron Fission Kr Rb Sr Zr Ru Isotopic masses included in 83,84 85,87 88,90 91,92,93 101,102, element yield 86 94,96 104,106 element yields relative to Zr Lisman et al-(1970) .0790 .0772 .1700 1.000 1.674 Xe Cs Ba Ce Nd Sm Isotopic masses included in 131,132 133,137 138 140,142 143,144 147,149 element yield 134 144 145,146 151,152 147,148 154 150 — — eiemeini. yieia Nd 3 Lisman et al.(1970) .9052 .7 596 .3639 .8441 1.000 .3156 Rider et al. (1967) .7399 1.000 Farrar et al. (1964) .7259 .8420 1.000 .8741 (.7418) .3876 .8905 .3949 (.8434) Average .8937a .7418 .3639* .8430 1.000 or e .3156 ±1.3% ±2 . 3% .3912 From relative yields (Tables 8,9) .8438 Normalized using their radiometric los Ru yield relative to 6.418% for 137cs 3 Including an assumed "1"61Sm yield (not reported) and with 147Sm reduced 1.9% (Table 10) Average of the Lisman et al-value and mean Farrar et al. value 4 Value of Lisman et al. only Average of Farrar et al.values - 31 - The yields are normalized in Table IS to the absolute Zr ana Nd yields of Lisman et al.(1970) except for the Ru isotopes which are based on the measured 10SRu - l37Cs ratio of 0.921 +_ 0.030 (Lisman et al.1969). Table 18: Normalized Mass Spectrometric Yields in a41Pu Thermal Neutron Fission* Mass Element Yield (%) Mass Element Yield (%) 83 Kr .199 131 Xe 3.078 84 Kr .355 132 Xe 4. 587 85 Rb .387 133 Xe 6. 711 ï , .637 Cs 6 86 Kr .600 6. 563' 134 Se 7. 87 Rb .740 975 135 Xe 7 ,670. , 88 sr .954 .97 53 Cs 6.975» 6 90 Sr 1.528 136 Xe 7.204 91 zr 1.818 137 Cs 6.418 92 zr 2.228 138 Xe 6.935 6 .890a 93 zr 2.897 Ba 6.8463/6 .368* \ Ior 6 .368* 94 zr 3.329 140 Ba 5.8123/5 .407 5.837a 96 zr 4.329 I Ce6 5.862 f or 5.862* 101 Ru 5.7761 141 CeB 4.,912 102 Ru 6.1461 142 Ce5 4,.767 104 Ru 6.6131 143 Nd 4,.464 106 Ru 5.9111 144 Ce6 4,•130. .126 Nâ 4,.123 • 145 Nâ 3 .17 5 146 Nd 2 .681 147 Sm 2 .173 148 Nd 1 .894 149 Sm 1 .417 150 Nd 1 .160 151 Sm 0.871 152 Sm 0.688 154 Sm 0.373 * Normalized to yields of 14.6% for Zr and 17.5% for Nd 1 Yields based on 106Ru atoms/137Cs atoms = 0.921 s Both values are from the measurements of Farrar et al-(1964). The authors prefer their Cs value 3 Frcm the results of Farrar et al- (1964' * From the results of Lisman et al.(1970) (l38Xe and 140Ba values are assumed erroneous) 5 Ce yields based on Ce atoms/Nd atoms = 0.8434 (the mean of last two values in Table 17) - 32 - 4. ERROR ASSIGNMENTS The errors assigned to the averages in Tables 1-20 are standard deviations where three or more measurements are included, or half the difference where there are only two measurements. These are summarized in Tables 19 and 20 for the heavy and light fission products respectively. They comprise the left-hand number of each pair assigned to an isotope or element, since no error has been assigned the "average" value based on only one measurement many of the left-hand er.ries are blank. The right-hand entry of each pair is an assigned value hereafter called an error. They are set equal to the left-hand value if one is available except where the latter is considered to be too small. Estimates are used here and wherever left-hand entries are missing. The Xe isotopes may be used to illustrate error assignments. Standard deviations from Table 6 in 333u and a36U fission show similar patterns for masses 131, 132, and 134 with a pronounced minimum at mass 132. Various mechanisms might be invoked to explain the pattern, but without a verifiable explanation it is unlikely that 133Xe yields are known more accurately than the other isotopes. The assigned errors for 13aXe are, therefore, set equal to those for 134Xe. Since the latter is the most abundant isotope this may be optimistic. For 136Xe there is only one measurement for each fissile nuclide and, therefore, no standard deviation. The error is set equal to /2 times those of 134xe since the latter are the averages of two measurements and it is assumed that there are no additional sources of error affecting 136Xe. For a39Pu and a41Pu the standard deviations from the averages have decreased relative to the uranium results while those for the measured values of Lisman et al.(1970) have increased. The agreement between the two sets of measured values is assumed to be fortuitous and the errors are set equal to those for 33BU fission. For Xe (the element), averages were taken only for a39Pu and 341 Pu with standard deviations of 2% and 1.3% respectively. This is in line with standard deviations from the average yield of other heavy elements and 2% is the minimum assigned in both tables except for Ce, Sr, and Mo which are adjacent to the normalizing elements Zr and Nd. Errors for the latter may be lower if the elements are linked directly by isobaric coupling. The yield of Ru in 341Pu fission is a special case since there is no isotope dilution link with Zr. The radiometric ratio of 106Ru to 137cs has a standard deviation of 3% while the isotope dilution measurements of Zr and Nd can be assigned errors of 2% in line with the other measurements. Including the errors in the 137Cs yields and the 10SRu relative abundance the error in the Ru yield relative to Zr is 5% taking the root mean square error of the components. In 339Pu fission there is also a Ru yield based on a radio- metric ratio of 106Ru to 137Cs (Lisman et al, 197 0). Since there is an additional isotope dilution measurement, however, a minimum error of 2% is assigned. - 33 - Table 19: Error Assignments for the Heavy Mass Peak Fissile Nuclide l31 I33 13; 136 l3B Xe Xe Xe Xe Xe a3Bu 0.7/0.7 0.3/0.4 0.4/0. 4 /o. 6 /2.0 a33 u 0.6/0.6 0.2/0.5 0.5/0. 5 /o. 7 /2.0 339 Pu 0.1/0.6 0.1/0.4 /o. 6 0.1/0. 4 /o. 6 2.0/2.0 341 Pu 0.1/0.6 0.3/0.4 /o. 6 0.2/0. 4 /o. 6 /o. 6 /0.6 1.3/2.0 133 l37 Cs l3BCS Cs Cs 137Ba 139Ba 140Ba Ba 336 U 0.7/0.7 /i.o 0. 7/0,,7 0.6/2. 0 A. 0 A..0 A.o 2.3/2.3 333U 0.7/0.7 /1.0 0. 6/0,.6 1.6/2. 0 2.2/2.2 339Pu 1.3/1.3 2.2/2.2 1. 3/1..3 2.4/2. 4 2.1/2.1 341 Pu 1.7/1.7 /2.5 1. 7/1,.7 2.3/2. 3 /i.o /2.0 l40Ce 14lCe l43Ce x*4Ce Ce 336 u 1.2/1.2 /1.4 1. 7/1 .7 1.3/1. 3 0.,5/1,.0 aaa u 0.5/0.5 0. 5/0 .5 0.1/0. 5 1,,5/1,,5 339 Pu 0.5/0.6 0. 8/0 .8 1.4/1. 4 1,.0/1 .0 341 Pu 0.2/0.5 /0.7 0. i/o .5 0-2/0. 5 0,.1/1..0 143Nd 144Nd 14BNd 14sNd 147Nd 148Nd 1B0Nd 336 u 0.9/0.9 0.9/0.9 0.4/1.0 0.2/1.0 /I.3 1.1/1.2 0,8/1.0 333J.U 0.7/1.4 1.3/1.3 1.4/1.4 1.0/1.4 1.2/1.4 3.8/3.8 339Pu 0.7/0.7 0.4/0.5 0.5/0.5 0.7/0.7 1.5/1.5 1.2/1.5 341Pu 0.5/1.0 1.2/1.2 0.4/0.9 0.9/0.9 1.0/1.5 3.0/3.0 147 163 166 Sm 140 Sm LSm 'Sm 'Sm Eu Eu 335 U 0.8/1.0 1.9/1.9 50.8/1.0 >0.8/1.0 2.7/2.7 6.3/6.3 0.3/1.0 A.2 333. 0.4/1.0 0.8/1.0 >1.0/1.0 >1.0/1.0 1.3/1.3 1.1/2.0 'PU 0.2/1.0 2.0/2.0 >2.0/2.0 >2.0/2.0 2.0/2.0 3.0/3.0 341 PU 0.6/1.0 0.7/1.0 /1.0 /1.0 0.9/1.0 /2.0 * Left-hand numbers o€ each pair are taken from Tables 1-18. Right-hand numbers are assigned errors - 34 ~ Table 20: Error Assignments for the Light Mass Peak Fissile Percentage Errors * for Huclide 83Kr 84Kr SBKr 86Kr Kr 8BRb 07Rb Rb a36u 0.7/0.7 0.8/0.8 /i.o 0.6/0.6 /2.0 0.4/0.4 0.2/0.2 0.6/2 .0 aa3 u 0.2/0.3 0.1/0.3 /0.5 0.1/0.3 0.7/2.0 0.3/0.4 0.2/0.2 1.1/2 .0 a39Pu 0.5/0.5 0,1/0.3 0 .1/0.5 0.3/0.3 1.9/2.0 /o.4 /o.2 1.9/2 .0 341 Pu 0.1/0.3 0.3/0.3 0 .1/0.5 0.1/0.3 /2.0 0.1/0.4 0.1/0.2 /2 .0 B9 a8Sr B9Sr 90Sr 9XSr Sr y 91Y Y a38 u 0.5/0.5 /0.7 0 .3/0.3 /0.7 1.5/1.5 /o.7 /o.7 /2 .0 a33 u 0.6/0.6 /0.7 0 .5/0.5 0.3/1.0 a39Pu 0.5/0.5 /0.7 0 .3/0.3 1.0/1.0 /o.7 /o.7 /2 .0 341 Pu 0.5/0.5 0 .3/0.3 /i.o 94 91Zr 9aZr 93Zr zr 9BZr 96Zr 33B u 0.9/0.9 0.7/0.7 0 .6/0.6 0.6/0.6 /I.O 0.5/0.6 a3a u 0.3/1.0 0.9/0.9 0 .8/0.8 0.8/0.8 /1.2 1.2/1.2 339Pu 1.1/1.1 0.1/0.8 0 .3/0.8 0.8/0.8 /1.2 0.3/0.8 241 Pu 0.1/1.2 0.3/1.0 0 .2/0.9 0.,1/0.9 0.1/1.0 9BMO 97Mo 98MO 100MO Mo 33S u 0.4/0.9 0.9/0.9 0 .9/0.9 0.,4/0.9 0.,5/1.0 233 u 1.0/1.0 0.8/0.8 0 .7/0.7 0..3/0.7 0.,9/1.0 239Pu /i.o /i.o /i.o /I.O /I.O l01Ru 1O3RU 103Ru 104Ru 106 RU Ru a3B u 0.3/0.3 0.4/0.4 0.3/0.3 0 .3/0.3 0 .7/1.0 333U 1.7/1.7 2.6/2.6 2 .7/2.7 1 .6/1.6 1 .5/1.5 23HPu 0.7/2.0 1.2/2.0 /4.3 1.3/2.0 4 .3/4.3 2 .1/2.1 241 Pu /2.0 /2.0 /2.0 /2.0 5.0 * Left-hand numbrrs of each pair are taken fi.om Tables 1 - 18. Right-hand numbers are assigned errors - 35 - 5. COMPLETING THE YIELD DISTRIBUTIONS To obtain a complete yield set for a particular fissile nuclide the mass spectrometric data must be augmented by radiometric and interpolated values. The final set must satisfy the condition that Zyi is equal or very close to 1.000 for both light and heavy mass peaks, where the_division between the two is the mean number of nucléons, Â, given by  = 0.5(Af + 1 -v) . Here Af is the nucléon number of the fissile atom and v is the total number of neutrons per fission (Hanna et al-1969). In addition the shapes of the light and heavy mass peaks must be such that Sy.A. = 2 Zy. where A. is the number of nucléons of the ith mass chain with yielà y.. The procedure followed to obtain the recommended sets is: (1) List all measured yields. Tables 21 to 28 list all the yield data considered. The first column" list the stable or long-lived (T|>20y) isobar at each mass and the measured mass spectrometric yields from Tables 12, 14, 16 and 18. The assigned uncertainties are equal to .01 y (U.s + U 3)| where y is the mass yield and U. and U are the assigned isotopic and element errors, respectively,from Tables 19 and 20. Where the mass spectrometric measurement used a short- lived radioactive nuclide, 141ce for instance, the mass spectro- metric yield is assigned to the stable isobar so that all mass spectrometric values appear in the same column. This assumes that direct yields of isobars with charge, Z, greater than the one measured are negligible. The next two columns list radiometric yields for isobars with one and two nuclear charges less than that of the stable or long- lived nuclide (Z -1, Z -2) . The recommended yields in the evaluation by Croall (1967)Sare uled wherever possible to summarize earlier results. The main exceptions are where his recommended value is based in part on a mass spectrometric measurement or on a relative radio- 99140» metric yield for which some standard, such as Mo or Ba is specified. The latter are renormalized to the yields recommended in the present evaluation. More recent radiometric data are also listed, plus the pile oscillator measurements of relative 13Bi yields (Okazaki and Walker (]965) and Nisle and Stepan (1968) normalized to the recommended 835U value). (2) Plot the data and use the curves to choose between discrepant radiometric values and to obtain interpolated yields. (3) Check for Ey. = 1.000, Since the mass spectrometric yields usually contribute much the greater part of Zy. it is simpler and less subject to error to make 2y. = 1.000 by small changes in the mass spectrometric yields rather than large changes in the radio- metric and interpolated yields. Also, a large change in the radio- metric yields would only be valid if they were subject to a common systematic error, a condition which is very improbable since they usually represent the results from many laboratories. - 36 - (4) check mass spectrometric against radiometric yields. Normally these agree within the errors. In the particular case of 335U fission, radiometric yields for a few masses agree well with each other and differ from the mass spectrometric values by 1-3%. This is taken into account in the final normalization of the mass spectrometric yields. (5) Check for _"y.A. = 2 Â, If this test is not satisfied the yield distribution is wrong but if it is satisfied it does not guarantee the yields are correct. However, it is useful as a test when there is a disagreement between yields at some masses. In particular the asymmetry about  on the sides of the valley shown in Figure 2 is essential if this test is to be satisfied unless the radiometric and mass spectrometric yields are changed outside the limits set by their errors, or the interpolated yields changed so much that the curves are no longer smooth. (6) List and plot the final complete set of yields. The latter are shown in Figures 1 and 2. A description of how the data is plotted and the curves fitted is given in the next section. 5.1 335U Fission (Tables 21 and 22) The mass spectrometric yields plotted in E'igure 1 are the recommended yields listed in the last column of each table. They differ by small corrections from the input from Table 12 as d'scussed below. Non-mass-spectrometric yields (mostly radiometric) a, •; shown as open circles. Error bars are included if they are gi iater than the circle diameter or the vertical stroke of the + showing mass spectrometric data. The smooth curve is intended as an aid to the eye and is used to obtain interpolated yields. It follows the mass spectro- metric values exactly and lies within the error limits of must radio- metr ic yields, Where only xadiometric yields are available the average value is used as the recommended yield with a few exceptions dis- cussed below. Between masses 101 anr? 132 the curve is asymmetric about A. In Figure 2, which compares the measurements as a function of their displacement from A, it can be seen that for the heavy masses the yields are uniformly lower for a given displacement except at A, uhorp there is a smooth transition from light to heavy masses, and it I ho extrema, where tine structure conies into play. The old radiometric value of 0.021% at mass 125 is not included in the .ivcraqc because it lies so far from the smooth curve:. in Figure 1 the reflection of the heavy mass curve about ! : un mass 120 to 159 is shown as a broken line between masses 104 •'• '•. 1 f I it:; :.he Light mass yields within their assigned errors rnnsM.'s 77 and 92, except at mass 84. - 37 - For S35u it was difficult to increase Sy-jA^ so that it would fall in the range 2A +_ Av (where Av is the uncertainty in the recommended value of v (Hanna et al., 1969)) because so many yields have been measured that interpolated yields large enough to change Sy^A^ significantly can be varied over rather narrow limits. One option is to make the recommended value for some radiometric yields close to that set by the error limits. In the valley an increase in the light mass yields and a decrease in the heavy mass yields is needed to increase Xy-jAj. The recommended yields at masses 81, 103, 105, 107 and 132 differ from the measured values in the direction which increases K\v A i i ' The sum of percent yields by type is Light Masses Heavy Masses ( MBSS Spectrometric 88.536 95.575 99.774 98,832 The total yields could be brought to 100% (Sy. = 1.00) by simply increasing the light and heavy mass spectrometric yields by 0.26% and 1.2%. However, this would not necessarily give the best agreement with radiometric yields or 2Â. For the heavy fission products, radicmetric yields provide an alternative normalization to the use of a uniform increase in the mass spectrometric yields. At three masses there are 2 or more radiometric yields in good agreement - at masses 137 and 140 these are 1% greater than the mass spectrometric yields and at mass 139 they are 3% greater. The radiometric yields of Bunney and Scadden (1965) at masses 143, 147, 149 and 153 are 0 to 4% lower than the mass spectrometric values of the left-hand column but are within the quoted errors. The radiometric yields of Bresesti et al. (1967) in the same mass range all lie outside the error limits. They are higher for mass 147 and lower for masses 143 and 153. Thus the most accurately measured radiometric yields support an increase of 1% in the heavy mass yields, except at mass 139. In this ce.ae, since the mass spectrometric value is based on a single measurement (Farrar and Tomlinson, 1962) and ali three values differ from their mean by less than their assigned error, the recommended value is the unweighted mean, 6.53% (taken after increasing the mass spectrometric value by 1.15% as noted in the next paragraph). - 38 - Table 21 Yields of Light Mass Fission products from Recom- Stable Fission % Yield of Radioactive Fission Product with Z equal to mended Mass product a Cumulative Ele- Z Yield (%) Z - 1 Z - 2 ment s Yield (M <77 .005 * e 77 Se 34 .0083 .0083 e C 78 Se 34 .0iû .99 3 .018 .020 79 Se 34 ,056e .056 80 Se 34 .12 * C 81 Br 35 .22^O2 .20 82 Se 34 .33 * b C 83 : B6 Kr 3 fa 1.96 3+ .040 1.96 e 87 Rb 37 2.532+ .051 . S 92 3.2 2.53 88 Sr 38 3.593+ .054 3.59 d 89 Y 3-i 4.737+ .078 4.79+.09 4.74 90 Sr 38 5.818+_ .090 5.82 b 91 Zr 40 5.951+ .090 6.11+.10e i.oo 5.75t.Ud 5.95 92 Zr 40 5.980+ ,054 5.9B 93 Zr 40 6.405+ .045 6.1+.7C 6.41 94 Zr 40 6.429+ .046 6.43 b 95 Mo 42 6.488+_ .050 i.oo 6.2;+. 4C 6. 53 96 Zr 40 6.299+ .038 6.30 97 Mo 42 6.032+ .078 .99 8 5.9+.5C 6.07 98 Mo 42 5.772+ .07 5 i. 5.81 99 Te 43 6.24+. 12y 6. 03+.08h1 6.14+.16C 6.14 100 Mo 42 6.274;+ .081 6.31 101 Ru 44 5.04.) + .052 i.oob 5.2+.4° 5.07 102 Ru 44 4.164+ .046 .999b 4.1+.3° 4.19 103 Rh 45 2.85+,20e 3.05 104 | Ru 44 1.822^ .019 1.83 b C 1051 Pd 46 x.oo .83+.20 .95 b C 106J Pd 46 .386^ .004 i.oo ,3B+.05 .39 C 107 Pd 46 .19+.04 .16 ioe Pd 46 .07 0 * 109 Ag M ,03ùC .030 11C Pd 4É .022 * 111 Cd 48 .CJ8C .018 112 Cd 43 .014 * n: Cd 48 .012 * Hi Cd 48 .0110 * 11 = In 49 .0104° .0104 lif- 48 .0105 * !cd Total Light Mass Yield 99.998 Interpolated value Including long-lived radioactive nuclides with Ti>20 y. The yield at mass 106 is the mass spectromecric yield of l06Ra c Calculated cumulative fractional yield for Zo-2 isobar Croall (1967) s Baerg a..d Bartholomew (1959). Relative yield normalized to 6.36% for 140B3 Bunney and Scadden (1965). Errors are set equal to the largest standard deviation for an individual measurement I.ismar. et al. (1970). Spectrophotcroetric detennination Larspn pt al. n 966) . Spertraphofometric determination von ilunlen and Hermann (1968) - 39 - Table 22 Yields of Heavy Mass Fission products from 33Su Recom- Stable Fission a Product % Yield of Kadioactiva Fission product with z equal to mended Mass emulative Ele- s Yield <*) z - l Z - 2 Yield (%) ment s s 117 Sn 50 .0105 * 118 Sn 50 .0105 * 119 Sn 50 .0105 * 120 Sn 50 .0110 * 1 121 Sb 51 .015° .014+.003- .013 .012±.001k 122 Sn 50 .013 • 123 Eb 51 016+ 00lj .016 124 Sn 50 .020 « e 125 Te 52 .021 .0291+.0033 0?9 .0291+.OO73 I\~ 126 Sn 50 .053 * i b ! 127 I 53 .124+_.015' .000. 135° • L03+ .004-1 • 1?4 128 Te 52 .935* 31«+ .0193 .34 129 I 53 .9C .992 1 12+7 18° .62;*.03' . aa C 130 Te 52 2.0+_.5 1.7 131 Xe 54 2.766+. 056 3.1+.3'7 2.80 132 Xe 54 4.123+. 084 .984" 4 7C 4.17 133 Cs 55 6.709+. 150 .999 6 5e 6.79 134 Xe 54 7.529+ 154 7.8+1.1C 7.61 135 Cs 55 6. 524;+ 150 .9fa6r 6 It.4 e 6.3Br 6.60 136 Xe 54 6.06 5+ 124 6.13 1 : 137 Cs 55 6.17 57 110 6 .23+.07 6.27+.15 " 6.24 138 Ba 56 6.689+ 167 7. 22+.. 29? . fi.76 139 La 57 6.368+ 160 6.55+.081 6.59+.11 6.5 3 140 ce 58 6.289+_ 100 .999 6 36+. 12C 6.36+.25n 6.36 P 6 38H . 15 C 9 b 141 Pr 59 5.803+ 100 6.0 5.46+.34 i.oo 6 38+_. 14d 5.87 142 Ce 58 5.896+ 115 1-, 5.96 143 Nd 60 5.88 5+ 053 5.88+.23e i.oob 5 .70+_. i2P 5.95 144 Nd 60 5.367+ 07 0 5.43 145 Nd 60 3.886± 039 3.9J 146 NI 6G 2.948+ 029 2.98 e P 147 Sm 62 2.230+ 030 i.oob 2 .21+_ 06 2.43+_.O6 2.26 148 Nd 60 1.661+ .020 1.68 149 Sm 62 1 . 069;+ .068 1.04+;.03e l.oe 150 Nd 60 .64 5+ .008 .652 151 Sm 62 .414+ .026 .419 152 Sm 62 .265+_ .016 .268 e P 153 Eu 63 .16 5+ .010 .159+.007 ,145.+ .O03 , .167 154 Sm 62 .0735+_.0050 .0743 155 Gd 64 .0317^.002 0 .0321 e q 156 Gd 64 .0137+.0010 .012 5+.0010 .013 e q 157 Gd 64 . 00614+ . 0048 . 0060+_. 0007 ,006i c 158 Gd 64 .'J02 . 0031+_. 00065 .003 e 1 159 Tb 65 .00099 +.00003 . 994 " .0011+_.000.>"* .001 .0007 * Total Heavy Mass 99.997 * Interpolated value a Including long-lived radioactive nuclides with Ti, > 20y. The yield at mass 139 is the mass spectrorcetric yield of '3'Ba; at 141, '" 'Ce r b Calculated cumulative fractional yield £o Zs-2 Isobar c. Croall (1967) „, d Baery and Bartholomew (1959). Relative yield normalized to 6.36'/foi Ba e Bunney and Scadden (1965). Errors are set equal to the largest standard deviation for an individual measurement . T g Lisman et al. (1970). The " 'Ce yield is re normalized to 6.24*, fo' • Cs h Larsen et al. (1966). Spectrophotometric determination i ven Gunten and Hermann (196 8) j Erdal et al.(1969) k Weiss (1965) I. Haeck et al. (19C5, 1966) m Brown (1955); Yield normalized to 6.36% for * Ba n Ciuffolotti (1968) p Bresesti et al (1967). Yields rpncrmalized to 5.87 for " Ce q Daniels and Hoffman (1S66) .,. r Hawkings et al. (1971). 115I y.ield is equal to rec lended -"Cs yield 1..5S thnit measured direct yield fcr "J Xe - 40 - The remaining mass spectrometric yields in the heavy mass peak are increased by 1.15% to obtain Syj_ = 1.00. This gives good agreement at masses 137 and 140 and is acceptable on the basis of the uncertainty in the absolute Nd yield used in the original normalization. The recommended yields for masses 143, 147,, 149 and 153 are close to the upper limits of the measured values of Bunney and Scadden (1965). The alternative of leaving the Nd and Sm yields unchanged would require an increase of about 1.5% in the remainder (the limit consistent with the isobaric coupling at mass 144) and would worsen the agreement between XAj_yj_ and 2A. After adjusting the heavy mass yields a straightforward increase in the light mass spectrometric yields will still leave - AiYi<2A by an amount greater than the uncertainty in v. Since the radiometric yields have already been changed as far as they reasonably can to improve agreement the recommended mass s-pectro- metric yields in the light mass peak were obtained by leaving the yields of Kr, Rb, Sr, Y and Zr isotopes unchanged and increasing the Nb and Ru yields by 0.6%. Biasing the light mass peak to this extent to increase S'.Aiyi is acceptable since the change is well within the errors assigned the Nb and Ru yields relative to Zr. The ratio of 66Kr to 13*Xe using the recommended yields is 0.2 576, in excellent agreement with the measured value of 0.2 57 +_ 0,005 (Blades et al.1956). 5.2 333U Fission (Tables 23 and 24) The measured 233u yields are tabulated as for 33oU except for additional mass spectrometric data. These are relative yields of the tin fission products (deLaeter and Thode, 1969) which re- quire normalization to other data. They range from mass 117 to 126 and the nearest radiometric yields are at masses 115, 121, 12 5 and 127. The two extreme normalizations, i.e. a smooth interpolation either of masses 117, 118, 119 and 120 between masses 115 and 121, or of mass 126 between masses 125 and 127, differ by a factor of 3. The latter normalization is less certain because of the two very different yields at mass 12 5 and only the former is listed in Table 24 and plotted in Figures 1 and 2. It is seen to give a good fit. to the curve drawn through the radiometric data up to mass 120 but diverges rapidly at higher masses with the lower of the two values at mass 125 being about 50% higher than the smooth curve through the mass spectrometric yields. - 4L - It is interesting that the tin yields from 333u fission are almost identical in shape to those from natural U after a long irradiation (i.e. with contributions from both S3Bu and a39Pu) and that both fit the a36U curve of Figure 1 almost perfectly. Thus if the 83Su curve is correct this result implies that the a33U, 83BU and aa9Pu yields have the same shape over the mass range 117 to 126. The yield curves for a33u and a39Pu would then be much more asymmetric about  than indicated by the radio- metric data. Since the information available now on this apparent discrepancy in shape between mass spectrometric and radiometric measurements seems inadequate, the a33u yields recommended here are assumed to follow a smooth curve, fitting most of the radio- metric yields, that is symmetric about a mass slightly displaced from A as in the case of a3BU. It is shown by the solid line between masses 116 and 125. The radiometric yields of Santry and Yaffe (1960) and the "integral mass spectrometer" yields of Ivanov et al-(1957) and Gorshkov and Anikina (1959) are consistently low when compared to mass spectrometric yields. The values listed here are the original values multiplied by 1.22 +_ 0.08 and 1.093 + 0.056 respectively. The multipliers are the average of the ratios of published yields to mass spectrometric yields in the left-hand yield columns of Tables 23 and 24 and the uncertainty given is the standard devi; tion from the average. In the two Russian papers, which did not differ significantly in this respect, the element yields were compared rather than these of the individual isotopes. Yields for 1B1Sm (Ivanov et al., 1957), 13aBa (Gorshkov and Anikina, 1959) and 91Y and 106Ru (Sa.ntry and Yaffe, 1960) were not used in obtaining the average ratios. To obtain agreement between Zy^A^ and 2 it was necessary to use interpolated values between masses 123 and 130 which lie below a smooth curve through the radiometric yield at mass 127 and to use the lower limit at that mass. The broken curve in Figure 1 shows the heavy mass peak after reflection about Â. As with 235U fission it fits the light masses closely between masses 78 and 90 except at mass 84. The sum of yields by type is Light ,<£) Heavy (>- Masses Masses Radiometric and Spectrophotometric 7.802 13.967 Interpolated 1.348 5.623 Mass Spectrometric 91.894 80.454 101.044 100.044 The recommer ded mass spectrometric yields are obtained by decreasing the values in the left hand yaeld column by 1.1 and 0.05% for the light and heavy masses respectively so that Sy^ is very close to 1.00 for each peak. Both corrections are well within the uncertainty in the normalizing Zr and Nd yields. - 42 - Table 23 Yields of Light Mass Fission Products from r Stable Fission tecom- % Yield of Radioactive Fission Product with Z equal to Product mended Mass Cumulative Ele- Z - 2 Yield(%) ment Z Yield (%, Z - 1 s £1 <77 01 * C 1 c 77 Se 34 .C2 0.993| .008 02 * 78 Se 34 06 * 79 Se 34 j1 16 * 80 Se 34 26 * Bl Br 35 .34^.04° 34 82 Se 34 .60 * 83 Kr 36 1 011+ 021 .77e 1.00 84 Kr 36 1 67a+ .035 1.66 a J Rb 37 2 210+_.045 2.la Hfa Kr 36 i 831 +.060 2.80 B7 Kb 37 4 030+ .082 3.98 88 Sr 38 5 591+_.065 5.53 89 Y 39 6 402+ .07 5 6 .5d 6.67+.30e 6. 33 6 .78+,47^ 5.74+.31g 90 Sr 38 6 889+ .080 7.55^.50 6.68+.319 6. 81 £ h 1 e £ 91 Zr 40 6 567J;.066 4.30i.29 7.28+_.15 0.998 '6.38+.l^ ?.88+_.46 6.49 92 Zr 40 6 749^ .061 6 67 93 Zr 40 7 131+ .057 7 05 94 Zîr 40 6 828+ .055 6 75 95 Mo 42 6 261+_ .055 6 19 96 Zr 40 5.725+ .069 5 66 97 Mo 42 5 417 + .071 5 36 98 Mo 42 5. 162+_.067 5 10 99 Te 43 5 06+. 131 5.1 4.96+.15-1 5 01 100 MO 42 4 414+^ .058 4 36 lui Ru 44 3 .244^ .07 3 3 21 102 Ru 44 2 .464+_ .07 5 2 44 103 Rh 45 1,60+.20d2.46+.20 1.82+.109 1 8 104 Ru 44 1 .042+ .030 1 030 105 Pd 46 .18+.04 53 106 Pd 46 .2 56+ .006 .28 .32+.04 .24+.029 .253 107 Pd 46 .13 * 108 Pd 46 .070 * 109 Ag 47 .047° .047 11C Pd 40 .029 * 111 Cd 48 .035 .0228+.0015 .023 .02Lt.002g 112 48 .015d .015+.001 .015 113 Cd 48 .015 * 114 Cd 48 .014 * 115 In 49 .C17C .017 Total Light Mass Yield 100 .003 Interpolated value. Including long-lived radioactive nuclides with T,-20y. The yield at mass 10'j is the mass spectrometric yield of loeRu s Calculated cumulative tracLional yield for z -2 isobar Cri>all (l"67) 5 StoinLier-j and Glfndenin (1955) Hattholoirew et al. (1959). Relative yields normalized to 6.36% for 14DBa Knntry ar,d Yaffe (£960). Measured yields multiplied by 1. 22+. OS canapathy et al. (1967). Renormal iz-3d to 5.01% for B9Mo Hunn.fy ar.rl Scadden (1965'. henormal i zed to a3fiu yields (Tables 21, 22) and 5.01% for JiTr I.ismnn et al. (14701. Spe ?t roohotometr IC measurement I''t 'I Table 24 Yields of Heavy Mass Fission Products from Stable a Recom- Fission Froduct % Yield of Radioactive Fission Products with z equal to mended Mass le- Cumulative Z - 1 2 ent s Yield (%) z - Yield (%) E s 1 116 Cd 48 .014 • 117 Sn 50 .014 3 .014 118 Sn 50 .01453 .014 5 119 Sn 50 .01473 .015 120 Sn 50 .01633 .016 121 Sb 51 ,018d .018 122 Sn 50 .0182 3 .025 • 123 Eb 51 .037 • 124 Sn 50 ,300^ .060 • C 1 125 Te 52 .060 .116.+ .013 .116 126 Sn 50 .078 3 .26 • b £ 127 I 53 .999 •72± io .62 128 To 52 1.0 » 129 I 53 1.7 • 130 Te 52 2.5 • d C 131 Xe 54 3.530+..075 2. 7 3.72+.27 3.53 3. 2U.219 132 Xe 5< 4.825+.. 100 4. 9-^.6c 4.2S+..429 ,c- 13 4.32+ ,40C 4.82 b 133 Cs 55 5. 990+.. 200 .9Çi5 6.78+ .689 5.99 9 134 Xe 54 6.148+.. 127 6. 37+.. 31 A 6.14 135 Cs 55 6.217+..213 . 71 2 4.83 5.1 5.25+ 45 6.21 4.7 5+ .4794.86+ 07™ 136 Xe 54 6.883+.145 6.es 137 Cs 55 6.766+..226 6.58±. 45* 6.13+.13" 6.76 138 Ba 56 5.B4 b 139 La 57 6 37+.14 d 6.46+T39P .996 6.0 6.36+.25 6.41 6 C 140 Ce 58 6.393+^.125 7 6.16+ .3196.36+. 06™ 6.39 P b 141 Pr 59 6.09±.37 6 47+.445 6.37+.429 1.00 7.01+ .18= 6.62 7 16+.18h 142 Ce 58 6.604^.130 y. 6.60 143 Nd 60 5.851+.082 6 02+..30" b f 5.85 C 1.00 4.6.+ 3 4. 50+. 34 144 Nd 60 4.62^.060 h 4.62 A. 74+..31S4.72+. .30h 145 Nd 60 3. 383+.. 047 3.38 146 Nd 60 2,550+.036 V, 2.55 h 147 Sm 62 1.704+.040 1 9C I 1.00" 1.661 .08 1.70 148 Nd 60 1.299+.013 1.30 149 Sm 62 .766+.018 0.766 150 Nd 60 .508+.. 019 0.50C 151 Sm 62 .314+.007 0 .33+.Olh .314 152 Sm 62 .213+.. 005 .213 153 Eu 63 .095 0.110^.002 I .105 154 Sm 62 .0456;+. 0011 .0456 155 Gd 64 1 .023 * 15b Gd 64 .0116+^.0003 .0116 157 Gd 64 .006 5+.. 0005 .0065 .004 * Total Heavy Mass Yield 99.996 * InterpolaLed value a Including long-li-ed radioactive nuclides with T^>20y b calculated cumulative fractional yield 1er Zs-2 'isobar c Croall (1967) d Steinberg and Glendenin (1955) t e Bartholomew et al. (1959). Relative yields normalize.j to 6.36X for Ba f santry and Yaffe (1960). Measured yields multiplied by 1.22+..IE a Ganapathy et al. (1967). Renormali=ed to 5.01* for "HO „„ h Bunney and Scadden (1965). Renormalized to ="u yields (Tables 21, 72) ant. 5.01% for Tc i Lisr.ian et al. (1970). Spectrophotometric measurement (1969) Relative Trass spectrometric yields normalized to 0.014% at j deLaeter and Thode t P Hawkinqs et al-(1971I)). '"i yield is equal to the recommended ' Cs yii^lrl less their 3b s3e XXe direct yieiyieldo ;.(t u f c-ion Nisle and stepan (1968). Relative yield normalized to fc.36 * for "I in ^u u-" , OV.azaki and Walker (19651. Relative yie-'ds normalized uo (,.36'i for both J ana a° u fission Ondrejcin (1966) Gorshkov and Anikina (1959). Measured yields multiplied by - 44 - Table 2 5 Yields of Light Mass Fission Products from Pu Recom- Stable a % Yield of Radioactive Fission Product with z equal to Fission Product mended Mass Cumulative Ele- Z Yield (%) z__ - l Z — 2 Yield(%) ment s s <77 .004 * 77 Se 34 .0073C .0073 78 Se 34 .02 5 .02 5 79 Se 34 .050 * SO Se 34 ,12 * 81 Br 35 .182C .18 82 Se 34 .22 * 83 Kr 36 .296^,006 O.27+.Olh 295 84 Kr 36 .479+.010 .477 H5 Rb 37 .560+.Oil O.65+.O2h C°Krm) .558 Ht. Kr 36 .7bli_.O15 .7 58 ri 7 Rb 37 . J74+..020 .970 «a Sr 3B 1.372+.015 1.37 y 29 1.744+.. 055 1.69+.03^ 1.74+.05e 1.74 Hc) Î.BO^.IS Sr 38 2.1181.022 2.05+_.046 2.11 9 0 E b d h '11 Zr 40 2.S52+.031 2.41+.11" 2.46+>0B .999 2.41+_.06 2.50+_.06 2.54 <>2 Zr 40 3.076+.034 3.06 '.13 Zr 40 3.940+.032 3.92 94 Zr 40 4.472;+.035 4.45 b =15 Mo 42 5.002+_.040 i.oo 5.06+.33® 4.78+.1J9 4.98 5.O5+_.2O ï>6 Zr 40 5.140+_.041 5.12 b 97 Mo 42 5.600+.078 .990 5.54+_.169 5.3O+.3Oh 5.58 98 Mo 42 5.883+.082 5.81 99 43 6.47_+.189 5.61+_.33e 6.17+_.19 6.10 TC 6.02+.181 100 42 7.037'.099 7.00 MO 101 Ru 44 6.063^.170 6.04 102 Ru 44 6.17S+.172 fa.15 103 Rh 45 5.970+.167 5.94 104 Ru 44 6.125+^.172 6.10 105 Pd 46 5.47+^. 06e 5.47 106 Pd 46 4.465+.212 4.04+^.22e 3.90+_.10h 4.45 107 Pd 46 3.5 * loa Pd 4b 2.3 • 109 Ag 47 1.13;+. 06e 1.56+..201 1.3 110 Pd 46 .65 • 111 Cd 48 .27+.04C ,29+.01h .28 112 Cd 48 .093+.003C .13+.01 .11 113 Cd 48 .070+. 00 5C .082;+. 004 .076 114 Cd 48 .049 * 115 In 49 .036C .0391 .038 116 Cd 48 .036 * 117 Sn 50 .03 5 * I 18 Sn 50 .035 * Total Light Mass Yield 100.003 Interpolated yield I r.:i.vtd uiui long-lived radioactive nuclides with T^>20 y. The yield at mass 106 is the average ot ci mass apectrometric and radiometric measurement of the 136Ru yield. CtilculaLed cumulative fractional yield for Zs-2 isobar fronll 1.1967); croall and Willis (1969) (a3vlPu reference yields) ivirthol.imew et al.(lc)59). Relative yield normalized to 5.6% for """Ba Marsden and YafEe (1965) .'.orukina et al (1971) l.ismnn et al.(1970'. Renormalized to 1.69^ for WBNd Komnni.ih (1972). Measured activities îelative to 236u fission products. Values here mirmnl îzed to 6.10% for iJTc and the recommended yields of T.ible 21 Kurd iincl r.i ln-urt' ( 1956) - 45 - Table 26 Yields of Heavy Mass Fission Products from ' "Pu Stable Fission Yield of Radioactive Fission Products Cumulative Product a Yield Mass with z equal to Ele-I "s Yield i») s Zs - 2 High Low tecom- ment 138 138 mended 119 Sn 50 035 .035* 120 Sn 50 c e 035 • .035" 121 sb 51 .041 .035 038 .038 122 Sn 50 038 * .038* 12 3 Sb 51 044 • .044* 124 Sn 50 h 055 • .055" 125 Te .114 + .0149 .996» .068c .105 100 .100 126 sn 50 20 • .20 • 127 1 53 .999b .37= .15 + .03» .40" 45 . 45 128 Te 52 85 * .85 • 129 I 53 ^ • 130 Te 52 2 5 * l.b ' e e 131 Xe 54 3.710 + .078 3.6 3 .80 + .14 3.72 J.75 3.73 BB + 12^ b e 132 Xe 54 5 .183 + .106 .061 4.9 5 .51 + .27e 5.19 5.24 5.21 4.96 + .12h 133 Cs 55 6 .867 + .187 6.54 + .13° .997 6.B5 + .14S 6.88 6.95 6.92 134 Xe 54 7.358 + • 140 7. 38 7.44 7.41 e 135 Cs 55 7.635 + .248 7.06 + .20" .8493 5.5 i .513 7.65 7.73 7.69 6.07+.09k 6.40+.421 136 Xe 54 g .422 + 134 4 6.5 ï .4 137 Cs 55 6 .670 + .182 5.40 + .39e| 6 13B Ba 56 6 . 090 + 127 69 6.75 6.72 1 6 10 5.37 5.74 •5 .306 T .li.- 139 La 57 5.4C 5.98 + .15d 5 5.74' 5.74 5.55 + .07" b 140 Ce 58 5.577 <_ .066 .998 5.36e 5.47 + .32e 5 59 5.64 5.62 5.24+.07k 5:"04+.18h b 141 Pr 59 4.9C 5 .11 + .06" .999 5.67+.lEa I. 70+.26f 5 27 5.27 5.27 6.11 > .31e" 5.18 + .13f 142 Ce 58 4.989 + .060 5.37 + .17h 5 00 5.05 5.02 143 Nd 60 4.498 + .032 4.27 + .17f 1.00b 5.1e 4 .28 + .21e 4 51 4.55 «.53 3.=9+.21£ Î.91+.07h 144 Nd 60 3.780 + .020 3.2 <_ .2™ 1.00b 3.7e~4 .0° + .20"e 3 79 3.33 3.81 3.85+. 09£ T.66+.07h 145 Nd 60 ;.043 + .015 3-54 r .16£ 3 05 3.08 3.06 146 Nd 60 2.515 + . oia 2 52 2.54 2.53 147 Sm 62 2.117 + .068 2.14 + .13£ 1.9 +_ lm 1.00D 1.46 + .08e 2 15 2.17 2.16 2.13+""09£ 2 23+.07h 148 Nd 60 1.675 + . 02 5 1.68 1.70 1.69 149 Sm 62 1,294 + . 047 1.30 + .05£ 1.14 + .05m 1.00 i.14 j .08£ 1.30 1.31 1.30 150 Nd 60 0 .982 + .015 C 984 .994 .989 151 Sm 62 0 .BOB + .032 .741 + .036f G.810 0.811 .814 152 Sm 62 0.615 + . 022 0.016 0.62 .619 153 Eu 63 .39C .370 + .015£ .3B .38 . 3B 39 +_ .02"> 154 Sm 62 .2B4 + . 010 .285 .28" .286 155 Gd 64 .171 + .0191 .17 .17 b 156 Gd 64 .12e .062 + .004* .986 .121 HI .005£ .12 .12 .124 + .005* .10 + .01'" 157 Gd 64 .0764" + .0037£ .076 .076 158 Gd 64 .041* .041 * 159 Tb 65 .0216 + .0007£ .021 .021 .019 j-.002" =•159 .015* .015 * Total Heavy Mass 99.936 Yield Interpolated yield Including long-lived radioactive nuclides with Tij > 20y Calculated cumulative fractional yield for Zs-2 isobar Steinberg and Clendenin (1955). Errors are assumed to be + -20« Bartholomew et al. (1959). Relative yield normalized to 5.6Ï for Ba Harsden and Yaffe (1965) Sorokina et 3I. Î1971) Lisman et al. (1970), Renormalize-l to 1.69» for " 1*1 Ramaniah (1972), Measured activities relative to U fission products. Values here renormalized to «.10» for "Tc and the recommended yields of Table 22 Croall and Willis (1969), ' "Pu reference yield Hawkings et al (1971). ''"I yield is equal to the recommtifi.-d 'Cs yield lesn their measured "sXe direct yield. ,..,_ Okazaki and Walker (1965), Relative to 6.36% for "5I and 6.34» for • .. in '!5U fission ,, Nisle and Stepan (1968), Relative to 6.36% for 15I m U fission Bunney et al. (195B). Yields renormalized to "*U yields of Table 22 Weighted average using inverse square of the uncertainties. The latter are assumed to be 3» if the value listed is less - 46 - 5.3 3J9Pu Fission (Tables 25 and 26) The measured a39Pu yields are tabulated as for 33Bu. The mass spectrometric yields plotted are the recommended values. The smooth curve is used to obtain interpolated yields. The curve branches to show the two possible fits to the mass spectro metric yields at mass 138. When reflected about  the heavy mass peak (broken line) fits the light masses well from mass 80 to 95 except at mass 84. As shown in Figure 2, the radiometric yields in the mass range 103 to 134 are well fitted by an asymmetric curve, as in the case of 835u fission. The sum of yields by type is: Light Masses Heavy Masses   Radiometric 1313.65. 656 12.365 Interpolated 6.S26. 929 5.313 Mass Spectrometric 79.79. 775 544 82.142 (high 138) 81.358 (low 138) 100 .339 99.806 or 99.066 The changes required in the mass spectrometric yields to obtain I,yi =1.00 for the light masses is a decrease of 0.4%, and for the heavy masses an increase of 0.22% or 1.2% depending on whether the high or low mass 138 yield is preferred. Two complete sets are listed in the column corresponding to these two yields and the associated differences in normalization. The choice of recommended yields is discussed in the next section (5.4). All correction factors are acceptable on the basis of uncertainty in the measured absolute yields of Zr and Nd. Agreement between mass spectrometric and radiometric yields is good at masses 89, 90, 91, 95 and 97, but for most masses where comparisons can be made in the heavy mass range either there is so much scatter in radiometric yields that they afford little help in choosing between the "high 138" and "low 138" sets or, if they do agree, the average differs from both of the recommended values by much more than the sum of the radiometric and mass spectrometric errors. The value of SyiAi is so close to 2 that no additional adjustments are required. - 47 - 5.4 841Pu Fission (Tables 27 and 28) The measured 84*Pu yields are tabulated as for a3eu. Two values are listed at mass 138, the lower one corresponding to the isotope dilution value of Lisman et al. (1970). if that is correct then the isobaric yields of 138Xe and 140Ba are wrong and the mass 140 yield is given by 140Ce. The mass spectro- metric yields plotted are the recommended values except near mass 138 where the curve branches to show the two possible fits to the mass spectre-metric yields. The smooth curve is use:1 to obtain interpolated yields. Some radiometric yields are measured relative to other 341Pu yields or as ratios between a39Pu and 341Pu yields. The results of Croall and Willis (1969) have been normalized to 9aTc rather than 137Cs as originally quoted because the latter is affected by the uncertainty in the mass 138 yield. The errors attached to the renormalized results are the same as those given by the authors for the 137Cs normalization. Interpolation in the valley, between masses 106 and 131, is primarily guesswork since yields have been measured at only 3 masses. As shown in Figure 2 these have been fitted with a yield curve which is asymmetric about A as was the case for a3Bu and 339Pu fission. The interpolated yield at mass 139 will depend on the choice of the mass 138 yield, and the different values are listed under "high 138" and "low 138". For the heavy masses the yields by type are: High 138 Low 138 Radio-metric 1.146 1.146 Interpolated 9.868 9.468 . Mass Spectrometric £8.308 87.786 99.322 98.400 Zyi can bë made equal to 1.00 by increasing the "high 138" mass spectrometric yields by 0.8% and "low 138" set by 1.8%. Even the latter is well within the uncertainty in the Nd yield used for the initial normalization. For the light masses the yields by type are: Radiometr ic 15.598 Interpolated 39.747 Mass Spectrometric Ru 24.446 Others 19.364 99.155 - 48 - Table 27 Yields of Light Mass Fission Products from 341pu Stable Fission Recom- Yield of Radioactive Fission Product with Z equal to product a mended Mass Cumulative Ele- z Yield (%) Z - 1 ZB - 2 Yield (%) ment S <78 .005 • 78 Se 34 .0082+.. 0005° .0082 79 Se 34 .016 * 80 Se 34 .033 * 81 Br 35 .065 • 82 Se 34 0.12 * 83 Kr 36 .199+.004 .205+.010° 0.202 84 Kr 36 .355+.007 .3467.013 0.360 85 Rb 37 .387+.008 0.392 86 Kr 36 .600+.012 0.608 87 Rb 37 .740+.015 0.750 88 Sr 38 .954+.010 0.966 89 Y 39 1.2 * 90 Sr 38 1.528+.016 1.55 91 zr 40 1.818+.022 1.67+.06d 1.84 92 zr 40 2.228+.022 2.26 93 Zr 40 2.897+.026 2.93 94 zr 40 3.329+.030 3.37 95 HO 42 i.oob 3.97+.15° 3.98+.09e 3.98 96 Zr 40 4.329+.043 4.39 97 Ho 42 .999b 4.64+.20C 4.83+..14e 4.73 98 HO 42 -a 5.2 * 99 Tc 43 6.26±.16e 6.15+.16 6.20 100 Ho 42 6.2 * 101 Ru 44 5.776+.300 5.91 102 Ru 44 6.146+.318 6.29 103 Rh 45 6.65 * 104 Ru 44 6.613+.343 6.77 105 Pd 46 6-75 * 106 Pd 46 5.911+.306 6.05 107 Pd 46 5.3 * 108 Pd 46 4.0 * 109 Ag 47 2.5 * 110 Pd 46 1.2 * 111 Cd 48 .54+.04C 0.55 112 Cd 48 0.28 * 113 Cd 48 .153+.. 008° 0.153 114 Cd 48 .070 * 115 In 49 .040 * 116 Cd 48 .030 * 117 Sn 50 .026 * 118 Sn 50 .025 • 119 Sn 50 .025 • Total Light Mass Yield 99.999 * Interpolated value a including long-lived radioactive nuclides with Tj >20y. The yield at mass 106 is the radio- metric yield of 10BRu which j.p used to normalize the relative yields of the other Ru isotopes b calculated cumulative fractional yield for Zs-2 isobar c croall and Willis (1969). RenormaUzed to 339Pu yields of Tables 25 and 26 and 6.19% for fl3Ho in a41Pu fission d sorokina et al.(1971) e Lisman et al.(1970). All yields renormalized to 1,92* for x*BNd - 49 - Table 28 Yields of Heavy rJiss Fission Products from 341pu Stable % Yield of Radioactive Fission product a with Z Fission Product equal to Cumulative Yields (*) Mass le- Z Yield (*) Z - 1 z . 2 High Low Recom- nent s 8 s 13() 138 mended 120 Sn 50 .025* .025 • 121 Sb 51 .025* .025 * 122 Sn 50 .025* .025 * 123 Sb 51 .027* .027 * 124 Sn 50 .031* .031 * 125 Te 52 .0416 + .0050e .042 .042 126 Sn 50 .08 * .08 * 127 I 53 .17 • .17 * 128 Te 52 .37 • .37 * 129 I 53 .80 * .80 • 130 Te 52 1.7 • .7 * 131 Xe 54 3.078 + .065 3.10 3.14 3.12 132 Xe 54 4.587 + .096 4.62 4.67 4.64 133 Cs 55 6.637 + .189 6.69 6.76 6.72 134 Xe 54 7 975 + .167 8.04 8.12 8.08 135 Cs 55 6 975 + .230 .968f 6.83* 7.66 + .229 7.03 7.10 7.06 7.76 + -.56*» 136 Xe 54 •j204 + 147 7 26 7.34 7.30 137 CB 55 6 418 + ,183 6 70 + .25<= | S 47 6.53 6.50 .'38 Ba 55 6 368 + .142 6 .94 + .22<=1 6.11 + .20C2 6 94 6.48 6.71 6 890 + .153 139 La 57 6 5 • 6.1 * 6.3 * 1 140 Ce 58 5 837 + .065 L.00b 5 64+.lld 6.30+. 14' 5 88 5.94 5.91 b 141 Pr 59 4 914 + .060 4.66 + .16C 4.81 + .14° L.00 4 50 j 4 95 5.01 4.98 1*2 Ce 58 -1 774 + .053 y. 4.81 4.86 4.84 143 Nd 60 4 464 + .044 4.62 + .21cl 4.66 + .21C2 L.00b 3 8B jI .16d 4.50 4.55 4.52 4.31 + • 15d 144 Nd 60 4.123 + .050 L.00b 4 08 ;1- .14d 4.15 4.20 4.18 145 Nd 60 3.175 + .029 3.01 + .14d 3.20 3.23 3.22 146 Nd 60 2.681 + .024 2.70 2.73 2.72 147 Sm 62 2.173 + .049 2.35 + 12d L.00b 2.34 ;I .09d 2.19 2.21 2.20 148 Nd 60 1.894 + .029 i 1.91 1.93 1.92 149 Sm 62 1.417 + .032 1.52 + 1.00 1.47 1.43 1.44 1.44 150 Nd 60 1.160 + .035 1.17 1.18 1.17 151 Sm 62 .B71 + .020 .846 + .050* .878 0.88 .882 152 Sm 62 .688 + .015 .693 0.70 .697 153 Ee 63 .522 + .022d .522 0.52 .522 154 Sm 62 .373 + .008 .376 0.38 .378 155 Gd 64 .231 + .022* .231 .231 156 Gd S* .170 + ,006d .998b 0.163 + .007d .167 .167 157 Gd 64 .130 + .006^ .130 .130 158 Gd 64 .090* .090* • 159 Tb 65 0462 + ,00l8d .046 .046 , 160 Gd 64 .020* .020* 161 Dy 66 00815 I .0032d .0082 .0082 .005* .005* Total Heavy Mass 100.001 Yield Interpolated value Including long-lived radioactive nuclides with Tlj > 20y Calculated cumulative fractional yield for 2,-2 isobar Croall and Willis (1969), Renormalized to SB*Fu yields of Tables 25 and 26 and 6.19* for "Mo in !lllPu fission Sorokina et al.(1971) Lisman et al-(1970). til yields renorsnalized to 1.92% for Nd Hawkings et al- (1971). 1|4I yield is equal to the reeomnended Cs yield less their measured 11!Xe direct yield .,-,„.« ito. ,„ Okasiaki and Wnlker (1965), Relative to 6.36» for IJ5I and 6.34» for Ba in Nisle and Stepan (1968), Relative to 6.36» for I1S1 in I3iU fission - 50 - 2y^ = 1.000 can be achieved in several ways. The one chosen which gives Sy^A^ = 2A within the uncertainty in v, is to keep the mass spectrometric yields other than Ru proportional to 14BNd as in the original report (Lisman et al, 1970), i.e. increase them by }••?% (the increase in the average of the "high 138" and "low 138" sets) and increase the Ru yields by 2.4%, well within the uncertainty in the measured ratio of 106Ru to 137Cs. In the light masses there is good agreement between radio- metric yields or between radiometric and the recommended yields based on mass spectrometric measurements. This is mainly so for the heavy masses as well. The pile oscillator results for 135i of Okazaki and Walker (1965) and Nisle and Stepan (1968) are appreciably higher than the yield based on mass spectrometric results. Since the 140Ba results of the former are also high it is possible that the difference in this case is due to an underestimate (by 7 - 10%) of the 341Pu content of their sample. Recommended yields for both 339Pu and 341Pu will depend on an assessment of how well the "high 138" and "low 138" yield sets agree with other measurements and satisfy certain other restrictions. The following points must be considered: T *5 ft o o Q (i) The relative measurement of Cs activities from Pu and 341 Pu fission by Croall and Willis (1969) agrees well with the relative "high 138" yields for these two fissile isotopes and is within the uncertainties of the relative "low 138" yields, but is quite different from the other possible combinations. (ii) The corrections for renormalization are smaller for the "high 138" set for both fissile nuclides, but those for the "low 138" sets are within the uncertainty of the initial normalization. (iii) Radiometric yields are more frequently smaller than the recommended values, and are therefore closer to the "high 138" set. The difference is not considered significant since the root mean square difference between the radiometric and mass spectrometric values relative to the uncertainty in the radiometric value is 1.8 for the "high 138" set and 1.9 for the "low 138" set. To summarize, on the basis of the Croall and Willis result either both "high 138" sets or both "low 138" sets should be used, and in this case the remaining evidence favors, very slightly, choosing the "high 138 mass" sets. The various measurements of the ratio of Ba to Nd atoms, however, favors the "low 138" set for 339Pu (2 isotope dilution measurements to one) while for 241Pu fission the reverse is true(2 isobaric link determinations vs 1 isotope dilution measurement). - 51 - Under the circumstances the safest choice is to average the two sets, as shown in the last columns of Tables 26 and 28. Thus the uncertainty in the 13SXe yield, for example, due to this source only, is +_ %%. There is one other check between 339pu and 341Pu yields - Hawkings et al.(1971) measured the x35i yield in 339Pu relative to 341Pu to be 0.966 ± 0.054. The ratio obtained from the re- commended yields, after correcting for the direct yield of l3eXe (Hawkings et al-, 1971) is 0.952, in good agreement with the ex- perimental result. 6. summary The recommended cumulative yields of Tables 21 to 28 are summarized in Tables 29 and 30. The uncertainties, AY, associated with the recommended yields are, for the mass spectrometric measure- ments, equal to those listed in Tables 21 to 28 taken in quad- rature with an estimated 1% uncertainty in the final normalization. Where only radiometric values are available the magnitude of AY is either the standard deviation from the mean or expected uncertainty based on the assigned errors; if agreement is poor and the yields are averaged AY will be approximately equal to half the spread. Where only one yield is used AY is usually equal to the error assigned by the authors, or, if that is lacking, chosen arbitrarily, usually as 20% of the value unless it fits well with yields at adjacent masses. For interpolated yields AY/Y is taken to be n.20%. The present recommended set for S3Bu agrees with the earlier evaluation (Walker, 1970) within the error, AY, except at mass 128. Here the measured radiometric yield (138Sn) is expected to be appreciably less than the cumulative mass yield and the disagreement is due to a reassessment of the direct yield of 138Sb. The only other published evaluation of recent origin with which the present one can be compared is that of Meek and Rider (1972). Since this is to be revised shortly (Rider, 1973) a detailed comparison will not be made here. - 52 - TABLE 29 Summary of Recommended Yields - Light Masses Percent Cumulative Yields in the Thermal Neutron Fission of Mass aasy 333 U 339 Pu 341 PU Y AY Y AY Y AY Y AY 77 0.0083 0.0008 0.020 0.004* 0.0073 0.0015 78 0.020 0.002 0.060 0.012* 0.025 0.005 0.0082 0.0005 79 0.056 0.006 0.16 0.03* 0.050 0.010* 0.016 0.003* 80 0.120 0.024* 0.26 0.05* 0.12 0.02* 0.033 0.007* i 81 0.20 0.02 0.34 0.04 0.18 0.02 0.065 0.013* 82 0.33 0.06* 0.60 0.12* 0.22 0.04* 0.120 0.024* 83 0.535 0.013 1.00 0.22 0.295 0.007 0.202 0.005 84 0.986 0.023 1.66 0.04 0.477 0.Oil 0.360 0.008 85 1.33 0.03 2.18 0.05 0.558 0.013 0.392 0.009 86 1.96 0.05 2.80 0.06 0.758 0.017 0.608 0.014 87 2.53 0.06 3.98 0.09 0.970 0.022 0.750 0.017 88 3.59 0.07 5.53 0.09 1.37 0.02 0.966 0.015 89 4.74 0.09 6 33 0.10 1.74 0.04 1.20 0.24* 90 5.82 0.11 5.81 0.10 2.11 0.03 1.55 0.02 91 5 95 0.11 6 49 0.08 2.54 0.05 1.84 0.03 92 5 98 0.07 6 67 0.09 3.06 0.04 2.26 0.03 93 6 41 0.07 7 05 0 09 3.92 0.05 2.93 0.04 94 6 43 0.07 6 75 0.09 4.45 0.06 3.37 0.05 95 6 53 0 10 6 19 0.10 4.98 0.08 3.98 0.09 96 6 30 0 07 5.66 0 09 5.12 0.07 4.39 0.06 97 6 .07 0 10 5.36 0 09 5 58 0.10 4.73 0 12 98 5.81 0 10 5.10 0 08 5.81 0.10 5.2 0.5 * 99 6.14 0 09 5.01 0 10 6 10 0.36 6 20 0 12 100 6.31 0 11 4.36 0 08 7 00 0 12 6 2 0 6 * 101 5.07 0.07 3.21 0 .08 6 04 0 19 ! 5 91 0 .32 102 4.19 0.06 2.44 0 .08 6 15 0 19 6 29 0 34 103 3.05 0.20 1.8 0.3 5 94 0 29 6 65 0.7* 104 1.83 0.03 1.030 0 .033 6 10 0 19 6 77 0.37 105 0.95 0.20 0.53 0.10 5.47 0 .16 6 75 0.7* 106 0.390 0.006 0.253 0.006 4 .45 0 .22 6 .05 0.33 107 0.16 0.04 0.130 0.026* 3.5 0 .7 • 5.3 0.8* 108 0.070 0.014* 0.070 0.014* 2.3 0.5 4 .0 0.8* 109 0.030 0.006 0.047 0.005 1.3 0.2 2.5 0.5* 110 0.022 0.004* 0.029 0.006* 0.65 0.13* 1.20 0.24* 111 0.018 0.003 0.023 0.004 0.28 0.01 0.55 0.04 112 0.014 0.003* 0.015 n .001 0.11 0.02 0.20 0.05* 113 0.012 0 .002* 0.014 0 .003* 0.076 0 .006 0.153 0 .008 114 0.011 0.002* 0.014 0.003* 0.049 0.010* 0.075 0.015* 115 0.0104 0.0021 0.017 0.003 0.038 0.002 0.040 0.010* 116 0.0105 0.002* 0.014 0.003* 0.036 0.007* 0.030 0.010* 117 0.0105 0 .002* 0.014 0.003 0.035 0.007* 0.026 0.010* * Interpolated value - 53 - TABLE 30 Summary of Recommended Yields - Heavy Masses Percent Cumulative Yields in the Thermal Neutron Fission of Mass S36 a33 338 L B u Pu : ' ,- 8*1 PU Y AY Y AY Y AY - . X; - AY lia 0.0105 0.002* 0.0145 0.003 0.035 0.007»1 6.025 0.010* 119 0.0105 0.002* 0.015 0.003 0.035 0.007* 0.025 0.0Ï0* 120 0.011 0.002* 0.016 0.003 0.035 0.007* 0.025 0.010* 121 0.0130 0.0017 0.018 0.004 0.038 0.003 0.025 0.010* 122 0.013 0.003* 0.025 0.005* 0.038 0.008* 0,025 0.010* 123 0.016 0.001 0.037 0.007* 0.044 0.009* 0.027 0.008* 124 0.020 0.004* 0.060 0.012* 0.055 0.011* 0.031 0.006* 125 0.029 0.004 0.116 0.013 0.100 0.015 0.042 0.005 126 0.053 0.010* 0.26 0.05* 0.20 0.04* 0.080 0.016* 127 0.127 0.010 0.62 0.12 0.45 0.09 0.17 0.04* 128 0.34 0.03 1.00 0.2?* 0.85 0.17* 0.37 0.08* 129 0.88 0.30 1.70 0.34* 1.50 0.30* 0.80 0.16* 130 1.7 0.5 2.50 0.50* 2.50 0.50* 1.70 0.34* 131 2.30 0.07 3.53 0.08 3.73 0.09 3.12 0.07 132 4.17 0.09 4.82 0.11 5.21 0.12 4.64 0.11 133 6.79 0.16 5.99 0.21 6.92 0.19 6.72 0.20 134 7.61 0.17 6.14 0.14 7.41 0.17 8.08 0.18 135 6.60 0.16 6.21 0.15 7.69 0.26 7.06 0.24 136 6 13 0.14 6.88 0.16 6.47 0.15 7.30 0.17 137 6.24 0.16 6.76 0.16 6.72 0.18 6.50 0.20 138 6.76 0.18 5.84 0.14 5.74 0.37 6.71 0.25 139 6.53 0.12 6.41 0.14 5.14 0.22 6.3 0.6 140 6.36 0.14 6.39 0.12 5.62 C.,09 5.91 0.11 141 5.87 %.12 6.62 0.50 5.27 0.35 4.98 0.08 142 5.96 0.13 6.60 0.12 5.02 0.08 4.84 0.07 143 5.95 0.08 5.85 0.10 4.53 0.06 4.52 0.06 144 5.43 0.10 4.62 0.09 3.81 0.08 4.18 0.06 145 3.93 0.06 3.38 0.06 3.06 0.03 3.22 0.04 146 2.98 0.04 2.55 0.04 2.53 0.03 2.72 0.04 147 2.26 0.04 1.70 0.05 2.16 0.07 2.20 0.06 148 1.68 0.03 1.30 0.022 1.69 0.03 1.92 0.03 149 1.08 0.07 0.765 0.021 1.30 0.05 1.44 0.04 150 o;65o - . 0.09 0.508 0.020 0.989 0.018 1.17 0.04 151 0.419 0.027 0.314 0.008 0.814 0.031 0.882 0.024 152 0.268 0.017 0.213 0.006 0.619 0.023 0.697 0.019 153 0.167 0.011 0.105 0.005 0.38 0.01 0.522 0.022 154 0.0743 0.0051 0.0456 0.0012 0.286 0.011 0.378 0.010 155 0.0321 0.0022 0.023 0.005* 0.17 0.02 0.231 0.022 156 0.0132 0.0007 0.0116 0.0003 0.120 0.010 0.167 0.005 157 0.0061 0.0004 0.0065 0.0005 0.076 0.004 0.130 C.006 158 0.0031 0.0006 0.041 0,008* 0.090 0.018* 159 0.0010 0.0001 0.021 0.001 0.046 0.002 160 0.020 0.004* * Interpolated value - 54 - ACKNOWLEDGMENTS I am indebted to several people who were kind enough to read a draft of this report and comment on the accuracy of the listed values and their treatment and presentation. My thanks to Drs. N. E. Holden (GE-KAPL), B. F. Rider (GE-Vallecitos) , M. V. Ramaniah (Bhabha Research Institute) and M. P. Duret (CRNL) and Professors K. Way (Duke University), H. G. Thode and R. H. Tomlinson (McMaster University). - 55 - REFERENCES The laboratory reports in the reference list do not give the laboratory of origin. Instead a key to laboratories based on the letters at the beginning of the report number is included at the end of the list of references. Anikina, M.P., Aron, P.M., Gorshkov, V. K., Ivanov, R. N., Krizhansky, L. M., Kukavadze, G. M., Murin, Â. N., Reformatsky, I. A., Ershier, B. V. (1958) "Mass Spectrometric Studies of Fission products of Uranium-233, Uranium-235^and^ Plutohium-23911. Proceeding of the 2nd Geneva"Conference on pèàcffuï ysësjdf Atomic Energy _15_, 446. Baerg, A.P., Bartholomew, R.M. (1957) "Yields In a3SU Thermal Neutron Fission" Can. J. Chèm. 2[5, 980. Bartholomaw, R.M., Martin, J.S., Baerg, A.P. (1959) in the Thermal Neutron Fission of 233u and ^^PU11 Can. J. Cném. _37, 660. Bayly, J.G., Duret, M.F., Poulsen, N.B., Tomlinsonj R.H. (1961) "The ia5Xe Yield in Thermal Fission of 339Pu" Can. J. Phys. 39, 1391, Bidinosti, D.R., Irish, D.E., and Tomlinsonj R.H^ (1961) "The Thermal Neutron Fission Yields of S33U" Can. J. Chem^ 39; 628; Blades, A.T., Fleming, W.H., Thode, H.G. (1956) "The Ratio of Xenon to Krypton in a36U Fission" Can. J. Chem. _34, 233. Bresesti, M., Burei, G., Ferrari, P., Moretto, L. (1967) "Radio- chemical Determination of Fission Yields for the Fission of Th by Pile Neutrons " J. Inorg. Nucl. Chem. 2^s 1189. Brown, F. (1955) "The Yield of 137Cs in the Pile Neutron Fission of Natural Uranium " J. Inorg. Nucl. Chem. \, 243. Buriney, L.R., Scadden, E.M., Abriam, J.O., Ballou> N.E. (1958) "Extension of the Fission Product Region and Yields of Heavy Products in the Neutron Fission of Plutonium-239" Second Geneva Conference on the Peaceful Uses of Atomic Energy .15, 444. - 56 ~ Bunney, L.R., Scadden, E.M. (1965) "Heavy Mass Yields in the Slow Neutron Fission of 233U and 335u" J. Inorg. Nucl. Chem. 21* 273. Chu, Y.Y. (1959) "Charged-particle-induced Fission: A Mass Spectrometric Yield Study" UCRL-8926. Croall, I.F., Willis, H.H. (1964) "Some Yields in the Thermal and Epi-Cadmium Neutron Fission of 339Pu" AERE-R4723. Croall, I.F. (1967) "Yields from Neutron Induced Fission" AERE-R5086. croall, I.F., Willis, H.H. (1969) "Yields from the Thermal Neutron Induced Fission of 341Pu" AERE-R6154. Ciuffo3otti, L. (1968) "The 140Ba Yields for Thermal and Fast Fission of 335U and 338u" En. Nucleare lj>, 272. Daniels, W.R., Hoffman, D.C. (1966) "Fission Yields of 156Eu, 167Eu, 158Eu and 159Eu" Phys. Rev. 145, 911. deLaeter, J.R., and Thode, H.G. (1969) "Relative Yields of Stable Tin Isotopes in Neutron-induced Fission" Can. J. Phys. 47, 1409. Erdal, B.R., Williams, J.C., Wahl, A.C. (1969) "Cumulative Yields of Tin and Antimony Nuclides from the Thermal Neutron Fission of a35U" J. Inorg. Nucl. Chem. 3±, 2993. Farrar, H., Fickel, H.R., Tomlinson, R.H. (1962) "Cumulative Yields of Light ]Fragments in 335u Thermal Neutron Fission" Can. J. Phys. 40i 1017. Farrar, H., Tomlinson, R.H. (1962) "Cumulative Yields of Heavy Fragments in 33SU Thermal Neutron Fission" Nucl. Phys. _34, 367. Farrar, H., Clarke, W.B., Thode, H.G., Tomlinson, R.H. (1964) "Cumulai .;ve Yields of the Heavy Fragments in the Thermal Neutron Fission of 341pu" Can. J. Phys. j42, 2063. Fickel, H.R., Tomlinson, R.H. (1959) "The Cumulative Fission Yields of Light Mass Fragments in the Thermal Neutron Fission cf 339Pu" Can. J. Phys. 21_, 916. "The Cumulative Fission Yields of 21 Heavy Mass Nuclides Produced in the Thermal Fission of 339Pu" Can. J. Phys. J7, 926. - 57 - Fleming, W., Tomlinson, R.H., Thode, H.G. (1954) "The Fission Yields of the Stable and Long-lived Isotopes of xenon, cesium, and Krypton in the Neutron Fission of 233u" Can. j. phys. 32 522. Fleming, W.H., Thode, H.G. (1956) "The Relative Yields of the Isotopes of Xenon in Plutonium Fission" can. J. Chem. ^4, 193. Ford, G.P., Gilmore, J.S., Ames, D.P., Balogna, J.p. Barnes, J.W., Comstock, A.A. (1956) "Mass Yields from Fission by Neutrons between Thermal and 14.7 MeV" LA-1997(LADC-3083). Fritze, K., McMullen, C.C., Thode, H.G. (1958) "Absolute Yields of the Isotopes of xenon and Krypton in the Neutron Fission of 239Pu" Proceedings of the 2nd Geneva Conference on the Peaceful Uses of Atomic Energy JLjj, 436. Ganapathy, R., Mo, T., Meason, J.L. (1967) "Fission of S33U by Thermal Neutrons" J. Inorg. Nucl. Chem. ^9, 257. Gorshkov, V.K., and Anikina, M.P. (1959) "Fine Structure of the Yield-mass Curve for 233u Fission Fragments" Soviet Atomic Energy 1_ 649 (translated from Atomnaya Energiya 1_, 144) . Hanna, G.C., Westcott, C.H., Lemmel, H.D. Leonard, B.R. Story, J.S., Attree, P.M. (1969) "Revision of Values for the 2200 m/s Neutron Constants for Four Fissile Nuclides" Atomic Energy Review VII, No. 4. Hawkings, R.C., Edwards, W.J., Olmstead, W.J. (1971) "Independent Yields of Mass-135 Xenons in the Thermal Neutron Fission of a33U, 236U, 229Pu and 341Pu" Can. J. Phys. 49, 785. Ivanov, R.N., Gorshkov, V.K., Anikina, M.P., Kukuvadze, G.M., Ershler,B.V. (1957) "Yields of Some Heavy Fragments in the Fission of 233u" Sov. J. of At. En. _3* I436 (Translated from Atomnaya Energiya _3, 546) . Krizhanskii, L.M., Maly, Ya, Murin, A.N., Preobrazhensky, B.K. (1957) "Rare Earth Yields in the Fission of 339Pu by Pile Neutrons" Sov. -. En. 2, 334 (Translated from Atomaya Energiyja 2_, 276). Kukavadze, G.M. Anikina, M.P., Goldin, L .L., Ershler , B.V.^1955) "Yields of Various Nd and Ce Isotopes in the Fission of U" proceedings of the conference of the Academy of Science of the USSR on the Peaceful Uses of Atomic Energy. Lane, F. (1969) "FISSPROD, a G-20 Computer program" AECL-3038. Larsen, R.P., Meyers, R.J., Popek, R.J., Smith, G.W., Williams, J (1966) «|335U Fission Yields11 ANL-7225, 232 Lisman, F.L., Abernathey, R.M., Maeck, W.J., Rein, J.E. (1970) "Fission Yields of Over 40 Stable and Long-lived Fission products for Thermal Neutron Fissioned a33U, a35U, a39Pu and a41Pu, and Fast Reactor Fissioned 33SU and a39u" Nucl. Sci. Eng. 4£, 191. Lisman, F.L. (1970) private Communication. Lisman,F., L., Maeck, W.J., Foster, R.E., Rein, J.E. (editors)(1966) "Burnup Determination of Nuclear Fuels - Project Report for the Quarter July 1 - September 30, 1966" IN-1064. Lisman, F. L., Maeck, W. J., Rein, J. E. (editors) "Burnup Determination of Nuclear Fuels - project Report for the Quarter July 1 - September 30, 1966" IN-1189. Lisman, F. L., Maeck, W. J., Rein, J.E. (editors) "Burnup Deter- mination of Nuclear Fuels - Project Report for the Quarter January 1 - March 31, 1968" IN-1215. Maeck, W. J., Rein, J. E. (editors) (1965) "Burnup Determinationof of Nuclear Fuels - project Report for the Quarter January 1 - March 31, 1965" IDO-14660. laeck, W. J., Rein, j. E. (editors) (1965) "Burnup Determination of Nuclear Fuels - Project Report for the Quarter April 1 - June 30, 1965" IDO-14663. Maeck, W. J., Rein, J. E. (editors) (1965) "Burnup Determination of Nuclear Fuels - Project Report for the Quarter July 1 - September 30, 1965" IDO-14667. Maeck, W. J. Rein, J. E. (editors)(1966) "Burnup Determination of Nuclear Fuels - Project Report for the Quarter April 1 - June 30, 1966" IDO-14681. Marsden, D. A., and Yaffe, L. (1965) "Mass Distribution in Thermal Neutron Fission of 339Pu" Can. J. Chem. _43, 249. Meek, M. E., and Rider, B. F. (1972) "Compilation of Fission Product Yields" NEDO-12154 (71NED41). Melaika, E. A., Parker, M. J., Petruska, J. A., and Tomlinson, R. H. (1955) "The Relative Abundances of Neodymium and Samarium Isotopes in the Thermal Neutron Fission of 335U and 333u" Can. J. Chem. _33_, 830. - 59 - Nisle, R.G., Stepan, I.E. (1968) "Measurement of the 13Bi Yield Ratios and Fission-Product Cross Sections in the Advanced Reactivity Measurement Facilities" Nucl. Sci. Eng. 3JL, 241. okazaki, A., Walker, W.H. (1965) "Measurement of the Yields of 13Bi and 14oBa in the Fission of 233u, 335U, a39Pu and 34xPu» Can j Phys. 43_, 1036. Ondrejcin, R.S. (1966) "Thermal Fission Yield of 137Cs and 333u" J. Inorg.Nucl. Chem. J28, 1763. Petruska, J.A., Thode, H.G., Tomlinson, R.H. (1955) "The Absolute Fission Yields of Twenty-eight Mass Chains in the Thermal Neutron Fission of a36U" Can. J. Phys. 33.» 693. Petruska, J.A., Melaika, E.A. Tomlinson, R.H. (1955) "The Fission Yields of the Cesium Isotopes Formed in the Thermal Neutron Fission of a36u and the Neutron Absorption Cross Section of 13BXe" can. J. Phys. 33, 640. Ramaniah, M.V. (1972) Private onununication. Rider, B. F., Peterson, J. P., Ruiz, C. P., Smith, F. R. (1965) "Accurate Nuclear Fuel Burnup Analyses - Sixteenth Quarterly Progress Report" GEAP-5060. Rider, B. F., Peterson, J. P., Ruiz, C. P., Smith, F.R. (1966) "Accurate Nuclear Fuel Burnup Analyses - Nineteenth Quarterly Progress Report" GEAP-5270. Rider, B. F., Peterson, J, P., Ruiz, C. P., Smith, F. R. (1966b) "Accurate Nuclear Fuel Burnup Analyses - Twentieth Quarterly Progress Report " GEAP-5403. Rider, B. F., Peterson, J. P., Ruiz, C. P., Smith, F. R. (1967) "Accurate Nuclear Fuel Burnup Analyses - Twenty-second Quarterly Progress Report" GEAP-5505. Rider, B. F. (1973) Private communication Santry, D. C, Yaffe, L. (1960) "Absolute Thermal Neutron Fission Yields of 333u" Can. J. Chem. J8, 421. Sorokina, A. V., Skovorodkin, N. V., Bugorkov, S. S., Krivokhatskii, A. S., Petrzhak, K. A. (1971) "Radiochemical Determination of Absolute Cumulative Yields of Fission Fragments in Slow-Neutron Fission of 341Pu and 339pu" Sov. At. En. J31, 806 (Translated from Atomaya Energiya ^i* 99)• Steinberg, E. P., Glendenin, L. E. (1955) "Survey of Radiochemical Studies of the Fission Products", proceedings of the 1st Geneva Conference on Peaceful Uses of Atomic Energy, 7_, 3. -60 - vonGunter, H.R., Hermann, H. (1968) "Absolute Fission Yields of 99 Mo and 139 Ba in the Thermal Neutron Fission of 335 U". Radio- chem.Acta 8, IIP. Wanless, R.K., Thode, H.G. (1955) "The Fission Yields of Isotopes of Xenon and Krypton in the Neutron Fission of 235u and 338u" Can. J. Phys. 2â> 541- Weiss, H.V. (1965) "Near-Symmetric Fission-Identification and Yield of 131Cd" Phys. Rev. 139B, 304. westcott, C.H., Walker, W.H., Alexander, T.K. (1958) "Effective Cross Sections and Cadmium Ratios for the Neutron Spectra of T;.-rmal Reactors". Second Geneva conference on the Peaceful Uses of Atomic Energy Jjk* 70. Wiles, D.M., Petruska, J.A., Tomlinson, R.H. (1956) "Some Cumulative Yields of isotopes Formed in the Thermal Neutron Fission of 339Pu". Can. J. Chem. 3±, 227. Laboratory Key AECL - Atomic Energy of Canada Limited, Chalk River Nuclear Laboratories, Chalk River, Ontario. AERE - Atomic Energy Research Establishment, Harwell, Berks., U.K. ANL - Argonne National Laboratory, Argonne, 111., U.S.A. GEAP - Nucleonics Laboratory, Nuclear Technology Dept., General Electric Co., Pleasanton, Calif., U.S.A. IDO - Phillips Petroleum Co., Atomic Energy Division, Idaho Operations, Idaho Falls, Idaho, U.S.A. IN - Idaho Nuclear Corp., Idaho Falls, Idaho, U.S.A. LA - Los Alamos Scientific Laboratory of the Univ. of California, Los Alamos, New Mexico, U.S.A. NEDO - Nuclear Technology and Applications Operation, General Electric Co., Vallecitos Nuclear Center, Pleasanton, Calif. USA. UCRL - Univ. of California Radiation Laboratory, Livermore, Calif., U.S.A. PERCENT CUMULATIVE YIELDS FDRM *U AMD IISU a — — p» to — o oo o o — — vQ H I O c M P> * CD !-• (0 01 01 (0 PERCENT CUMULATIVE YIELDS FOR "'Pu AND '"Pu - 62 - 2 M 6 10 12 IN 16 IB MASS DISPLACEMENT FROM A~. THE MEAN MASS Figure 2 - Cumulative Yields vs Displacement from A, the mean mass Additional copies of this document may be obtained from Scientific Document Distribution Office Atomic Energy of Canada Limited Chalk River, Ontario, Canada K0.L1JQ Price - $1.50 per copy 87^73 Jrsj*"1i "v^ fiTO^ ^"^nrifefl