Review 7 PapeB . rMb

STATUS OF BETA- AND GAMMA-DECAY AND SPONTANEOUS- FISSION DATA FROM TRANSACTING ISOTOPESt

C. W. Reich Idaho National Engineering Laboratory Aerojet Nuclea. Co r Idaho Falls, Idaho U.S.A.

Abstract

Several categoriey-related an - 6 f do s deca e transyth datr -fo a actinium isotopes are assessed in the light of their potential use in applied areas e statuf AugustTh o . s a s , 1975 f thes,o e dat sums i a - 2 transactiniumarize14 r fo d m nuclides with 228neutrons from spontaneous fissio e brieflar n y treated. Commentd an s observations abou e interrelatioth t e importanth f o n t nuclear-data activities of measurement, compilation and evaluation and needs assess- mene given ar te applications-oriente Th . d fil f decao e y data prepared at our laboratory for ENDF/B is discussed. Finally, a summary by G. Rud- OSIRIe statue th th sta f f So so m wor n delayed-neutroo k n energy spectra f individuao l precursor s includedi s .

1. INTRODUCTION In this paper e revie,w d summarizan w e currenth e t statua f o s broad range of categories of decay data for the transactinium nuclides (Z>90) selectioe Th .specifie th f no c type decaf so y data whice ar h treated here was based on a consideration of their general importance for various applications of decay data. For each individual nuclide, measured values (and, where reported, their uncertainties) of these chosen decay parameters are listed. This compilation of measured values provides a convenient means of assessing the adequacy of the present data for use in specific applications. It should be emphasized that these t constitutvalue f evaluateno o o d t s se r a "recommendedeo d " values.

Mork performed under the auspices of the U.S. Energy Research and Development Administration. 265 e inclusioTh f decao n subjece y th dat n i at matte f thiro s meet- ing, the first one of international scope on the subject of transactiniurn- isotope nuclear data, provides another illustratio e increasinth f o n g recognitio e importancth f o n f radioactive-nuclido e e decaye on dat s a categor f "Nucleayo r Data." While data from radioactive-decay studies have contribute e dbasi th muc o ct h concept f nucleaso r physics, their relevance to a number of applied problems i.s now becoming more widely appreciated. For example, decay data for fission products constituted a major topi r discussiofo c e IAEth A t a nPane l Meetin n Fission-Produco g t Nuclear Data [1]. Also, the scope of the Evaluated Nuclear Data File (ENDF/B w beeno ns expande)ha o incorporatt d e such data, partl responsn i y e o theit r obvious importanc assessmene th r fo e f certaito n safety questions in nuclear reactors e recentlTh . y release de firs th Versio s ti versioV I n n f ENDF/o o contait B detailea n f decao t y se ddat a [2]. Wite increasth h - ing interest in assessing the impact of radioactivity on the environment, attentio s beini n g focuse monitorine th t onl no n do y f radioactivo g e effluents associated with the operation of nuclear power plants but also n alo l aspecte nucleath f o s r fuel cycle, includin e managementh g e th f to waste productsafeguardine th d e an reprocesses th f o g d fuel material. Among the components of such an assessment are the identification of the important radioactive nuclides and the establishment of a commonly accepted and utilized base of relevant, evaluated decay data. In some cases, this evaluatio a vigorou e neer y th poinfo d ma nt sou t progra f experimentao m l measurements to provide such data where they are either nonexistent or not of the required accuracy. Through its subject matter and organization, the present meeting represents e transactiniurth r ,fo n nuclides e ste,on p toward the effective use of nuclear decay data in the solution of import- ant problems of both an applied and a basic character.

1.1. Applications o providT framewora e discussioe th decae r th fo k yf o ndat o t a e treatedb appropriats i t ,i o e applicationpoint e th t som f tou o e f o s such data. Since detailed discussions of the applications of these data appea a numbe n i r f paperro s presente t thia d s meeting e giv,w e here only a brief listing. In reactor-related applications, decay data are needed e propeth r r fo assessmen e impacth f f radioactivitto o environe th n o y - ment from all components of the fuel cycle, from the mine through the reprocessing plant, and including the accounting for and safeguarding e fissionablth f o e material. Important operational problems include not only monitoring of the effluents from the nuclear-power plants, but

266 alse storagth o d handlin e an spen th f to g fuel n long-terI . m operation of fast reactors, there is a considerable build-up of transactinium isotopes, leading to the accumulation of a sizeable inventory of nuclides r whicfo h spontaneous fissio a significan s i n t decaye modeth d ;an evaluatio e neutroth f o nn source ter sucn i m h systems following shutdown is an important problem.

Biomedical applications represent another area where decay data have an important impact. In calculations of the absorbed dose, for example s necessari t i , o knot yt onl e energno w th y y releas n radioi e - active decay, but also the form in which this energy is emitted (e.g., conversion electrons, x-rays, 3 and y radiation and a particles). To o thid s realistically require a quits e detailed knowledg e decath yf o e e quantitativschemeth n I . e assa f radioactivityo o determint y e amounth e t of a given radioactive nuclide present, a knowledge of the nuclide half- e energieth lif d d absolutan ean s e intensitie e radiationth f o s s being measured in the analysis is necessary. Because of the widespread use of Y-ray spectroscopy employing Ge(Lt) spectrometers to do such assays, Y-rae th y absolute intensities represen ta particularl y important subset of decay data.

1.2. Special features of transactinium-nuclide decay data Experimentally, the study of the decay properties of the trans- actinium nuclide mann i ys i sway s little different froy m an tha f o t other clas f nucleio s . However e transactiniu decae th ,th f yo m muclei exhibit muca s h richer variet f phenomeno y e th e casar th tha fo es i n nuclides commonly encountere e regioth n i dn below (and slightly above) e 1=82th magic number r exampleFo . d electron addition an ,i - 3 o t -n capture (and $+) decay, a-particle emissio spontaneoud an n s fission-- with promp d delayean t d neutron emission—occur. Furthermore, these nuclides frequentl r threo yo edecatw differenta vi y , competing processes. The relative probabilities (branching ratios f thes)o e decay modee ar s important.

Finally, internal conversion and its associated phenomena assum n importanea t rol transactinium-nuclidn i e e decay data because of the large internal-conversion coefficients that result from the large Z-valuee generallth d an s y lower energie j-raye th f o s transitions. Con- sequently e discret,th e electron e x-rayth d s an scontai a significann t fraction of the energy associated with the Y-decay process. Knowledge

267 of the conversion-electron spectrum may be important in its own right or for the determination of absolute y-ray intensities for some appli- cations.

Taken together, this increased variety of modes of decay provides e measureth r with valuable additional informatio r gaininfo n g insight inte make-uth o f theso p e nuclides greatlt i t bu ,y complicate e probth s - lem f dato s a compilatio d evaluationan n , particularly when datr varioufo a s application e desiredar s .

1.3. The role of theory in transactim'um-nuclide decay data

1.3.1. Nuclear model r stronglfo s y deformed nuclei The transactinium nuclides are all included in the general cate- gory of "strongly deformed" nuclei, in that their equilibrium shapes e characterizear y relativelb d y large axially symmetric deformations. Because of this, the coupling scheme which describes their elementary mode motiof o s n assum a ebasi c simplicity (see,e.g., [3])exampler Fo . , their energy-level schemes exhibi a numbet f strikino r g features such as the existence of a well-developed rotational-band structure. The spins (and parities f thes)o e observed rotational state n frequentlca s e b y deduced from energy-spacing considerations alone. From such considerations and data on the within-band y-ray intensities, one can extract multi- polarity information concerning these transitions. Furthermore, the ordering and properties of the "single-particle" states in the strongly deformed nuclei can be calculated fairly simply [4], and such calculations e foun ar o givt d a gooe d descriptio e propertie th f mano nf o y f theso s e states, particularly of those that lie at fairly low (£0.5 MeV) excitation energies r thesFo .e deformed nuclei, nuclear physicists with experience in nuclear-structure studie n frequentlca s e thesus y e various calculational tools and arguments based on "systematics" to make accurate state assign- ments and transition-probability estimates on the basis of rather frag- mentary data. (These ideas and their application to the level structure of the strongly-deformed odd-A nuclei in the rare-earth region have been treate detain i d l elsewhere, e.g. e strongly-deforme n [5].th i , n I ) d doubly-od d nucleonsd od nuclei o tw e couplin e ,th , a definitth eac n f i ho g e "single-particle" state, gives rise to two non-rotational states. In one of these the two intrinsic spins are parallel and in one they are antiparallel, the former lying lower in energy (the so-called Gallagher- Moszkowski rule [6]). The ordering of isomer pairs in doubly-odd deformed 268 nuclei appears to be quite well accounted for by this rule and it has been used to assign the relative positions of the two isomers observed i 250nn i 236Es d N.pan

1.3.2. X-ray and discrete-electron spectra The internal-conversion process is well understood theoreti- e internal-conversiocallyth d ,an n coefficients e calculateb (ICC n )ca d [7] with high accuracy. (For some multipolarities, small systematic differences between theory and experiment exist, but even here, these known differences can themselves be employed to provide reliable ICC values.) Consequently, the conversion-electron spectrum associated with a given y ray can be accurately calculated from the v-ray energy and multipolarity (the latter either measure r deduceo d s describea d subn i d - section 1.3.1 above).

The energies and relative intensities of the prominent components of the K x-ray spectrum produced in radioactive decay of a given nuclide can be predicted with sufficient accuracy to be useful for many applica- tions, provided thae decath t y schem s knowni e . Recent relativ K x-rae y intensity data in the region 96^ZS99 [8] and 81fZf96[9] give generally good agreement with calculations for the stronger lines although they do indicate some disagreement (^1% e Kg/Kt Z-96a th n a)i intensity ratio. Whil L x-rae energie e th e yth e accuratelserief b so n ca s y obtained from the binding-energy dat f Beardeo a d Buran nr [10] e relativ,th e intensities L line e sth cannof o t presentl e accuratelb y y calculated. Nonetheless, estimateso x-raL e yth f intensity whic e generallar h y adequat r manfo e y applications (e.g., energy-release and dose-estimate calculations) can be made [11]. Similarly, realistic calculations of the Auger electron spectrum canno made estimatet b bu e s adequat r manfo e y applicationn ca s be generated [11].

1.4 Jopics to be discussed in this paper In the remaining chapters of this review, we present the current status of selected categories of decay data for the transactinium nuclides. In Chapte e discusw , 2 r s several important existing compilations (and some currentl preparationn i y f transactinium-nuclid)o e decay data. Chapter maie th n , 3 thrus f thio t s paper, contain discussioa s e reasonth f o ns for the selection of the data to be listed and a tabular summary of the decay data themselves. Chapter 4 contains a brief discussion of yielde th d energan s y distribution f prompo s d delayean t d neutrons from spontaneous fission. Chapte 5 presentr s some general observations con- 269 f decao e earninyus dat e applien i th ag de improvin th area d s an f cono g - ditions under which relevant data wite requireth h d accurace b n ca y identified and supplied in a timely manner.

In Appendix A, the data content and layout of the decay data for Version V of ENDF/B is discussed within the context of the ENDF/B Actinide File. Finally a summar, f delayed-neutroo y n spectral measure- ments by Rudstam and co-workers at the OSIRIS Facility at Studsvik, Sweden is given in Appendix B.

. 2 REMARK N DECAY-DATO S A COMPILATION E TRANSACTINIUTH R FO S M NUCLIDES While several compilation f decao s y data oriented specifically toward the fission-product nuclides exist (e.g., [12], [13], and the relevant portions of the ENDF/B-IV Fission-Product File), no equivalent such compilations presently exist solely oriented toward users of trans- actinium-nuclide decay data. Those compilations in which decay data for the transactinium nuclides do occur are generally oriented toward a much larger class of nuclides and/or a much broader (or restricted) category f datao . Numerous compilation a rathe f o s r specialized data content (e.g., half-lives, y-rays arranged accordin o energyt g r nuclide,o r ,o nuclide half-life) exist in which transactinium nuclides are included. Some of these have been discussed in the review paper by Rudstam [14] in the context of their fission-product decay-data content; and the reader is referred to that review for further information concerning them.

w brieflno e W y discuss several compilations containing trans- actinium-nuclide decay data which are quite useful to workers in both basic and applied areas. They have also been utilized in the preparation e wor th f muco k f o hcontaine n thii d s paper. 2.1. Nuclear Data Sheets (Academic Press, New York, continuing) Thes e standarar e d reference materia r non-neutrofo l n nuclear data. The most recent issues of this series which are relevant to the transactinium-nuclide deca e followingyth date ar a : A=230, 234, 238, 242 - Y. A. Ellis, Vol. 4, No. 6 (1970) A=232, 236, 240 - M. R. Schmorak, Vol. 4, No. 6 (1970) A=229, 233 - Y. A. Ellis, Vol. 6, No. 3 (1971) Artna-Cohen. A A=231- 5 ,23 , Vol. 6, No 3 (1971. ) . EllisA 6 (1971. Y . A=237, - No Vol ) 1 , 6 .,24 A=23Artna-Cohen. A - 9 6 (1971 . , No Vol) , 6 . 243fAf261 - Y. A. Ellis and A. H. Wapstra, Vol. 3,No. 2 (1969) 270 e DatTh ae even- Sheetth r A fo snuclide s with A>24 e currentl3ar y being revised [15] d som ,an f theie o r contents have bee e npreparatio th use n i d n of the data summary given in Chapter 3 of this review.

These data sets are quite useful, particularly for the basic nuclear physicist and the specialized evaluator, but the quite broad coverage of different types of nuclear data renders its use difficult for many applications-oriented people. Somewhat disconcerting for many applied e practicuserth s i s f listine o leve th ln o g scheme e transth s - ition (i.e., photon + conversion-electron) intensities for the y-rays instea f simplo d e phototh y n intensities e relativelTh . y long cycle times between revision e A-chainth f o s s also present e appliea sproble th r dfo m users, althoug e companioe issuinth th h f o g n "Recent References" helps keep the nuclear physicist or evaluator aware of the fairly recent data. e file Th e presentlar s y being extensively computerized d consideratio;an n is being given to various means of decreasing the cycle time.

. MC . Lederer 2 2. Hollande. M . Perlman. I ,J d an r , Tabl f Isotopeo e s Sixth Edition (John Hi d Sonsle an yw York ,Ne . 1967) This has been a standard reference work for radioactive-nuclide decay data and has been widely used, especially by the applied user. Its major difficulty is long cycle time between editions. Somewhat disconcerting is the practice of listing the j-ray intensities on the level schemes in suc a hfashio f theso m nesu thaintensitiee th t f eaco t h ou sleve s i l 100%, so that the actual y-ray relative intensity data cannot easily be inferred by reference to the decay scheme. At present, this data file is extensively computerized, which should simplify editin d updatingan g . A seventh editio s presentli n n preparationi y e datth a d bas;an r fo e e nuclideth s with AS23 r thifo 1s edition, . LederesupplieM . C y rb d [16], was extensively used in the work described in Chapter 3 below.

. GoveB . Wapstre 197. H 2.3N , Th . 1d A . Atomian a c Mass Evaluation, Nuclear Data Tables A, Vol. 9, No. 4-5 (1971) This compilation contain relevanl Q svalueal r fo st decay pro- cesses, derived from careful consideration and adjustment of all experi- mental information relating to atomic-mass differences. Also important is a listing of the uncertainties in these adopted values. The Q values use n thii d s review paper were taken fro n unpublishea m d revisio f thio n s compilation [17].

271 2.4. R,Vaninbroukx, Half-Lives of Some Long-Lived Actinides: a Compila- tion, Euratom Report EUR-5194e (1974) This report contain n up-to-data s e collectio f half-lifo n e data on a number of the longer-lived isotopes of U and Pu and of 241Am and 252Cf. Recommended half-life values are given; and generally these value e e presenlistear th s n i dt paper.

. KonshinA . . Maner2.5V F .d ,an o e StatuEnergy-Dependenth f so t v-Values e Heavth yr fo Elements (Z>90) from Therma f o 1v-Valueo t 5l d Mean r V fo s Spontaneous Fission, Atomic Energy Review 10 (1972) 637 This excellent survey contain a complets e compilatioe th f o n v data published up to August, 1972. Of relevance for the present review is the tabulation of the prompt v values for the spontaneous fission of 21 transactinium isotopes ranging from 232th to 257Fm.

2.6.__ E. K. Hyde, I. Perlman and G. T. Seaborg, The Nuclear Properties of the Heavy Elements, Vol. I-III, (Prentice-Hall, Englewood Cliffs, 1964) Very comprehensive, these three volumes treat essentially all aspect f transactiniuo s m nuclear data s suchA . , thee quitar y e valuable reference material for those interested in gaining a knowledge of most facets of this subject. However, since they have not been updated, much of their data content is not up-to-date and hence not particularly useful o usert s whose data needs requir a currene evaluated tan f data o t .se d

2^7. Actinide Data Filr ENDF/Bfo e , VersioV n Mention shoul e fac th made t b df o etha a tfil f Actinido e e Nuclear Data is currently being prepared under the auspices of CSEWG for issue in Versio f ENDF/Bo V ne componen On . f thio t s Actinide File wil e evaluateb l d decay data for the included isotopes. Because of its relevance to this meeting e conten,th d organizatiotan e decath yf o ndat n thio a s file will be discussed in Appendix A below.

3. STATUS OF SELECTED DECAY DATA FOR TRANSACTINIUM ISOTOPES In Tabls summarizei I e e currenth d t statu f selecteo s d decay data on the transactinium isotopes in the mass region 228fA_257. We first discuss the organization of the table and then briefly comment on some pointe th o emergf t so e from this assessmen decay-date th f to a status.

272 TABLE I Summary of selected decay data for the transactinium nuclides (Z >_ 90) with 228 <^A ^ 257. The quantities in parentheses represent the uncertainties in the last significant figure (or figures) of the associated value. For further discussion, texte th .e se Intensity of Branching Half-life Data ground-state Statuf o s Decay 3 r-ray transition data Decay Ratios No. of Q transitionf ! c.-e. Scheme [b] Nuclide Modes (« Value Range Meas. (keV) (%) Er (keVhlv («) data Status References and Comments

228Th Decay chain termi- 1.913(l)y — — — — (2614. 66(10) ;35. 93(6)) -- — [1]. I values are equi- natinc with 208Pb \ 583.14(3);30.(2) / libriume valueth r fo s decay chain.

229 Th a 100. 7340.(160)y -- -- 5168.0(12) 0.01 193.63(6);4.5 A(mag.) B [2]. Iy value deduced from absolute c.e. inten- sitie theoreticad san l ICC.

229pa e.c. 99.75 1.4(4)d — 306. (13) -- C [2,3] a 0.25 _. 5835. (5) <0.5 — B

CO 229u e.c. £80. 58.(3)m 1318. (14) -- C [2] -o — — — 09 a £20. 6472.4(31) 64. C

230 Th a 100. r, 7.7(2)xlO'*y — 4767.2(15) 76.3 67.73(3);0.38 B(mag.) B [4,5] lllc] 17 S.f. <5xlO- >1.5xl0 y —

230p a e.c. 89.6(5) 17.4(4)d 1304.0(25) 0 951.99(5);29.3 A(S1) A [4,6-8]. Iv value listed B- 10.4(5) : 560. (6) 0 B is average of 28.3(3)[6] a 0.0032 ~ 5438.0(20) 23. (5) C and 30.3[8].

230u a 100. 20. 8d -- — 5991.4(20) 67.5(5) 72.13;0.54 — B [4]

231Tn B- 100. 25.52(l)h 387. (5) 0 84.17;7(1) A(mag.) A [2,9] /+0.0141 231Pa a 3.257(10)xlO"y 3 5147.3(10) 283.56(6);!. 3 A(mag.) A [2,9]. I value estimated •vlOO. \-0. 023) 11. Y lo[C] 16 to be uncertain by ^ 20%. S.f. <3xlO- I.lxl0 y Tabl I e(continued )

2311J e.c. VIOO. 4.2(l)d _„ __ 360. (50) __ 84.18;- B(mag.) B [2,9]. The value 7% is a 0.0055 __ — —— 5550. (50) — .. — C given for this absolute Iy. s uncleai t w I thiho r s value measureds wa .

______231Np e.c. <99. 48.8(2)m w 1840. (80) 370.9(3);-- B [9] a >1. -- — -- 6400. (50) — -- -- C

10 (+0.043\ 232Th a 100. 1.407(7)xl0 y 5 4082. (4) 77. 59. (1); B(emuls.) B [1,9]. Y not observed. 1-0-017/ Transition (i.e., Y+c.e.) intensit 23= y . (2)%. 232 __ Pa r 100. 1.31d __ 1337. (10) 0 150.(1);12. A(mag., A [4,9]. Iy value from Si) measured (B,Y) coincidences and conversion-electron intensities. +1.0) a MOO. 72.6(7)y {-0.9} 2 5413.92(25) 68.6(6) 129. 0(2) ;0. 082 B(emuls.) B [4,9]. IY value from rela- "*" lo[c] 13 tive-intensity data [4,11] S.f. vio- 8.(6)xl0 y and I =0.21% for the 57.6- keV Y? From a- in tensity and c.e. data, however,I CO T -a is expecte ^0.058.e b o t d 232Np e.c. 100. 14.7(3)m — -- 2700(SYST.) <1 327.3(3);52. — B [4,9]

232pu e.c. >80. 34.1(7)m _. __ 1060J[SYST.) __ __ C C [9] a <20. — — — 6700. (50) 62. — C C J+1.31) 233Th B- 100. 22.29(5)m 4 1245.1(24) 85. 86.50(5);2.6(4) A(mag.) A [2,9]. Sum of 6" intensi- V0.17/ ties to ground and first excited state (6.7 keV).

233pa 6- 100. 27.0(l)d — -- 572.3(25) 3. 311.89(1);36. A(mag.) A [2,9] 233u a MOO. 1.592(3)xl05y Vo!o39j 11 4908.5(12) 84.4 317. 15(2), 0.008(1) A(mag.) A [2,9,12]. Tjj from [10]. c] 17 Thi Y valua I factos s i e r S.f. 1.3xlO-^ 1.2(3)xl0 y — — — -- — — of ^2 smaller than is obtained from the absolute Y-intensity normalization use [2,9]n i d .

2 __ — __ 33NP e.c. VI 00. 36.2(l)m 1100. (SYST) -"96. 312.1(3); 0.75? B e.cf o [9]m . Su transi. - a •vO.OOl __ -- __ 5700. (SYST) — -_ — C tion intensitie o first s t three members of ground- state band. Table I (Continued)

233pu e.c. 99.88 20.9(4)m — — 2030. (SYST) __ 235.4(3); __ B [9] a 0.12(5) — — — 6416. (20) -- ' -- C

23"Th B- 100. 24.101(25)d -- -- 262.5(25) 0 112. 81(5);0. 24(1) A(mag.) A [4,9] 23"Pa B- 100. 6.68(l)h {±0.05} 2 2208(5) 0 883.237(33);12. A(mag.) A [4,9] /+0.08) 23^mPa B- 99.87 1.170(4)m 4 2292. 98. 1001.025(22);0.59 A(mag.) A [4,9]. Energy of isomeric t-0.03/ state not precisely known. I.T. 0.13(3) A value of ^84 keV is used in [91. 23 (+0.074) "U a MOO 2.446(7)xl05y 7 t 53.222(19);0.15\ 1-0. 007/ 4856.4(19) 72.5(30) \120.905(12);0.050f B [4,9]. T, from [10]. 16 __ Quoted I '(120) values S.f. 2(l)xl0 y range from -\-0.04% [4o ]t 0.23% [11]. 23"Np e.c. +6+ 100. 4.40(5)d — — 1808. (9) 26. 1558.7(6);18. A(mag.) A [4,9]

23«,pu e.c. 94. 8.8(l)h 390. (12) C C [4,9] — — {no Y'S observed} to 6. 6310. (5) 68. C C -J 01 235Th B' 100. 6.9(2)m — -- -- 0. -- -- C [2,9] (+0.2) 235pa B" 100. 24.0(2)m 2 1400. (100) — -- — C [2,9]

8 f+0.092) 235U a -a oo. 7.038(20)xl0 y 1-0.098/ 8 4678.8(25) 4.6 185. 712(10) -.54. — A [2,9]. T^ from [10] . S.f. 2.6xlO-7tc] 2.7(10)xl017y {±0.8} 2 — -- — — --

235 ______Np e.c. MOO. 396. (l)d 123. (1) vLOO. C [2,9]. Iy from measured 1 a 0.0014 -- -- — 5188. (4) 1.5(2) 84.20hl.lxlO- * _- B Y/a intensit a-decad an y y branching ratio.

235pu e.c. ^100. 25.0(l)m {±0.7} 2 1130. (60) ^56. 49.3(3);!. 84 __ B [2,9] a 0.0030(6) ------5958. (31) 100. — — C

236Th B" 100. 37.5(15)m _ _ __ 46. 110.7(5);5. __ B [9]. d I Ian g values inferred from Y'ray in- tensities from sources containing both parent and daughter activities.

236pa B- 100. 9.1(2)m — — 3100. (200) — 642.0; — — C [4,9] Table I (Continued)

7 (+0.12 1 23SU -v-100. 2.34(2)xl0 y 3 4569.2(24) 74. 112.750(16);0.019 B(emuls.) B [4,9]. \ from [10]. a Vo.0015f S.f. 1.2xlO-7[cl 2.xl016y — — -- — -- — --

6 236Np B" 100. 1.29(6)xl0 y — — 986. (10) — — — C [4,9]

236m [d] Np B- 48.(1) 22.5(4)h — _. 537. (8) 38.(7) 44.63(10);- A(mag., A [4,9] rm Si) e.c. 52. (1) -- -- — 986. (10) 40. 642. 42(10);!. 0(2) A(Si) A ._ __ _„ 236pu a i-lOO. 2.851(8)y 5866.7(20) 68.9(5) 109.0;0.012 B [4,9] S.f. Sxio-s^J 3.5(l)xl09y ------— -- -- —

237 _ __ ._ Pa 6" 100. 8.7(2)m 2250. (10) 19.4 853. 7(2);34. 1(34) B [9,13,14]. Q6 from [13]. IK is total B intensity to first 3 members of ground- state band. Ivalue from

absolutmeasureY d an B e- y ments. to -j 237u — _ Oi 8" 100. 6.75(l)d 519.3(11) 0. 208. 005(23) ;23. 3 A(mag.) A [9,14]. A 4it S-Y measure- ment (see [2]) gives IY(208)=20.2%.

6 237Np a 100. 2.14(l)xl0 y — _ 4957.2(14) 2.6 86.49(10);12.6(13) A(mag., A [9,14] Si)

237PU e.c. i-lOO. 45.63(20)d _ _. 224. (5) 60. 59.54(1);- _ B [9,14]. Value given for a a 0.0033(3) — — — 5754. (5) 21. (4) — — C branch is sum of intensi- ties to ground and first excited states.

237Am e.c. >99. 73.0(10)m — _ 1540(SYST) £5. 280. 230(20);47. 3(20) A(mag.,Si) A [9,15] a 0.025(3) — — — 6200(SYST) — -- -- C

238Pa B" 100. 2.3(l)m — — 3960(300) 0. — — B [4,9]

9 1+0.092 \ 238U a •vlOO. 4.468(10)xl0 y 4 4270.6(39) 77. 49.55(6);- — B [4,9]. \ from [10]. 1+0.0003) 5[c] 15 f+1.291 S.f. 5.1xlO- 8.81(7)xl0 y 7 — — — — --

238Np B" 100. 2.117(2)d -- — 1292.5(32) 0. 984. 45(2) ;24. A(mag.) A [4,9] Tabl I (Continuede )

238pu a •^100. 87.8(8)y tw 4 5593.30(21) 71.1(12) 99. 871(10);0. 0074(1) B(mag., A [4,9]. Tjj from [10]. Si) Iv measured [15], A S.f. 1.84(5)xlO'7 4.77(14)xlOI0yE s] valu f 0.080eo s %alsi o reported [11r ]fo IY(99.8).

238Am e.c. ^100. 1.63(5)h 2257. (32) ^. 962.8(1);29.(2) A(Si) A [4,9] a 1.0(4)xlO-1( — — 6042. (31) C

239U B- 100. 23.54(5)m ._ _ 1267.4(29) 20. 74.66(2); 59.3 ? B(mag.) B [9,14]. Ig value repre- intensit$ f o sentm su sy grouno t firsd dan t excited states.

M).012\ /228.19(1);11.3(2)) 239Np 100. 2.354(2)d 4 721.5(19) 0. A(mag.) A [9,14]. I values from 8~ 1-0.0081 \277.60(3);14.3(2)( [17]. Y WJ.011 1 /129. 28 ;0. 0062(1) 1 239pu ^100. 2.430(25)xlO'«y 10 5243.6(8) 73. A(mag., A [9,14]. T^ from [10]. a I-0.0235J 1413. 69;0. 00151(2)]' loCc] 15 I!) Listed a-branch intensity to S.f. 4.4xlO- 5.5xl0 y 1 -o s actualli y that feeding -o e 0.073-keVth , 26.1-m isomeric state in 235U. IY value froe mar s [16]. Value f 0.0056o s d %an 0.0015%, respectivelye ar , reporte r IYdfo (129 d an ) Iy(413 n [11]i ) .

239Am e.c. >99.9 11.9(l)h — — 803.8(24) -v,56. 277.604(16);15.(3) A(mag,Si) A [9] a 0.01(1) -- -- — 5924.4(20) 0.33(2) 48. 3(15);0. 005(2) B

2UOU _. _ Z~ 100. 14.1(2)h 500. (60) 0. 44.10(7);!. 69(20) B(mag.) B [4,9]. IY measured using equilibrium 2ttltPu source.

2tONp 3" 190. 65.(3)m -- — 2090. (60) 0. 566.4(2)^29. — B [4,9]

2"»omNp 8- 99.9 7.50(6)m ._ _. 2090. (60) 41. (5) 597.40(7);12.5(6) B(mag., A [4,9]. This isomer I.T. M).l -- -. .. -- — — eraul s . ) probably lies above 65-m precise 21t0th t Npebu , energy differencs i e unknown. The QB value listed is that of the 2 *°Np ground state. IY value measured using equilibrium 2"'tPu source. Table I (Continued) ( 45. 235(20);0. 045(1) ) /+0.21) »,„ a 6.55(7)xlQ3y 7 5256.16(25) 76. <104.233(lO);0.0070(l)> A(mag., A [4,9]. TH from [10]. I t-0.31/ (642.30;1.45(5)xlO-J 5 Si) measured tfsing assayed /+0.137) s[c:l 5 S.f. 5.0xlO- (-0.1431 sources [16]. Values of 0.045%, 0.01d %an 4.1xlO~5%, respectively, are given for these 3 Y rays in [11].

21 «_ __ *OAm e.c. >99.7 50.8(3)h 1346. (20) 0. 987. 79(6);73. 3(25) B(Si) B [4,9]. qe.c. value a 1.9X10-1* — — — 5670. (SYST) — — — C reported by [18], from K to total capture ratio.

^^Cifl a MOO. 28. d __ _. 6397.0(6) 71.1 _ __ C [4,9] e[c] 6 S.f. 4.0xio- 1.9(4)xl0 y -- -- — ------—

2*+ IND B" 100. 16.0(2)m — — 1360. (100) -- — — C [9,14]

2-1 pu B- MOO. 14.89(9)y 5 20.81(20) 100. __ -_ A [9,14]. IY value from i-o!29f measured y/a ratio and o a 0.00245(8) — — 5139.4(11) 0.35 148.60(4);1.90(2)xlO-1' — B branching ratio In Y A . to value of 2.2(2)xlO-lt is -J deduced from the data CO of [19]. f26.1) 21tl 432. (4)y 6 5637.93(14) 0.35 59.537(1);35.9(3) A(mag.) A [9,14]. T^ from [10]. Am a MOO. t-5.7/ /+0.093) loCc] 11( — — — S.f. 4.1xlO- 1.05(2)xl0 y V-0.247/ 2 — — 2mCra e.c. 99.0 32.8(2)d __ __ 771. (5) <4 471.805(20);72.(3) A(mag. ) A [9,15] a 1.0(1) — — — 6184.8(15) oils 145.536(9);- — C (+0.01) 2*2Pu a MOO. 3.87(5)xl05y 5 4981.7(12) 78.9 44. 915(13) ;0. 042 — B [4,9]. Tjj from [10]. 1-0. 22/ Four of the T^ values are 10 /+0.481 S.f. 5.55xlO-"[c 6.97(8)xl0 y 3 — — — -- — measured relativ o halfet - 1-0.51/ live f otheo s isotopesu P r .

21 2 „_ __. •57 [d] * Am B" 82.7 16.01(2)h 665. (5) TJ/. rJ 42.12; — B(mag.) B [4,9] [d] e.c. 17.3(3) — — —— 752. (5) 6. 44.54; — B(mag.) B

2 2m +0 ______" Am I.T. 9yjt-j9 5 f\ « 152. (7)y 48.63 48.63;- A(mag.) A [4,9]. Qj j value is the e isomerienergth f o y c a 0.476U4) 5637.5(38) 0. 49.3;0.20 B 8 c n _ __ state. Qa value is that S.f. 1.6xlO- t 9.5(35)xlO y 1 f grouno d stat E(I.T.)e+ . IY(49.3 s obtainei ) d from a-branching intensity and measured y/a value. Table I (Continued) f+1.51 / 44. 08(5>,0. 030(51 2"2Cni a VI 00. 162.9(l)d 4 6215.96(14) 74.0(5) B(mag.) A [4,9] 1-0.44J \157-.6(3);0.20(5)7 c 6.6(l)xl06y J+0.6J S.f. 6.8xlO-6[ ] \-0.5f 2 — -- — —

2 __ _ "3Pu 8" 100. 4.957(2)h 583.2(39) 58. 84.0(2);23.(2) A(S1) A [9]. IY value from measurement f 2o s" 3Puy's in equilibrium with 21*7Cm. An M84) value of 27.6% is also reported:

2 — — "3Am a VI 00. 7370(40)y 5438.1(10) 0.16 74.67;66.(3) A(S1) A [9]. Iy value from 13 /+15.8) determination of abso- 1.8xlO-s[c] 4.2(4)xl0 y 2 — -- S.f. (-0.9 / -- — -- lute y-ray emission rates from calibrated source [20].

228.2;10.6(3) a 99.7 30y 2 6168.3(10) 1.5 B(mag.) A -C, fcl 277.6;14.0(4) [9]. IY value from absolute -y-ray emission e.c. 0.26 8.7(24) 100. A rates from calibrated CO source [20]. -a 2 3 CD — __ -- " Bk e.c. >99. 4.6(2)h 1507. (6) 87.4(1); - C(S1) C [9,21]. IY value from a 0.15 -- -- « 6871. (5) 15.4(10) 187.1(5);0.06 B measured Y/<» ratid oan a-decay branching. /+0.08\ ""Pu a ^100. 8.2(l)xl07y 4 4663.7(10) 80.6(8) « — [9,21,22]. T,,. from [10]. 1-0.7 J C S.f. 0.12[c] 6.55(32)xl010y — -- — — — —

""Am 6" 100. 10.1(l)h -- — 1429.0(20) 0. 744.1;61. B(mag.) B [9,21,22] ""niAm _ 0- -vlOO. 26. m 1498. (10) -v.80. 42.9; -- C(mag.) B [9,21,22]. QB value e.c. 0.039(3) ------72. (7) — — __ C taken from measured energ f ground-stato y e B- transition.

2 0.01 \ "*Cm a 18.11(l)y 2 •a 00. 0.011/ 5901.70(11) 76.4(2) 42.824(8);0.026 B(mag.) B [9,21,22] 0.115\ S.f. L346(2)xlO-1* 1.345(3)xl07y [e] ? 5 -- — -- — — 0.093/

""Bk e.c. >99. 4.35(15)h _. __ 2280(SYST) __ 217.6(3); __ C [9,21] a 0.006 — — -- 6777. (10) •^50. -- ~ C Table I (Continued) 2*s f+0.03\ Pu B- ioo. 10.56(2)h V-0.08J 2 1260. (30) MO. 327.2(5);23.3 B(Si) B [9,21] - valuIB s ,i e " brancB su f mo h inten- e lowessitieth o s7 t t states.

2"5Am B" 100. 2.05(l)h — — 898.3(25) 78. 252.3(7);6.1(6) B(Si. B [9,21]. ly valu s froi e m mag.) measured Y/B ratio.

2 5 5623.5(19) 0.5 173. ;14. -- [9,21]. I value from Y/O " Cm a 100. 8475. (58)y 1-210J 2 C Y ratio. TV values measured relative to T, (2I"*Cm).

2 5 " Bk e.c. 99.9 4.98(2)d 819. (5) 0. 252.7(3);30. B(mag.,Si) C [9,21]. Valu f Io eY (474) a 0.105 -- -- 6464. (5) 15.5(5) 474.5(15);0.022 C from Y/a ratio.

2"5Cf e.c. ^70 43.6(8)m — 1563. (7) — C [9,21] a ^30 — 7255.8(20) — — C

2 "6PU 6- 100. 10.85(2)d — — 374. (10) 0. 223.75{2);28(2) C(mag.) B [9,21,22] to 2 CO «Am 8- 100. 39.(3)m — -- 2300. (50) 0. 679.(1);53. -- B [9,21,22] o 2,emAm 0" 10Q. 25.0(2)m — — 2300. (50) -vO. 798.80(4);26. B(Si) A [9,21-23]. QB assumed same as for ground state. 2"6Cm a VLOO. 4748.(14)y m 3 5476.1(26) 79.(1) 44.545(9); — C [9,21,22]. I,, values generally give*n relative 7 [e] JH).03\ 0.0261(1) 1.82(l)xl0 y 2 to Tj, (24ltCm). S.f. 1-0.021 2*6Bk e.c. 100. 1.83(15)d 1600. (SYST) see com- 800.0(5);70. B(Si) B [9,21,22]. Feeding of ment ground-state band <20%. Intensity of ground-state branch assume zeroe b o t .d IT value from [22]] [9 . gives 56% for this value.

2-ecf a MOO. 35.7(5)h 5476.1(26) 77.9(2) 147(4);0. 0035(2) C [9,21,22]. IT from «Y f+0.361 coincidence measurements. 2.3xlO-1([c] 1.74(12)xlQ3y 3 S.f. 1-0.4 i —

2^6£s e.c. 90. 7.7(5)m — 3830(SYST) — — C [9,21,22] a 10(2) -- 7700(SYST) — C Table I (Continued)

2*7Am B- 100. 22(2)m ~ — — — 285. (2);- C(Si) c [9,21]

247 Cm a 100. 1.56(5)xl07y — — 5352.1(35) 13.8(7) 402.4(5);72.(6) — B [9,21]. I value determined from relative Y-emissiod an - a n rates.

2"Bk a 100. 1.38(25)xl03y — -- 5889. (5) 5.5(5) 265.(10);

2"Cf e.c. 100. 2.45(15)h — — 6600. (SYST) 0. ? 295. (5); - — C [9,21]

2"Es e.c. 93. 4.8(2)m — — 2350. (SYST) -- — C [9,21] a 7. 7441. (30) :: C

5 /+0.11 ) a 91.67 3.50(4)xl0 y 3 5161. (5) 81.9(13) c [9,21,22]. \ and Tjjs.f.) 2"8Cm \-0.103f values from averaged Tk(a) 6 j+o. \ 8.33(7) 4.20(4)xl0 y 2 — and a/s.-f. values. Tkfa) S.f. (-0.085J - generally obtained relative

2"8Bk B- >9y — 750. (SYST) — — c [9,21,22] __ to e.c. _- 600. (SYST) V ^ Ol~~ c 00 21(8nlBk 70. 19(3)h «} 2 750. (SYST) — •"" — c [9,21,22]. Q values c assumed the same as e.c. 30. 600. (SYST) those for the ground state. /+9.71 248Cf a MOO. 335.3(33)d 2 6369. (30) 83.0(5) -- c [9,21,22] i-l.tf S.f. 0.0026[C] 3.5(2)xlO"y 2 --

248 £5 e.c. >99. 26.(4)m 2 3060. (SYST) .. .- — c [9,21,22] {-!'} a M).25 -- — — 7150. (SYST) — " — c

2*+ 8 POT a 99.9 37.(4)s — 8001. (20) 80. c [9,21,22] S.f. 0.1 10.(5)h — — —

2"8Md e.c. 80. (10) 7.(3}s -- 5110. (SYST) -- — c [9,22] a 20. — 6800. (SYST) 25. c

<**9Cm B- 100. 64.(3)m — — 903. (9) -- — — c [9,21] Table I (Continued) 2 ^Bk 6" •HOO. 314. (8)d ~~ 126.1(19) 100. • — A [9,21] a 0.00145(8) — 5523.3(19) 6.7 327. 2(5); „ B 8 9 S.f. 4. 6xlO- W 1.87(9)xl0 y

2"9Cf a -UOO. 350.4(24)y 3 6295.6(7) 2.4(1) 388.1(1);66.(2) B(S1) A [9,21]. I value from <3:8 measured y-raY y emission 7 sM-O.lll S.f. 5.0(l)xlO- V0.84J 2 rate. 2 9 * Es e.c. 99.5 1.7(l)h — — 1405. (7) •^46. 379.4(5);^46. C(S1) B [9]. IoCi value is a 0.5(1) 6881. (5) C suf feedino m o lowest g t states2 . 2"9Fm a 100. 2.6(7)m — — 7700. (SYST) — — — C [9,21] 21)9Md e.c. 24.(4)s 3760. (SYST) C [9] a SS: — — 8460. (SYST) — — ._ C 25°Cm S.f. 100. 1.13(5)xlOIty — — — — — — — [9,21] to »°Bk 6- 100. 3.222(5)h — — 1775. (8) 5. 988. 96(15) ;45. B(mag.) B [9,21,22] co to 250Cf a ^100. 13.08(9)y 6129.2(6) 83.5(12) 42.852(5);- B(mag.) B [9,21,22] 1) [e:l /+0.041 S.f. 0.077(2) 1.69(4)xl0 y l-0.03f 2

250Es[fl e.c. 100. 8.3(2)h -- — 2000. (SYST) — — B(S1) C [9,22] e.c. 100 2.1(2)h -- -- 2000. (SYST) -- -- — C [9,22]. Q value listed is the same as that for "^ the ground state. 25°Fm a >90. 30.(3)m 7548. (30) — — ~ C [9] S.f. -v-lO.y — — 25omFm I.T. — 1.8(l)s — — -- ~ — — C [9] 25°Md e.c. 94. (3) 52.(6)s — 4530. (SYST) -- — -- C [9] a 6. ._ 8250. (SYST) C 251 Bk 6' 100. 57.0(17)m 1130. (SYST) 0. C [9,21], Intensitf yo ground-state B~ branch deduced from probable differenc groundn i e - state spins and parities (Al=3,air=no.). Tabl I e(Continued )

251Cf a 100. 897.(45)y 2 6171.8(14) 2.7(3) 176.6(1);17.(1) B(S1) B [24]. T, from data in ti.\ [21], I* value from ay- coincidence measurements

251Es e.c. >99. 33.(l)h „_ „_ 375. (9) %65. 177.6(3); 5. — C [9,21]. Value given a 0.52 — — — 6593. (5) -x.80. — — C for ground-state e.c. branch is total feeding f firso member3 t f o s ground-state band.

251 __ _ __ Fm e.c. 98.1 5.30(8)h 1490. (SYST) C [9]. IY (425) determined a 1.9(2) — — — 7366. (15) 1.5( 1) 425. 4(1);0. 97(13) B(Si) A from measurea d d an y intensities together with a/e.c. branching.

251Md e.c. £90. 4.0(5)m _« __ 3030. (SYST) — — — C [9] a -- ~ -- -- 8050. (SYST) — — — C (43. 399(25) -,0.0148(9)1 252Cf B [9,22]. I values from a 96.90 2.640(3)y {±0.019} 4 6217.0(5) 84.2(3) 060. (15);0. 0020(6/ ) y [e] ay-coincidence measurements. S.f. 3.10(2) 85.3(5)y oo <399.7(3);0.23(3)\ 252Es a 78.(6) 350.(50)d — — 6746. (5) 80.2(9) A [9,22]. I (399,418) 00 1418. 5(3) ;0.23(3)/ values determined from ay- e.c. 22. (2) 1130. (SYST) 0. 785.1(1);15.(2) B(Si) A coincidence measuremend an t listed a-branching ratio. IY (785) deduced from intensity-balance considera- tion e.cd san . -branching ratio. (+0.2) 252Fm a -aoo. 22.8(6)h 2 7154. (20) ^-85. — — C [9,21,22] VO.l/ S.f. 0.002^ 115.(60)y 1 — — — -- ——

252Md e.c. — 2.3(8)m — -- 3750. (SYST) — -- -- C [9]

252No a •^70. 2.4(2)s __ __ 8546. (15) .. — — C [9] S.f. -^30. ^7.s — — — ------~~

25 [9,21] 3Cf B- 99.69 17.82(9)d -- 299. (10) -vlOO. o y'|n s reportedv C a 0.31(4) ._ 6136. (5) 0. -- C

253Es a UOO. 20.47(2)d __ — 6739.58(23) 89.8(2) 389.18(4);0.026 A(mag.) A [9,21,25] 6 5 e] S.f. 8.7(2)xlO" 6.4(2)xl0 yf — — — -- — — — Table I (Continued) 253 ______Fm e.c. 88. 3.00(13)d 341. 4) -_ C [9,21]. IY value from a 12. (1) -- — -- 7206. ,4) 1.3(2) 271.8(4);2.6(4) B(Si) B aY-coincidence measure- ments and a-branching ratio. ""Of a 0.310(16) 60.5(2)d __ _ 5931.4 83. (2) __ _„ C [9,21,22] , (s.f.T . ) S.f. 99.690 60.7{2)d -- — - -- -- calculated frtfm a^a+S-f.) rati d listean o , valueT d . (63.(2);2.0(3) I ""Es a 100. 276. d — — 6626. (5) MD.005 B(emuls.) B [9,21,22]. IY (63) value \150.(2);0.020(3)f from aY-coincidence and Y-emission rate measure- ments.

25tmEs 6- 99.6 39.3(2)h __ __ 1164. 11) ^16 693. 67(7);24. 7(17) B(mag.) A [9,21,22]. IY values from a 0.33(1) — — — 6704. 5) 4io(5) 211. 8(1);0. 10(1) B(Si) A measured Y-emission rate e.c. 0.078(6) -- — — 668. SYST) 100. C relative to a-rate from 251 *Fequilibriumn i m . Q values calculated from those for the ground state CO assumin n isomeric-stata g e co energy of 78(1) keV. 25"Fm a 99.941 3.24(l)h i 7315. (5) 85. (1) 151. (5);0. 0010(3) C [9,21,22] rLeJ S.f. 0.0590(3) 229.(l)d -- -- — 2S "Md e.c. _. 10.(3)m — — 2490. (SYST) —— — — C [9], Qe.c. value is that (1)[g] ground-state th r fo e decay.

2511 Md e.c. _ 28.(8)m __ __ 2490. (SYST) ______C [9]. Qe.c. value is that for the ground-state decay. (2)[g] 25"No a 100. 55(5)s -- — 8235. (15) ^85. -- -- C [9,21,22]

25"mNo I.T. -- 0.28(4)s -- -- - — — — C [9]

255Es 6- 92.0 39.8(12)d _. __ 290. (SYST) ______C [9,21]. \ (s.f.) derived a 8.0(4) — — — 6400.2(15) 87.7 — — C from 6"/s.f. rati Tj.d an .o 2 S.f. 0.0041(2) 2.63(15)xl03y — — -• — -- — — 255Fm a ^100. 20.04(8)h /+0.03\ 2 7242. (4) 0.070(7) 204. 1(2);0. 024(2) A(mag., A [9,21,25] valuY I . e from (-0.14) Si) a-emisd an - Y s ion-rate S.f. 2.4(10)xlO-5 (9.6^;J)xl03y[e] — — -- — — -- measurements . Tabl I e(Continued ) 255 Md e.c. 90. 27.(2)m _._ .. 1080. (SYST) .. __ .. C [9], A value for e.c, /a a 10. (1) — ~ -- 7950. (SYST) — 430. (40);- — C of 93/7(1) is also reported .

255 (+0.171 No a 100. 3.16(12)m \-0.16f 3 8445. (9) 3.(D — ~ c [9,21]

256Fm a 8.1(3) 157. (2)m _ _ 7034. (5) __ __ _ c [9,22]. Tj, (s.f.) calcu- S.f. 91.9 2.85(4)h — -- — — — — lated from measured a/(a+s.f .) ratid an o listed Tj, value. 256Md e.c. 90.6 76.(3)m {±1.} 2 1940. (SYST) __ __ _ c [9,22]. E.c od branc.an h a 9.4(4) ~ — 7843. (20) 4.(1) 400. (20);- -- c intensities are an average reporte2 f o d values, 90.1/9.9(5) and 91.5/8.5(8), for a/(e.c.+o). 257 Fm a 99.79 100.5(2)d — — 6866.2(31) 0.4(2) 241.2(7);10.(1) B(Si) B [9,21]. IY values from S.f. 0.210(5) 131.(3)y[e] ay-coincidence measurements. to co 257Md e.c. 90. 5.2(3)h {±0.2} 2 430. (SYST) ______C [9,21] en a 10. (3) — — -- 7600. (SYST) ------C

257No a 100. 24.5(14)s {±1.5} 2 8452. (30) — — — C [9,21]

[a].Unless otherwise indicated, these intensity values give percen th ea give f to n decay mode which directly populate groune th s d e statth f eo respective daughter nucleus. Consequently thosn ,i e cases where more thae decaon n y nucleu a modn appreciabla f o es ha s e intensity, they must not be interpreted as being expressed as % of decays of the parent nucleus. [b]. Unless otherwise noted, the listed absolute I values are derived from intensity-balance considerations within the decay scheme. They are always give %/decan i n y (i.e., photons/100 decays e parenth f )to nuclidesY . [c]. Spontaneous-fission branching ratio calculated from the listed values of T, (s.f.) and T, .

>2 %

21(2 [d]. "iNpAm)(236 ., These values represent intensities in % of decays of the parent nuclide rather than in t of decays via the respective decay mode. [e]. Tj, (s.f.) value derived fro a/s.fe mth .listee th rati d d an o valu Tj,f o e . [f]. (2SOEs,25om Es) e relativTh . e orderin groune th isomerid f an do g c experimentallyt stateno s i s , established orderine Th . g given hers i e based on the expectation that the coupling of the odd neutron and the odd proton will produce a high-spin ground state and a low-spin isomeric state. The short-lived activity is observed to feed low-spin states in the daughter nucleus, while the longer-lived activity does not. This indicates that the short-lived activity has a low spin and thus strongly suggests that it is the isomeric state. Table I (Continued) [g]. (251|Md(l), 251*Md(2)). The relative position in 25"Md of these two activities is not yet established.

REFERENCES FOR TABLE I

[I]. M. J. Martin and P. H. Blichert-Toft, Nuclear Data Tables A 8, Nos. 1-2, (1970) 1. [2]. Nuclear Data Sheets 6, No. 3, (1971).

[3]. AguerP .. . LiangF PeghairA ,. C d , Nuclean . Phys. A202 (1973. 37 ) [4]. Nuclear Data Sheets B 4, No. 6, (1970).

[5]. E. F. Tret'yakov, N. I. Tret'yakova and V. F. Konyaev, Izv. Akad. Nauk SSSR, Ser. fiz. 35 (1971) 2306; Bull. Acad. Sci. USSR, Phys. Ser. 35 (1972) 2094. ~~ —

[6]. W. Lourens, B. 0. Ten Brink and A. H. Wapstra, Nucl. Phys. A152 (1970) 463.

[7]. W. Kurcewicz, K. Stryczniewlcz, J. Zylicz, S. Chojnacki, T. Morek and I. Yutlandov, Acta Phys. Polonica B2_ (1971) 451. ^ [8]. ValkeapaaT . , J.' Heinone . Graeffe6 d nan , Phys. Scripta 5_ (1972) 119. CO os Lederer. M [9]. C . , private communication (July, 1975 appeao (t ) Tabln i r f Isotopeseo , Seventh Edition). [10] Vaninbroukx. R . , Euratom Report EUR-5194e (1974). [II]. J. E. Cline, USAEC Report IN-1448 (rev.), (Jan., 1971); see also J. E. Cline, R. J. Gehrke and L. D. Mclsaac, USAEC Report ANCR-1069 (Supplement to IN-1448), (July, 1972). [12]. L. A. Kroger, C. W. Reich and J. E. Cline, USAEC Report ANCR-1016 (1971) 68; L. A. Kroger and C. W. Reich (to be submitted for publication). [13]. N. Kaffrell, N. Trautmann and R. Denig, Z. Physik 266. (1974) 21. [14]. Nuclear Data Sheets 6, No. 6, (1971). [15]. I. Ahmad, F. T. Porter, M. S. Freedman, R. K. Sjoblom, J. Lerner, R. F. Barnes, J. Milsted and P. R. Fields, Phys. Rev. C.(to be published). Morrow. [16]J Gunnin. . R ,R ,d an USAEk C Report UCRL-51087 (July, 1971). Greenwood. C Helme. . G [17]R . d R .ran , Nucl. Technology 25. (1975) 258. Tabl I (Continuede ) [18]. I. Ahraad, R. F. Barnes, R. K. Sjoblom and P. R. Fields, J. Inorg. Nucl. Chem. 3£ (1972) 3335. [19] Ahmad. I . M. ,.A Friedma Unik. 0.d P an n , Nucl. Phys. A119 (1968. )27 [20], I. Ahmad and M. Wahlgren, Nucl. Instr. and Methods 99 (1972) 333. [21]. Nuclear data Sheet (1969)2 . 3_sB No , . Schmorak. [22]R . M . , private communication (July, 1975 o appea)(t Nuclean i r r Data Sheets). [23]. L. 6. Multhauf, K. G. Tirsell and R. A. Meyer, Phys. Rev. C (to be published). [24]. E. Browne and F. Asaro, USAF.C Report UCRL-19530 (1969) 8. [25]. I. Ahmad and J. Milsted, Nucl. Phys. A239 (1975) 1.

CO oo 3.1. Comments on the Content and Organization of the Table 2 nuclideEntrie14 r d isomerifo san s c state e containear s n i d Table I. These constitute essentially all the nuclides in this mass region for which some decay data, other than simply a half -life, are available e tableth n e havI ,w . e listed numerical value d theian s r uncertaintie e variouth r sfo s quantities extene th o tT .tha t these uncertainties are correct, they indicate the "status" of a given quantity. It shoul e emphasizeb d d that y intendetheswa o n e o servn valuet di e e ar s f "recommendeo t se aa s d data." e tableIth n e liste, th som f do e data refea transition o t r s and a-decay-related half-lives. Thes e includeear o illustratt d e th e various data categories and are not to be regarded as being in contra- diction to the more extensive treatment of a-particle data in the review paper B6 [18] presented at this meeting.

r eacFo h nuclide e observeth , d decay mode d theian s r branching ratio n percent(i s e given)ar . Thi s followe i se half-lif th y b d e data, which include the total nuclide half-life in all cases and the spontaneous- fission (s.-f.) half-life where it exists. In some cases, the s.-f. half- lif measures i e d directly (an e s.-fdth . branching rati s inferredi o ) and in some cases the s.-f. branching ratio is measured directly (and the s.-f. half-life is inferred). The manner in which these two quantities were e variouderiveth r sfo d nuclide s indicatei s n footnotei d e th o t s table.

In a number of cases, several measurements of the nuclide half- life have been made; and it is frequently found that the measured values differ from each othe y amountb r s thae mucar t h larger thae quoteth n d uncertainties. In these cases, we have listed (1) an "averaged" value e half-lif uncertaintyth s it r d fo an e , togethe e rangrth wite) (2 (abovh e and below the average) spanned by the measured values and (3) the number f measuremento s included arrivinn I . t thosa g e measurement e includedb o t s , we have occasionally discarded some older measurements (where more recent ones seemed more reliable d som)an e whose quoted uncertainties were signi- ficantly larger tha ne one thosth s f usedo e . Where indicatee th n i d References Column, these "averaged" values were taken from the recent compilation of Vaninbroukx [19]. In the remainder of the cases, the listed valuweightea s i e d averagmeasurementse th f eo , wit a I/h a weighting factor usede uncertaintTh . ye "internalgiveth s i n " error, namely,

288 where n is the number of measurements and w-j is the weighting factor (i.e., e i1/o-jtth h measurementf o ) . Compariso f thio n s internal-error estimate with the range of values gives some indication of how the differences among the measured values compare with their quoted uncertainties. As statee purposth t df thi o no eabove s si procedurt i , o product e e "recom- mended" half-life value n thesi s e cases s mereli t i ;y intende o illustratt d e in a fairly concise way the status of the experimental situation.

e tabl Ith e nliste ar e e Q-valueth d r eacfo s h decay mode (except spontaneous fission). This give e totath s l energy availabl e decayth o t .e The notation "SYST" accompanying a value indicates that is estimated from systematics. Listed next is the intensity of the transition directly froe parenth m te grounstatth o dt e e daughte statth f o e r nucleus (exclud- ing isomeric-transition decay). This beeha s n included since mann i , y cases t indicate,i e precisioth s n with which y-ray intensitiee b n ca s inferred from intensity-balance considerations withi e decath n y scheme. These absolute intensities, where not directly measured (i.e., by ay- or 4TT 3y- coincidence measurements) are generally deduced by requiring that the sum of the transition (i.e, photon + conversion-electron) intensities e y-rayf alo th l s feedin e grounth g de direc th stat d tan e feeding froe th m parent nucleus equal 100%. Weak ground-state feeding indicates that, in_ principle, fairly precise absolute y-ray intensities can be deduced, while strong direct feeding of the ground state generally indicates that the derived absolute-intensity values will be less precise.

Als oe tabl giveth e energ n ar e i nd absolute-intensit an y y values for a prominent y-ray (or y-rays) associated with the various decay modes (except spontaneous fission) of each nuclide. Because of the wide- spread use of y-ray spectroscopy for quantitative assay of radioactivity and of the many applications involving such assay, these data are of considerable importance.

We have given only qualitative indicators for the status of the conversion-electro e deduceth f no d dat d decaan a y scheme n thiI .s nota- tion, A indicates a quite well studied and reasonably complete situation; B denotes some data, but an incomplete situation; while C indicates only fragmentary data or decay scheme. If no c.-e. data exist, this column is left blank ,e decawhilth f yi e schem s completeli e y unknowns i C a , still indicated in that column. Clearly, the borders between these various symbols are not sharply drawn. The notations "mag.", "emuls." and "Si"

289 e c.-eith n . status column indicate that magnetic spectrometers, magnetic spectrographs, and silicon detectors, respectively,were utilized in the conversion-electron measurements.

Wher e variouth e s quantitie t knownno e ,ar sgenerall o entrn y y appears in the table.

At the right in the table are given the references from which the data have been taken and appropriate comments. The numbering of the references refer s separati e table botto o thosth th t d s an et f ma o ee from that employed in the text. While it would have been generally » desirabl o refet e aln i r l e originacaseth o t s le dat paperth a r includefo s d in Table I, this was not done because of the quite extensive referencing which this would have required.

A large e spontaneous-fissiobod th f dat o yn o a n isomers, whose existenc d propertiean e s provid a strikine g illustratio e influencth f o n e of shell-structure effects on the formation of a second minimum in the nuclear potential well, is not included here. It was felt that a treat- men f thesto e interesting nuclear states lay outsid e scopth e f thieo s meeting.

3.2. Discussion of specific points Becauswidespreae th f y-raf o o e e yus d spectroscop meana s f a yo s both qualitative and quantitative assay of radioactivity, the y-ray-energy and especially the absolute-intensity data are of great importance. For this reason, comments pointing up discrepancies and differences in reported intensity values are occasionally included in Table I (see,e.g., 232U). The intensity of the prominent 185.71-keV j-ray from the 235U decay represents n interestina g situation. Onle measuremenon y f thio t s quantits i y reported [20]—in an APS Bulletin Abstract in 1957—and no uncertainty was quoted. Hence, quantitative assay of 235U samples using only ^-ray spectrometry involves data of unknown accuracy.

The absolute intensities of the y-rays from the more common Pu isotopes present unresolved problems at this time, in that the two most extensive reported measurements [21,22] exhibit considerable disagreements. This situation has been studied in detail in the context of safeguards researc y Ottmab h Weitkamd an r p [23] o compar,wh e isotopic ratiou P f o s isotopes determined from mass-spectrometric analyses with those determined

290 from y-ray spectrometry. These results are shown in Table II. Ottmar and Weitkamp report: For computation of the y-spectrometric isotopic ratio values as listed in the Table, absolute y intensities have been used. The resulte calculatear 4 columnn i sd an d 3 s froonle th my o comprehensivtw e set f absolutso ey intensitie f plutoniuo s m and americium isotopes published unti w [21,22]no l e agreeTh . - ment of the two sets of results with each other and with the mass-spectrometric data is poor. This indicates that the reported erro rabsolute valueth r fo se intensitieo to e ar s optimistic. Among other things, they conclude: One prerequisit e accuratth r fo ee y spectrometric determination f Plutoniuo m isotopic e availabilitratioth s i s f betteo y r nuclear data. Since absolute y intensities can hardly be pieasu^ to the degre f accuraco e y necessary, intensity ratios shoul e deterb d - mined as outlined in Chapter 4. This requires samples with very accurately known isotopic composition.

As a daughter nucleus from 239U decay, 239Np is important in a numbe f applicationo r s suc, e.g.as h , measurement e neutroth f o sn capture cross sectio 238f o ns indicateUA . e absolut Tabln th i d , I e e intensities of the two prominent y-rays near ^0.2 MeV are known with precisions some- what bette y-raA r tha. y 2% ndouble t ^10a t 6 keV, more intense than either of these two, also occurs in the 239Np decay. Its use in quantitative spectral analysi generallnot is s y advisable, partly becaus thaat e t energy absorption within the samples can be important and partly because it lies in the energy region of the K x-rays from the near-lying elements.

e intensit Th prominene th f o y t 59.5-keV y-ray from 2ltlAm decay is now quoted with an uncertainty of V|%. We have derived the value given in Table I from a 1/a-weighted average of the two most recent measurements, 35.3 ± 0.6% [24] and 36.3 + 0.4% [25]. It is interesting and perhaps fortuitous that this value is now back to what it was in 1957 [26 d use ]y an IAEAb d , namely 35.9%, althoug e uncertaintth h s i y now roughly a factor of 2 smaller.

e low-energTh y (f30keV) photons from 2tfl e frequentlAar m y used s intensity-calibratioa n standard r low-energfo s y photon detectors. Five peaks are commonly utilized, namely the La, La, LnP, and Ly lines at 11.9, 13.9, 17. 20.d 8an 8 keV, respectively 26.35-kee th d ,an V y-ray detailA . - ed treatment of the absolute-intensity values of these lines has been reporte y Campbelb d d McNellean l s [27]. They conclude thae uncertainth t - ties in these absolute intensities range from ^2.5% for the La line to r weakerL£anfo d 26.35-keV lines.

291 TABL . RESULTII E A GAMM F O SA SPECTROMETRIC DETERMINATIOF O N ISOTOPIC RATIOS IN PLUTONIUM. (This table is taken from Ottma Weitkamp[23].d ran )

Isotopic Mass Y-spectrom. values Y lines used Error ratio spectro- calculated with r analysifo s components(*)^ metri c absolute (keV) value intensities from refs. FI FH FP Other [21] [22239p] u y y [21]

239Pu/238pu 3118 (10)* 3260 (6) 4809 (22) 203.55 152.77 4 0.2 2 3333 (14) 4513 (32) 769.38 742. 77+ 2 0.2 12 2753 (4) 3680 (21) 769.38 766. 41+ 2 0.2 2 2855 (10) 6673 (18) 769.38 786.38 02 0. 2

239pu/2t*0pu 10.512(0.4) 12.57(10) 40.41(25) 161.45 160.35 4 0.3 5 12.74 (8) 40.21(22) 646.02 642.30 5 0.3 2.5

239Pu/241pL( 121.39(1.1) 113.7(10) 139.6(22) 203.55 208.00 8 1.1 0.3 239Pu/241Am 901.6(2.3) 635.2(11) 671.0(26) 422.57 419.19 5 0.3 6 846.9(20) 1214 (33) 451.45 454.58 7 0.3 13 588.1(18) 1232 (31) 640.15 641.31 1 73 0. 7 604. ) 819.9(11(4 6 ) 646.02 662. 37 * 3 0.3 0.6 498. ) 639.0(24(9 3 ) 652.19 652.38 5 0.3 4 607.6 (5) 618.7(11) 658.99 662.37 4 0.3 0.7 601.0 (9) 686.16 688.70 6 0.3 2.7 599.4 (7) 913.2(23) 717.76 721.92 4 0.3 2.6

t FJ, FH, Fp denote errors for the ratios of absolute intensities, half-lives and measured peak areas, respectively. *Values in parentheses are errors in percent (emphasis ours). "^Possible interference from fission-produc tY rays .

. 4 SELECTED SPONTANEOUS-FISSION DATA The spontaneous-fission half-life data are summarized in Table I above e subjectTh . f prompso d delayean t d neutron yield d energan s y spectra from spontaneous fission are characterized by an extensive literature; and we consequently confine our remarks here to brief comments concerning a w recenfe t developments.

292 4.1. v values from spontaneous fission The subject of v, the average number of neutrons emitted per fission s bee,ha n treated exhaustivel e excellenth n i y t recent reviey b w Maner d Konshian o n [28]. Since tha tw additionatimfe a e l measurements of v from the spontaneous fission of several nuclides have been reported. However, these essentian valuei e ar s l agreement with those give n [28]i n , so that this review still presents a good overall picture of the status of spontaneous-fissio v nvalues . The value of v for the spontaneous fission of 252Cf occupies a central position in the area of v measurements since it is the "standard" relativ o whict e h othe v rvalue e measuredar s . e th Thi s i s othethe cas onlr not espontaneouslfor y y fissioning isotopes als,but o —and more important—fo e fissionablth r e isotope s wella s . Howevert ,a the present time there are still discrepancies in the value of this quantit s determinea y d using different measurement techniques (see eth discussio n [29 i nd [28]) ]an n thi.I s context appropriats i t i , o t e point out that a remeasurement of v for 252Cf is currently in progress [30]. This experiment utilizes the manganese-bath technique; and parti- cular attentio s beeha nn give o identifyint n e variouth g s sourcef o s error and to the quantitative determination of their effects. At the time of the writing of this review the results from this experiment are not available.

4.2. Neutron energy spectra from spontaneous fission prompt-neutroThe n energy spectrum following spontaneous fission is customarily assumed to be well described by a Maxwellian distribution function, viz. N(E)OCE1/2 exp(-1.5E/Eav.),

wite quantitth h y Eav being determine o mosd tw fro te datae th mTh . widely studied fission-neutron spectr e thosar a e from spontaneous fission of 252Cf and thermal-neutron-induced fission of 235U. The extensive data on thes o energtw e y spectra have quite recently been carefully evaluated by Grundl and Eisenhauer [31] to determine to what extent they can be described by a Maxwellian function. These authors conclude that, over the energy range 0.25 toSMeV, the reference Maxwellian shapes differ from the final evaluated shapes by £ 2%, with the average-energy parameters

(Eav,) determine 2.1e b o 30.02t 1 d 7 1.9d Mean V 7 ± 0.014 MeV, respectively, for 252Cf spontaneous fission and 235U thermal-neutron-induced fission.

293 In the area of the energy distribution of delayed neutrons fol- lowing spontaneous fission e wis, w o calt h l attentio a serie o t nf o s quite interesting experiments bein e OSIRIgth carriet a S t Facilitou d y at Studsvik, Sweden. In these experiments the individual delayed- neutron precursors, produced in thermal-neutron fission of 235U, are isolate r detailefo d d study using on-line isotope separation. While these studiet providno o d s e "integral" energy-spectral information, then ca y (in principle) yield such information when combined wite appropriatth h e fission-product yields A numbe. f interestino r g feature e delayedth f so - neutron energy distributions of individual precursors are observed, such e occurrencth s a f boteo h discret d continuouan e s components A summar. y e presenth f o t statu f theso s e result bees ha sn prepare y Professob d r Rudstam. This is included as Appendix B of this review.

5. COMMENTS AND OBSERVATIONS o makT e mosth et effectiv f availablo e us e e resourcee th n si area of Nuclear Data, good communication among the measurers, the users, and the compilers and evaluators of nuclear data should exist. The field of neutron cross sections provides an excellent example of one category of nuclear data in which a fruitful interaction has existed among these three component f nuclear-datso a activity e presenth t A t. time, however, no relationship of comparable scope exists within the area of radioactive- nuclide decay data. This situation has been commented on before (see,e.g., [1,32]).

Because of the use of radioactivity in a number of widely varied applied area d scientifian s c disciplines e "use,th r community f decao " y data is quite diverse. Consequently, the identification of a satisfact- orily representative sample of such users represents a formidable problem.

The existence of different categories of measurers of decay data e recognizedneedb o t s e vasTh .t majorit f informatioyo n constituting the present base of decay data has been provided by those interested in nuclear-structure physics. Generally speaking, these workers are not aware of the specific data needs of applied users, particularly specific accuracy requirements. This is especially true with respect to absolute y-ray intensities and half-life values, which are necessary for any applica-

tions where quantitative assa Yf ->"adioactivityo requireds i y . High- precision measurements of these quantities are not generally required in order to extract the interesting basic nuclear-physics information

294 fro a decam y study additionn I . measuremene th , f theso t e quantities with the desired precisions (say, <5% for absolute y-ray intensities) requires specialized calibration technique d instrumentationan s r Fo . these reason date s th mana f needo y f usero se inadequatelar s y satisfied at the present time.

Important in the development of a program to meet the requirements r decafo y dat recognitios i a e importancth f o n f radioactive-nuclido e e metrology. This metrology function would be mainly to develop and improve selected measurement techniques to provide a recognized capability for performing measurements requiring high precision. While in fact these measurements are of basic nuclear-physics quantities, the orientation of the effort would be to provide specific information for application to specific problems. Suc metrologa h y program would most effectively be organized around existing capabilit majon i y r laboratories engaged in nuclear research in order to provide continuity and the required tech- nical suppor associaten i t d disciplines. Example f high-precisioo s n measure- ment f selecteo s d decay-scheme parameter r applications-orientefo s d purposes are provided by work carried on in several Western-European laboratories (see, e.g., [33,34]).

Attention should also be given to the desirability of utilizing a common data content and format for the organization of decay data to meet applied needs. A common base of data presents a number of advantages e applietth o d user, among whic e indicatw h e two. First t possessei , s "traceability," that is, it provides a standard origin for the data used by different groups. Second, it permits uniformity in the application of decay data to the quantitative measurement of radioactivity. Examples f applieo d needs include environmental monitorin d radiologicaan g l health- hazard evaluations. In the preparation of regulations and guidelines by regulatory agencies to insure uniformity in the reported results of measurements standardizatioe ,th f referenco n e material affordea y b d common data base is a necessity and has legal implications. A structure for such data modeled along that for the ENDF/B decay-data file might be useful.

Interest has been expressed concerning what type of presentation (computer medi r publisheo a d form f deca)o mose y th dat ts i conveniena t from the point of view of the user. It is our opinion that such data should certainly be available in a simple and easily readable form, i.e., in print. Compared with categories of nuclear data such as, e.g., 295 neutron cross sections, the amount of information involved is relatively smal d havinan l availablt i g n handbooksi e , report r tableo s s makes it s use quite straightforward and simple. If required for some applications, e.g., for use in data-analysis codes, the relevant data can readily be prepare a suitabl n i d e computer-based medium n fact (I e deca. ,th y datn o a ENDF/B-I e storear V n computeo d r tape, although thee alsar y o available in the form of computer listings in a "people-readable" format [2] if desired.)

ACKNOWLEDGEMENTS

Contribution d communicationan s s fro a numbem f interesteo r d peopl e gratefullar e y acknowledged majoA . r sourc f decao e y datr fo a this review was provided by the extensive data sets for individual trans- actinium nuclides with A >230 supplied by C. M. Lederer of the Table of Isotopes Projec Schmora. R t LBLe Nuclea a t. th M . f o kr Data Project ta ORNL supplied listing f selecteo s d decay data frorecens hi m t revision of the Nuclear Data Sheets for the even-A mass chains with A >243. R. M. Harbour of SRL produced and supplied a listing of references to sponta- neous-fission-related data froe Nucleath m r Science Abstracts . G Rud. - stas prepareha m e summarth d f delayed-neutroo y n energy spectra given i n Appendi . B xDat a requirement d helpfuan s l comments were. R sen y b t Dierckx of Euratom, Ispra and by A. H. W. Aten, Jr., of the IKO, Amster- dam. Communications of data on various aspects of transactinium-isotope nuclear data were received from . TakekoshE :. Umezaw H d f an JAERIio a ; A. Hashizume and H. Kawakami of the Institute of Physical and Chemical Research, Wako-Shi, Saitama, Japan and the Institute for Nuclear Study, Universit f Tokyoo y , Japan, . MeadowrespectivelyW . J . Smit B d s . an hA d ;an of ANL. Helpful discussions were held with J. R. Smith, R. L. Heath and e . INELHelmeG th . .R f o r Finally e constructivth , e . commentG . R f o s Helmer and his careful reading of the manuscript were most helpful.

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[l] Fission Product Nuclear Data (Proc. Conf. Bologna, 1973), IAE 169- A , IAEA, Vienna (1974). ] REICH[2 W.. C , , HELMER . G.R , , PUTNAM H.. ,M , Radioactive-Nuclide Decay Data for ENDF/B, U.S. AEC Report ANCR-1157 (August, 1974).

296 [3] NATHAN, 0., NILSSON, S. G., "Collective Nuclear Motion and the Unified Model," Ch. 10, Alpha-, Beta-, and Gamma-Ray Spectroscopy (SIEGBAHN, K.,Ed.), North-Holland, Amsterdam, (1966). [4] NILSSON, S. G., Mat, Fys. Medd. Dan. Vid. Selsk. 29 (1955) No. 16; GUSTAFSON, C., LAMM, I.-1., NILSSON, B., NILSSON, S. G., Ark. Fys. 36_ (1967) 613; NILSSON, S.G.,TSANG, C.F., SOBICZEWSKI, A., SZYMANSKI, Z., WYCECH, S., GUSTAFSON, C., LAMM, I.-L., M0LLER, P., NILSSON, B., Nuclear Physics A131 (1969) 1. ] BUNKER[5 , M.E., REICH W.. ,C , Revs. Mod. Phys. 4_3 (1971) 348. [6] GALLAGHER, C. J., MOSZKOWSKI, S. A., Phys. Rev. TJJ_ (1958) 1282. [7] HAGER, R. S., SELTZER, E. C., Nuclear Data A 4_ (1968) 1. ] DITTNER [8 BEMIS, F. E.. C . ,,P Jr., Phys. Rev ^A . (1972) 481. [9] SCHMIQT-OTT, W.-D., HANSEN, J. S., FINK, R. W., Z. Physik 250 (1972) 191 [10] BEARDEN, J. A., BURR, A. F., Revs. Mod. Phys. 39^ (1967) 125. [11] MARTIN, M. J., BLICHERT-TOFT, P. H., Nuclear Data Tables A8 (1970) 1. [12] BLACHOT, J., deTOURREIL, ReporA R.CE , t CEA-N-1526 (1972); DEVILLERS, C., BLACHOT, J., LOTT, M., NIMAL, B., N'GUYE DATN VA N , NOEL, J.P., deTOURREIL, R., Nuclear Dat Sciencn i a Technologd ean y (Proc. Conf. Paris, 1973), Vol. I, 477, IAEA SM-170/63, IAEA, Vienna (1973). [13] TOBIAS, A., Data for the Calculation of Gamma Radiation Spectra and Beta Heating from Fission Products (Revisio , Centra3) n l Electricity Generating Board Report RD/B/M2669 CNDC (73) P4 (June, 1973). [14] RUDSTAM, G., Fission Product Nuclear Data (Proc. Conf. Bologna, 1973), Review Paper 12, Vol. II, 1, IAEA-169, IAEA Vienna (1974). [15] SCHMORAK . R.,M , Private Communication (July, 1975). [16] LEDERER M.. C , , Private Communication (July, 1975). [17] GOVE, N. B., Private Communication (May, 1973). [18] ZELENKOV, A., Review Paper B6^ submitted to this conference. [19] VANINBROUKX, R., Half-Live f Somo s e Long-Lived ActinidesA : Compilation, Euratom Report EUR-5194e (1974). [20] PILGER C.. R ,, STEPHENS S.. ,F , ASARO, F., PERLMAN, I., Bull. Am. Phys. Soc., Ser. II 2_ (1957) 394. [21] GUNNINK, R., MORROW J.. ,R , U.S ReporC .AE t UCRL-51087 (July, 1971).

297 [22] CLINEU.S, ReporC E. . AE . ,J t IN-1448 (rev.) (January, 1971); CLINE, J. E., GEHRKE J.. ,R , McISAAC , U.S C ReporD. .AE . ,L t ANCR-1069 (Supplement to IN-1448) (July, 1972). [23] OTTMAR, H., WEITKAMP, C., Symposiu Practican o m l Applicationf o s Researc d Developmenan h e Fiel th f Safeguard o n dt i s (Proc. Conf. Rome, 1974), IAEA, Vienna, (1974). [24] PEGHAIRE, A., Nuclear Instr. and Methods 75^ (1969) 66. [25] LEGRAND, J., PEROLAT, J. P., BAG, C., GORRY, J., Int'l. J. Appl. Rad. and Isotopes 26. (1975) 179. [26] MAGNUSSON, L. B., Phys. Rev. ]07_ (1957) 161. [27] CAMPBELL, J. L., McNELLES, L. A., Nuclear Instr. and Methods 117 (1974) 519. [28] MANERO KONSHIN, F. , A.. . Energ,V , At y Rev. JO. (1972) 637. [29] AXTON, E. J., Neutron Standard Reference Data (Proc. Conf. Vienna, 1972), 261, IAEA-Pl-246-2/31, IAEA, Vienna (1974). [30] SMITH, J. R., Private Communication (August, 1975). [31] GRUNDL A.. ,J , EISENHAUER M,. ,C , Bulleti . PhysAm n . Soc. SerI .I 20_ 0975) 145; and Proc. Conf. on Nuclear Cross Sections and Tech- nology, Washington, D.C. (1975) (to be published). [32] REICH, C. W., HELMER, R. G., Bull. Am. Phys. Soc.. Ser. II 2£ (1975) 134 d Proc;an . Conf n Nuclea.o r Cross Section Technologyd an s , Wash- ington, D.C. (1975) (to be published). [33] HANSEN, H. H., deROOST, E., van der EIJK, W., VANINBROUKX, R., Z. Physik 269 (1974) 155, and references contained therein. [34] DEBERTIN, K., SCHOTZIG, U., WALZ, K. F., WEISS, H. M., Private Communication (March, 1974).

APPENDIX A THE ENDF/B DECAY-DATA FILE

s mentioneA Chapten i d above1 r ,a fil f actinide-nuclido e e decay dat currentls i a y being prepare r inclusiofo d Version i n f o V n ENDF/B. It will contain data on 46 nuclides and isomeric states. It thus seems appropriate within the context of this meeting to present a discussion of the philosophy underlying the ENDF/B decay-data file and to describe its organization and the types of information it contains. 298 As originally set up for Version IV of ENDF/B, the decay-data fil s orientewa e d towar e specifith d c objectiv f providino e a datg a base adequate for use in summation-type calculations of the fission- product decay-heat source ter reacton i m r cores. However e planth n -,i ning of the file organization and content it was recognized that such a file--within the ENDF/B structure—should address itself to as broad a rang f reactor-relateo e d applications (and y implicationb , n i e us o t , other areas as well) as possible, within the limits of a realistic conten d size t intendetan s such A no .e fil s ,th o replacwa et d e such broadly based data compilation e Nucleath s a sr Data e TablSheetth r eo s f Isotopeo s (see Chapte above2 r rathet )bu o represent r carefulla t y evaluated subset of those data, oriented toward the needs of a certain identified grou f usero p d presentean s a forma n i d t readily usably b e them. The Version-IV data file which was set up to satisfy these require- ment s beeha sn discusse detain i d l elsewhere [2,32] r ENDF/B-VFo t , the content has been expanded somewhat to permit detailed information on more radiation forms.

The file is most simply discussed by reference to actual examples of specific data sets. We have chosen two examples, 85>11Kr and 128I, to serve as vehicles for the discussion. Although not actinides, these relatively simple cases provid a egoo d orientatio e filth eo t structuren . Decay-data sets. In card-image format s preparer ,a ou r fo d laboratory r "working,,o " fil85mr 128d e fo showKe r an Iar Tablen i n s A-I and A-II, respectively. (The process by which they are transcribed into final ENDF/B format will be mentioned below.) The first card con- tains the following information: Z and A values (in the form 1000 Z + A) followed immediately by an isomer flag. A blank or zero in the latter column indicates the ground state of the nucleus, a 1,2... indicates a first, secon . isomeri.. d c state. (Isomer arbitrarile ar s y restricted to nuclear states with half-lives >0.e liste1ar s d separatseca dan . e "nuclides e file.th n i ") Followin e firsg th thie chemi tn th o s car e -ar d cal symbol e spie stata d paritnumbe,th th an d n ean f o yr indicatine th g numbers of "comment cards" to follow.

Next come a sgrou f cardo p s which provid e documentatioth e r fo n and pertinent comments about the data set. These are followed by a card givin e half-lifeth g s uncertaintyit , e units,th e numbe,th f decao r y numbee e nuclidmodeth th f energd f o ro s an e y spectr e listedb o t a .

The numbering of the references is that used in the text.

299 This is followed by cards (equal in number to the indicated number of decay modes) giving the following information about each decay modetype th f decayeo : n isomeri;a whethet no c r o e daughter statth n i e r is fed; the Q-value in keV for the decay mode; its uncertainty; the branch- ing rati n percent (i oe deca th yf s uncertainty) o modeit d ;an e decaTh . y modes thur treatefa s e denotear d s followsa d , 1;3" :electron-captur e and/or e+, 2; isomeric-transition, 3; a-particle, 4; neutron, 5; sponta- neous fission, 6; and proton, 7. If one type of decay (e.g., &-) feeds both the ground state and an isomeric state in the daughter nucleus, this is treated as two distinct decay modes. Any radiations (e.g., an isomeric transition) associated with the decay of the daughter-nucleus isomeric state are listed with the daughter-nucleus decay data.

e nexTh t card contain e average-energth s y informatio n keVi n / disintegration ordere E electronth ( n i :) uncertainty)s ;it ; (E photon) ; its uncertainty; (E heavy particle) ; and its uncertainty. These average energies contai e followinth n g contributions. \E electron) includee th s average energy froprocessel al m s involving electrons, suc s e~a h, s,

conversion electrons and Auger electrons. The photon + term includes not only y-rays, but also all other electromagnetic radiation (e.g., x-rays and annihilation radiation) emittee decath n yi d process e thirTh . d energy includes contributions from a-particle emission, protons and neutrons. (It could also include spontaneous-fission fragment contributions as well, if desired.)

Next comes the listing of the various radiation spectra. Each listing consist o typetw f cardso s f o e firss Th .f theso t e containe th s following information: a normalization factor (to convert relative inten- sities to absolute intensities); its uncertainty; the number of individual transitions listed e radiatioth ; n type e averag;th r pe eV energke n (i y decay) associated with the radiation type; and its uncertainty. The numberin e radiatioth f o g n type s similai s o that r t givee n th abov r fo e decay modes, with the additional conventions: 8 denotes discrete electrons (e.g., conversion electrons); 9 denotes photons not arising as transitions between nuclear states; and 0 denotes y radiation. The second of these card types contains the specific spectral information, with one card for each individual transition. e caseExcepth sr discussefo t d belowe ,th data given here ordere listeth ar e n i :d energy s uncertainty,it ; intensity uncertaintys anit d e.-cr Fo ed .+ an .deca y (radiatio Table n se typ e, 2 e A-II o set )f tw intensit o s y informatio e givenar n : namele y th tha f o t electron-capture component of the transition and that of the 3+ component. 300 In this case averagth e e energy liste e +th tha s componeni df to t only. - transitions3 d r 6+an Fo , provisio alss i n o madr includinfo e a "multig - polarity flag," givin e spectruth g me particulashapth f o e r transition. The symbol "ID" indicates a first-forbidden unique shape; and the computer program takes this into account in its calculation of (E^^for that trans- ition. In the absence of such a notation (which is the case for allowed r first-forbiddeo n non-unique transitions n allowe)a d shap assumeds i e .

The data for radiation type 9, x-rays and annihilation radiation, e enterear d somewhat differently e firsTh . t ("normalization") cars ha d the same arrangemenothee th r radiatiofo s a t n types onlt e ,bu th y intensity data are given (since the energies in this case are in prin- ciple known). Thes e entere e orderear th n i d: K-x-ray intensitys ,it uncertainty; L-x-ray intensity, its uncertainty; annihilation radiation intensity s uncertainty,it a "sourc d an ; e flag." This latter quantity indicates the decay process with which the radiation is associated, and hence indicate e Z-valueth s f whic o se x-ray th he characteristicsar n I . Table A-I r example,fo ,o set thertw f x-rays so f whice o ear e h, on follows 3" decay (and hence is characteristic of Z=37) and one which is associated with isomeric-transition decay (and hence is characteristic of Z=36). Where measured x-ray intensities exist, they are listed here. In most cases, however, such measurement t existno d theso d s,an e intensity data will have to be calculated from the other decay-scheme data, as mentioned in Section 1.1. above e valueTh . s liste Tabln i d n faci e te A- theorear I - tical values, calculated from the decay-scheme data by the procedures out- lined in [11].

Radiation y radiation)typ( 0 e , when available always i , e th s last datt listedse a . Provisio e existenc th o madcard s r i ntw fo ef s o e for each y-ray transition. The first of these contains the following information: energy s uncertainty,it ; intensity s uncertaintyit , ; multi- polarit a sourc d an ye flag, indicating with which decay proces e y-rasth y is associated. (Although only pure multipoles are indicated, the alpha- numeric information hern describca e e mixed multipole d uncertaintiean s s in the contributions of these different multipoles.) If internal-con- version-coefficient date knowar a n (or somn ,i e casese inferred)b n ,ca , a second card is included. This contains the K-shell ICC (a|<), its uncertainty), a|_, its uncertainty, af/i and its uncertainty. To avoid confusion with the energy cards, the first 10 columns of these ICC cards (corresponding to the location of the energy value) are left blank, as shown in Table A-I. 301 More complicated decay processes can be treated within the structur f thieo s data file. Delayed-neutron emission (3~ decay followed by neutron emission), for example, would be listed as decay mode "15" - 1 r neutronfo 5 d .an - And3 r y-raya , fo emitted fro exciten a m d statf o e e nucleuth s remaining afte e neutroth r n emission would carr a sourcy e flag "15." Spectra characterize y botb d a discreth a continuou d an e s component, such as delayed neutron spectra, are listed in the following manner. The discrete components are listed as usual: energy, uncertainty; intensity, and uncertainty. For the continuous component, the energy value e chosear s n (and listed t equall)a y spaced intervals acrose th s distribution, with a sufficient number of points chosen to permit a suitably accurate representatio distributione th f o n e intensitTh . y (and where appropriate, the uncertainty) values corresponding to these energy points are listed, not in the columns where the discrete data are given, but in the next two groups of columns (corresponding to positions of a fifth and a sixth entry). In this fashion, the discrete and the continuous component e readilb n ca s y recognized.

Before the data described above are entered into ENDF/B, two separate processings are carried out. The first of these, carried out r laboratoryou t a , consists primaril n "energyf listine a dato y th n i al al g- intensity" format and affects only the listings for radiation types 8, 9, an. 0 Conversion-electrod Auger-electrod an n n spectrat , no whic e ar h liste r laborator ou s suca dn o h y file, coul e calculateb d d theoretically from the data given in this file and entered as a listing of energy and intensity values for the various lines. Where desired, lines from a given subshel e groupeb a singln s ca la d e line, wit n appropriata h e averaged energy for that shell. The x-ray and annihilation data are con- verted into a listing of energy and intensity values for the individual transitions e partiae variouTh th . datC r IC lsfo a j-ray transitione ar s e datdelete th e individuaa d th cardan dr fo s l transition e preparear s d in the format: energy, uncertainty; intensity, uncertainty; total con- version coefficient, uncertainty; and the source flag.

Following this, these date transmittear a L e NNCSBN th t o a Ct d for conversion to the standard ENDF/B format (e.g., half-lives in sec., energies in eV, etc.).

302 TABLE A-I. Sample listing of decay data forf"K 85 r decay prepared e INEth L n i format. No. of S I A Z Iir Comment Cards [36J0851 KR 1/2- 4

COMMENT D DOCUMENTATIOAN S N

PREPARED FCR FIL : E 1/75 CWR REFERENCES: Q- 1<573 REVISION OF V.APSTRA-GOVE MASS TABLES. OTHER- F.K. HOHN, H.L. TALBERTi JR. AND J.K. HALBIGt NUCL. PHYS. A152, 561 (197C).

f o . No No f o . T, a Units Decay Modes Spectra % 2 4.480 H 0.008 3 Decay Final -state Mode isomer Q a Branchina g 1 0 991.7 2.3 01. 78.8 3 0 304.47 0.03 1. 5 21.2

Select.a v/a E phot./ | 251.62 157.14

No f o . Radiation Normalization a Transitions Type 0.788 0.013 1 0 2. 1 226.1

V « V 0 2. 840.100.07 Nof o . Radiation Normalization a Entries Type

9 2 0 1. 0.792 x-raL K x-ray Intya a Intann. . . rad. Int a . source flag 2.05 0.13 1 3.96 0.23 3

No f o . Radiation E Normalizatio a n Transitions Type < Y> 0 156.35 2 1.40 s ** \ Multi polarity Source fl 15C.99 0.05 53.8 1.8 Ml 1 0.0400 0.0008 0.0045 0.0002 0.0010 O.OC01 304.47 O.C5 10.0 0.4 H4 3 0.432 0.020 C.064 0.003 0,013 C.001

303 TABLE A-II. Sample listin f decago Iy decaydat 128 r fo a , preparen i d e IMEth L format.

No. of z A IS ITT Comment Cards 53|l28| I 1 + 3 _J COMMENTS AND DOCUMENTATION

PREPARED FCR FILE: 1/75 CWR REFERENCES: Cr 1973 REVISIO F WAPSTRA-GOVO N E NASS TABLES. OTHER- SEE R.L. AUBLEt MtCL. DATA SHEETS 9, 157U973)

No. of No. of Tl/2 a Units Decay Modes Spectra 24.99 0.02 H 2 1 Decay final -state Mode i somer Q a Branching a 1 0 2127. 5. 93.9 2 0 1256. 5. 6.1

E (Eelect.) a ( phot.) a

No. of Radiation Normalization a transitions type <*»-> o 1.0 4 1 751.1 a a Efl- Ie- 544. 5. C.012 1158. 5. 1.9 1684. 5. 15. 2127. 5. 77.

No. of Radiation a Normalization transitions type (E6*> 1.0 2 2 0.CC13 a E le.c. a IB+ a 510. 5. 0.14 C.O 1258. 5. 6. C.C02

No. of Radiation Normalization a Entries type 1.0 1 9 1.28 K x-ray Int. c L x-ray Int. a ann . rad. Int. a Source flag 4.48 C.72 C.CC4 2 1 No. of Radiation Normalization transitions type

C.16 7 0 83.88 Source EY a !Y a Multi polarity flag 442.91 0.07 100. 1 526.62 0.10 9.6 1 613.1 0.5 0.015 O.OC4 1 743.5 0.2 0.9 C.I 2 969.4 0.4 2.4 0.3 1 1139.7 C.2 C.C60 0.008 1 1434.5 0.5 O.OC33 C.OCC7 1

304 APPENDIB X For the IAEA meeting on "Transactinium Isotope Nuclear Data"

Summar delayed-neutrof yo Researce n th wor t a k h Councils' Laboratory, Studsvik

G Rudstam

The Swedish Research Councils' Laboratory, Studsvik, Nykoping, Sweden

The isotope-separator-on-line facility "OSIRIS" has been used for a survey of delayed-neutron activities including accurate half-life determinations (17 new delayed-neutron precursors were detected in the course of the work). In addition to this, the energy spectra of the neutrons have been measured for 24 precursors. The results are summa- rized below d reference,an originae th o st l publication manuscriptr so s are given.

Precursor Half-life Energy spectru delayee th f mo d neutrons measured sec 79 (Zn,Ga) 2.63±0.09a) e energTh y spectru bees mha n measured b) 80 Ga 1.66±0.02a) The energy spectru bees mha n measured b) 81 Ga 1.23±0.01a) The energy spectru bees mha n measured b) 82 Ga 0.60±0.01a)

83Ga 0.3U0.01a) 85 As 2.08±0.05a) 87 Br 55.5±0.03a) The energy spectrum contains several prominent peaks, notably at energies 130, 183, 253, and 440 keV. Smaller peaks are found at 315, 400, 534 and 614 keVc) 88. Br 16.710.02a) Structur spectrue th n ei m with peak 127t sa , 160, 205, 235, 390, 540 and 670 keVd'e)

89Br 4.37±0.03a) Peaks (although not very pronounced) found at energies 270, 400, 610, 680, 7400 ,80 and 900 keV

90 Br 1.96±0.05a) Energy spectrum without discrete structure

305 Precursor Half-life Energy spectru delayee th f mo d neutrons measuredc ,se 91Br 0.541+0.005 The energy spectrum has been measured 92 Br 0.36510.007a) 92 Rb 4.3410.06 93 Kr 1.3310.05a)

93Rb 5.85±0.03a) energe Th y spectrum shows some structure with peaks at 155, 200, 235, 275, 330, 365 and 460 keVf) 94 Rb 2.69+0.02a) e energTh y spectru bees mha n measured g) 95 Rb 0.400+0.004a) The energy spectrum has been measuredg) 96 Rb 0.203+0.003a)

97Rb 0.172+0.003a)

98Rb 0.14110.010

123 Ag 0.39i0.03h 127 In 3.7610.03h) 128 (Cd.In) 0.94+0.05h) 128 In 11+1 h)

129In 0.99+0.02h) e combineTh o isomerdtw spectrue t th a s r fo m mass 129 has been measured

129In 2.510.2h)

130 h) In 0.58+0.01 The energy spectrum has been measuredb)

131 In 0.29+0.01h)

132 In 0.310.1h)

306 Precursor Half-life Energy spectrum of the delayed neutrons measured sec

133 h) Sn 1.47±0.07 134 Sn 1.04±0.02h) The energy spectrum contains one very pro- minenandV ke addition,n 0 ti 50 pea t a k , some smaller peaks at 320, 435, 760, 860 and 134 c) Sb 10.3±0.4h> 1020 keV 135 Sb 1.82±0.04h) The energy spectrum contains three large peaks at 1040, 1205 and 1450

136Sb 0.8210.02 136, Te 17.5+0.4h) The spectrum contain singla s e dominant peak andV ke additionn ,i 9 at42 ,seriea f so smaller. pea~ks at 251, 313, 466, 525, 593, keV6 76 c*d an 2 69

137I 24.25+0.12h^ spectruA m with very pronounced structure. Large peak found-ae sar t 272, 380, 487, 583, 756, 863, 965 and 1140 keV and smaller ones at 166, 325, 425, 515, 695 and 1063 keVc) 138, 6.4610.15h) Some structure particulan ,i 0 keV37 ,t a r found in the spectrum '

139I 2.30i0.05h) spectrue Th m contains some evidencr efo structure with peak 130t sa , 190, 2905 ,48 5 an56 d 140, 0.5910.01h) Indicatio d peakf no an 450t a s0 ,55 keV0 80 d^

0.48±0.03h) combinee Inth d energy spectrum I from 141 141 peaks C foune an sar d160,300,395t a d 0 ,45 witV ke h 0 anindication55 d f furtheso r f\ peak5 225t 68 sa d ,an 340 0 ,61

141Cs 22.2±0.4h)

142Cs 1.69+0.09h) Peaks are found at 370 and 750 keV'•d)

307 Precursor Half-life Energy spectru delayee th f mo d neutrons measured sec

143Cs 1.78±0.01h) Peaks are seen at 125, 180, 225, 310 and keV0 35 f')

144 hi Cs 1.00±0.0 2' Little structur somt ebu e suggestiof no 0 18 d an 0 peak13 t sa

145Cs 0.58±0.01h)

146Cs 0.343±0.007h)

The techniques used in the half-life measurements are described in

energe Th ref y. .measurement s were carrie usint ou d ga He-spectrometer ,

as describe refn . i d.

continuatioa s A studiee th f delayen o so d neutron sa serie f so

measurements of neutron branching ratios is being planned. The equipment

is completed experimente th d ,an reade sar starto yt .

References

a) G. Rudstam and E. Lund, Delayed-Neutron Activities Produced in Fission. Mass Range 79-98, to be published in Phys. Rev.

Rudsta. Shalev. G S d ) b man , wor progressn i k .

c) S. Shalev and G. Rudstam, Nucl. Phys. A230 (1974) 153.

Rudstam. Shale. G S d ) an vd , manuscript under preparatio publicationr fo n .

Rudstam. Shale. G S d ) van e , Proceeding Panea f Fission so lo n Product Nuclear Data, Bologna, 26-30 November 1973, Vol. Il367. lp .

Rudsta . Shalev. G S d ) f man , Nucl. Phys. A235 (1974) 397.

Rudstam. G Lun. d E dan ) ,g wor progressn i k .

h) ERudstam. .G Lund an d , Half-Live Delayed-Neutrof so n Activities Produced in Fission. Mass Range 122-146, submitted to Nucl. Phys.

i) G. Rudstam, S. Shalev and O.C. Jonsson, Nucl. Instr. and Methods 120 (1974) 333.

308