The Whole Body Monitor HUGO II at Studsvik Design and Operation

L. Devell, I. Nilsson and L. Venner

AKTIEBOLAGET ATOMENERGI

STUDSVIK, NYKOPING, SWEDEN 1970

AE-378

THE WHOLE BODY MONITOR HUGO II AT STUDSVIK. DESIGN AND OPERATION

L Devell, I Nils son and L Venner

ABSTRACT « The whole body monitor laboratory at Studsvik is presented with special attention to descriptions of localities, equipment, calibration and types of measurements. The main monitor, shielded by 53 tons of iron, is equipped with a 8 in. diam. x 4 in.Nal(Tl) detector and a 51 2- channel Nuclear Data analyzer and located at ground level in the Health and Safety Laboratory a few hundred metres from the various labora­ tories and reactors at Studsvik. Since the start in June 1 963 and up to January 1 969 more than 4500 measurements have been performed, most of them for radiation dose control purposes. In about 40 % of these latter measurements, in­ ternal contamination exceeding the normal detection limit of a few nCi has been observed. Only a few cases so far have exceeded the maximum permissible quarterly dose set by ICRP.

Printed and distributed in January 1970. LIST OF CONTENTS

1. INTRODUCTION 2. THE LABORATORY 2. 1 Iron room 2. 2 Subject handling facilities 2. 3 Monitor operating room 2. 4 Remaining laboratory facilities 2. 5 Ventilation and temperature control

3. GEOMETRIES, DETECTORS AND ELECTRONIC EQUIPMENT 3. 1 Standard chair geometry 3. 2 Scanning bed 3. 3 Equipment for background control 4. RADIATION BACKGROUND 4. 1 Background reduction 4. 2 Stability of background 4.3 Body influence on the background 5. CALIBRATION AND SENSITIVITY 5.1 Plastic phantoms 5.2 Ingestion of radionuclides 5.3 Intercomparisons 5. 4 Minimum detectable amount of activity

6. NORMAL MEASURING PROCEDURES 7. ACTIVITY CALCULATION METHODS 8. TYPES OF MEASUREMENTS 9. EXPERIENCES FROM THE MONITORING 10. ACKNOWLEDGEMENT 11. REFERENCES - 3 -

1. INTRODUCTION Internally deposited radionuclides are normally most effectively studied by means of whole body counters. This technique is therefore well suited for the monitoring of internal contamination of employees working with radioactive materials. The monitor HUGO II was put into regular operation in June 1 963 and was built mainly for measuring internal contamination of the employees at the nuclear research station Studsvik, which includes a 30 MW (t) testing reactor of swimming pool type, three zero power reactors, hot cells and laboratories for handl­ ing of irradiated fuels and materials, centre for radioisotope produc­ tion and facilities for storage and disposal of radioactive waste. Experience from the operation of the first whole body counter (HUGO I in Stockholm) of the company [l ] was exploited for the design of HUGO II at Studsvik. Sensitive equipment was chosen in order to meet different requirements and to facilitate special investigations. In this report the design and normal use and operation of the monitor are de­ scribed. Results from the measurements [2, 3, 4] and special studies L5, 6] are presented elsewhere.

2. THE LABORATORY The ground floor of an existing building, originally designed as 2 an assembly hall with an area of 1 43 ra , could be used for the WBC laboratory and offered some essential advantages. The building was sit­ uated close to the border of the research station area, which decreased the risk of background disturbances from the reactors and other strong activity sources as much as possible in case of incidents. Further, as no internal walls restricted the dimensions of the building blocks for the background shield, the latter could be of simpler construction, and heavy and efficient machines could be used to mount these blocks. A drawback was that no attempts could be made to reduce the background by choosing a special low-activity building material. A plan of the labo­ ratory is shown in Fig. 1 .

2. 1 Iron room The background shield is built of laminated sheets of virgin iron, Fig. 2. The inside dimensions of the monitoring room are 2. 5 x 3. 0 x

* 50 MW" (t) since October 1969 - 4 -

x 1.9 (height) m. This allows the use of two measuring geometries, one chair and one stretcher. The total thickness of walls, roof and floor is 1 6 cm and the weight 53 tons. The inside surfaces are covered with 3 mm lead sheets, lined to the iron with epoxy resin. The steel­ works produced the sheets directly with the final dimensions, so that no further work on them was necessary before mounting. The thickness of the iron sheets is 4 cm. One sheet covers the whole area of the walls, but in the roof and floor each layer consists of two sheets. The sheets are mounted to form labyrinths at the corners and other joints to avoid direct radiation from the outside. All joints are tight-welded inside and outside to avoid radioactive contamination between the sheets, which would be unremovable in case of an incident during the calibration work for example. In the inner sheet of the roof, channels are cut out to allow passage for the ventilation air. These channels are also formed as laby­ rinths to protect against external radiation. The door has two hinges with ball bearings and is very easily handled despite its weight of 2. 8 tons. It is laminated of two pieces, 4 and 12 cm thick respectively. The doorway is 0.9 x 1.9 m. A lead glass window is mounted in the door to allow observation of the patient. The window is also thought to be an ef­ ficient anticlaustrophobial feature. Finally the room is painted inside in light colours with a resistant varnish, allowing the use of efficient decon­ tamination treatment if necessary.

2. 2 Subject handling facilities The risk of contamination of the low-activity area in a WBC labora­ tory within a nuclear research station is obvious. To reduce this risk and to eliminate, as far as possible, external skin and hair contamina­ tion, the subjects have to use a special entrance procedure, including undressing and showering. After this they pass into the first room within the low-activity area, which is a dressing-room where they put on a special dress. Then they pass through the monitor operation room and enter the iron room. The personnel working in the laboratory and visitors only have to pass the operators' dressing-room, where they change to special, clean shoes before entering the monitor operation room. - 5 -

2. 3 Monitor operating room

The monitor operation room is mainly occupied by the racks and a table for the instruments for the iron room, equipment, but the space is big enough also for an operator's desk and instruments for special measurements, e. g. a thyroid counter which may be used out­ side the iron room.

2. 4 Remaining laboratory facilities

Further localities in the low-activity area are a laboratory used for service and special experiments, offices for the personnel, and a room for handling of the phantoms and solutions for calibration. The iron room is connected to the monitor operation room by an intercommunication system. It is also equipped with a separate loud­ speaker connected to the light radio program.

2. 5 Ventilation and temperature control

The laboratory is air-conditioned with an ordinary, but high quality, system including particle filters. The ventilation system is designed to give an higher air pressure in the low-activity areas than 3 in general areas. The iron room is ventilated with about 200 m of air per hour. The air is taken from a separate intake and is filtered and conditioned for humidity and constant temperature. The temperature is stabilized within ± 1 C. The air pressure in the room is + 8 mm H?0, which is 3 mm higher than the pressure in the monitor operation room.

3. GEOMETRIES, DETECTORS AND ELECTRONIC EQUIPMENT

3. 1 Standard chair geometry

As mentioned, the space in the iron room allows the use of two counting geometries. The one first put in operation and commonly used is a chair geometry, Figs. 3 and 4. The detector is a 8 in. diam. by 4 in.Nal(Tl) crystal equipped with three photomultipliers of 7. 5 cm diameter. This geometry was chosen because of its convenience from the point of view of installation, calibration and service, and of its high sensitivity to isotopes deposited in the essential parts of the body with - 6 -

good resolution. The main purpose of the measurements in this geom­ etry is to make a rough determination of the radioactivity and to identify nuclide and not to make a very careful evaluation of the amount and lo­ calization of the activity. A block diagram of the electronic equipment for the standard chair geometry is shown in Fig. 5. The three P. M. tubes are all sup­ plied with the same high voltage. Individual differences in sensitivity are compensated with potentiometers in the individual dynode voltage divider chains. The signal outputs are coupled in parallel and fed dir­ ectly to the input of the pulse height analyser. This is a Nuclear Data type 1 30 A with 51 2 channels, each with a capacity of 1 0 counts. The analyser may be used with 2 or 4 subgroups of 255 or 1 27 channels (one channel is occupied by the timer). Transfer is possible between the sub­ groups, positively or negatively, which allows background reduction and convenient comparison between different measurements. The ana­ lyser is also equipped with a data processing unit which makes it pos­ sible to get the sum of the total counts or any desired interval of a spec­ trum. Four instruments are available for presenting the result of a meas­ urement. The spectrum may be received in analogue form on an oscillo­ scope cathode ray tube and on a paper chart with an X-Y writer and in digital form with a typewriter and a strip puncher for use in a digital computer. The analyser is also coupled to a scaler which counts the to­ tal number of pulses stored in the memory of the analyser.

3. 2 Scanning bed The second geometry is a stretcher arranged with detector scan­ ning facilities. In this geometry it is possible to determine the distribu­ tion of activity within the body and, by use of collimators, localize iso­ topes to different parts of the body. It is at present equipped with one 4 in. diam. by 4 in. Nal(Tl) detector mounted under the stretcher on a stand which can be moved on rails along the stretcher by a motor. It is pos­ sible to build up different collimator and detector arrangements on this stand. The output signals from the scanner detector are also fed to the analyser and total scaler. After every 5 cm movement of the scanner - 7 -

detector the scaler value is printed out and the scaler is reset. The figures received in this way are used for a profile diagram, Fig. 6.

3. 3 Equipment for background control The iron room is equipped with a separate detector for continuous checking of the background. This detector consists of a plastic scintil­ lator 1 0 x 30 cm (diam. x height). The pulses from the background detector are fed to an amplifier followed by a counting rate meter and a chart recorder. This equipment offers a convenient method of double checking should uncertainties occur regarding the reliability of a measurement depending on background fluctuations.

4. RADIATION BACKGROUND

4. 1 Background reduction The applicability and sensitivity of a whole body counter are to a great extent a question of extreme background reductions. All materials used for the background shield were therefore carefully chosen and pre­ pared to achieve this purpose. Further measures were taken to avoid contamination from the tools and the workers. By courtesy of the steel­ works it was possible to measure the radioactivity directly in a number of steel ingots and then choose the best ones. Before the sheets were rolled, the surfaces of these ingots were burnt with weld-flames, which reduced dirt, contamination and oxides. When the mounting of the steel sheets was finished, the first back­ ground measurement resulted in 1 680 cpm within an energy region of 0 - 3. 0 MeV. The lead lining further reduced the background to 1 280 cpm. Background spectra before and after the lining with lead are shown in Fig. 7. The shield gives a total background reduction by a factor of about 50, measured by the main detector.

4. 2 Stability of background The stability of the background has been very satisfactory, with no disturbances from naturally occurring radionuclides or from nuclear weapons testing. Only on two occasions has an interference from the - 8 -

operation of the R2-reactor been observed. In these cases small peaks 41 from Ar appeared, but the disturbances were of short duration. For the calculation of internal contamination an 800-minutes count of the background overnight is used. Such a background measurement is normally used for a period of one to a few days. In the energy range 0-2.5 MeV normal background is about 1 21 0 3 cpm or 0.37 cpm per cm of detector volume. The standard deviation for single 800-minute measurements during a period of almost two months was 2. 5 %, while the counting error (a) was only 0. 1 %. The variation of background when using normal counting time, which is 20 minutes, was 0. 6 % during one day arbitrarily chosen for observation. The standard deviation observed and the counting error were equal in this case. Over a period of 6 years the background has increased sys­ tematically less than 30 cpm. 4. 3 Body influence on the background The body itself increases the background somewhat due to scat­ tering effects. At high energies the increase is slight, e. g. 2 % at 1 . 46 MeV and 4 % at 0. 67 MeV for a 70 kg phantom. In the energy band (40 - 280 keV) used for the evaluation of bremsstrahlung from pure beta emitters the corresponding increase is, however, 18 %. For the determination of body burdens of gamma emitters, backgrounds obtained without phan­ tom are used for convenience, and this causes insignificant errors with the method of calculation used. In the evaluation of beta emitters a spe­ cial technique is applied, which takes into account the different scatter­ ing effects and backgrounds for increasing body weights.

5. CALIBRATION AND SENSITIVITY

The equipment has been calibrated by means of plastic phantoms filled with solutions of different radionuclides. The calibration has been checked by measurements on volunteers who have ingested known amounts of Cs and K (HUGO I). On different occasions the accuracy has been tested by inter comparisons with other whole body counters. - 9 -

5. 1 Plastic phantoms

Four identical plastic phantoms of the type shown in Fig. 8 have been used. One of them has exclusively been reserved for background 40 1 37 measurements. Two others have been used for K and Cs respec­ tively. The last one has been filled with different ((3, v)-emitting nu- 51 1 VJ i, r T 31 ™ 54 „ 65 _ 60 , .T 24 , . ... elides such as Cr , I , Mn , Zn , Co and Na , but calibra- 35 45 tion has also been carried out with the ^-emitting nuclides S , Ca , Tl , P and Y . The peak efficiency curves are shown in Fig. 9, which is valid for the normal chair geometry. The sensitivity (pulses per disintegration) of beta emitters is also given in Fig. 9, which shows surprisingly small differences between the four geometries studied. 5. 2 Ingestion of radionuclides

Known amounts (1.6 - 2.4 |i,Ci) of a standardized solution (IAEA) 1 32 1 32 of Cs were ingested by six volunteers. The nuclide Cs has a 1 37 gamma energy of 669 keV, which is very close to the Cs 662 keV 1 37 line and is therefore suitable for checking the Cs calibration. The urine excretion after administration was measured in a standardized geometry. The activity found in urine was added to the body activity, which was calculated by means of the plastic phantom calibration. In 1 32 Fig. 1 0 the calculated values of the Cs content are compared with the actual intakes. After an initial period of homogenization in the body, agreement within 4 % was reached. The faecal excretion was not sam­ pled or measured for cesium content, but the error introduced was about 2 - 4 % according to data given by Pendleton et al. L7]. Correc­ tion for this approximation could thus give an almost perfect agreement.

5. 3 Intercomparisons

Cesium and potassium content in male subjects of normal weight and height has been compared after measurement in four counters out­ side Sweden and four counters inside the country. In Fig. 1 1 data are summarized from such intercomparisons. The figure gives the devia­ tions from the HUGO II results. The magnitudes of the deviations found were about the same as the uncertainties reported by the different la­ boratories. - 10 -

5. 4 Minimum detectable amount of activity The low radiation background due to the lead lined heavy iron shield and the high detector efficiency due to the crystal size give at normal evaluation a minimum detectable activity amount of a few nCi of radionuclides which have a high gamma-ray yield. This means that a marked photo peak must appear in the spectrogram. In Table 1 are listed the detection limits of beta emitters.

TABLE 1 Detection limits of beta emitters for 20-minute counting time and 3 CT confidence level

Detection limits Max.permis - sible quar­ MPBB ' Nuclide (y-ci) terly intake male female ' (1-tCi) (»*Ci)

H3 a) " a) 7000 1000 14 c 70 b) 35 b) 1400 300 P32 0. 2 0.1 40 6 35 s 70 35 1 50 90 Ca 20 10 20 30 Ni63 a) - a) 60 200 Sr90 2 b) 1.5 b) 0. 7 2 90 Y 0.08 0.05 40 3

Sr90-Y90 c) 0.08 0.05 0. 7 2 a) detection not possible due to extremely low beta energy b) estimated c) in equilibrium d) lowest value according to ICRP -11-

6. NORMAL MEASURING PROCEDURES The patient changes his clothes and takes a shower before the count. A dress, consisting of shirt and trousers and cotton socks, is used. Counting time is 20 minutes in the chair geometry. The pulses are sorted in 127 channels (20 keV/channel) of the analyser and, after counting, written by the typewriter and punched on the tape. The gamma spectrum can also be visualized by means of the X-Y recorder. If a substantial contamination is found, often a scanning measure - 1 31 ment is carried out. In case of significant contamination with I , a special thyroid count is made.

7. ACTIVITY CALCULATION METHODS At the beginning, the activity calculations were carried out by.hand using data from the typewriter, the appropriate detector efficiency etc. 1 37 Later, a program for calculating the Cs and potassium content by computer was designed. In the past two years all routine measure­ ments have been calculated by the computer IBM 360/30 at Studsvik. The main steps in the processing of the data are as follows:

1) Patient data and measurement identification data are punched on cards.

2) The computer subtracts the background spectrum from the gross spectrum by means of information on the punched tape.

3) The net pulses are summarized for 1 -3 energy bands around each channel of the spectrum. The energy bands cover 2-1 3 channels. The energy bands are fewer and. the band widths are narrower at low energies.

4) Compton counts are subtracted from the sum of the net counts.

5) The remaining net counts in the various bands, proportional to the radioactivity of a nuclide with the relevant gamma energy, are multiplied by the appropriate factors for conversion to PCi (100 % gamma yield is assumed). For energies corresponding to certain common nuclides the relevant gamma yield is also applied. Thus, in summary, for steps 3-5 - 12 -

x am _ N._^m±, ,l, + N. x n^, A. ( z ) imn e • E. lirtn xz-n where A. = activity of a nuclide with gamma energy corresponding to channel i

E. = detector efficiency in channel i-km to i-n for photons lmn ] c with energies corresponding to channel i 6 * / 0. 45- 10~ UCi/dpcm = conversion factof r ( —. -r—<•— — N) v countinr.oiint.inga timtimee ' e = gamma yield (calculation is always carried out for e s 1 and also for specific values < 1 corresponding to common nuclides at certain energies)

N = net pulses

i = channel under consideration

m = number of channels above channel i in the relevant energy band

n = number of channels below channel i in the band

Normally, if there are only a few peaks in the gamma spectrum, the results from the broadest energy band are used; but if interferences between peaks occur, the results from a narrower band give more ac­ curate results. A drift in the energy setting of as much as one channel, which in fact seldom occurs, causes no significant error in the activity calculations by the method described if nuclide identification is correct.

6) The primary output from the computer includes for each measure­ ment patient data, measurement identification data, a plotted net spectrum and a list of calculated activity values. For every spec­ trum channel the list gives one result (two results for channels coded for special gamma yields) for each of the 1 -3 energy bands around the channel. -13-

7) The plotted net spectrum is inspected for photo peaks and identi­ fication of nuclide. Type of nuclide and amount of activity, read from the list, are punched on cards.

8) Different computer programs are available for assorting the data stored on the cards, e. g. at certain intervals a list of contaminated employees is distributed to the opertional health physicists and to the central dose record.

8. TYPES OF MEASUREMENTS

Since June 1963 and through 1968 about 4500 measurements have been carried out mainly for dose control purposes at Studsvik. The dif­ ferent types of measurements are as follows:

1 ) Check of internal contamination of a group of about 90 subjects (1 0 % women) from different laboratories and working conditions and representing employees thought to be most exposed to internal contamination. This check is performed monthly. The composi­ tion of the group is revised periodically, but has not changed very much.

2) Measurements on acute cases in connection with incidents or ab­ normal working conditions. About 10 measurements each month in this category is a normal figure.

3) Special surveys of the employees at selected laboratories.

4) Control group measurements.

As a basis for the measurements of internal contamination a con­ trol group is measured quarterly. This group usually consists of 1 1 male and 8 female employees not working on radioactive materials. The male subgroup has been measured since 1959, at first in HUGO I and since 1963 in HUGO II, and the female since 1963. An attempt is made to keep the same individuals in the group, but of course changes occur, e. g. when employment ends. 1 37 The Cs content of the group is presented in Fig. 1 2. - 14 -

The increase found in the middle of 1968 was due to reindeer meat dishes at the Studsvik canteen. Fig. 13 shows the total number of measurements for different years and subdivided into different relative body burden categories.

9. EXPERIENCES FROM THE MONITORING

In spite of the relatively large number of contaminations found at HUGO II, only a few cases exceeding the recommendations of ICRP have been recorded. The heaviest body burdens, up to a few M.Ci, have been from the nuclides I , Cd , I and Br . Special surveys have shown that small amounts of activity may often be found in the employees' personal clothing and, less surprising­ ly, on their hands. Contaminated hands are shielded with lead during whole body counting in order to eliminate the disturbance in the meas­ urement of internal contamination. At Studsvik almost all of the supervision of internal contamination is carried out by the whole body monitor. Only for a few elements, e. g. tritium, uranium and plutonium, is urine sampling and analysis used. Except for these latter cases the whole body monitor gives a true picture of the body burden, which urine sampling and analysis seldom does. Further, due to the rapidity and sensitivity of the monitor, rather de­ tailed information can be obtained about the contamination situation both in general and in special cases. This allows appropriate measures against unsatisfactory working conditions to be taken at an early stage.

10. ACKNOWLEDGEMENT

The authors wish to express their sincere thanks to their former collaborator, Mr. I. 6. Andersson, for his inspiring guidance of the pioneering research work in the field of human body counting within the company. - 15 -

11. REFERENCES ANDERSSON, I O and NILSSON, I, Measurement of radioactivity in the human body. I9 60. (AE-45)

DEVELL, L, VENNER, L and MANDAHL, B, Monitoring for internal contamination of nuclear energy per­ sonnel. First Nordic radiation protection conf. Proc. Stockholm 6-9 Febr. , 1966. Ed. by K Liden and E Lindgren. (Acta Radiol. Suppl. 254) Stockholm 1966, p. 111. ANDERSSON, I O, NILSSON I and ECKERSTIG, K, Measurement of gamma radioactivity in a group of control subjects from the Stockholm area during 1959-1963. 1963. (AE-119) CARLSSON, J and WAHLBERG, T, Report on the personnel dosimetry at AB Atomenergi during 1968. 1969. (AE-369) ANDERSSON, I O and NILSSON, I. Exposure following ingestion of water containing radon-222. Assessment of radioactivity in man. Proc. symp. Heidelberg, 11-1 6 May 1964. (IAEA) Vienna 1964. Vol. 2, p. 317.

VENNER, L and DEVELL, L, Retention of Xe*33 after inhalation. Paper prepared for the Nordic Radiation Protection Conf. Oslo 2-4 Oct. 1968. (In Swedish). PENDLETON, R C et al. , A trophic level effect on l^Cs concentration. Health Phys. 11 (1965) p. 1503.

Fig. 1. PLAN OF THE LABORATORY. Fig. 2. SECTION THROUGH THE IRON ROOM. SCALE I :25.

Fig. 3. THE STANDARD CHAIR GEOMETRY. DIMENSIONS IN mm. SCALE 1 :1 0 Fig. 4. THE LABORATORY.

IRON ROOM MONITOR OPERATION ROOM

CAE LE ! ! HV BC) X 1 | SUPPLY i j 1 1

3 PK = S DUMC)N T PULSE SCALER 6363 HEIGHT (TOTALS) Nal(Tl)- CRYSTAL ANALYZER 8in.DIAM. NUCLEAR DATA DISPLAY ND 130 A OSCILLOSCOPE

TAPE X-Y PUNCHER RECORDER

TAPE TYPE­ READER WRITER

Fig. 5. BLOCK DIAGRAM OF THE ELECTRONIC EQUIPMENT FOR THE CHAIR GEOMETRY. 4C- \

35- 1 DAY AFTER CONTAMINATION ,—» 3 DAYS —. o-.-o 7 DAYS E 30 O UJ 25

i-20h z 3 O ° 151-

10-

• a LEAD COLLIMATOR

£in.«DIAM.*Ain. NaKTl) CRYSTAL Fig. 6. EXAMPLE OF PROFILE DIAGRAM: CONTAMINATION WITH I 131 1 1 1 1 1

— —

••\ BEFORE LEAD LINING • * * —* * — t * ^ »*t ** l\ «/\ * 1 \j^ \ * * \ * lf \ vv* \ -

\ FINAL BACKGROUND —

*C *

1 1 1 1 1 500 1000 1500 2000 2500 ENERGY (keV)

Fig. 7. BACKGROUND SPECTRUM OF THE 8 in. DIAM. BY 4 in. Nal(Tl) DETECTOR. INNER DIMENSIONS (mm) VERTICAL CROSS SECTION LENGTH

HEAD ELLIPSE 190x140 2,00

NECK CIRCLE * 130 100

OVER-ARM CIRCLE 0 100 300

UPPER-BODY ELLIPSE 200x300 400

LOWER PART OF ELLIPSE 200x360 200 THE BODY

FOREARM CIRCLE cf 76 450

THIGH CIRCLE f 150 400

LEG CIRCLE 0 12C 400

MATERIAL 4 mm POLYETHYLENE

Fig. 8. PHANTOM FOR CALIBRATION. T 1 1 r T r -I 1 1 1 1 r GAMMA PEAK EFFICIENCY

TOTAL BODY

32 ,90 -1Ca iTl i i

BETA 0-280 keV BAND EFFICIENCY 1 LOWER PART OF THE BODY 2 THIGH 3 THIGH-BONE U TOTAL BODY

J I I L J I I L J L 1

GAMMA PHOTON ENERGY OR MAXIMUM BETA ENERGY (MeV)

Fig. 9. EFFICIENCY OF THE 8 in.DIAM. BY 4 in. Nal(Tl) DETECTOR. i—i—r

SUM OF BODY BURDEN AND EXCRETED *•*-». ACTIVITY

BODY BURDEN DETERMINED BY WBC AND STANDARD CALIBRATION

ACTIVITY EXCRETED^ WITH URINE 1_J L 0.1 h 1h 5h Id 5d lOd 25d

TIME AFTER INGESTION

Fie. 10. CONTROL OF THE CALIBRATION AFTER Cs132 INGESTION. 00 . z o to a: 137 °i, Cs a: o2-

/. // / /

-20 -15 -10 +5 HO +15 +20 DEVIATION FROM HUGO IT RESULTS IN PERCENT

to z o to POTASSIUM OS. u. <3 °2 UJ u' CD QC '/• 2 LU , z z '/ / T T -20 •15 -10 0 +5 +10 + 15 >20 DEVIATION FROM HUGO n RESULTS IN PERCENT

Fig. 1 1 . INTERCOMPARISONS OF Cs1 3? AND POTASSIUM CONTENTS. 40

30 CONTROL GROUP CHANGED

o c CO £20

Li. O

LU Q OH Z> CO 10 >- Q O \ ,« / CD v / v /

0L J L 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968

Fig. 12. THE Cs 137 CONTENT IN THE CONTROL GROUP DURING 1959 - 1968. 1500

(/) 1000

LU

LU a: CO < LU

LL O

C£ 500 LU CO

1963 1964 1965 1966 1967 1968

Fig, 1 3. NUMBER OF MEASUREMENTS AND CONTAMINATIONS.

LIST OF PUBLISHED AE-REPORTS 345. Application of the microwave discharge modification of the WHzbach tech­ nique for the tritium labelling of some organics of biological interest. By T. Gosztonyi. 1968. 12 p. Sw. cr. 10:-. 1-300 (See the back cover earlier reports.) 346 A comparison between effective cross section calculations using the Inter­ mediate resonance approximation and more exact methods. By H. Hagg­ 301. The present status of the half-life measuring equipment and technique at blom. 1969. 64 p. Sw. cr. 10:-. Studsvik. By S. G. Malmskog. 19S7. 26 p. Sw. cr. 10:-. 347. A parameter study of large fast reactor nuclear explosion accidents. By J. R. 302. Determination of oxygen in aluminum by means of 14 MeV neutrons with Wiesel. 1969. 34 p. Sw. cr. 10-. an account of flux attenuation in the sample. By D. Brune and K. Jirlow 348. Computer program for inelastic neutron scattering by an anharmonic crystal. 1967. 16 p. Sw. cr. 10:-. By L. Bohlin, I. Ebbsjo and T. Hogberg. 1969. 52 p. Sw. cr. 10:-. 303. Neutron elastic scattering cross sections of the elements Ni, Co, and Cu between 1.5 and 8.0 mev. By B. Holmqvist and T. Wiedling. 1967. 17 p 349. On low energy levels in '"W. By S G. Malmskog, M. Hojeberg and V. Sw. cr. 10:-. Berg. 1969. 18 p. Sw. cr. 10:-. 304. A study of the energy dependence of the Th232 capture cross section in 350. Formation of negative metal ions in a field-free plasma. By E. Larsson. 1969. 32 p. Sw. cr 10:-. the energy region O.I to 3.4 eV. By G. Lundgren. 1967. 25 p. Sw. cr. 10:-. 305 Studies of the reactivity effect of polythene in the fast reactor FRO. By L. 351. A determination of the 2 200 m/s absorption cross section and resonance integral of arsenic by pile oscillator technique. By E. K. Sokolowskl and R. I. Tiren and R. Hakansson. 1967. 25 p. Sw. cr. 10:-. Bladh. 1969. 14 p. Sw. cr. 10:-. 306. Final report on IFA-10, the first Swedish instrumented fuel assembly Irra­ 352. The decay of '»'Os. By S. G. Malmskog and A. Backlin. 1969. 24 p. Sw. diated in HBWR, Norway. By J-A. Gyllander. 1967. 35 p. Sw. cr. 10:-. cr 10:-. 307. Solution of large systems of linear equations with quadratic or non-qua­ 353. Diffusion from a ground level point source experiment with thermolumine- dratic matrices and deconvolution of spectra. By K. Nygaard. 1967. 15 p. scence dosimeters and Kr 85 as tracer substance. By Ch. Gyllander, S. Sw. cr. 10:-. Hollman and U. Widemo. 1969. 23 p. Sw. cr. 10:-. 308. Irradiation of superheater test fuel elements in the steam loop of the R2 354. Progress report, FFN, October 1, 1967 - September 30, 1968. By T. Wied­ reactor. By F. Ravndal. 1967. 94 p. Sw. cr. 10:-. ling. 1969. 35 p. Sw. cr. 10:-. 309. Measurement of the decay of thermal neutrons in water poisoned with the 355. Thermodynamic analysis of a supercritical mercury power cycle. By A. S. non-1/v neutron absorber cadmium. By. L. G. Larsson and E. Motler. 1967. Roberts, Jr., 1969. 25 p. Sw. cr. 10:-. 20 p. Sw. cr. 10:-. 356. On the theory of compensation in lithium drifted semiconductor detectors. 310. Calculated absolute detection efficiencies of cylindrical Nal (Tl) scintill­ By A. Lauber. 1969. 45 p. Sw. cr. 10:-. ation crystals for aqueous spherical sources. By. 0. Strindehag and B. Tollander. 1968. 18 p. Sw. cr. 10:-. 357 Half-life measurements of levels in "As. By M. Hojeberg and S. G. Malmskog. 1969. 14 p Sw. cr. 10:-. 311. Spectroscopic study of recombination in the early afterglow of a helium plasma. By J. Stevefelt. 1968. 49 p. Sw. cr. 10:-. 358. A non-linear digital computer model requiring short computation time for studies concerning the hydrodynamics of the BWR. By F. Reisch and G. 312. Report on the personnel dosimetry at AB Atomenergl during 1966. By J. Vayssier. 1969. 38 p. Sw. cr. 10: -. Carlsson and T. Wahlberg. 1968. 10 p. Sw. cr. 10:-. 359. Vanadium beta emission detectors for reactor in-core neutron monitoring. 313. The electron temperature of a partially Ionized gas in an electric field. I. D. Andersson and B. Sbderlund. 1969. 26 p. Sw. cr. 10:-. By F. Robben. 1968. 16 p. Sw. cr. 10:-. 360. Progress report 1968 nuclear chemistry. 1969. 38 p. Sw. cr. 10:-. 314. Activation Doppler measurements on U238 and U235 in some fast reactor 361. A half-life measurement of the 343.4 keV level in "sLu. By M. Hojeberg spectra. By L. I. Tiren and I. Gustafsson. 1968. 40 p. Sw. cr. 10:-. and S. G. Malmskog. 1969. 10 p. Sw. cr. 10:-. 315. Transient temperature distribution in a reactor core with cylindrical fuel 362. The application of thermoluminescence dosimeters to studies of released rods and compressible coolant. By H. Vollmer. 1968. 38 p. Sw. cr. 10:-. activity distributions. By B-l. Ruden. 1969. 36 p. Sw. cr. 10:-. 316. Linear dynamics model for steam cooled fast power reactors. By H. Voll­ 363. Transition rates in "'Dy. By V. Berg and S. G. Malmskog. 1969. 32 p. mer. 1968. 40 p. Sw, cr. 10:-. Sw. cr. 10:-. 317. A low level radioactivity monitor for aqueous waste. By E. J. M. Ouirk. 364 Control rod reactivity measurements in the Agesta reactor with the pulsed 1968. 35 p. Sw. cr. 10:-. neutron method. By K. Bjoreus. 1969. 44 p. Sw. cr. 10:—. 318. A study of the temperature distribution In UOi reactor fuel elements. By 365. On phonons in simple metals II. Calculated dispersion curves in aluminium. I. Devoid. 1968. 82 p. Sw. cr. 10:-. By R. Johnson and A. Westin. 1969. 124 p. Sw. cr. 10:-. 319 An on-line water monitor for low level ^-radioactivity measurements. By E. J. M. Quirk. 1968. 26 p. Sw. cr. 10:-. 336. Neutron elastic scattering cross sections. Experimental data and optical model cross section calculations. A compilation of neutron data from the 320. Special cryostats for lithium compensated germanium detectors. By A. Studsvik neutron physics laboratory. By B. Holmqvist and T. Wiedling. Lauber, B. Malmsten and B. Rosencrantz. 1968 14 p. Sw. cr. 10:—. 1969. 212 p. Sw. cr 10:-. 321. Stability of a steam cooled fast power reactor, its transients due to mode­ 367. Gamma radiation from fission fragments. Experimental apparatus — mass rate perturbations and accidents. By H. Vollmer. 1968. 36 p. Sw. cr. 10:—. spectrum resolution. By J. Higbie. 1969. 50 p. Sw. cr. 10:-. 322. Progress report 1967. Nuclear chemistry. 1968. 30 p. Sw. or. 10:-. 368. Scandinavian radiation chemistry meeting Studsvik and Stockholm, Sep­ 323 Noise in the measurement of light with photomultipliers. By F. Robben. tember 17-19, 1969. By H. Christensen. 1969. 34 p. Sw. cr. 10:-. 1968. 74 p. Sw. cr. 10:-. 369. Report on the personnel dosimetry at AB Atomenergi during 1968. By 324. Theoretical investigation of an electrogasdynamic generator. By S. Palm- J. Carlsson and T Wahlberg. 1969. 10 p. Sw. cr 10:-. gren. 1968. 36 p. Sw. cr. 10:-. 370. Absolute transition rates in "»lr. By S G. Malmskog and V. Berg. 1969. 325. Some comparisons of measured and predicted primary radiation levels In 16 p. Sw. cr. 10:-. the Agesta power plant. By E. Aalto, R Sandlin and A. Krell. 1968. 44 p. 371. Transition probabilities in the 1/2 + (631) Band in !3SU. By M. Hojeberg and Sw. cr. 10:-. S. G. Malmskog. 1969. 18 p. Sw. cr. 10:-. 326. An investigation of an irradiated fuel pin by measurement of the production 372. E2 and M1 transition probabilities in odd mass Hg nuclei. By V. Berg, A. of fast neutrons in a thermal column and by pile oscillation technique. Backlin, B. Fogelberg and S. G. Malmskog. 1969. 19 p. Sw. cr. 10:-. By Veine Gustavsson. 1968 24 p. Sw. cr. 10:-. 373. An experimental study of the accuracy of compensation in lithium drifted 327. Phytoplankton from Tvaren, a bay of the Baltic, 1961-1963. By Torbjorn germanium detectors. By A. Lauber and B. Malmsten. 1969. 25 p. Sw. Willen. 1968. 76 p. Sw. 10:-. cr. 10:-. 328. Electronic contributions to the phonon damping in metals. By Rune Jonson. 374. Gamma radiation from fission fragments. By J. Higbie. 1969. 22 p. 1968. 38 p. Sw cr. 10:-. Sw. cr. 10:-. 329. Calculation of resonance interaction effects using a rational approximation 375 Fast Neutron Elastic and Inelastic Scattering of Vanadium. By B. Holm­ to the symmetric resonance line shape function. By H. Haggblom. 1968. qvist, S. G. Johansson, G. Lodin and T. Wiedling. 1969. 48 p. Sw. cr. 10:-. 48 p. Sw. cr 10:-. 376. Experimental and Theoretical Dynamic Study of the Agesta Nuclear Power 330. Studies of the effect of heavy water in the fast reactor FRO. By L. I. Tiren, Station. By P.-A. Bliselius, H. Vollmer and F. Akerhielm. 1969. 39 p. Sw. R. Hakansson and B. Karmhag. 1968. 26 p. Sw. cr. 10:-. cr. 10:- 331. A comparison of theoretical and experimental values of the activation Dop­ 377. Studies of Redox Equilibria at Elevated Temperatures 1. The Estimation pler effect in some fast reactor spectra By H. Haggblom and L. I. Tiren. of Equilibrium Constants and Standard Potentials for Aqueous Systems up 1968. 28 p. Sw. cr. 10:-. to 374°C. By Derek Lewis. Sw. cr. 10:- 332. Aspects of low temperature irradiation in neutron activation analysis. By 378. The Whole Body Monitor HUGO II at Studsvik. Design and Operation. D. Brune. 1968. 12 p. Sw. cr. 10:-. By L. Devell, I. Nilsson and L. Venner. 1970. 26 p. Sw. cr. 10:-. 333. Application of a betatron in photonuclear activation analysis. By D. Brune, S. Mattsson and K. Liden. 1968. 13 p. Sw. cr. 10:-. 334. Computation of resonance-screened cross section by the Dorix-Speng system. By H. Haggblom. 1968. 34 p. Sw. cr. 10:-. 335. Solution of large systems ot linear equations in the presence of errors A constructive criticism of the least squares method. By K. Nygaard. 1968. 28 p. Sw. cr. 10:-. 336. Calculation of void volume fraction in the subcooled and quality boiling regions. By S. Z. Rouhani and E. Axelsson. 1968. 26 p. Sw. cr. 10:—. List of published AES-reports (In Swedish) 337. Neutron elastic scattering cross sections of iron and zinc in the energy region 2.5 to 8.1 MeV. By B. Holmqvist, S. G. Johansson, A. Kiss, G. Lo- 1. Analysis be means of gamma spectrometry. By D, Brune. 1961. 10 p. Sw. din and T. Wiedling. 1968. 30 p. Sw. cr. 10:-. cr. 6:-. 338. Calibration experiments with a DISA hot-wire anemometer. By B. Kjell- 2. Irradiation changes and neutron atmosphere in reactor pressure vessels- strtim and S. Hedberg. 1968. 112 p. Sw. cr. 10:-. some points of view. By M. Grounes. 1962. 33 p. Sw cr. 6:—. 339 Silicon diode dosimeter for fast neutrons. By L. Svansson, P. Swedberg, 3. Study of the elongation limit in mild steel. By G. Dstberg and R. Atter- C-O. Widell and M. Wik. 1988. 42 p. Sw. cr. 10:-. mo. 1963 17 p. Sw. cr. 6:-. 340. Phase diagrams of some sodium and potassium salts in light and heavy i. Technical purchasing in the reactor field. By Erik Jonson. 1963. 64 p. water. By K. E. Holmberg. 1968 48 p. Sw. cr. 10:-. Sw. cr. 8:-. 341. Nonlinear dynamic model of power plants with single-phase coolant reac­ 5. Agesta nuclear power station. Summary of technical data, descriptions, tors. By H. Vollmer. 1968. 26 p. Sw. cr. 10:-. etc. for the reactor. By B. Lilliehook. 1964. 336 p. Sw. cr. 15:-. 342. Report on the personnel dosimetry at AB Atomenergi during 1967. By 1. 6. Atom Day 1965. Summary of lectures and discussions. By S. Sandstrom. Carlsson and T. Wahlberg. 1968. 10 p. Sw. cr. 10:-. 1966. 321 p. Sw. cr. 15:-. 343. Friction factors in rough rod bundles estimated from experiments in parti­ 7. Bu-.lding materials containing radium considered from the radiation pro­ ally rough annuli - effects of dissimilarities in the shear stress and tur­ tection point of view. By Stig O W. Bergstrom and Tor Wahlberg. 1967. bulence distributions. By B. Kjellstrom. 1968. 22 p. Sw. cr. 10:-. 26 p. Sw. cr 10:-. 344. A study of the resonance interaction effect between U,U and "'Pu in the Additional copies available Irom the library of AB Atomenergi, Fack, S-611 01 lower energy region. By H. Haggblom. 1968. 48 p Sw. cr. 10:—. Nykdping, Sweden.

EOS-tryckerierna, Stockholm 1970