&

MINISTER FOR RESOURCES AND ENERGY   SENATOR GARETH EVANS Q.C.

z7 April I9ti7

3Â±/87

RADIOLOGICAL SAMPLING AT OAR VALLEY

1 have received a report (attached ) on levels or

radioactivity in soil samples taken by the Australian

Radiation Laboratory (ARLJ in the vicinity or Oak Valley,

on Aboriginal land north-west of the Maralinga former

atomic test range in Soutn Australia.

I received the report on 23 April and on the same day sent

a copy to the Premier or Soutn Australia whose Government

is responsioie for tiie welfare of both tne Aboriginal

people at Oak Valley and the school teachers based at

Yalata who travel to dan Valley.

Tne samples were taken in response to a request "from the

South Australian Department of Education after teachers at

Oak Valley expressed concern aoout the possibility of

local radiological hazards linked to tne british atomic

tests and minor trials which toox place during the 1950s

and 1960s.

The analyses in the report do not point t o 'any significant

radiological hazard to the local population, but do reveal

the presence of low levels of both naturally occurring and

introduced radionuclides.

In particular, a loose cluster of five of the samples

taken on the roau to Oax Valley {but well outside the

community area) indicated tne presence of minute

quantities of plutonium and one of the four samples taken

inside the community area also indicated a small trace of

plutonium. Ã¢ÂÂ

There has oeen no previous indication ot introduced

radionuclides at tnese locations, and tne rinding or

piutoniui.i in these samples was unexpected.

in all cases the levels of plutonium detected m  tne soil

samples were significantly lower than levels considered

safe for continuous habitation.  The hignest concentration

or plutonium detected in the ARL samples was U.UcS

becguerels per gram (Bg/g), while the concentration in tne

sample within Oak Valley Community area was U.U1 oq/g.

Tnese results should be considered against the figure of

U.b dg/g proposed oy the uti Environmental Protection

Agency (EPA) as the level below wnich land can be

considered suitable for unrestricted use.

I understand that Soutn Australian orficials have during

the past 24 hours informed both the Oak V a n e y  Community

and the teachers at Yalata of the ARL results.

ARE scientists will visit Oak Valley this week and carry

out a local ground survey with field instruments in and

around the community area to estaolisn whether m e r e  is m

fact any contamination at levels which constitute a

potential radiological hazard.  The sensitivity or the ARL

field instruments is such that tney can detect plutonium

at concentrations greater than U.  b Bq/g, tnat is, down to

the EPA figure. Regardless or wnetner tne r leld

measurements detect any traces or plutonium, further soil

samples will be taken for laboratory analyses at ARL which

will detect the presence of radionuclides at mucn lower

levels than is possible with field instruments.

- 2 -

- 3 -

'  >

Tne concentrations or radionuclides detected oy ARE are

well below acceptable safety levels ana snuala not ue a

cause for a lari,i in eitner the aoorlyinai or nou-Aoor lyinai

populations in tiie area. A meet m y  or tne maralinya

Consultative -  Group, comprising representatives of

Aboorlyinai groups including the Oak Valley Community and

representatives of the Commonwealtn and relevant State

Governments will ue convened at Oak Valley as soon as

possible to explain and discuss the situation.

* * * * *

CANBERRA

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^MRepor t vn He n < )  z"S’ / levels 1n Sol) Semples from the Road  / o y  z X /  to Oak Valley. In the accompanying table (Table 1) we present results of our analyses for   ra d io a c tiv ity  1n the 25 soil samples collected from along the road to Oak   V alley, and at Oak Va1  ley I t s e l f .  These samples were obtained on Wednesday   1st April 1967 In the presence of Ye lata  school teachers Mr Graeme Robertson,   Ms Kathy Heath and Mr Lindsay May. The sampling sites are shown on the accompanying map, with samples numbers   21 , 22, 23 and 24 being from soil nearby to the water tanks, school yard,   school house and an undisturbed area respectively at Oak Valley. Sample   number 25 was from a point oh the Cook r o a d . 10 km west of the Oak Valley   road. Just to recap, each soil sample was a composite of five Individual   samples (to ensure that they are representative) each of 84 m m  diameter and 25   m m  depth. This composite sample was sieved to less than 1 mm size (to remove   small stones) and split (homogenised). Approximately $50 g of each sample was   counted for a long period (generally 12 hours or more) by high-resolution   gamma-ray spectrometry. The results 1n Table 1 present the amounts (activities) of radioactivity   in each gram of soil for the various radionuclides (radioactive elements)   detected by the gamma-ray spectrometry. The unit of amount of rad1oectfv1ty   1s the becquerel, Bq. Uranium-238 (23flU) occurs naturally 1n all soils, end radium-226 (226Re) and lead-210 (210Pb) ere naturally-occurring 'daughterÂ· nuclides resulting from the radioactive decay of urenlum-238. The other major  Ã¢ÂÂ¢  ÃÂ¯ 232  naturally-occurring radioactive element in soil 1s thorium-232 Th) which   1s not detected by gamma-ray spectrometry. However, It has two Ã¢ÂÂ daughtersÂ·,   thorium-228 (i26Th) and radium-226 (“ Â®*a) which are both 1n equilibrium   (same amount Of radioactivity 1n terms of 6q/g) with the parent thorium-232. 2 I he I eve IS 04  ( ofl ÃÂ· , ÃÂ»ÃÂ¹  1 1  vl l y  1  uunU in Hie iV' s o l i  samples -tor {ItÂ·,  eve , 238 226 ?! 0 ??6 )?6  fidlur'a liy-or.cur r tng r a d i o n u c l i d e s  ( U, R.i, Pi), Ra . Th) show some v a r i a b i l i t y  w i t h  s o i l  t y p e ,  as e xpect ed, but e l l  a re  c o n s i s t e n t  w i t h t l i r  rdfiyi 01  values found 1n s o i l  t hr ou g ho u t A u s t r a l i a . 40  PoLasstum-40 ( X) also occurs wi d el y 1n n a t u re , as a component of   s o i l s ,  d ri n k in g  water and even the human body. Again, the le vels detected 1n   the 28 s oi l samples are t y p i c a l  f o r  A u s t r a l i a n  s o i l s . Ã¢ÂÂ¢  137  The other two radionuclides detected, caes1um-137 ( cv) and 2 A1  amer1clum-241 ( Am), are not n a tu ra lly  occurring. Caesium-137 results from fa llo u t from atomic explosions, and the levels detected 1n the present  s o il samples probably contain components from both the Marellnga tests and global f a l l o u t  (e .g . French atmospheric tests 1n the 1970's). However,  although detectable, the levels of caesium-137 are extremely low and well  w ithin acceptable lim its . - 739  Amerlcium-241 1s the Indicator of plutonium-239 ( PuJ which 1s not   detected d ir e c tly  by gamma-ray spectrometry. The levels of amer1c1um-24l reported 1n Table 1 are Just at the limit of detection for gamma-ray spectrometry Involving long counting times. If 1t 1s assumed that the material originates from the Vixen 6 trials at Taranaki, then one must multiply by a factor, which we have established from other measurements to be   about ten, to get the p1uton1um-Z39 activities (e.g. the value of 0.008 Bq/g   for sample 14 translates to 0.08 6q/g of pluton1um-239). These levels are   extremely low and are not considered, 1n our assessment, to represent any   discernible health risk. i To place these small concentrations of plutonium 1n context, we note that   we measure levels of several hundred becquerel per gram of pluton1uei-239 within a few hundred metres of the test site at Taranaki. A very conservative   figure of 0.5 Bq/g of plutonium has been proposed by the U.S. environmental   Protection Agency In their 19B5 Interim recommendations as being the level   below which land can be considered suitable for unrestricted use. The U.S.   Department of Energy, 1n cleaning up Pacific Island tost sites, has used plutonlum-239 concentration levels of 1.5 Bq/g es being Safe for continuous   habitation, 3 Bq/g at safe for agricultural use, and 6 Bq/g as safe for casual   visits. Therefore, the levels of plutonium In the present soil semples are clearly w e l l  below accep table safety l e v e l s . ÃÂ¾} v WÂ«Y ÃÂ¯ ÃÂ¿ÃÂ±ÃÂ¹ÃÂÃÂ r I ion , the ÃÂ(ÃÂ ÃÂÃÂ½ 11  )(?$ ef natural I y  are VimUlai lo or greater than ttie acIlylTte-s of juitvi on I um- Z39 1n a l l  samples   except ny no. 14. furthermore, the hea 1-th r t i k i  from I n h a l a t io n  or Ingestion of many of these n a tu r a ll y - o t c u r r l n g  elements are s i m i l a r  to those for equivalent a c t i v i t i e s  of amertctum-241 or p iuton Ium-239. As an approximate guide, the amounts of r a d io a c tiv ity  required to be Inhaled or Ingested, fo r   some selected radionuclides, to give an e ffe c tiv e  dose of one m l l l l s l e v e r t   (mSv) are given 1n Table 2. The risk of contracting e fa ta l cancer from a received dose of one m l l l l s l e v e r t  1$ 1 1n 100,000. This Is the same ris k  as   t h a t  of contracting lung cancer from smoking 100 c ig a re tte s . The ris k  of   being k il l e d  1n a car accident 1n Australia Is about 1 1n 5000 per year. The data 1n Table 2 I l l u s t r a t e  th a t In ha la tion 1s the most Important exposure route fo r plutonium 1n s o ils , and while a detailed c a lc u la tio n  Is quite complicated, 1t 1s f a i r l y  straightforw ard to estimate roughly the significance of the concentrations we have measured. Typical dust loadings 1n   the MaraUnga area under moderately windy conditions are about 0.01 mg per   cubic metre (the greatest dust loading able to be to le rated  by humans fo r short periods Is about 10 mg per cubic m etre). The average human breathes about 9000 cubic metres of a i r  per year, and could therefore Inhale under such   ty p ic a l conditions 9000 x 0.01 Â« 90 mg of dust 1n a year. For the most active sample, assuming the concentration of   plutonium 1ÃÂ· the respirable fraction 1s the same as that 1n the soil, this   leads to a worst-case Intake of 0.09 x 0.06 Â« 0.007 Bq per year. You will see from Table 2 that such an Intake of plutonium would   not be significant, and In fact corresponds to an effective committed dose   equivalent of 0.0006 mSv. Normal background radiation levels contribute of   the order of 1 to 2 mSv per year. fteoff Williams   Peter Burns 22 A p ril 19ÃÂ7 4 - Tablc _1 A c t i v i t i e s  { I n  B q /y ) of rad 1unuc1  Ides detected  by gamma-ray spectrometry   1n.so1l samples col fee ted beside the road to Oak Va1 ley and ot "Oak V a l l e y .  NO   Indicates hut d ete cted . T  he p r e c is io n  of the counting measurements 1s   g e n e r a l ly  of the order of 10 percent or b e t t e r . Sample No. 23%  226Ã¢ÂÂ  Rfl  ?ib v   Pb Ra  22B Th 40K  137 C$  241 Am 1 0.011 0.009 0.045 0.015 0.014 NO 0.008 NO 2 0.00b 3 4 0.015 0.009 0.046 0.015 0.014 0.095 0.006 NO 0.010 0.042 0.014 0.014 0.087 0.005 NO 5 6  7 8 0.023 0.009 0.059 0.013 0.014 0.10V- 0.004 NO 9 0.010 0.0120.059 0.018 0.017 0.093 0.007 NO 10 0.009 0.008 0.039 0.011 0.017 0.069 0.008 NO 11 0.011 0.009 0.040 0.011 0.011 0.065 0.007 0.002 12 0.013 0.010 0.035 0.013 0.013 0.090 0.005 NO 13 0.020 0.014 0.046 0.019 0.020 0.148 0.007 0.002 14 0.012 0.014 0.050 0.019 0.018 0.143 0.005 0.008 15 0.017 0.0140.041 0.020 0.019 0.153 0.003 0.002 16 0.008 0.015 0.044 0.020 0.021 0.165 0.004 NO ÃÂ 0.013 0.014 0.069 0.020 0.020 0.165 0.006 0.003 18 0.012 0.009 0.058 0.012 0.013 0.091 0.008 NO 19 0.008 0.010 0.030 0.019 0.015 0.105 0,003 NO 20 0.012 0.0090.039 0.014 0.015 0.130 0.005 ND 21 0.010 0.010 0.027 0.013 0.011 0.060 0.002 NO 22 0.009 0.0090.032 0.01$ 0.014 0.113 0.004 0.001 23 0.013 0.0110.046 0.016 0.016 0.114 0.005 NO 24 0.007 0.0070.018 0.012 0.011 0.093 0.002 ND 25 0.013 0.012 0.034 0.019 0.018 0.938 0.004 NO * NOTE: Severalsamples have still to be measured and these lines are left blank In this draft Table. -5- 'X lrtbif; ? "The act W i t t e s  (Bq) of selected ra d io n u c lid e s, for the forms found 1n   Soil  1 s , icyu 1  red to Uv I n ha l ed  or I ngested to give en e f f e c t i v e  dose of 1 mSv. Rad t onuc1Ide Inhalation In g es ti o n 23flu 40 160,000 226Ra 400 4,000 ?’ Â°p D 200 800 232   c Th 4 1,400 228 Th 12 10,000 228 Ra 800 ‘ 2,000 40 It 200,000 200,000 137, CS 120,000 80,000 241 An 8 1 ,800 239. Pu 12 60,000 l i V l k n l  . Â·. ’.  Ã¢ÂÂ   0 D 2 A -  icKoÂ«\ Ã¢ÂÂ¢O P A O to lo  < v t p s J * t. )  ’ . Â·*Â· V M 3  -  Ha-cVien’  cÂ«_r a' -  lOK 3d - -7Z —  r  Â·Â· -  *00 ly (Cs*- bÂ·^ ÃÂ¼ 0*4-    S d m , i ^5 s i t e ?

n < )  z"S’ / levels 1n Sol) Semples from the Road  / o y  z X /  to Oak Valley.

In the accompanying table (Table 1) we present results of our analyses for

ra d io a c tiv ity  1n the 25 soil samples collected from along the road to Oak

V alley, and at Oak Va1  ley I t s e l f .  These samples were obtained on Wednesday

1st April 1967 In the presence of Ye lata  school teachers Mr Graeme Robertson,

Ms Kathy Heath and Mr Lindsay May.

The sampling sites are shown on the accompanying map, with samples numbers

21 , 22, 23 and 24 being from soil nearby to the water tanks, school yard,   school house and an undisturbed area respectively at Oak Valley. Sample

number 25 was from a point oh the Cook r o a d . 10 km west of the Oak Valley

road. Just to recap, each soil sample was a composite of five Individual

samples (to ensure that they are representative) each of 84 m m  diameter and 25

m m  depth. This composite sample was sieved to less than 1 mm size (to remove

small stones) and split (homogenised). Approximately $50 g of each sample was

counted for a long period (generally 12 hours or more) by high-resolution

gamma-ray spectrometry.

The results 1n Table 1 present the amounts (activities) of radioactivity

in each gram of soil for the various radionuclides (radioactive elements)

detected by the gamma-ray spectrometry. The unit of amount of rad1oectfv1ty

1s the becquerel, Bq.

Uranium-238 (23flU) occurs naturally 1n all soils, end radium-226

(226Re) and lead-210 (210Pb) ere naturally-occurring 'daughterÂ· nuclides

resulting from the radioactive decay of urenlum-238. The other major

Ã¢ÂÂ¢  ÃÂ¯ 232

naturally-occurring radioactive element in soil 1s thorium-232 Th) which   1s not detected by gamma-ray spectrometry. However, It has two Ã¢ÂÂ daughtersÂ·,   thorium-228 (i26Th) and radium-226 (“ Â®*a) which are both 1n equilibrium

(same amount Of radioactivity 1n terms of 6q/g) with the parent thorium-232.

2

I he I eve IS 04  ( ofl ÃÂ· , ÃÂ»ÃÂ¹  1 1  vl l y  1  uunU in Hie iV' s o l i  samples -tor {ItÂ·,  eve

, 238 226 ?! 0 ??6 )?6

fidlur'a liy-or.cur r tng r a d i o n u c l i d e s  ( U, R.i, Pi), Ra . Th)

show some v a r i a b i l i t y  w i t h  s o i l  t y p e ,  as e xpect ed, but e l l  a re  c o n s i s t e n t  w i t h

t l i r  rdfiyi 01  values found 1n s o i l  t hr ou g ho u t A u s t r a l i a .

40

PoLasstum-40 ( X) also occurs wi d el y 1n n a t u re , as a component of

s o i l s ,  d ri n k in g  water and even the human body. Again, the le vels detected 1n

the 28 s oi l samples are t y p i c a l  f o r  A u s t r a l i a n  s o i l s .

Ã¢ÂÂ¢  137

The other two radionuclides detected, caes1um-137 ( cv) and

2 A1

amer1clum-241 ( Am), are not n a tu ra lly  occurring. Caesium-137 results

from fa llo u t from atomic explosions, and the levels detected 1n the present

s o il samples probably contain components from both the Marellnga tests and

global f a l l o u t  (e .g . French atmospheric tests 1n the 1970's). However,

although detectable, the levels of caesium-137 are extremely low and well

w ithin acceptable lim its .

- 739

Amerlcium-241 1s the Indicator of plutonium-239 ( PuJ which 1s not

detected d ir e c tly  by gamma-ray spectrometry. The levels of amer1c1um-24l

reported 1n Table 1 are Just at the limit of detection for gamma-ray

spectrometry Involving long counting times. If 1t 1s assumed that the

material originates from the Vixen 6 trials at Taranaki, then one must

multiply by a factor, which we have established from other measurements to be

about ten, to get the p1uton1um-Z39 activities (e.g. the value of 0.008 Bq/g

for sample 14 translates to 0.08 6q/g of pluton1um-239). These levels are

extremely low and are not considered, 1n our assessment, to represent any

discernible health risk.

i

To place these small concentrations of plutonium 1n context, we note that

we measure levels of several hundred becquerel per gram of pluton1uei-239

within a few hundred metres of the test site at Taranaki. A very conservative

figure of 0.5 Bq/g of plutonium has been proposed by the U.S. environmental

Protection Agency In their 19B5 Interim recommendations as being the level

below which land can be considered suitable for unrestricted use. The U.S.

Department of Energy, 1n cleaning up Pacific Island tost sites, has used

plutonlum-239 concentration levels of 1.5 Bq/g es being Safe for continuous   habitation, 3 Bq/g at safe for agricultural use, and 6 Bq/g as safe for casual

visits. Therefore, the levels of plutonium In the present soil semples are clearly w e l l  below accep table safety l e v e l s .

ÃÂ¾} v WÂ«Y ÃÂ¯ ÃÂ¿ÃÂ±ÃÂ¹ÃÂÃÂ r I ion , the ÃÂ(ÃÂ ÃÂÃÂ½ 11  )(?$ ef natural I y  are VimUlai lo or greater than ttie acIlylTte-s of juitvi on I um- Z39 1n a l l  samples   except ny no. 14. furthermore, the hea 1-th r t i k i  from I n h a l a t io n  or Ingestion of many of these n a tu r a ll y - o t c u r r l n g  elements are s i m i l a r  to those for equivalent a c t i v i t i e s  of amertctum-241 or p iuton Ium-239. As an approximate guide, the amounts of r a d io a c tiv ity  required to be Inhaled or Ingested, fo r   some selected radionuclides, to give an e ffe c tiv e  dose of one m l l l l s l e v e r t   (mSv) are given 1n Table 2. The risk of contracting e fa ta l cancer from a received dose of one m l l l l s l e v e r t  1$ 1 1n 100,000. This Is the same ris k  as   t h a t  of contracting lung cancer from smoking 100 c ig a re tte s . The ris k  of   being k il l e d  1n a car accident 1n Australia Is about 1 1n 5000 per year. The data 1n Table 2 I l l u s t r a t e  th a t In ha la tion 1s the most Important exposure route fo r plutonium 1n s o ils , and while a detailed c a lc u la tio n  Is quite complicated, 1t 1s f a i r l y  straightforw ard to estimate roughly the significance of the concentrations we have measured. Typical dust loadings 1n   the MaraUnga area under moderately windy conditions are about 0.01 mg per   cubic metre (the greatest dust loading able to be to le rated  by humans fo r short periods Is about 10 mg per cubic m etre). The average human breathes about 9000 cubic metres of a i r  per year, and could therefore Inhale under such   ty p ic a l conditions 9000 x 0.01 Â« 90 mg of dust 1n a year. For the most active sample, assuming the concentration of   plutonium 1ÃÂ· the respirable fraction 1s the same as that 1n the soil, this   leads to a worst-case Intake of 0.09 x 0.06 Â« 0.007 Bq per year. You will see from Table 2 that such an Intake of plutonium would   not be significant, and In fact corresponds to an effective committed dose   equivalent of 0.0006 mSv. Normal background radiation levels contribute of   the order of 1 to 2 mSv per year. fteoff Williams   Peter Burns 22 A p ril 19ÃÂ7 4 - Tablc _1 A c t i v i t i e s  { I n  B q /y ) of rad 1unuc1  Ides detected  by gamma-ray spectrometry   1n.so1l samples col fee ted beside the road to Oak Va1 ley and ot "Oak V a l l e y .  NO   Indicates hut d ete cted . T  he p r e c is io n  of the counting measurements 1s   g e n e r a l ly  of the order of 10 percent or b e t t e r . Sample No. 23%  226Ã¢ÂÂ  Rfl  ?ib v   Pb Ra  22B Th 40K  137 C$  241 Am 1 0.011 0.009 0.045 0.015 0.014 NO 0.008 NO 2 0.00b 3 4 0.015 0.009 0.046 0.015 0.014 0.095 0.006 NO 0.010 0.042 0.014 0.014 0.087 0.005 NO 5 6  7 8 0.023 0.009 0.059 0.013 0.014 0.10V- 0.004 NO 9 0.010 0.0120.059 0.018 0.017 0.093 0.007 NO 10 0.009 0.008 0.039 0.011 0.017 0.069 0.008 NO 11 0.011 0.009 0.040 0.011 0.011 0.065 0.007 0.002 12 0.013 0.010 0.035 0.013 0.013 0.090 0.005 NO 13 0.020 0.014 0.046 0.019 0.020 0.148 0.007 0.002 14 0.012 0.014 0.050 0.019 0.018 0.143 0.005 0.008 15 0.017 0.0140.041 0.020 0.019 0.153 0.003 0.002 16 0.008 0.015 0.044 0.020 0.021 0.165 0.004 NO ÃÂ 0.013 0.014 0.069 0.020 0.020 0.165 0.006 0.003 18 0.012 0.009 0.058 0.012 0.013 0.091 0.008 NO 19 0.008 0.010 0.030 0.019 0.015 0.105 0,003 NO 20 0.012 0.0090.039 0.014 0.015 0.130 0.005 ND 21 0.010 0.010 0.027 0.013 0.011 0.060 0.002 NO 22 0.009 0.0090.032 0.01$ 0.014 0.113 0.004 0.001 23 0.013 0.0110.046 0.016 0.016 0.114 0.005 NO 24 0.007 0.0070.018 0.012 0.011 0.093 0.002 ND 25 0.013 0.012 0.034 0.019 0.018 0.938 0.004 NO * NOTE: Severalsamples have still to be measured and these lines are left blank In this draft Table. -5- 'X lrtbif; ? "The act W i t t e s  (Bq) of selected ra d io n u c lid e s, for the forms found 1n   Soil  1 s , icyu 1  red to Uv I n ha l ed  or I ngested to give en e f f e c t i v e  dose of 1 mSv. Rad t onuc1Ide Inhalation In g es ti o n 23flu 40 160,000 226Ra 400 4,000 ?’ Â°p D 200 800 232   c Th 4 1,400 228 Th 12 10,000 228 Ra 800 ‘ 2,000 40 It 200,000 200,000 137, CS 120,000 80,000 241 An 8 1 ,800 239. Pu 12 60,000 l i V l k n l  . Â·. ’.  Ã¢ÂÂ   0 D 2 A -  icKoÂ«\ Ã¢ÂÂ¢O P A O to lo  < v t p s J * t. )  ’ . Â·*Â· V M 3  -  Ha-cVien’  cÂ«_r a' -  lOK 3d - -7Z —  r  Â·Â· -  *00 ly (Cs*- bÂ·^ ÃÂ¼ 0*4-    S d m , i ^5 s i t e ?

are VimUlai lo or greater than ttie acIlylTte-s of juitvi on I um- Z39 1n a l l  samples

except ny no. 14. furthermore, the hea 1-th r t i k i  from I n h a l a t io n  or Ingestion

of many of these n a tu r a ll y - o t c u r r l n g  elements are s i m i l a r  to those for

equivalent a c t i v i t i e s  of amertctum-241 or p iuton Ium-239. As an approximate

guide, the amounts of r a d io a c tiv ity  required to be Inhaled or Ingested, fo r

some selected radionuclides, to give an e ffe c tiv e  dose of one m l l l l s l e v e r t

(mSv) are given 1n Table 2. The risk of contracting e fa ta l cancer from a

received dose of one m l l l l s l e v e r t  1$ 1 1n 100,000. This Is the same ris k  as

t h a t  of contracting lung cancer from smoking 100 c ig a re tte s . The ris k  of

being k il l e d  1n a car accident 1n Australia Is about 1 1n 5000 per year.

The data 1n Table 2 I l l u s t r a t e  th a t In ha la tion 1s the most Important

exposure route fo r plutonium 1n s o ils , and while a detailed c a lc u la tio n  Is

quite complicated, 1t 1s f a i r l y  straightforw ard to estimate roughly the

significance of the concentrations we have measured. Typical dust loadings 1n

the MaraUnga area under moderately windy conditions are about 0.01 mg per

cubic metre (the greatest dust loading able to be to le rated  by humans fo r

short periods Is about 10 mg per cubic m etre). The average human breathes

about 9000 cubic metres of a i r  per year, and could therefore Inhale under such

ty p ic a l conditions

9000 x 0.01 Â« 90 mg

of dust 1n a year. For the most active sample, assuming the concentration of

plutonium 1ÃÂ· the respirable fraction 1s the same as that 1n the soil, this

leads to a worst-case Intake of

0.09 x 0.06 Â« 0.007 Bq

per year. You will see from Table 2 that such an Intake of plutonium would

not be significant, and In fact corresponds to an effective committed dose

equivalent of 0.0006 mSv. Normal background radiation levels contribute of

the order of 1 to 2 mSv per year.

fteoff Williams

Peter Burns

22 A p ril 19ÃÂ7

4 -

Tablc _1

A c t i v i t i e s  { I n  B q /y ) of rad 1unuc1  Ides detected  by gamma-ray spectrometry

1n.so1l samples col fee ted beside the road to Oak Va1 ley and ot "Oak V a l l e y .  NO

Indicates hut d ete cted . T  he p r e c is io n  of the counting measurements 1s

g e n e r a l ly  of the order of 10 percent or b e t t e r .

Sample No. 23%  226Ã¢ÂÂ  Rfl  ?ib v

Pb Ra

22B Th 40K

137 C$

241 Am

1 0.011 0.009 0.045 0.015 0.014 NO 0.008 NO

2 0.00b

3

4 0.015

0.009 0.046 0.015 0.014 0.095 0.006 NO

0.010 0.042 0.014 0.014 0.087 0.005 NO

5 6

7 8 0.023 0.009 0.059 0.013 0.014 0.10V- 0.004 NO

9 0.010 0.0120.059 0.018 0.017 0.093 0.007 NO

10 0.009 0.008 0.039 0.011 0.017 0.069 0.008 NO

11 0.011 0.009 0.040 0.011 0.011 0.065 0.007 0.002

12 0.013 0.010 0.035 0.013 0.013 0.090 0.005 NO

13 0.020 0.014 0.046 0.019 0.020 0.148 0.007 0.002

14 0.012 0.014 0.050 0.019 0.018 0.143 0.005 0.008

15 0.017 0.0140.041 0.020 0.019 0.153 0.003 0.002

16 0.008 0.015 0.044 0.020 0.021 0.165 0.004 NO

ÃÂ 0.013 0.014 0.069 0.020 0.020 0.165 0.006 0.003

18 0.012 0.009 0.058 0.012 0.013 0.091 0.008 NO

19 0.008 0.010 0.030 0.019 0.015 0.105 0,003 NO

20 0.012 0.0090.039 0.014 0.015 0.130 0.005 ND

21 0.010 0.010 0.027 0.013 0.011 0.060 0.002 NO

22 0.009 0.0090.032 0.01$ 0.014 0.113 0.004 0.001

23 0.013 0.0110.046 0.016 0.016 0.114 0.005 NO

24 0.007 0.0070.018 0.012 0.011 0.093 0.002 ND

25 0.013 0.012 0.034 0.019 0.018 0.938 0.004 NO

* NOTE: Severalsamples have still to be measured and these lines are left

blank In this draft Table.

-5-

'X

lrtbif; ?

"The act W i t t e s  (Bq) of selected ra d io n u c lid e s, for the forms found 1n

Soil  1 s , icyu 1  red to Uv I n ha l ed  or I ngested to give en e f f e c t i v e  dose of 1 mSv.

Rad t onuc1Ide Inhalation In g es ti o n

23flu 40 160,000

226Ra 400 4,000

?’ Â°p D 200 800

232   c Th 4 1,400

228 Th 12 10,000

228 Ra 800 ‘ 2,000

40 It 200,000 200,000

137, CS 120,000 80,000

241 An 8 1 ,800

239. Pu 12 60,000

l i V l k n l  . Â·. ’.  Ã¢ÂÂ   0 D 2 A -  icKoÂ«\

Ã¢ÂÂ¢O P A O to lo  < v t p s J * t. )  ’ . Â·*Â· V M 3  -  Ha-cVien’  cÂ«_r a' -  lOK 3d - -7Z —  r  Â·Â· -  *00 ly (Cs*- bÂ·^ ÃÂ¼ 0*4-    S d m , i ^5 s i t e ?

-  lOK 3d - -7Z —  r  Â·Â· -  *00 ly (Cs*- bÂ·^ ÃÂ¼ 0*4-    S d m , i ^5 s i t e ?

3d

- -7Z

—  r  Â·Â· -

*00 ly (Cs*- bÂ·^ ÃÂ¼ 0*4-

S d m , i ^5 s i t e ?

