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MEMORANDUM FOR: Vandy Miller, Chief Material Licensing Branch FROM:
An-Liang Soong Uranium Process Licensing Section Uranium Fuel Licensing Branch
SUBJECT:
ESTIMATES OF POTENTIAL RADIATION DOSE OF WASTE BURIAL AREA AT VETERANS ADMINISTRATION HOSPITAL, LOS ANGELES, LICENSE NO. 04-00181-04 An estimate cf the potential radiation dose to an individual resulting from the '
buried radioactive material on the VA's property has been calculated and s
attached to this memo.
4 In the dose calculations, both external and internal exposure pathways were considered. The internal exposures were calculated based on two projected pathways:
(1) ingestion of food (beef, milk, and vegetables) that is produced on the burial site (2) inhalation of airborne radioactive material as a result of wind resuspension.
The results of the dose calculation are provided in the ' summary on page 4 of the attached report.
(@
An-Liang Soong
(
Uranium Process Licensing Section Uranium Fuel Licensing Branch I
Enclosure:
Estimates of Potential Radiation Dose
%s 8204150469 820216 PDR FOIA NELSON 82-11 PDR g
s Estimates of Potential Radiation Dose This report shows a calculation of potential radiation dose to an individual
.from two potent ai l intake pathway; resulting from the b0ried radioactive material on the Veterans Administration propertj at the Veterans Administration Center, Los Angeles, California.
The report contains the' dose calculations from both external and internal exposure pathways.
The internal exposures were calculated based on two
. projected pathways:
(1) dietary ingestion of-food produced on the burial site and (2) inhalation of airborne radioactive material as a result of wind resuspension.
In the course of the dose assessment, not.all site-specific parameters were available; therefore, a generally conservative approach was used and this may have resu?ted in a high estimate of dose.
I.
Models for Estimating P,adiation Dose A.
External Exposure The basic equation used for estimating the external dose of a radioactive point source emitting gamma radiation is:
F D (R/hr) = r x B
(1) whereDisdoserateR/hr;R-m{stotalgammaexposurerateconstant r
of a radionuclide unit in
- A is the activity of the radio-h nuclide in the media, the End is Ci; F is the shielding factor of the media; B is the buildup factor of the media, and d is the distanc,e between the source and the radioactive source in media.
B.
Internal Exposure The internal dose co:miitment is calculated according to the following basic equation:
D = C X U x DCF (2) where D is the dose commitment to a given organ of an individual in mrem /yr; C is the concentration of a radionuclide in the media of 3
3 exposure in pc/m ; V is the usage factor unit in m /yr, and DCF is the dose conversion factor that converts a given concentration of the radionuclide and the intake rate of that radionuclide to the radiation dose.
The unit of DCF is rem /pCi.
2 II.
Radionuclide Source Terms Ac' cording to the NRC's records, the radioactive waste materials were
~
buried under 15 feet of dirt in three adjacent locations on hospital controlled property.
The locations of the three burial sites, desig-nated as A, B, and C, are shown in figure 1.
The essential radioactivity still remaining in each area is summarized in the following table:
Table 1 Essential Radioactivity in the Burial Site, mci as of 1981 Location Size Radioactivity mci 2
2 (ft )
(m )
200 x 50 929 2.0
..?. 9 0
0 B
200 x 400 7432 316.0 12.5 0.25 0
C 100 x 400 3712 122.2 37.2 0
'O.009 1.21 x 10
440.2 52.6 0.26 0.009 III.
Dose Calcul.ation A.
External Radiation Dosimetry Since H-3 and C-14 are low energy heta emitters, and Cl-36 emits 0.51 Mev gamma radiation with 0.003% intensity, the only contributor to the external exposure that will be considered here is radionuclide Na-22.
The external exposure rate at 1 meter above the surface from -
the Na-22 as a point source under 15 feet of soil is calculated by using equatien (1) with the following parameters:
a I
r = 1. 2 at 1 meter from a point source hr Ci A = the radioactivity in Ci, 9 x 10-6Ci B = 100 for 15 feet of soil as media b
F = < 10~10 d = 5.57 meters rxAxFxB 1.2 x 9 x 10-6 x 10-10 x 100 D(R/hr)
=
d2 5.572 "Itadiological !!eal th Handbook,1970, 'page 131 bEstimates assume that mass absorption. coefficient of soil for ga tr.a energy 1.2 Mcv is about 0.05 cm /9 2
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Internal Radiation Dosimetry 1:
Inhalation Mode Radiation dosimetry to an individual in each of the three burial locations is calculated based on the assumption that in each location the buried material, mixed with 1 meter of soil, was brought to the surface during thc reclamation project, and the top 1.0 cm layer of the contaminated soil became airborne by the process of resuspension.
The calculated dose commitment to an individual from' inhaling the contaminated air is expressed in the following table:
Table II Dose Inhalation location Dosea (mrem /yr) due to the radionuclide
!!-3 C-14 Cl-36 fla-22 (wholebody)
(bone)
(wholebody)
(whole body)
A 1.3E-7 2.04E-6 0
O B
2.5E-6 1.2E-6 6.7E-8 0
C 2.3E-6 6.8E-6 0
1.lE-10 2.
Ingestion Mode The radiation dose calculation from the ingestion pathway is based on the conservative assumption that all the food consumed by one individual either grew on or was produced on these sites after a reclamation project.
Tne dose comnitment tc an individual from -
ingestion of food (beef, milk, and vegetables) contaminated via resuspension and by root uptake was calculated and expressed in 31he dose calculation is orovided in Acoendix A of this report.
-4 9
5 the following table:
Table III Dose. Commitment Resulting from Ingestion Pathway Mse to Critical Organa Radionuclides Bone Marrow Dose (mrem /yr)
Whole Body (mrem /yr)
H-3 7.4 x 10-6 C-14 1.1 x 10 3 Cl-36 1.5 Na-22 3.2 x 10 '*
IV.
Summary 1.
For the dose due to external radiation exposure, the calculated result indicates a dose level of 3.5 x 1G-9 ur/hr at 1 meter above the surface.
This exposure is about 1/109 of the dose rate from the background external level which is about 10 ur/hr. Ha-22 has. a radioactive half-life.of 2.6 years.
The. exposure rate is decreased by a factor of 0.8 each year; therefore, long term health.effect is.not antici-pated.
2.
For the dose due to inhalation of contaminated resuspended air, the results indicate that:
in location A, the dose to the total body (for H-3) is 1.3 x 10 7 mrem /yr, and the dose to the bone (for C-14) is 2.04 x 10-6 mrem /
(for H-3 and Cl-36) yr; in location B, the dose to the total body is 2.6 x 10-6 mrem /yr, and dose to the bone (for C-14) is 1.2 x 10-6 mrem /yr;- and in location C, tha dose to the-i total body (for H-3 and Na-22 is 2.3 x 10 6 mrem /yr, and dose to the bone (for C-14) is 6.8 x 10-6) mrem /yr.
l 3.
For the dose due to ingestion pathway, the results indicate the dose to the total body (for H-3, Cl-36 and Na-22) to be 1.5 mrem /yr and dose to the bone marrow (for C-14) to be 1.1 x 10-3 mrem /yr.
4.
The calculated maximum individual internal exposure (ingestion and inhalation) is on the order of 1.5 mrem /yr to the whole body, or about 1/60 of the dose from natural background radiation.
"Tik. dose calculTtien is provided in nogendix B of this report.
Appendix A Dose Calculation From Inhalation Mode 9
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J I
The dose is calculated by equation (2) with the following parameters:
1.
The calculated contaminated soil concentration and resuspension airborne concentration of radioactivity is expres.cd in the following table:
Table A-1 Concentration in Soil and Air Calculated gc Calculated resuspended Location Soil Concentration g
concentration uc/m3
~
C-14 Cl-36 Na H-3 C-14 Cl-36 Na-22 H-3 A
8.6E-7b 1.2E-6 0
0 1.1E-10c 1:6E-10 0
0 B
1.7E-5 6.8E-7 1.4E-8 0
2.lE-9 8.5E-ll 1.7E 0 C
1.5E-5 4E26 0
9.7E-10 1.9E-9 5E-10 0
1.2E-13 2.
Dose conversion factors, DCF, for inhalation mode are obtained from Oak Ridge National Laboratory prSlication ORNL-4992, "A Methodology for Calculating Radiation Dose from Radioactivity Release to the Envi ronmen t. " They are:
DCF for H-3 (total body as critical organ) is 1.5.x 10 4 rem /pc for C-14 (bone as critical organ) is 1.7 x 10 3 rem /pc for Cl-36 (total body as critical organ) is 4.8 x 10 3 rem /pc
~
for Ha-22 (total body as critical organ) is 1.1 x 10-2 rem /pc 3The resuspensio'n factor, 5 x 10-9 1/m, is obtained from NRC publication NUREG-0707, "A Methodology for Calculating Residual Radioactivity Levels following Decomissioning," page 9.
2 x 103 uc m3 I.D~" M bRead as 8.6 x 10 7, soil concentration EE = 3H N- (soll density) 9 2.5 g/cm s cl.10 x 10-10 L'S = 8.6 x 10-7 gE x 2.5 gg7 soil density x 1 cm surface soil l
x 5 x 10-9 1/m (resuspension factor) x 10' cn_-
2 m2
?
2 3
3.
An individual's breathing rate is 8000 m /yr.
Dose due to inhalation mode is calculated by equatioh (2):
i) for burial site.A:
D
= C x U x DCF H-3
,., = 1.1 x 10-10 pc/m3 x 8000 rem m yr x 1.5 x 10 4 sc 3
= 1.3 x ~107 mrem /yr (whole body)
D
= 1.5 x 10 10 pc/m3 x 8000 C-14 m /yr x 1.7 x 10-3 rem /pc 3
j
= 2.04 x 10 6. mrem /yr (bone)
DCl-36= 0 DNa-22= 0
.5 x 10 6 mrem /y (whole body)
- ii) for buria.1 site B:
D
=
H-3 D
1.2 x 10 6 mrem /yr (bone)
C-14 i
0
= 6.7 x 10-8 mrem /yr (whole body) 01-36 Dyg_gg= 0 iii) for burial site C:
D
= 2.3 x 106 mrem /yr (whole body)
H-3 C-14 = 6.8 x 10-6 mrem /yr (bone)
D D
=0 i
C1-36 D
= 1.1 x 10 10 mrem /yr (whole body)
,,,4,-
y y._,.,
o 8 Appendix B Dose Calculation for Ingestion Pathway 6
1.
For H-3 and C-14 The estimated dose due to ingestion pathway of H-3 and C-14 is calculated based on the assumption that the food and drinking water are in equilibrium with the specific activity of H-3 in the, atmosphere', and the specific activity of C-14 in human tissue is equal to the average steady state value in the atmosphere.
The methodology of the calculation is presented fully in ORNL-4992, "A Methodology for Calculating Radiation Dose from Radioactivity Release to the Environment." The dose conversion rates for H-3 and C-14 given under the conditions described above are 3.68 x l
1 09 mrem yr per Cm-3 and 2.2 x 10+12 mrem yr per Ci m-3, respectively.
-1
-1 The maximum airborne concentration of radioactivity for H-3 and C-14 are given in Table B-1.
Therefore, the dose due to ingestion of H-3 is:
D
= 3.68 x 10-9 mrem x m x 2 x 10-1s Ci 3
H-3 yr H
int
= 7.4 x 104 mrem /yr (whole body) i 1
D
= 2.2 x 10 2 mrem x m3 x 5 x 10-16 Ci C-14 yr 6
m'I
= 1.1 x 10 3 mrem /yr (bone marrow) 2.
For Cl-36 and Na-22 a.
Ingestion dose from vegetable intake 1.
Root uptake i
)
Dose commitment, mrem
= Concentration in soil, pCi/g (see Table B-1) xBjy, bioaccumulation factor (see Table B-2) x.1.94 x 105 g/yr (vegetable intake per yr) x dose conversion factor rem /uCi (see Table B-3) x 103 mrem / rem l
2.
Resuspension Dose conmitment, arem
= Concentration in soil, pCi/g (see Table B-1) x 2.5 x 10P g of soil /N x 5 x 10' m 1 (resuspension factor) x 10-2 m/sec (deposition factor)
^
e 2
x 3.15 x -107 sec/yr x eCi/ day (see Table B-3) pCi/m2-day x dose. c6nversion factor, rem /pCi (see Table B-3) x 103 mrem / rem b.
Ingestion dose from meat intake 1
-1.
Root uptake Dose, mrem = Conc. in soil, pCi/g (see Table B-1) jy(, bioaccumulation factor, (see Table B-2) x F xB d
f_
see Table B-2) kg x 10'+ g/ day (grass eaten) x 94 kg/ year (meat intake) x DCF rem /pCi (see Table B-3)'x 103 mrem / rem l
2.
Resuspension
~
Dose mrem
= Conc. in soil, uc/g (see Table B-1) x 2.5 x 10 g of soil /m2 x 5 x 10-9 m 1 (resuspension factor)
]
x 10-2 m/sec (deposition factor) x 3.15 x 107 sec/yr x uCi/ day (see Table B-3)
Wiii2-day x DCF rem /pci (see Table B-3) x-10-3 mrem / rem 4
c.
Ingestion from milk intake 1.
Root uptake Dose, mrem = Conc. in soil, pCi/g (see Table B-1) j x bioaccumulation factor, Bjy (see Table B-2) x 104 g/ day (grass intake) x trcasfer coefficient Fm, day /t (see Table B-2) x 0.31
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3 2.
Resus' pension 4
Dose, mrem = Conc. in soil, pCi/g x 2;5 x 10 g of soil /m2 x 5 x 10 9 m-1 (resuspension factor) x 10-2 m/sec (deposition factor)
~
x 3.15 x 107 sec/yr.x pCi/ day (see Table B-3) p Ci /m'-day
.x DCF rem /pCi (see. Table B-3) x 103 mrem / rem Table B-1 Maximum Concentration in Soil and Air 4
(data' are obtained from Table A-1)
Radionuclide Conc. in Soil, uCi/g Conc. in Air, Ci/m3 Cl-36 1.4E-8 Na-22 9.7E-10 H-3 2E-15 C-14 SE-16 lable B-2 The Veg/ Soil Bioaccumulation Factor, B., and Transfer Coefficients, Fm (Milk) Ff(gjats)
Radionuclide B
veg/ soil Fm,a day /t F,a day /kg a
jy I
Cl-36 50 l'.7E-2 8E-2 Na-22 5.2E-2 4E-2 3E-2 i
I U
l NRC Rec. Guide 1.109 and Ng, ICRL-50163, Part IV.
l I
i
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Table B-3 a
^
Dose Conversion Factor,
rem /uCi for Ingestion Pode and Radionuclide Transfer Factorb
' uCi/ day Radionuclide' DCF* rem /uCi uCi/ day-m-
- Cl-36 7.9E-3 50 Na-22 1.8E-2 50
- 0RNL-4992, Table 4-3 pp. 4-90
.bThe transfer factor' for Cl-36 and Ha-22 were assumed to be 50 for ' egetable, v
meat, or milk intake.
This assumption was chosen conservatively with'the aid of the intake transfer factor for radionuclide with mass number larger than 27.
(Table 2-8, ORNL-4992) 9
.