ML20042C155
| ML20042C155 | |
| Person / Time | |
|---|---|
| Issue date: | 02/25/1982 |
| From: | Johnson T NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Rich Smith NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| FRN-46FR38081, RULE-PR-61, RULE-PR-WM-4 46FR38081, NUDOCS 8203300276 | |
| Download: ML20042C155 (6) | |
Text
V$ Q 38D dl py Q,..
I p,n-+
DISTRIBUTION FEB 0 5198 NMSS r/f PA 4* :
WM r/f gs-/j )/
WMLL r/f WMLL s/f N'N ^
TCJohnson HEMORANDUM FOR:
R. Dale Smit.h, Chief Low-Level Waste Licensing Branch REBrowning JBMartin Division of Waste Management RTLee PHl.ohaus FROM:
Timothy C. Johnson Dra -
/p[- Q. 'jx Low-l.evel Waste Licensing Branch
+
Division of Waste Management 6
'N,
SUBJECT:
CURIUH-242
- a.C 4,<2.,
,d Enclosed is an evaluation to detemine an acceptable conc Tration'3 9193h'i j 9-
, np Ic '
fora r" : /s ng' o:n,iw m
6[
ti Cm-242 for disposal at near-surface disposal facilities. This should i>e docketed under our 10 CFR 61 rulemaking activity in accor%
i with our policy for preparing technical evaluations.
Original Signed By Timothy C. Johnson Low-Level Waste Licensing Branch Division of Waste Management
Enclosure:
As stated i
u L
8203300276 820225 PDR WASTE WM-4 PDR WMLL l
cmce>
c.
sunnwe >
- ill 02../.2......
one>
sac ronu ais oow nacu aao OFFICIAL RECORD COPY usem asi-sz-m i
. C,
~'
EVALUATION OF Cm-242 CONCENTRATION FOR DISPOSAL
Purpose:
The purpose of this evaluation is to determine an acceptable concentration for disposing of wastes containing short-lived Curium 242 in near-surface-disposal facilities.
I
Reference:
1.
Propostd rule,10CFR61, " Licensing Requirements for Land Disposal of Radioactive Waste," Federal Register, Vol. 46, l
t No.142, July 24,1981, Table 1, p. 38097.
2.
Draft Environmental Impact Statement on 10CFR61, " Licensing Requirements for Land Disposal of Radioactive Waste,"
N'JREG-0782, Vol. 2, p. 7-16.
3.
Radiological Health Handbook, U.S. Department of Health, Education, and Welfare.
Revised Edition, Jan.1970 pp. 28-29.
j 4.
Table of Isotopes by C.M. Lederer, J.M. Hollander, and i
I. Perlman, Sixth Edition, pa 144, 147.
l Results:
Near-surface disposal of Cm-242 exceeding 10 nCi/g would be l
~
~
acceptBle to NRC staff, if the upper concentration limit does not exceed 2 uCi/g. The concentratfor. of the daughter product l
of Cm-242, Pu-238, would,. however, need to be included in the total 10 nC1/g cumulative concentration with the other long-lived al.pha-emitting TRU nuclides in the wastes.
i i
h
2-Evaluationi In Table 1, Draft 10CFR61, an exception of TRU nuclide concentration is listed for Pu-241, a short-lived transur'anic which has a long-lived alpha-emitting daughter, Am-241.
Using the same rationale provided by Chapter 7 of the Draft Environmental Impact Statement to
. 10CFR61 (NUREG-0782, Volume 2), we calculate the ratio of the specific activity of Cm-242 to Pu-238 to be about 200. The upper concentration limit for Cm-242 is recommended to be 2 uCi/g (See Appendix I).
Furthermore, Cm-242 is a short-lived isotope (163 days). By the
[
time the 100 year institutional control period ends, any Cm-242 l
disposed of in a near surface disposal facility will be negligible.
(See' Appendix II).
b I-N Aate Calculated by Checked by
$[
- Date E-Z3-F2
/ Date 2./7.Ff 82.
Approve A Lv2 9
a g
e l
l
~ ~ - -.
=_
~.
- Appendix I. (From Reference 3):
Specific Activity The rate of decay per gram or specific activity is equal to AN and f
A N = 0.693 d/T 1/2 = dis /sec/gm where T 1/2 = half-life (seconds)
N
= Number of atoms per gram A
= Decay constant (1/ seconds) i
.0 Number of atoms per gram for Cm-242 =
242.
g.
Therefore, i
NCm-242 = 2.49 x 1021 atom /g (1)
.0 Number of atoms per gram for Pu-238 =
238.
g.
Therefore, NPu-238 = 2.53 x 1021 atoms /g (2)
Since the half life of Cm-242 is 163 days (Reference 4) and the half life of Pu-238 is 86 years (Reference 4), the ratio of specific activity of Cm-242 to Pu-238 is:
0.693 x No. of atoms per gram of Cm-242 half-life (seconds) of Cm-242 0.693 x No. of atoms per gram of Pa-238 half-life (seconds) of Pu-238 Substituting (1) and (2) into equation (3), we get:
i 1
0.693 x 2.49 x 1021 (atoms /g)(365 day /yr)-
163 (days) x 86400 (sec/yr)
(4) 0.693 x 2.53 x 1021 (atoms /g) 86 (yrs) x 86400 (sec/yr)
'g,
_.,-.m
~..,,,.,. _
i i
Reducing equation (4) yields:
2.49 x 1021 (atoms /g) 365 (days /yr) 86 (yr) = 190 2.53 x 1021 (atoms /g) 163 (days)
Due to the inaccuracies of measuring TRU nuclides, we round off this value to 200.
Therefore, to compute the specific activity of Cm-242 to produce 10 nCi/g of Pu-238,-
we multiply the ratio of specific activities (200) times 10 nCi/g (the long-lived TRU limit) to get 2 uCi/g for Cm-242. Therefore, a waste with 2 uCi/g of Cm-242 will decay to 10 nCi/gm of Pu-238.
4 f
r P
r l
5
,.?-
Appendix II In order to show that Cm-242 will have negligible effect after disposal, we use
, the decay equation to compute the Cm-242 activity at the time institutional control over the disposal site is assumed to be lost. We assume that the institutional control period is 100 years. Therefore, I=I e-0.693 t/T 1/2 n
where I,
= Cm-242 activity at some original time I
= Cm-242 activity after a time interval, t T1/2 = Half-life of a particular radioactive element t
= Period of decay, years After 100 years institutional control:
t
= 100 years T 1/2 of Cm-242 = 163 days I
=I e-0.693 x 100 (yr) x 365 (days /yr) 0 163 (days) h
= 4.0 x 10-68 o
Therefore, after 100 years only 4.0 x 10-68 of the initial Cm-242 activity will remain. Therefore, its activity after the institutional control period will be n:gligible assuming that only uCi amounts of Cm-242 are initially pres ent.
l e
@