ML20238C707
| ML20238C707 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/03/1987 |
| From: | Standerfer F GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 0209P, 209P, 4410-87-L-0121, 4410-87-L-121, NUDOCS 8709100315 | |
| Download: ML20238C707 (4) | |
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I GPU Nuclear Corporation Nuclear
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s Middletown, Pennsylvania 17057 0191 717 944 7021 TELEX 84 2386 Writer's Direct Dial Number:
(717) 948-8461~
4410-87-L-0121 Document ID 0209P September 3, 1987 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Dear Sirs:
Three Mile Island Nuclear Station, Unit 2 (TMI-2)
Operating License No. DPR-73 Docket No. 50-320 Post-Defueling Monitored Storage Environmental Evaluation Pursuant to GPU Nuclear letter 4410-87-L-0093 dated June 23, 1987, attached is the GPU Nuclear response to NRC Comment 1 provided in NRC Letter NRC/TMI-87-039 dated May 8, 1987.
Specifically, the attached response
~
provides the bases for the transuranic source term (i.e., 2 x 10-o Ci/yr) ceferenced in Table 3 of the GPU Nuclear Environmental Evaluation for TMI-2 Post-Defueling Monitored Storage submitted via GPU Nuclear letter 4410-87-L-0025 dated March 11, 1987.
I Sincerely, e
,p
. R. Standerfe Director, TMI-2 FRS/RDW/eml Attachment cc: Regional Administrator, Region 1 - W. T. Russell Director, TMI-2 Cleanup Project Directorate - Dr. W. D. Travers B709100315 070903 PDR ADOCK 05000320
[h P
PDR GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation L_
1 ATTACHMENT 4410-87-L-0121 l
1 NRC COMMENT 1 I
Provide the bases for the transuranic source term (2 x 10-8 C1/yr) given in l
Table 3.
j l
GPU NUCLEAR RESPONSE I.
Basis for the Transuranic Source Term Value The value of 2 x 10-8 C1/yr for the transuranic source term during Post-Defueling Monitored Storage (PDMS) was calculated as described below.
Measurements prior to Reactor Building (RB) basement sediment pumping operations indicated that there could exist 1.7 to 3.2 kg of fuel fines mixed with other materials in the RB basement.
The initial pumping of basement sediment is now completed and follow-on flushing will take place.
It is assumed that 2 kg will remain throughout PDMS. The total core inventory of transuranic elements remaining after eight (8) years of decay was calculated using the ORIGEN computer code. This inventory is provided below as indicated in Table 2 of the PDMS Environmental Evaluation.
l ISOTOPE Ci INVENTORY Ci FRACTION Pu-238 7.73 x 102 6.30 x 10-3 Pu-239 8.98 x 103 7.32 x 10-2 i
Pu-240 2.38 x 103 1.94 x 10-2 Pu-241 1.09 x 105 8.87 x 10-1 Am-241 1,71 x 103 1.40 x 10-2 TOTAL 1.23 x 105 1.00 The transuranic elements can be assumed to be associated with the fuel.
The total value of 1.23 x 105 C1 averaged over 98,000 kg of fuel equals 1.25 Ci per kg of fuel. Assuming a suspension factor of 1 x 10-8 (the basis for this i
value is provided in the following section) and a conservative value of 50 RB l
air enanges/yr in conjunction with a conservative value of 99% filter efficiency results in:
(2 kg-fuel) (1.25 Ci/kg-fuel) (1 x 10-8) (50 RB air changes /yr) (.01 filtrate)=
1.25 x 10-8 Ci/yr or more conservatively 2 x 10-8 C1/yr (i.e., the basis for the transuranic source term value).
II. Basis for the Suspension Factor Value There are no readily referenced values available for suspension factors applicable to normal conditions during PDMS.
The value for the suspension factor was estimated using several approaches.
In all cases, it is assumed that the fuel is uniformly distributed over the 9,000 ft2 (i.e., 8.4 x 106 cm2) of basement floor outside of the D-Rings.
1 L
l ATTACHMENT-4410-87-L-0121 Approach 1 Applicable K factors of 10-11 m-1 and 2 x 10-10 m-1 from NUREG/CR-3332, " Radiological Assessments: A Textbook on Environmental Dose Analysis," were used.
The top 1/4" (i.e.,.635 cm or 6.35 x 10-3 m) of concrete in the RB basement floor contains most of the activity. Thus, the I
applicable K factors of 10-11 m-1 and 2 x 10-10 m-1, multiplied by the l
depth of contamination, gives the KZ airbc.;1e fraction (i.e., suspension factor) of approximately 6 x 10-14 and 1 x 10-12, respectively.
Approach 2 l
Another approach to calculate a suspension factor is to multiply K by the ratio of applicable volume to surface area.
This ratio of the applicable volume (i.e., the volume of RB air communicating with the RB basement floor conservatively estimated as all air volume below the 305' elevation floor) to the surface area of the floor is 21:1m 1 (Multiplying this ratio by the K factors of 10-11 m-1 and 2 x 10-10 reference Approach 1 results in suspension factors of approximately 2 x 10-10 and 4 x 10,
respectively.
l Approach 3 Another value of K of 1 x 10-9 m-Ican be referenced from NCRP-76, l
i
" Radiological Assessment: Predicting the Transport, Bioaccumulation and Uptake i
by Men of Radionuclides Releases to the Environment."' This value results in I
an approximg2, using the depth of contamination method as discussed abovef l
and 6 x 10-Approach 4 The value of K can also be roughly estimated from TMI-2 data. The airborne concentration of Pu-238, Pu-239, and Pu-240 observed during the four (4) month l
desludging operation was in the 4 x 10-15 uC1/cm3 range (as measured by an I
AMS-3 near the defueling platform).
This airborne is due to many sources, noteably the defueling equipment. However, this approach assumes the same concentration currently exists at the 282' elevation of the RB.
The surface loading value of the basement can be determined by dividing the value of 2 kg fuel, from Part I, by the RB basement floor area outside of the D-Rings (i.e.,
2 8.4 x 106 cm ).
This results in a surface loading value of 2.4 x 10-2 gm-fuel /cm. Averaging the total Ci inventory from Part I for Pu-238, Pu-239, and Pu-240 (i.e.,12.1 x 103 C1) over 98,000 kg of fuel equals 1.2 x 10-4 Ci/gm-fuel or 1.2 x 102 UCi/gm-fuel. Multiplying the latter value by the surface loading value (i.e.
2.4 x 10-4 gm-fuel /cm2) equals approximately 3 x 10-2 uC1/cm2., Dividing this value into the airborne concentration of 4 x 10-15 uC1/cm3 yields a K estimate of 1.3 x 10-13 cm-1 or 1.3 x 10-11 m-1 This results in an airborne fraction of approximately 3 x 10-10 using the 21:1 ratio and 8 x 10-14 using the depth of contamination method.
ATTACHMENT 4410-87-L-0121
.I III. Summary
'The following is a listing of suspension factors derived from the above analysis:
6 x 10-14 (Approach 1) o 8 x 10-14 (Approach 4) o o
1 x 10-12 (Approach 1) 6 x 10-12 (Approach 3) i o
2 x 10-10 (Approach 2) o 3 x 10-10 (Approach 4) l o
o 4'x 10-9 (Approach 2) f o
2 x 10-8 (Approach 3) l Thus, the value of 1 x 10-8 was selected as a reasonably conservative value for use as a suspension factor since this results in a higher (i.e., more conservative) transuranic source term value. It is noteworthy that even if the most conservative suspension factor from the above approaches (i.e., 2 x 10-8) had been utilized in the computation in Section I, the resulting transuranic source tera value would still have been approximately 2 x 10-8 Ci/yr.
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