ML20059A769
| ML20059A769 | |
| Person / Time | |
|---|---|
| Site: | 07000734 |
| Issue date: | 10/22/1993 |
| From: | Asmussen K GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER |
| To: | Emeigh C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20059A772 | List: |
| References | |
| TAC-L30607, NUDOCS 9310270115 | |
| Download: ML20059A769 (22) | |
Text
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GENERAL ATOMICS October 22,1993 696-2137 VIA EXPRESS Mall SERVICE:
Mr. Charles W. Emeigh, Section Leader Licensing Section I Licensing Branch Division of Fuel Cycle Safety & Safeguards, NMSS Office of Nuclear Materials Safety & Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Docket No.70-734; License No. SNM-696; Response to Request for Addi-tional Information on SVA Decommissioning Project Soil Sampling Plan (TAC No. L30607)
References:
1)
Asmussen, Keith E., Letter No. 696-2114 dated August 23,1993 to Mr. Charles W. Emeigh " Submittal of General Atomics' SVA Decommis-sioning Project Soil Sampling Plan" 2)
Emeigh, Charles W. Letter to Keith Asmussen, dated October 6,1993,
" Request for Additional Information on Soil Sampling Plan" (TAC No.
L30607)
Dear Mr. Emeigh:
General Atomics (GA) recently submitted its " Soil Sampling Plan for Phase il of the SVA Decommissioning Project," dated August 20,1993 for NRC review and approval (Ref 1). By your letter dated October 6,1993, GA was requested to provide clarification by responding to specific comments (Ref 2). Accordingly, enclosed are GA's responses to each of the comments. For convenience, each specific comment is restated followed by GA's corresponding response.
Several of GA's responses involved making revisions to its soil sampling plan. There-fore, also enclosed is a revised version of GA's " Soil Sampling Plan for Phase II of the SVA Decommissioning Project," dated October 21,1993. The revisions are as described in the enclosed responses. Under separate letter, GA is also submitting a copy of the enclosed revised plan to the State of California, Department of Health Services (Attn: Mr. Ben Kapel).
GA trusts that you will find the enclosures appropriate and responsive to your request for additionalinformation, and we are hopeful of your expeditious approval of the enclosed p!dn.
EG-Int 9310270115 931022 PDR ADOCK 07000734 PDR g(
C 92121-1194 PO BOX 8%CR SAN Di[GO, CA 92166 9784 5619 4 % 3000 I
3%O GENE RAL ATOMICS COURT, SAN DIEGO. Ces n'F l.k'
- Mr. Charles W. Emeigh, U.S. NRC Oct her 22,1993 696-2137 Page 2 If you have any questions regarding our request or the enclosed plan, please do not hesitate to contact me at (619) 455-2823.
Very truly yours, WWh Keith E. Asmussen, Director Licensing, Safety and Nuclear Compliance KEA:shs
Enclosures:
- 1) Responses to NRC's Comments on " Soil Sampling Plan for Phase II of the SVA Decommissioning Project," dated October 21,1993
- 2) Plan titled, " Soil Sampling Plan for Phase II of the SVA Decommissioning Project," dated October 21,1993 i
cc:
Mr. Michael Cillis, U.S. NRC, Region V (1 copy)
Mr. Robert Pate, U.S. NRC, Region V (1 copy)
Mr. Robert Wilson, Project Manager, NMNS, U.S. NRC Headquarters (1 copy) i l
t e
i 1
I
t RESPONSES TO NRC'S COMMENTS ON "SOll SAMPL.ING j
l
- PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT" l
October 21,1993 PAGE 1 OF 5 l
l GENERAL GA will not commence the final survey in a zone or section of the site until remediation is completed. After the final survey has begun, all results will be reported, including pre-and post-remediation if additional remediation is deemed necessary based upon the results of the final survey.
l Also, if elevated areas (areas above release criteria) are identified during the final survey, they will be evaluated for acceptability using NUREG/CR-5849 averaging methods, regardless of whether or not remediation will be conducted.
SPECIFIC COMMENTS AND RESPONSES l
1.
COMMENT Page 1, paragraph 4 - The thorium limit of 10 pCi/g is for total thorium. There were no individual limits for Th-232 and Th-228. This should be clarified in the discussion of applicable limits.
RESPONSE
The release criteria section of the plan (section ll) has been revised to clarify the release criteria as being 10 pCi/g for natural thorium (i.e., Th-232 and Th-228); and the separate limits for Th-232 and Th-228 have been deleted.
2.
COMMENT j
Page 2, paragraph 2 - NUREG/CR-5849 recommends two criteria for determining i
acceptability of elevated areas. The first is the (100/A)* criterion described in the licensee's plan. The second criterion is that the weighted average over a 100 m2 area should be less than the average guideline. The 100 m averaging criteria is 2
not in the plan and should be added.
RESPONSE
2 The 100 m averaging criteria has been added to section II (2) of the plan.
3.
COMMENT Page 2, paragraph 6 - Wh at method was used to determine background concentra-tions with a 95% confidence?
RESPONSE
The objective for background determination is that the average level should accurately represent the true background average to within i 20% at the 95%
confidence level (page 8.15 of NUREG/CR-5849). The total number of background measurements needed to satisfy this objective was calculated using Equation 8-22 on page 8-15 of NUREG/CR-5849. Using this formula, it was determined that nine (9) samples would be a sufficient number of samples to accurately represent the
i 4
RESPONSES TO NRC'S COMMENTS ON "SOlt SAMPLING
^
PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT" October 21,1993 PAGE 2 OF 5 true background average to within i 20% at the 95% confidence level (see l
attachment 1 for these results). Based on these results, ten (10) samples were used to determine background concentrations.
4.
COMMENT Page 2, paragraph 1 - Why is the Th-232 concentration determined by averaging Th-228 and RA-228?
The Ac-228 concentration alone should be more representative of the Th-232 concentrations.
RESPONSE
We propose to average the Th-228 and Ra-228 because gamma spectroscopy results indicate that the thorium and its daughters are in equilibrium. However, per your recommendation, GA will use the Ac-228 concentration to determine Th-232 concentrations.Section IV (2) of the plan has been changed to reflect this.
5.
COMMENT Page 3, paragraph 3 - How are the MDA's calculated?
RESPONSE
The detection limits provided in page 3, paragraph 3 were not intended to be Minimum Detectable Activity values (as defined in the NUREG/CR-5849 document).
l They were defined as estimated detection limits based on hundreds of samples counted over the past few years. To demonstrate this, six samples which had been counted for one hour and which showed U-235 concentrations ranging from 0.22 to 0.53 pCilg were again counted for 15 minutes. Activity levels above 0.3 pCi/g (as j
determined by the 60 minute count) were detected in a 15 minute count in all cases.
l A table with these results are provided in Attachment 2.
l Paragraph 3 of page 3 has been changed to read " estimated detection limits" rather than " typical limits of detection" which implied a calculated value for each sample.
l 6A.
COMMENT Page 4, paragraph 4 - An affected area is an area known to be contaminated, or
)
one that is potentially contaminated, based on process knowledge and previous surveys. It is incorrect to define affected areas as those areas with contamination in excess of the release criteria. The classification of the areas to be surveyed should be reassessed using the correct definition of affected areas.
RESPONSE
An affected area is defined in paragraph 5 of section V (2) as an area having potential for radioactive contamination or having known radioactive contamination.
There are two small known areas in the facility with elevated levels. With the exception of these two areas, there are no known areas with contamination of i
a RESPONSES TO NRC'S COMMENTS ON " SOIL SAMPLING PLAN FOR PHASE 11 OF THE SVA DECOMMISSIONING PROJECT" October 21,1993 PAGE 3 OF 5 values above fie release criteria. The results of the analyses of eighteen (18) core samples collected from underneath the concrete slab showed fourteen (14) natural background levels and four (4) which were slightly above background, but less than
~50% of the reiaase critena.
In view of the above, and in response to the concern expressed by NRC, GA is classifying me entire area beneath the concrete slab as an affected area and l
proposes to co-lect samples from this area on a triangular grid with a sampling interval of 5 m on a side (encloced area of approximately 10.8 m ) for a 95%
i 2
z assurance that elevated areas in excess of 10 m surface area are identified (per recommendation of EPA procedure, referenced on Page 4.16 of NUREG/CR-5849 i
ORAU-92/C57, June 1992). GA soil sampling plan has been revised accordingly.
l 6B.
COMMENT Page 6, paragraph 1 - What is the justification for not performing subsurface 2
sampling if the area of surface soil contamination is less than 5 m ?
RESPONSE
j When an area is remediated, soil samples will be collected and further remediation conducted until there is no indication of residual soil contamination above the I
release levels. This process should be sufficient to demonstrate compliance with the guidelines. However, additional subsurface sampling was proposed to provide, l
what GA believes to be, a conservative approach to demonstrating compliance with 2
the criteria. The use of a 5 m area can be justified on the basis of the averaging 2
allowed over a 100 m area (the area is only 5% of the area over which results can l
be averaged).
7.
COMMENT j
Page 7, paragraph 2 - Will the soil sample results be tested for acceptability at the 95% confidence levelin accordance with draft NUREG/CR-5849, Equation 8.137 f
RESPONSE
After the averages satisfy the guideline values and conditions, the results will be i
further evaluated to deteanine whether the data for each survey unit provides a j
95% confidence level that the true mean activity meets the guidelines using
]
Equation 8-13 of Reference 4 (this equation is recommended by the Environmental Protection Agency as a method to test data, relative to a guideline value, at a desired level of confidence.
The test will be applied to three (3) groups of samples. The first group will be the samples collected from the grid pattem shown in Figure 4. The second group will l
be the samples collected every 5 meters from underneath the drain lines and the third group will be the subsurface soil samples.
T Page 4 of 5 i
ATTACHMENT 1 4
Number of Points for Average Background to Within 20% at the 95% Confidence Level Radionuclide Average Skg. Conc.
Degrees of Freedom S
T-value Numberof Samples (DCilo)
Required i
Ac-228 1.31 9
0.34 1.833 5.658 Th-228 1.19 9
0.32 1.833 6.074 U-235 0.14 9
0.045 1.833 8.678 U-238 2.03 7
0.456 1.895 4.530 l
4 l
l i
l l
1 a
4 d
Page 5 of 5 ATTACHMENT 2 COMPARISONS OF URANIUM 235 AND THORIUM RESULTS FOR A 15 MINUTE -VS 60 MINUTE GAMMA SCAN Sample U-235 U-235 Th-228 '
' Th-232 ID '
(15 min)
(60 min)
(15 min)
(60 min) j (15 min)
(60 min) i Sec 2-0.18 t 0.10 0.2210.05 1.06
- 0.25 1.1710.15 1.01 i 0.39 1.25 10.25 209 #2 Sec 2-0.35 i0.10 0.2110.05 1.42 10.26 1.27 t 0.14 1.3110.45 1.32 i 0.27 209 #4 SVA-66 0.3710.09 0.35 10.04 1.21 0.25 1.37 20.11 1.14
- 0.42 1.53 10.22 SVA-64 0.37 i 0.13 0.34 i 0.07 1.50 10.26 1.57 t 0.16 2.17 i 0.45 1.70 i 0.28 SVA-97 0.4310.11 0.4010.06 1.3410.21 1.28 i 0.11 1.8110.42 1.36 i 0.23 SVA-21 0.5210.11 0.53 10.06 1.9410.28 1.7510.12 2.0710.49 1.96 i 0.23 Samples collected from the soil bank cast of the SVA facility during removal of contaminated soil caused by roof drain lines.
Th-228 was determined by averaging the 238 kev Pb-212 peak and the 583 kev TI-208 peak (if only one peak was reported, that peak was used).
Th-232 concentration was obtained using the Ac-228 concentration obtained by averaging the 338 and 911 peak (if only one Wak was reported, that peak was used).
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