ML20217J327
| ML20217J327 | |
| Person / Time | |
|---|---|
| Site: | Plum Brook |
| Issue date: | 03/30/1998 |
| From: | Campbell D NATIONAL AERONAUTICS & SPACE ADMINISTRATION |
| To: | Mendonca M NRC (Affiliation Not Assigned) |
| References | |
| 0540, 540, NUDOCS 9804060264 | |
| Download: ML20217J327 (5) | |
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National Aeronautics and Space Adminisuafon Lewis Research Center ,
Cleveland, OH 44135-3191 MAR 3 01998 Reply m Ann d 0540 United States Nuclear Regulatory Commission Attn: Mr. Marvin Mendonca Senior Project Manager Office of Nuclear Reactor Regulation ;
Washington, DC 20555-0001 l
Subject:
Request for Additional Information (TAC No. 97823)
This responds to your letter dated November 19, 1997, j requesting additional information and clarification relative to I NASA's proposal to continue and to amend License Nos. R-93 and l TR-3 for the NASA Plum Brook Reactor Facility (PBRF) . The l following responses to your specific requests for additional j information are affirmed consistent with 28 U.S.C. S1746. For i clarity, your questions are restated in bold font.
- 1. The respense to item 1 of the NRC's July 10, 1997, request l for additional information (RAI) appears to be an extremely conservative estimate of the radiological exposures in that it does not account for the effect of the decay of the shorter lived radioactive materials and the specific contribution of this decay on the exposure (i . e . ,
radiological exposures were based on a ratio of curie content and did not account for the specific energy or curie content of the significant isotopes such as cobalt 60). Therefore, provide an estimate of the radiological '
exposure given the decay and radioactive energy effects of l the specific isotopes.
l The enclosure hereto is responsive to the above question. The enclosure represents the most current information available to 1 me. l
- 2. The other responses to NRC's July 10, 1997 RAI indicated it ;
was prudent to wait on dismantlement because of the l uncertainties associated with low level waste disposal i facilities. They also indicate that there was no \
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significant difference between the logistics and planning decommissioning activities and the radiological exposures now or in the future. Since it is not clear when the waste disposal situation will have fewer uncertainties, provide a commitment to complete ~ decommissioning. activities by the end of 2007, which includes budgeting of funds through the termination of the license. Include a schedule to submit a complete decommissioning plan'to the NRC-by the end of 1999. Include in your, plans provisions for. facility stabilization in, case waste disposal facilities become unavailable. ,
NASA is a-federal agency'which relies upon' annual appropri-ations from Congress to conduct its operations.. While we recognize our responsibilities as a licensee and. intend to fully comply with NRC requirements, th'e agency cannot be certain that its'requestifor funding will be; approved by Congress. With"that caveat, NASA'intendsito work toward completing decommissioning. activities relative'at the PBRF by the end of 2007.. NASA i's currentifcondu'cting a study to g
define the kinds and quantities'of low level nuclear waste that will be generated by decommissioning'.and to estimate the cost of any necessary demolition and, site' restoration. Based on the estimated kinds and quantities of low level nuclear waste identified by the-study, NASA wil1Jbegin discussions with waste disposal sites.to arrive at contractual terms for disposal. We anticipate that the data provided by the study and our discussions with waste disposal facilities will enable NASA to prepare a decommissioning plan that is complete except for the specific timing and availability of appropriated funds. The study is currently anticipated to be completed by the end of CY 1998. NASA intends to provide the NRC, by the end of CY 1999, with a decommissioning plan that incorporates the results of the study, including provisions for providing facility stabilization should the availability of waste disposal facilities be interrupted.
After the study outlined above is completed and total decommissioning costs can be estimated with sufficient accuracy, NASA intends to seek, as part of its annual budget submission process, the necessary appropriations to accomplish decommissioning. The appropriations submission ~will seek-sufficient-funds to. accomplish all necessary demolition and site restoration and waste disposal. Contingent on timely
' Congressional appropriation of sufficient funds for such purpose,' NASA commits to take all appropriate and reasonable steps toward completing decommissioning activities by the end of 2007.
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I declare under penalty of perjury that the foregoing is true and correct.
Executed on Y / 3. 8, , 1998.
Donald J. pb 1 Director !
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=0 Request for Additional Information (TAC No. 97823)
~ Respon' s e to (hestion #1:
NASA's response to item 1 of the NRC's July 10,1997, RAI was based on dose rate calculations found in the 1980 PBRF Environmental Repon. While researching the response to the current RAIit was determined that much more detailed (and therefore more accurate) estimates of occupational dostge had been made as pan of the 1985 Engineering Study For this reason the 1985 Engineering Repon information and calculations were used as the basis for this response.
The 1985 Engineering Report contained a detailed analysis of what would be involved in decommissioning the PBRF, including detailed occupational dose ' estimates. They were calculated by considering all of the detailed, step by step activities involved in decommissioning, the average crew size for each activity, the estimated duration of each activity, and the average expected dose rates in each work area based on measured and estimated data. The isotopes present, their relative abundance, and their physical location within the PBRF were also taken into account.
The 1985 Engineering Report estimated the total occupational dose from decommissioning would be 342.0 man-rems, assuming decommissioning was conducted over four years and actually staned in 1988. This value will serve as the baseline for this response, and must be adjusted for isotope specific decay.
The radionuclide inventory at the PBRF was initially established by calculation in 1978.
These values were veri 6ed by actual field measurements as part of the 1985 Engineering Report. The results are shown in Table 1, including the calculated values for the inventory in 1997, and at five year intervals into the future, allowing for normal decay.
The most abundant nuclide in the PBRF is hydrogen 3 (tritium). However, since it is well contained within the metal matrix of the beryllium reflector pieces and is such a weak beta emitter it was not considered to contribute to the occupational dose. The remaining isotopes are found in the stainless steel portions of the reactor core (some of which were removed from the Reactor Tank and placed in the Hot Dry Storage vaults following shutdown) and to a lesser degree as part of the corrosion film which is distributed relatively uniformly throughout various primary and auxiliary piping systems and components. Cobalt 60 is by far the most abundant of these remaining isotopes. Its quantity and the strength of its 1.3 Mev gamma emissions make it the overwhelming contributor to occupational dose.
The actual measured dose rates within the facility over the years have in fact decayed at a rate approximating that of cobalt 60. The result of applying the decay rate of cobalt 60 to the baseline estimate for occupational dose level 6 shown in Table 2.
Enclosure >
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In 1978 the estimated public dose from the PBRF decommissioning was 8.2 man-rems.
This value wap generated as part of the 1978 study which formed the basis of the 1980 Enviro'nmental Report. It was not reduced for decay in 1980 or 1985 because the limiting factor for the public dose rate was viewed as being the regulatory limit for shipping containers of 200 mrem / hour at one foot from the container's surface. It was believed to be conservative to assume the shipper would package up to the legal limit, so the dose to the public would be driven by field strength, not radionuclide inventory. It was also believed that the shipments of waste would be the major contributor to the public dose. It is believed to be overly conservative to continue to not take decay of the inventory into account, so as with occupational dose the 1985 figure of 8.2 man rems for decommissioning beginning in 1988 was reduced by applying the decay rate of cobalt 60. The resulting revised estimate of public dose level is shown in Table 2.
Table 1: PBRF Radionuclide Inventory (Curies)
Reactor Tank HaN LNe (yrs) 1978 1988 1997 2002 2007 2012 3H 12.3 156,300 89260.27 53757.51 40559.74 30602.10 23089.12 60 Co 5.2 2640 696.34 209.86 107.78 55.35 28.43 55 Fe 2.4 7340 408.95 30.41 7.18 1.69 0.40 152 Eu 12.8 1 0.58 0.36 0.27 0.21 0.16 154 Eu 16 1 0.65 0.44 0.35 0.28 0.23 50 NI 8.00E+04 0.5 0.50 0.50 0.50 0.50 0.50 63 Ni 92 45 41.73 39.00 37.56 36.17 34.83 26 Al 7.40E+05 1.4 1.40 1,40 1.40 1.40 1.40 137Cs 30 1 0.79 0.64 0.57 0.51 0.46 90 Sr 28 1 0.78 0.62 0.55 0.49 0.43 Hot Dry Storage l
3H 12.3 34,600 19696.46 11862.31 8950.04 6752.76 5094.92 l
60 Co 5.2 16,100 4246 34 1279.80 657.28 337.57 173.37 55 Fe 2.4 14.600 813.44 60.49 14.28 3.37 0.80 l
! Table 2: Estimated Dose Levels for PBRF Decommissioning Year Decommissioning 1988 1997 2002 2007 2012 i Starts Occupational Dose (man- 342.0
- 103.1 52.9 27.2 14.0 rems)
Public Dose (man-rems) 8.2 2.5 1.3 0.7 0.3
- "1985 Engineering Report", Table 4.1-3, page 4.1-30