ML20206P324
| ML20206P324 | |
| Person / Time | |
|---|---|
| Site: | 07003073 |
| Issue date: | 05/01/1998 |
| From: | Lux J KERR-MCGEE CORP. |
| To: | Brown S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20206P330 | List: |
| References | |
| NUDOCS 9901110205 | |
| Download: ML20206P324 (4) | |
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KERR-McGEECORPORMION nanaan ewen. ouwon em. onwou nm May 1,1998 g~
Mr. Stewart Brown,
Low-Level Waste & Decommissioning Projects Branch Division of Waste Management Office of Nuclear Materials Safety & Safeguards U. S. Nuclear Regulatory Commission
. Washington, D. C. 20555 Rei Docket No. 70-3073,
- License No. SNM-1999 Cushing, OK Facility a
Dear Mr. Brown:
Kerr-McGee Corporation (KMC) submitted a design for a Radioactive Materials Storage Area
'(RMSA) in September,1997. In November,1997, KMC submitted a plan to decommission Pit 4, an acidic hydrocarbon waste pit at the Cushing refinery site.~ A portion of Pit 4 is 4
contaminated with thorium. This submittal was subsequently revised based on NRC's review and feedback. The RMSA will contain neutralized acid sludge from Pit 4 that exceeds BTP Option 1 limits until it can be sent to a licensed disposal site. To minimize the release of thorium contaminated sediment, the RMSA was' designed to retain rainfall. KMC will analyze and then i
discharge water from the RMSA via a valved discharge pipe through the dike. KMC proposed to -
perform gross alpha analysis of the water prior to discharge to ensure that regulatory release 3
. limits will not be exceeded; later isotopic analysis will provide further confirmation that the limits
- were not exceeded.
i NRC approved the design, enabling constmetion of the RMSA, but restricted KMC from placmg licensed material in the RMSA until. KMC demonstratcs that procedures and controls will prevent discharge that exceed a fraction (20 - 30%) of effluent release limits stipulated in Appendix B of 10 CFR 20. KMC submitted a Safety Evaluation Report (SER) that demonstrated under worst-g case conditions, the regulatory limit would not likely be exceeded. However, KMC did not 3
emphasize that the SER presented a worst-case analysis or describe expected conditions after planned controls are implemented for the RMSA. NRC therefore stated, in a letter dated April 6, 1998, that the proposed operation of the RMSA does not appear to maintam the conceritration of licensed material in the release of impounded water As low As Reasonably Achievable (ALARA).
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\\A A meeting at NRC headquarters on April 14 clarified NRC's concerns. KMC committed to respond promptly to expedite approval of the operation of the RMSA. NRC stated that the approval of the Pit 4 decommissioning plan and the RMSA operation is best done concurrently.
' This combined action is necessary to enable KMC to begin work as promptly as possible.
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1 o-This letter provides the additional information requested by NRC to show that the RMSA will be
. operated in a manner such that releases are a small fraction of the regula:ory limit. A revised SER, based on conservative yet more realistic conditions, shows that this is the case.
l ALARA Comraitment - KMC is committed to maintain discharge concentrations averaging less than 20% of the effluent limits. This revised SER takes into consideration some of the controls KMC plans to employ. The SER projects a typical release (still with conservative assumptions) to be less than 1 % of the limit. The following explains how KMC plans to cperate the RMSA to provide controls to maintain releases ALARA.
Placement of Waste - The original SER was based on the assumption that the waste placed in the RMSA would form a hemispherical " pile" of unconsolidated sediments. In practice, the waste 4
will be spread with a blade and compacted in place. Because the neutralized waste is a compactable material, it will not be subject to as much erosion as the loose soil pile presented in the original SER.
Sediment Loadi_ng - The original SER assumed that one half of one year's precipitation would be discharged in one release, and that 10% of all the soil that eroded from the pile in a year was discharged in that release. In ~ practice, water will be discharged in periodic releases, and only after allowing time for particulate settling. A hay bale filter surrounding the discharge area will provide filtration to additionally reduce the introduction of sediment to the discharge area.
Finally, a floating skunmer will keep the discharge entrance off the bottom of the RMSA to muumize the potential resuspension of sediment near the discharge pipe.
l Because the RMSA may be used as a mixing area for wastes from other RMAs (in the future),
KMC will discharge from the RMSA periodically to keep the material as dry as practical. The revised SER projects that KMC will discharge water from the RMSA 10 times per year, so the quantity of water released at any one time is 10% of the estimated annual total.
KMC is neutralizing and discharging water from other water treatment ponds under a permit
. issued by the Oklahoma Department of Environmental Quality. The source of this water is stormwater that falls on Pits 1,2, and 5 (these pits are not radiologically contamimted). After contacting the acidic material for a day or two, the stcrmwater is too acidic to release and must be neutralized before releasing it to surface water. KMC adds a 50% solution of caustic soda (NaOH) to the water, using pumps and eductors to " stir" the pond. KMC sampled the permitted treatment ponds to generate estimates of suspended solids for use in the revised SER. After agitation, a sample of water from the treatment pond yielded 216 mg/l TSS. After waiting 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the TSS dropped to 5 mg/l as sediment settled out of suspension. This value was used to represent a more likely value for sediment load in the revised SER. After seven days, the TSS for the same sample had dropped to 3.5 mg/1.
KMC considers the thorium in treated Pit 4 material to be insoluble. The SER therefore calculated the total activity of thorium to be the product of the activity of the waste and the concentration of suspended solids. Dissolved thorium will be a small fraction of this activity.
However, analyses performed under the effluent monitoring program will identify ALL thorium, i
both dissolved and suspended. Because the predicted concentration in a discharge is less than 1 %
.of the limit, the small potential increase in activity from dissolved thorium is not expected to be distinguishable from the activity due to suspended sediment.
Apolication of Limits - NRC stated that the limits cited in KMC's submittals apply to releases to surface water, rather than to open land areas. KMC will extend the discharge pipe so that collected water from the RMSA will be released tn 2 mrface water drainnge pQ ensure j
l that the Part 20 regulatory limits are applied in the appropriate manner.
Characteristics of Licensed Material - The original SER assumed that licensed material from other areas besides Pit 4 would be placed in the RMSA. This raised questions about quantity, i
radionuclide species, and concentration assumptions. To expedite use of the RMSA for Pit 4, the l
SER was revised to include only estimated volumes and radionuclide concentrations of material l'
from Pit 4. The quantity of licensed material released during discharge is the product of the concentration of total suspended solids and the concentration oflicensed material in those solids.
Only Pit 4 waste was considered in this SER, and a conservative concentration for Pit 4 waste is the average concentration of Zone 1 material, which is 6.1pCi/g Th-232. Zone 2 material may dilute the Zone 1 material slightly, but KMC has no basis on which to assume any final concentration, so the Zone 1 average was used in the analysis. KMC will not place material from other RMAs in the RMSA without subsequent NRC approval.
l Liauid Effluent Monitoring Program - NRC expressed greatest concern regarding the efficacy of KMC's liquid effluent monitoring program. KMC, in conjunction with health physics professionals, developed a method for gross alpha analysis of water to demonstrate compliance L
with effluent limits, and proposed to discharge water based on this pre <lischarge gross alpha analysis. NRC stated that the liquid effluent monitoring plan must address three concerns:
- 1. All nuclides in the decay chain must be considered, not only Thorium-232,
- 2. The proposed method of gross alpha analysis must be sensitive enough to "see" a fraction of the limit, and
- 3. Pre-discharge samples may not be representative of water at the time of discharge, so the plan must provide for sampling at the time of discharge as well.
First, all nuclides are considered in the SER; nuclides in the decay series past radon were omitted from the evaluation. Second, KMC has attached an evaluation showing that gross alpha analysis can detect approximately 30% of the limit, providing an ample margin of safety. Third, KMC will discharge on the basis of pre-discharge samples, and then collect a sample of the discharge at least midway in the release to measure water that is flowing out of the pipe. KMC expects the analysis of this discharge water to yield the same or lower concentrations than pre-discharge results. Finally, KMC will not rely exclusively on gross alpha analysis to demonstrate compliance with regulatory limits. KMC will utilize isotopic analysis of pre-discharge and j
discharge samples to provide confirmation that limits were not exceeded. If correlation of gross alpha and isotopic analyses show that gross alpha analysis is adequate to demonstrate compliance
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with effluent limits, the frequency of isotopic analysis may be decreased.
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l Categorical Exclusion - NRC also indicated that KMC had not provided adequate information from which to either perform an environmental assessment of the impact of these releases or to apply the categorical exclusion from such an environmental assessment. KMC believes this l
submittal contains sufficient information for NRC to determine that a categorical exclusion is appropnate, or to perform an environmental assessment if one is needed.
Finally, KMC has applied for a permit to discharge stormwater from the RMSA under the Oklahoma Pollutant Discharge Elimination System. This permit will address non-radiological criteria only. All discharges must comply with conditions stipulated in the OPDES permit in addition to NRC's Part 20 criteria. KMC 'will not operate the RMSA without DEQ and NRC approval.
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If you have any questions or comments, please call me at (405) 270-2694.
Sincerely,
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Jeff Lux Project Manager xc:
C. L. Cain, NRC Region IV L
Rick Reiley, Cushing Citizens' Oversight Committse Gene Smith, ODEQ.
Darrell Shults, ODEQ l
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