ML20206P346
| ML20206P346 | |
| Person / Time | |
|---|---|
| Site: | 07003073 |
| Issue date: | 01/31/1998 |
| From: | Darois E External (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20206P342 | List: |
| References | |
| NUDOCS 9901110222 | |
| Download: ML20206P346 (4) | |
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l Safety Evaluation Report i
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Kerr McGee Cushing, OK l
" Evaluation of Potential Radioactivity Concentration from the Efiluent of the i
l Proposed Radioactive Material Storage Area due to Stormwater Discharge" Prepared By Eric L. Darois, CHP Radiation Safety & Control Senices, Inc.
Stratham,NH 03857 603-778-2871 i
January 1998 I
i 9901110222 990210 "
PDR ADOCK 07003073,-
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V 1.0 Introduction l
- Kerr hfcGee's Cushing site in Cushing OK, has requested an amendment to radioactive materials license l
1 SNM-1999. This amendment request is in support of the construction of a radioactive material storage area, RMSA. The purpose of this RMSA is to store soil contaminated with radioactive (licensed) material. The intent is to place this soil within a diked area to collect surface and rain water. The size and configuration of the RMSA is designed to retain half of the total mean annual precipitation volume of 420,000 cubic feet.
This evaluation provides a very conservative estimate of the concentration of radioactive material in the discharge point in the event that the dike area is filled with water and is discharged to unrestricted areas.
l The calculated concentration values are then compared to the limiting concentration values provided in 10CFR20.
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2.0 Discussion and Armlysis 2.1 Source Term i
Reference 4.1 provides estimates of radioactivity concentrations and contaminated soil volumes in each radioactive materials area (RMA) at the Cushing site. These activity estimates are provided for each concentration range, or option. The total activity in each RMA may be determined by the product of the activity concentration (pCi/g) and the total mass of soil. Since reference 4.1 provides only the estimated soil volume, a conservative estimate of soil density of 2 g/cc is used to compute total mass. Table 1 provides a summary of the volume, activity
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concentration and total activity for each of the four major isotopes and for each of the RMAs J'
from u hich soil may be moved within the next 2 years to the proposed RMSA.
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Table 1: Estimated Total Radioactivity Contained in the Proposed RMSA at Maximum Capacity U-234 U-235 U-238 Th-232 RMA Option (1) Volume (2) Total Total Total Act.,
Total Act.,
Cat.
ft^3 pCi/g Act., Ci pCi/g Act., Ci pCl/g Ci pCi/g Cl 5
2 15200 1.08 9.00E 04 0.04 3.33E-05 1.21 1.01E-03 10.73 8.94E-03 5
4 1200 83.41 5.49E-03 3.24 2.13E-04 17.51 1.15E-03 3.77 2.48E-04 3
2 234400 18.25 2.34E-01 0.68 8.73E-03 2.23 2.86E-02 8.31 1.07E-01 2
2 52800 3.15 9.11E 03 0.09 2.60E-04 0.36 1.04E-03 9.86 2.85E-02 2
4 400 26.58 5.83E-04 1.01 2.21E-05 4.89 1.07E-04 20.38 4.47E-04 Total 3.04e+05 2.512-01 9.26E-03 3.20E-02 1.45E-01 (1) values taken from reference 4.1; tables 6.2,6.3, and 6.5.
(2) conservatively assumes a soil density of 2 g/cc.
2.2 EfIluent Concentrations 10CFR20 limits the annual average concentration discharged in liquid efIluents to unrestricted areas to values less than those specified in Appendix B table 2 column 2 to 10CFR20 for each radionuclide. In order to bound the maximum expected annual average concentration for comparison to the 10CFR20 values, estimates of the radioactivity concentration at the discharge point of the RMSA is needed. Calculation of this concentration requires knowledge of the Page 2 of 4 RSCS. Inc.
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r" potential water volume within this area and the potential amount of radioactisity suspended in the water. Reference 4.2 provides an analysis of the expected rainfall and storm-water discharge
- pattern at the Cushing site. Using the dimensions of the proposed RMSA, reference 4.2 naimata the annual discharge of water from the RMSA to be approximately 210,000 cubic feet.
The uranium and thorium species contained within the contaminated soil is considered insoluble l
in water. Therefore, any radioactivity in the water would likely be a result of a suspension of matenal caused by mechanical processes such as soil erosion. The depth of soil erosion in one year is conservatively estimated as 2 inches. This is considered a reasonable value determined from experience gained at a local Kerr-McGee remediation site in Cleveland Oklahoma.
The volume of eroded soil is estimated assunung that the 304,000 cubic feet of soil is mounded in a hemisphere. Using this geometry with the 2 inch erosion depth, the estimated volume of eroded soil is calculated as 2883 cubic feet. The amount of radioactisity that stays suspended in the water is conservatively assumed to be 10% of the total eroded from the hemispherical mound j
of contaminated soil. The actual fraction that stays suspended is likely to be well below this value since discharges will include a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> settling interval following significant rainfall events. However, since this evaluation attempts to bound the discharge concentration, then this assumption is applied to maintain a large conservative margin.
Table 2 provides a summary of the calculated soil and water concentrations for each isotope using the conservative assumptions discussed above. Table 2 also provides the 10CFR20 environmental compliance level (ECL) from 10CFR20 as well as the fraction of this leve!
(FECL) that corresponds to the calculated concentration. This indicates that the maximum liquid
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effluent concentration combined for all radionuclides (FECL) at the discharge from the dike, j
would be less than 0.% of the 10CFR20 ECL values.
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The NRC cffluent concentration limits (ECLs) from 10CFR20 Appendix B represent annual average concentration limits at the boundary of the unrestricted area (site boundary). The effluent released from the dike area of the proposed RMSA is on property owned and controlled by Kerr-McGee. The distance from the release point to the unrestricted area boundary (site boundary) is approximately 200 meters of downward sloping land. This additional property would provide additional dilution flow from the annual rainfall of 31.5 inches. The increased dilution flow would further reduce the concentration at the unrestricted area boundary thereby ensuring that concentrations would be well less than the 10CFR20 ECL values. Additional controls to the discharge point will include the placement of a silt fence (hay bails) to limit the discharge of high concentrations ofinsoluble materials.
Table 2: Estimated Annual Average Radioactivity Concentrations from the 4
Erosion of 2" of Soil from the Proposed RMSA Filled with 304,000 cubic feet of Waste Material Assuming a Hemispherical Configuration and 10% Suspension in Water.
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U-234 U-235 U-238 Th-232 Total Soil Actmty Conc., Cvft*3 8,24!. 07 3.05E-08 1.05E-07 4.77E-07 Total Activityin a 2" layer (2883 fla3). Ci 2.38E-03 8.79E-05 3.03E-04 1.37E-03 10% of Total Act in 2" layer, ci 2.38E-04 8.79E-06 3.03E-05 1.37E-04 Estwnsted Water Conc., uCi/cc 4.13E-08 1.53E-09 5.27E-09 2.39E-08 ECL (10CFR20) uCi/cc 3.00E-07 3.00E-07 3.00E-O'7 3.00E-08 9 ;g FECL 0.138 0.005 0.018 0.796 1
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3.0 Conclusions
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This evaluation provides a very conservative evaluation of the maximum concentrations of radioactive i
matenal in the liquid efiluent of the proposed RMSA. The following is a summary of the conservative
. nmptions applied to this analysis.
The entire radmactivity content from RMA 2,3, and 5 are placed into the RMSA in one year (i.e.no sorting of the matenal willoccur).
Rain events will cause soil crosion in the RMSA at a rate of 2" per year with an annual rainfall of 31.5" per year.
10% of the radioactivity in the eroded soil will be maintained suspended in the water until discharged.
The discharge point represents the boundary of the unrestricted area.
Vegetative cover would not reduce the rate of erosion within the RMSA.
With these conservative assumptions applied, the annual average concentration at the effluent point is shown to be less than the limits prescribed in 10CFR20. Additionally, the contents of the proposed RMSA will not increase over a short interval. It is reasonable to expect that the process of" filling" the
' RMSA will occur over several years. This time period will allow for sampling and analysis of the water contained within the RMSA dike area as the activity inventory increases. This will proside ample opportunity to develop alternate plans in the event that actisity concentrations approach the limits specified in 10CFR20. If future planning requires that contaminated soil be placed into the RMSA from RMAs not analyzed in this report, then an additional safety evaluation will be performed based on actual data determined from the operation of the proposed RMSA.
From this it appears reasonable that the storage of contaminated soil within the proposed RMSA will not cause liquid effluent concentrations to exceed the values specified in 10CFR20 presided that appropriate monitoring and controls are applied to the management of the area.
4.0 References 4.1
" Cushing Facility ALARA Analysis", prepared by Chase Emironmental Group, Inc, March 1995.
4.2 Letter from Gary Maggert, Burns & McDonnell Inc., to Jeff Lux et. al. dated 9/26/97; "KMC Rad Storage Area. Cushing Oklahoma, Discharge of Storm-water, Project No. 96 710-4 201 03.'
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