ML20206P333
| ML20206P333 | |
| Person / Time | |
|---|---|
| Site: | 07003073 |
| Issue date: | 05/31/1998 |
| From: | Darois E External (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20206P330 | List: |
| References | |
| NUDOCS 9901110211 | |
| Download: ML20206P333 (6) | |
Text
.
l l
I l
Safety Evaluation Report I
for 1
Kerr-McGee Corporation 1
Cushing, OK i
l l
" Evaluation of Potential Radioactivity Concentration from the Effluent of the Proposed Radioactive Material Storage Area Containing Pit 4 Materials Due to Stormwater Discharge" Prepared By Eric L. Darois, CHP Radiation Safety & Control Services, Inc.
l Stratham,NH 03857 603-778-2871 May 1998 i
99o1110211 9805017 PDR ADOCK 07003073 C
5/98
-,.,-e
g_
c..
l.0 Introduction Kerr-McGee has requested an amendment to radioactive materials license SNM-1999.
This amendment request is in support of the construction of a radioactive material storage l
area (RMSA). The purpose of this RMSA is to store treated waste contaminated with i
radioactive (licensed) material from Pit 4. The intent is to place this treated waste in 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 j-feet.
l l
Although this evaluation makes several conservative assumptions, it is believed to l
provide a reasonable and reliable estimate of the concentration of radioactive material at the discharge point in the event that the dike area is filled with water and is discharged to unrestricted areas. The calculated concentration values are then compared to the limiting concentration values provided in 10CFR20.
2.0 Discussion and Analysis 2.1 Source Term
" Radiological Characterization Survey" (May,1991) provides the concentration of thorium and total uranium for Pit 4. Kerr-McGee is confident that the uranium in Pit 4 is not licensed material because the average total uranium concentration in Pit 4 is much below the mean background concentration for the site. Therefore, the uranium concentrations are listed in Table 1 for reference' but are not included l
in the subsequent analysis. These values are for a series of bore holes made throughout the area at varying depths of up to 11 feet with analysis for each I foot segment of the bore hole. A treated waste density of 1.6 g/ce, based on in-place density measurement of treated waste in the landfill, is used to compute total -
mass. Table 1 provides a summary of the volume, activity concentration and total thorium (thorium 232 & 228) and uranium activity from Pit 4 from which waste may be moved to the proposed RMSA. Concentrations presented below are pre-treatment concentrations. Because of reagent addition, actual concentrations in the RMSA are expected to be lower by approximately 30% although this additional reduction has not been incorporated into the calculations.
l Page 2 of 6 RSCS, Inc.
5/98
t l
o Table 1: Radionuclide Inventory of Pit 4, Zone 1 l
Bore Numbe Depth Volume Mass (g)2 Average Total Activity (pCi)
Hole r of (ft)
(yd )
Concentration 1
3 l
Code Grids' (pCi/g)!
l
\\
Thorium Uranium Thorium Uranium B-01 4
7 2589 3.17 E9 23.7 l
0.26 l 9.39 E10 1.03 E9 B-02 2
8 1480 1.81 E9 8.7 l
0.99 l 1.97 E10 2.24 E9 B-03 2
2 369 4.51 E8 5.2 l
0.55 l 2.9 E9 3.10 E8 B-04 2
11 2035 2.49 E9 5.5 l
1.58 l 1.7 E10 4.92 E9 B-05 1
11 1018 1.25 E9 4.1 L__0.0 6.39 E9 0
Total 7502 9.176 E9 1.4 El1 8.5 E9 Average Concentration = Total Activity + Total Mass l
Thorium = 15.3 pCi/g Uranium = 0.93 pCi/g (1) values taken from " Radiological Characterization Survey", May,1991 (2) assumes a treated waste density of 1.6 g/cc l
2.2 Effluent Concentrations 10CFR20 limits the annual average concentration of radionuclides discharged in liquid effluents to unrestricted areas to values less than those specified in
. Appendix B, Table 2, Column 2 to 10CFR20. As stated in 10CFR20, the concentration values given in Column 2 of Table 2 are equivalent to the radionuclide concentrations whien, ifingested continuously over the course of a year, would produce a total effective dose equivalent of 0.05 rem. For comparison to the 10CFR20 values, an estimate of the radioactivity concentration at the discharge point of the RMSA is needed. Calculation of this concentration requires the average concentration of the radionuclides present in the material and l
an estimate of the amount of suspended solids that could result from mixing the materials or from erosion.
l The thorium species contained within the treated waste is considered insoluble in water. Therefore, any radioactivity in the water would likely be a result of a suspension of material caused by mechanical processes such as erosion. In order to estimate the amount of radioactive material that would remain suspended in the Page 3 of 6 RSCS, Inc.
5/98 s
d e
discharge water, another pond was sampled and analyzed for Total Suspended Solids (TSS), in milligrams per liter (mg/l). This pond (Pond 5) collects runoff from Pit 5, which contains waste similar to that in Pit 4. These TSS values are considered representative of the TSS that would result from the placement of the 1
Pit 4 material into the RMSA. Samples were submitted for TSS analysis of agitated water and after allowing settling times of 1,2, and 7 days. These values provide a conservative estimate of TSS because the waste in Pit 5 is loose, while j
the Pit 4 material will be compacted when placed into the RMSA. TSS values for the Pit 4 materials are expected to be lower since erosion should be lower for the compacted material.
A report by Southwest Laboratory of Oklahoma provided the data used as an appropriate and representative value for TSS. A value of 5 mg/l was selected as representative of the potential discharges of collected stormwater from the RMSA. The 5 mg/l value was derived from a sample allowed to settle 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after mixing prior to analysis, was selected because a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> settling period is a practical amount of time for Kerr-McGee to hold back effluent after significant rainfall or treatment of the waste involving agitation.
Table 2 provides a summary of the calculated waste and water concentrations for each isotope using the assumptions discussed above. The assumption was made that all progeny of Th-232 are in secular equilibrium with the parent. Therefore, the average total thorium concentration derived from Table 1, which is for Th-232 and Th-228 combined, is divided in half for the assumed concentration of each member of the decay chain. Table 2 includes values for the decay chain down to the gaseous isotope (radon-220) because emanation from the pile would effectively reduce the amount of this isotope and all subsequent progeny to negligible levels. In addition to direct emanation from the pile, there are many opportunities for further emanation to occur such as: during processes that involve agitation or treatment of the waste; from the collected storm water runoff; and throughout the process of discharging collected storm runoff water.
Table 2 also provides the 10CFR20 environmental compliance level (ECL) from 10CFR20 as well as the fraction of this level (FECL) that corresponds to the calculated concentration. This indicates that the maximum liquid effluent concentration for all radionuclides combined (FECL) at the discharge from the dike, would be less than 2.31 E-3 of the 10CFR20 ECL values.
Pvge 4 of 6 RSCS, Inc.
5/98
~..-.
8 4
l 1 0 l
Table 2: Estimated Emuent Concentrations (based on 5 mg/l TSS) l Isotope Average Water ECL:
FECL Waste Concentration (pCi/ml)
(fraction of
. Concentration
( Ci/ml)
Table 2,-
Column 2 l
Th-232 7.6 3.80 E-11 3 E-8 1.3 E-3 Ra-228 7.6 3.80 E-11 6 E-8 6.3 E-4 i
Ac-228 7.6 3.80 E-11 3 E-5 1.3 E-6
)
Th-228 7.6 3.80 E-11 2 E-7 1.9 E-4 Ra-224 7.6 3.80 E-11 2 E-7 1.9 E-4 Total.
2.S E-3 l
2.3 Engineering Controls t
The NRC effluent concentration limits (ECLs) from 10CFR20 Appendix B represent annual average concentration limits at the boundary of the unrestricted area (site boundary). Although Kerr-McGee intends to utilize l
additional engineering controls to further reduce the concentrations of the effluent, no attempt to quantify these reductions has been included.
The discharge of storm water runoff from the RMSA will first pass through a silt fence (hay bales), further reducing the concentrations of insoluble materials. The actual discharge will then be accomplished using a floating skimmer (or equivalent) that will drain the effluent via a discharge pipe to a tributary.
i
[
l' 3.0 Conclusions The following conservative assumptions were made in this SER:
r l
The density of compacted waste in the RMSA will likely be lower than the disposal e
cell density used (1.6 g/cc).
The expected reduction ofisotopic concentration of the treated waste by added reagent is not included.
{
No accounting for engineering controls.
TSS value based on only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> retention time.
Pag,e 5 of 6 l
RSCS, Inc.
5/98 i-
.o This evaluation provides a conservative, but reasonable and reliable estimate of the l
' concentration of radioactive material in the liquid effluent of the proposed RMSA. The j
annual average concentration at the effluent point is shown to be well below the limits l
prescribed in 10CFR20.' Material may be stored in the RMSA for several years.
Sampling' and analysis of the water contained within the RMSA will provide ample opportunity to develop altemate plans in the event that activity concentrations approach the limits specified in 10CFR20. If future plannmg requires that waste be placed into the RMSA from RMAs not analyzed in this report, then an additional safety evaluation will be performed based on data ' collected during the operation of the RMSA.
i l
It appears reasonable that the storage of treated waste within the proposed RMSA will not cause liquid effluent concentrations to approach even a small fraction of the values
'specified in 10CFR20. That fraction will decrease as appropriate monitoring and engineeringtontrols are applied to the management of the area.
4.0 References 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".
i
" Radiological Characterization Survey", submitted to Oklahoma Department of Health (now Oklahoma Department of Environmental Quality) May,1991 l
Southwest Laboratory of Oklahoma report # W8393 i
i t
1
(
l RSCS, Inc.
5/98
.. -.