ML15224B046
| ML15224B046 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/03/1986 |
| From: | Miraglia F Office of Nuclear Reactor Regulation |
| To: | Walker R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8610150048 | |
| Download: ML15224B046 (15) | |
Text
October 3, 1986 Docket Nos. 50-269, 50-270 and 50-287 MEMORANDUM FOR:
Roger D. Walker, Director Division of Reactor Projects, Region II FROM:
Frank J. Miraglia, Director Division of PWR Licensing-B, NRR
SUBJECT:
ELEVATED RADIONUCLIDE LEVELS IN FISH AND SEDIMENT (TIA 85-07)
REFERENCE:
Oconee Nuclear Station, Units 1, 2 and 3 Enclosed is our response to your request for assistance (TIA 85-07) to evaluate the elevated levels of radiocesium in fish and sediment in the environment around the Oconee Nuclear Station. Specifically, you asked us to:
- 1. Reexamine the current Offsite Dose Calculation Manual (ODCM) and determine if its methodology is appropriate and consistent with observations; and
- 2. Review the environmental impact of chemical treatment pond CTP-3 including the need for limiting the amount of radioactivity in the pond; the need for additional requirements for monitoring sediment in the pond; the need for ground water monitoring near the pond; and the need for additional sampling of fish and sediment in Lake Hartwell.
Based on the results of effluent measurements and modeling of the environ mental exposure pathways, we have concluded that the concentrations of radioactive materials and the levels of radiation in the environment have been significantly higher than expected. The higher radioactive levels may be caused by significant dose contribution not presently addressed by the methodology of the ODCM. Potential contributions may be from fish, feeding from the bottom of the lake or from currently unmonitored normal releases of radioactive materials from the chemical treatment ponds in the form of seepage to nearby waterbodies. CTP-3 appears to be similar to the other two chemical treatment ponds, CTP-1 and CTP-2, because it receives radioactive materials from the plant, it is located in a restricted area and it is potentially subject to the uncontrolled release of inventory from pond failure or other causes; yet the Oconee Technical Specifications limit radioactive material inventory for CTP-1 and CTP-2 only.
We recommend that the licensee be informed of our evaluation and that a meeting or telephone conference be held with the licensee and Region II to discuss how the licensee is planning to assure compliance with the regulations as implemented through the Technical Specifications. At the meeting, we propose to recommend that the licensee, first, intensify the environmental monitoring program to confirm the observed elevated levels of radiocesiums 8610150048 861003 PDR ADOCK 05000269 p
ENCLOSURE EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON ELEVATED LEVELS OF RADIOCESIUMS IN THE ENVIRONMENT AROUND THE OCONEE NUCLEAR STATION DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1, 2 AND 3 DOCKET NOS. 50-269, 50-270 AND 50-287 By Task Interface Agreement (TIA) No. 85-07 dated February 14, 1985 (memorandum dated October 5, 1984 from R. C. Lewis, Region II to D. G. Eisenhut, DL),
Region II requested assistance from NRR in evaluating elevated levels of radiocesiums in fish and sediment in the vicinity of the Oconee Nuclear Power Plant. Region II had been notified by Duke Power Company, the licensee for the Oconee Nuclear Station, that the radioactive levels for cesium-134 and cesium-137 in fish samples exceeded the levels in samples of catfish taken in May 1984 (Reference 1).
Specifically, the TIA requested that we:
- 1. Reexamine the current Offsite Dose Calculation Manual (ODCM) and determine if its methodology is appropriate and consistent with observations.
- 2. Review the environmental impact of chemical treatment pond CTP-3 including the need for limiting the amount of radioactivity in the pond; the need for additional requirements for monitoring sediment in the pond; the need for ground water monitoring near the pond; and the need for additional sampling of fish and sediment in Lake Hartwell.
- 3. Prepare a letter report to Region II.
Our evaluation, conclusions and recommendations follow.
-2 The Oconee Technical Specifications are based on the guidance of NUREG-0472, "Standard Radiological Effluent Specifications for Pressurized Water Reactors."
Both the Oconee Technical Specifications and NUREG-0472 incorporate provisions for:
- 1. Limitations on doses to members of the public from radioactive materials in liquid effluents released from the plant to provide assurance that the releases of radioactive material in liquid effluents will be kept "as low as is reasonably achievable" in accordance with 1Q CFR Part 50;
- 2. Radioactive liquid effluent monitoring instrumentation and sampling to monitor and control the release of radioactive material during actual or potential releases;
- 3. An ODCM to contain the methodology and parameters to be used in the cal culation of offsite doses from radioactivity in effluents; and
- 4. A radiological environmental monitoring program which supplements the radiological effluent monitoring program by verifying that the measurable concentrations of radioactive materials and levels of radiation in the environment are not higher than expected based on effluent measurements and modeling of the environmental exposure pathways.
The Oconee Technical Specifications require certain radioactive liquid effluent monitoring instrumentation to monitor and control, as applicable, the releases of radioactive material during actual or potential releases.
Continuous monitors or samplers monitor the liquid radwaste effluent line, turbine building sumps, low pressure service water system, and CTP-3 discharge line.
NUREG-0472 does not suggest monitoring or sampling of effluents from ponds or ground water near ponds, since NUREG-0472 did not account for a plant design with ponds.
-3 The ground water gradient at Oconee is toward the effluent discharge area.
No ground water monitoring or sampling is currently performed. Therefore, to the extent that CTP-3 and other similar chemical treatment ponds at Oconee are not lined or otherwise designed to minimize seepage, a potential may exist for significant unmonitored normal releases of radioactive materials to occur through the ground water to nearby waterbodies, and thereby for concentrations of radioactive materials and levels of radiation in the environment to be higher than expected as shown by the effluent measurements.
The dose calculations in the ODCM are the vehicles that implement the requirements of 10 CFR Part 50, Appendix I, which states that conformance should be shown by calculational procedures based on models and data so the actual exposure of an individual through appropriate pathways will not to be substantially underestimated. The Oconee ODCM (Reference 2) is based on and follows closely the guidance given in Regulatory Guide (RG) 1.109, "Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I." The calculational models described in RG 1.109 are general approaches that we have developed instead of using of specific parameters for specific sites.
RG 1.109 encourages the use of site-specific values, assumptions and methods. In R.G.1.109, the calculational model for the aquatic foods pathway assumes that the concentrations of radionuclides in aquatic foods are directly related to the concentrations of the nuclides in the water. The model, therefore, does not take into account the effects of the buildup of concentrations of nuclides in bottom sediments on the doses from ingesting aquatic foods. However, for calculating annual direct doses from shoreline deposits, the R.G.1.109 models do take into account the effect of transfering radionuclides from the water to the sediment and the cumulative effect on the concentrations of the radionuclides in sediment over the facility operating life.
The Oconee ODCM states that ingestion of potable water and aquatic foods is the only exposure pathway in the aquatic environment to contribute significantly to the total dose.
-4 For dose contributions from liquid radioactive effluent releases, it is assumed that the maximum exposed individual is an adult who consumes fish caught in the discharge area and drinks water from the nearest downstream water supply. The calculational model in the ODCM does not include the effects on bottom-feeding fish (e.g., catfish) or the buildup of concentrations of radioactive materials in bottom sediments from the transfer of radioactive materials from the water to the bottom sediment. Since a significant unanalyzed dose contribution is present at Oconee from the consumption of bottom-feeding organisms, concentrations of radioactive materials and levels of radiation in the epvironment may be higher than expected based on modeling of the environmental exposure pathways.
The Oconee Technical Specifications require the collection and analysis of samples, at specified frequencies and numbers of locations of surface water, drinking water, shoreline sediment, milk, fish (bass and catfish) and broad-leaf vegetation. The sampling locations are described in the ODCM. The Technical Specifications set reporting levels for radionuclide activity concentrations in the environmental samples that indicate activity concentrations of radio active materials and levels of radiation may be higher than expected on the basis of the effluent measurements and the modeling of the environmental exposure pathways. It is estimated that the annual dose to the maximum exposed individual in the vicinity of the Oconee site, from consuming fish caught over a year with steady activity concentrations at the reporting levels, of the two potentially most significant radionuclides, cesium-134 and cesium-137, is approximately 5.5 millirems to the total body and 7.7 millirems to any organ (liver).
By comparison, the Oconee Technical Specification sets dose limits during any calendar year of 9 millirems to the total body and 30 millirems to any organ from liquid effluents of the three-unit station. The dose limits are based on 10 CFR Part 50, Appendix I. The methodology of the Oconee ODCM calculates the dose by adding the dose from eating fish caught in the discharge area and drinking water from the nearest downstream water supply.
-5 The reporting levels for radionuclide activity concentrations in fish samples
.had not been exceeded.at Oconee until early May 1984, when the reporting levels for cesium-134 and cesium-137 (1,000 and 2,000 picocuries per kilogram wet weight, respectively) were exceeded in catfish samples:
1,300 for cesium-134 and 7,600 for cesium-137 (Reference 1).
The staff estimates an annual dose of approximately 14 millirems to the total body and 21 millirems to any organ to an individual maximally exposed by eating catfish at reportable concentrations of radiocesiums.*
The presence of other radionuclides would increase the dose. Again, the Oconee Technical Specification limits the dose to 9 and 30 millirems, respectively.
The activity concentrations in other fish samples (bass and carp) collected at the same time and location were reported to have been well within the reportable levels. Activity concentrations reported for catfish samples taken later in May 1984 were not in excess of the reportable levels (Reference 1).
For the years 1976, 1977 and 1979 through 1983, the non-control fish samples were collected exclusively at locations 5.8 miles south and 7.8 miles south-southeast of the plant; but in-1984 and 1985, the highest mean radiocesium activity concentrations were reported for fish samples collected at a sampling location 0.8 mile east southeast of the plant.**
According to the Oconee Nuclear Station Environmental Radiological Monitoring Program.Annual Operating Report for 1984 (Reference 3), a total of 41 fish samples were analyzed in 1984 with the highest reported activity concentrations being 3,700 picocuries per kilogram wet weight for cesium-134 and 7,600 picocuries per kilogram wet weight for cesium-137. Mean reported activity concentrations for 1984 were 250 and 670 picocuries per kilogram wet weight, respectively. For 1985, the mean values were 42 and 170 picocuries per kilogram net weight, respectively. For the years 1976, 1977 and 1979 through 1983, the mean reported activity concentrations ranged from 93 to 180 and 290 to 450 picocuries per kilogram wet weight, respectively (Reference 3)**.
- Note:
Staff-estimated annual doses to a maximally exposed individual based on consumption of catfish with the activity concentrations of radio cesiums reported in Reference 1 are provided in Table 1.
- Note: A summary is provided in Table 2 of reported activity concentrations of radiocesiums in samples of surface water, bottom sediment, and fish for the years 1976, 1977 and 1979 through 1985, as taken from Reference 3.
-6 The 1984 Oconee Radioactive Effluent Release Report states that the calculated annual maximum total body dose to an individual was from the fish consumption pathway and that the dose was less than 0.5 millirem. The reported calculated annual maximum organ dose was also from the fish consumption pathway and was less than 0.5 millirem (liver) (Reference 4).
The reported relative contribution of the radiocesiums to these calculated doses was approximately 80 percent in each case.
In the 1984 and 1985 Oconee Environmental Radiological Mopitoring Program Annual Reports, the licensee identified differences between calculated doses based on the radiocesium results of the environmental radiological monitoring program and calculated doses based on liquid waste release data for radio cesiums.
For both years the calculated liver dose for teens and adults based on the liquid waste release data is approximately 0.3 millirems per year.
However, the calculated doses based on the environmental monitoring results are approximately 4 and 2 millirems per year for 1984 and 1985, respectively.
Thus, a significant difference exists between the staff and the licensee both on calculated doses based on the environmental monitoring results and calculated doses based on the liquid waste release data.
The significant difference causes us to question whether we may be assured that the releases of radioactive materials in liquid effluents will be kept "as low as is reasonable achievable" and that the actual exposure of an individual.through appropriate pathways is not substantially underestimated, in accordance with 10 CFR Part 50.
The above information supports the conclusion that the concentrations of radioactive materials and the levels of radiation in the environment near Oconee may be significantly higher than expected on the basis of the effluent measurements and the modeling of the environmental exposure pathways.
The higher radioactive levels may be caused by significant dose contribution not addressed by the methodology of the current ODCM, namely consumption of
-7 bottom-feeding fish, or from possible significant, currently unmonitored, normal releases of radioactive materials from the chemical treatment ponds in the form of seepage to nearby waterbodies.
As suggested in the Oconee Environmental Radiological Monitoring Program Annual Reports for 1984 and 1985, based on the comparison of effluent releases, environ mental monitoring and dose calculations, buildup of radionuclides in the aquatic environment over the operating life of the station may be another significant dose contribution from fish consumption not addressed by,the methodology of the ODCM. The ODCM dose calculational methodology does not analyze liquid effluent releases in years other than the year for which the doses are calculated.
The Oconee Technical Specifications limit radioactive material inventory in chemical treatment ponds CTP-1 and. CTP-2. The "Bases" section of the Technical Specifications state that the inventory limits of the chemical treatment ponds are based on limiting the consequences of an uncontrolled release of the pond inventory in accordance with 10 CFR 20.106. 10 CFR 20.106 requires that releases to unrestricted areas not exceed the limits in 10 CFR Part 20, Appendix B, Table II. The inventory limits are not explicitly stated in the Technical Specifications, but a formula is given to calculate the total activity limits for CTP-1 and CTP-2.*** The formula incorporates the 10 CFR Part 20, Appen dix B, Table II limits for each radionuclide. It is not clear whether the limits
- Note:
The calculated activity limits for CTP-1 and CTP-2 based on the formula provided in the Technical Specifications are given in Table 3 for cesium-134, cesium-137, and eight other radionuclides.
-8 apply to the individual ponds or to the sum of the activities in both ponds.
Also, the Technical Specifications provide limitations on the quantities of all radioactive materials transferred to CTP-1 and CTP-2 based on the inventory limits.
CTP-3 appears to be similar to the other two chemical treatment ponds, CTP-1 and CTP-2, since it receives radioactive materials from the plant, it is located in a restricted area, and it is potentially subject to the uncontrolled release of inventory from pond failure or other causes; however, the Oconee Technical Specifications set radioactive material inventory limits for CTP-1 and CTP-2, only.
Dated:
Principal Contributors: C. Nichols and E. Branagan
References
- 1.
Letter from H. B. Tucker, Duke Power Company to James P. O'Reilly, NRC, Region II, dated June 13, 1984.
- 2. Offsite Dose Calculation Manual for Duke Power Nuclear Stations, as revised through Revision 10. Revision 10 submitted by letter from Hal B. Tucker, Duke Power Company, to J. Nelson Grace, NRC, Region II, dated March 5, 1986.
- 3. Duke Power Company, Oconee Nuclear Station Annual Operating Report for 1976 and Environmental Radiological Monitoring Program Annual Reports for the years 1977 and 1979 through 1985.
Reports for 1984 and 1985 submitted by letters from Hal B. Tucker, Duke Power.Company, to J. Nelson Grace, NRC, Region II, dated April 30, 1985 and 1986, respectively.
- 4. Duke Power Company Oconee Nuclear Station 1984 Radioactive Effluent Release and Solid Waste Disposal Report. Submitted by letter from Hal B. Tucker, Duke Power Company, to J. Nelson Grace, NRC, Region II, dated April 1, 1985.
TABLE 1 STAFF ESTIMATED DOSES TO A MAXIMALLY EXPOSED INDIVIDUAL BASED ON REPORTED ACTIVITY CONCENTRATIONS OF Cs-134 AND Cs-137 IN CATFISH SAMPLES TAKEN FROM LAKE HARTWELLa Dateb/Nuclide Reportedc Activity Dose, mrem/yrd Concentration, Total Body Liver pCi/Kg-wet weight May 2, 1984 Cs-134 1300 3.2 4.0 Cs-137 7600 11 17 Sum 14 21 May 18, 1984 Cs-134 370 0.94 1.2 Cs-137 2000 2.9 4.5 Sum 3.8 5.7 aBased on assumed consumption of 21 kg/yr of catfish with the reported activity concentrations of radionuclides, and the dose conversion factors in Table E-11 of Regulatory Guide 1.109. Concentrations of other radionuclides were not reported in Reference 1. The presence of other radionuclides would increase the doses.
bDate sample was collected. Data was taken from Reference 1.
cThe reporting levels (pCi/Kg-wet weight) in Oconee's Technical Specification are 1000 for Cs-134 and 2000 for Cs-137.
dTwo significant figures are used to be consistent in calculations.
The number of significant figures does not imply the accuracy in these calculations.
TABLE 2
SUMMARY
OF REPORTED ACTIVITY CONCENTRATIONS OF CESIUM-134 AND CESIUM-137 IN ENVIRONMENTAL SAMPLES, 1976, 1977, 1979-1985*
Radionuclide Activity Concentration for Location with Highest Annual Mean Surface Bottom Fish Water, Mean Sediment,**Mean pCi/kg(wet)
Year/Nuclide pCi/1 pCi/kg(dry)
Mean Maximum 1976 Cesium-134 2.8(-)***
3,300(-)
-(-)
-(-)
5,970(-)
-(-)
1977 Cesium-134 36( LLD) 10,200( LLD) 180( LLD) 530( LLD)
Cesium-137 31(7.5) 15,800(703) 360(89) 1,200(136) 1979 Cesium-134 0.3( 0) 4,400( 0) 93(3.0) 220(-)
Cesium-137 2.8(0.4) 12,000(48) 390(45) 710(98) 1980 Cesium-134 0.2( 0) 2,900( 0) 110(5.8) 350(-)
Cesium-137 5.4(0.5) 9,400(77) 400(54) 990(140) 1981 Cesium-134 3.3( 0) 2,400( 0) 140(4.4) 220(-)
Cesium-137 3.9(1.2) 8,000(120) 450(59) 730(140) 1982 Cesium-134 1.9(0.20) 1,800(17) 120(1.7) 200(-)
Cesium-137 4.9(0.84) 6,200(3.1) 290(50) 430(88) 1983 Cesium-134 0.6(0.04) 1,000(40) 120( 0) 370(-)
Cesium-137 0.7****(0.07) 4,600(44) 330(32) 750(68) 1984 Cesium-134 0.3(0.8) 78(21) 390(2.2) 3,700(-)
Cesium-137 0.5(1.7) 52(41) 1,000(30) 7,600(72) 1985 Cesium-134 1.0(2.0) 76(45) 79(2.7) 200(13)
Cesium-137 1.0(1.1) 95(170) 290(36) 540(78)
-CONTINUED ON NEXT PAGE -
-2 TABLE 2 (CONTINUED)
For each year except 1984 and 1985, samples of surface water and samples of bottom sediment were obtained at five locations each in addition to the control location and fish samples were obtained at one non-control location. An exception is that two non-control locations were used for surface water samples in 1977.
For each year except 1976, 1977, 1984 and 1985, the above values were obtained from surface water samples taken at a location 0.9 mile ESE of the plant, bottom sediment samples taken at a location 0.7 mile ENE of the plant, and fish samples from fish collected at a location 7.8 miles SSE of the plant, except as noted. In 1976 and 1977, the values were obtained from surface water samples taken at a location 0.25 mile SSE of the plant, bottom sediment samples taken at a location 0.25 mile E of the plant, and fish samples from fish collected at a location 5.8 miles S of the plant.
For Cesium-134 in all years and for Cesium-137 in each year except 1984 and 1985, the LLD values are 15 pCi/l for surface water, 150 pCi/kg(dry) for sediment, and 130 pCi/kg(wet) for fish.
In 1984 and 1985, the LLD values for Cesium-137 were 18 pCi/l for surface water, 180 pCi/kg(dry) for sediment, and 150 pCi/kg(wet) for fish; and radiocesium concentrations are reported for non-control locations as follows:
for surface water 0.8 mile ESE, sediment 4.2 miles SSE, and fish with highest mean radiocesiums 0.8 mile SSE of the plant.
- Values are taken from Duke Power Company's Oconee Nuclear Station Annual Operating Report for 1976 and the Environmental Radiological Monitoring Program Annual Operating Reports for the years 1977 and 1979 through 1985 (Reference 3).
Report for 1978 is not readily available.
- Samples in 1984 and 1985 are for shoreline sediment.
- Values in (
) are for samples obtained at control locations.
- Sample location is 0.2 mile NNE of plant.
TABLE 3 CALCULATED ACTIVITY LIMITS FOR CHEMICAL TREATMENT PONDS (CTP-1 AND CTP-2)
BASED ON TECHNICAL SPECIFICATION FORMULA Nuclide MPC, pCi/m1 Pond Activity Limit, Cia Mn-54 1E-04 17 Fe-59 5E-05 8.5 Co-58 9E-05 15.3 Co-60 3E-05 5.1 Zn-65 1E-04.
17 Zr-95 6E-05 10 Nb-95 1E-04 17 1-131 3E-07 0.051 Cs-134 9E-06 1.5 Cs-137 2E-05 3.4 a Pond limit is equal to the product of 1.7 x 105 Ci-ml/uCi times the maximum permissible concentration (MPC) for the general public in
.units of VCi/ml
-2 in bottom-feeding fish and sediments, including the collection and analysis of more-frequently obtained samples near the point at which radioactive materials are released. Then, if the elevated levels are confirmed, we would recommend that the licensee determine the extent to which significant unmonitored normal releases of radioactive materials occur from the chemical treatment ponds through the groundwater to nearby waterbodies. Finally, if warranted, we would recommend that the licensee develop an acceptable revised model of the environ mental exposure pathways at Oconee and incorporate it into the ODCM. We would also recommend that the licensee develop revisions to the Oconee Technical Specifications to limit radioactive inventory consistently for the three chemical treatment ponds.
With the enclosed evaluation, we have completed our efforts on TIA 85-07.
Original signed by Frank J. Miraglia Frank J. Miraglia, Director Division of PWR Licensing-B, NRR
Enclosure:
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