ML16152A423
| ML16152A423 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/22/1985 |
| From: | Lainas G Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16152A422 | List: |
| References | |
| NUDOCS 8504050017 | |
| Download: ML16152A423 (8) | |
Text
7590-01 UNITED STATES NUCLEAR REGULATORY COMMISSION DUKE POWER COMPANY DOCKETS NOS. 50-269, 50-270, AND 50-287 ENVIRONMENTAL ASSESSMENT AND FINDING OF NO SIGNIFICANT IMPACT The U.S. Nuclear Regulatory Commission (the Commission or staff) is considering approval of the storage and recycle of certain very low-level radioactive waste proposed by Duke Power Company (the licensee) for the Oconee Nuclear Station, Units 1, 2 and 3, located in Oconee County, South Carolina. The licensee's proposal also included disposal by burial of some of the waste. However, such disposal in this case is subject to approval by the State of South Carolina under the Agreement entered into pursuant to Section 274b of the Atomic Energy Act of 1954, as amended. Under 10 CFR 150.15(a) the NRC retains jurisdiction only as to the storage and handling of the waste at the licensee's site.
ENVIRONMENTAL ASSESSMENT Identification of Proposed Action: The proposed action by the NRC would approve the storage and eventual recycling of the shells from the heaters contaminated at levels below reference values in IE Circular No. 81-07, "Control of Radioactively Contaminated Material" (May 14, 1981, USNRC).
The proposed action is in accordance with the licensee's request by letter dated September 18, 1984, as supplemented on November 28, 1984. The feedwater heaters are from the secondary systems of Oconee Units 1 and 2. The heater sections will be disposed of in seven-foot to twelve-foot deep trenches and covered with a thickness of three feet of uncontaminated soil.
At noted above, this latter activity is subject to approval by the State.
The Need for the Proposed Action:
Five feedwater heaters were replaced during the Oconee outage between June and October 1983.
Three feedwater 3504050017 850322 PDR ADOCK 05000269 P
PDR J
7590-01
-2 heaters were from Unit 1 and two feedwater heaters were from Unit 2.
The feedwater system is designed to provide adequate feedwater flow at the required pressure and temperature to the steam generators for all unit operating conditions.
The closed feedwater cycle condenses the steam and the treated feedwater is returned to the steam generators. The shells of the feedwater heaters are fabricated from steel and attached at one end to the stationary tube sheet. The feedwater heater tube bundles are composed of a large number of U-tubes, roller expanded at each end into a single tube. The physical dimension of the feedwater heater is approximately 35 feet long and 5 feet in diameter. The licensee plans to cut the feedwater heaters to reduce their total volume prior to disposal.
The reason for the licensee's proposed disposal plan is to dispose of the feedwater.heaters at a substantially lower cost than the offsite disposal alternative discussed elsewhere in this report.
Environmental Impacts of the Proposed Action:
Duke Power plans to cut the feedwater heaters to reduce their total volume prior to disposal.
The parts of the heaters will be segregated into two categories: (1) parts (i.e., heater shells) in which the detected levels of surface contamination are below reference values in IE Circular No. 81-07; and (2) more highly contaminated parts (i.e., tube bundles). The principal radionuclides detected on the more highly contaminated surfaces of the heaters and their concentrations (pCi/gm) at the time of sampling are as follows:
Manganese-58 (Mn-58), 0.35; Cobalt-60 (Co-60), 10.1; Cesium-134 (Cs-134), 0.52; and Cesium-137 (Cs-137), 1.9. The total volume of the feedwater heaters is
-3 estimated to be about 10,500 ft3 before cutting and segregation, and about 4,500 ft3 after cutting. The total weight of the heaters is about 260 tons of which 160 tons would be disposed in trenches, and about 100 tons would be stored and eventually recycled. The total activity of the five heaters is conservatively estimated to be about 6.5 mCi with Co-60 and Cs-137 accounting for the largest fractions (i.e., 0.79 and 0.15, respectively) of the total activity. The total activity and volume of the five heaters represent about 0.0002% and 8.2%, respectively, of the average annual total activity and volume of solid wastes generated at the Oconee station for the years 1976 through 1980 (see Table 1 below).
Table 1 RADIOACTIVELY CONTAMINATED SOLID WASTES GENERATED AT OCONEE NUCLEAR STATIONa Year Volume, ft3 Activity, Ci 1976 78,400 783 1977 37,800 7,370 1978 55,800 5,930 1979 57,600 2,590 1980 46,600 2,910 Average 55,200 3,920 a Values were derived from Table 12 of Tichler, J., and Benkowitz, C., "Radioactive Materials Released from Nuclear Power Plants, Annual Report 1980", NUREG/CR-2907, Volume 1, January 1983.
A. Disposal of Sections of Heaters The NRC staff has reviewed the potential pathways for exposure to members of the general public from the radionuclides in the disposed parts of the heaters (see Table 2 below).
-4 Table 2 ESTIMATED DOSES TO AN INDIVIDUAL STANDING ABOVE THE FEEDWATER HEATERS Nuclide Average Concentration, Dose Rate, Annual Dose, pCi/gma mrem/hrb mremc Uncovered Covered Mn-54 0.35 3.1 E-04 5.3 E-08 0.001 Co-60 10.1 2.7 E-02 4.6 E-06 0.009 Cs-134 0.52 8.8 E-04 1.5 E-07 0.001 Cs-137 1.86 1.1 E-03 1.9 E-07 0.001 TOTAL 2.9 E-02 4.9 E-06 0.01
- a. From p. 3 of enclosure to letter from H. B. Tucker to H. R. Denton, dated November 28, 1984.
- b. The dose rate was calculated assuming a semi-infinite source. The following effective energies (in units of Mev/dis) were derived from the Radiological Health Handbook, Jan. 1970: Mn-54, 0.84, Co-60, 2.5; Cs-134, 1.6; and Cs-137, 0.56. The dose rate is reduced by a factor of about 5800 based on an approximate attenuation coefficient of 0.13/cm for 3' of cover soil, and a build-up factor of 25 (Jaeger et al, "Engi.neerina Compendium on Radiation Shielding", Volume 1, "Shielding Fundamentals and Methods", 1968).
- c. Based on an occupancy time of 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />s/yr.
These potential pathways include: (1) external exposure from standing on the ground above the disposal site; (2) internal exposure from ingestion of food grown on the disposal site; (3) internal exposure from inhalation of resuspended radionuclides; and (4) internal exposure from drinking water.
The dose to a member of the public from the most likely exposure pathway (i.e., external exposure) is conservatively estimated to be 0.01 mrem/yr to the total body. Doses to a member of the public from ingesting food grown on the disposal site and from inhalation of resuspended radio nuclides are estimated to be minimal due to the proposed soil covering.
-5 Doses from drinking contaminated water are estimated to be minimal due to the relatively low-level concentrations of radionuclides in the heaters, and the expected retention of radionuclides in the soil if the radionuclides migrated from the heaters. The estimated doses are a small fraction of one year's exposure to natural background radiation (about 100 millirems for the State of South Carolina (Oakley, D. T., "Natural Radiation Exposure in the United States, ORP/SID 72-1, June 1972).
Duke Power states that exposure of workers during the cutting and segregation of the heaters will be in accordance with the station Health Physics Procedures and station directives. Workers will be properly dressed during the disposal procedures. The doses to workers from external exposure are estimated to be small compared with the average annual dose per nuclear plant worker of about 0.8 rem (NUREG-0713, Brooks, B. G., "Occupational Radiation Exposure at Commercial Nuclear Power Reactors 1981", Volume 3, November 1982).
B. Storage and Recycling of Scrap The licensee proposes to store and eventually recycle scrap material from the heaters (consisting primarily of the shells of the heaters) contaminated at levels below reference values in IE Circular No. 81-07 entitled "Control of Radioactively Contaminated Material." IE Circular 81-07 addresses the practicality of surveying contaminated surfaces, detection limits and the potential radiation doses from materials uniformly contaminated at the detection limits.
The detection limits indicated in IE Circular 81-07 are beta-gamma activity of 5000 dpm/100 cm2 total contamination, and 1000 dpm/100 cm2 removable beta-gamma
-6 contamination. The guidance of IE Circular 81-07 further specifies that if alpha contamination is suspected, appropriate surveys and/or laboratory measurements capable of detecting 100 dpm/100 cm2 fixed and
?0 dpm/100 cm2 removable alpha activity should be performed.
The staff has estimated potential doses to members of the general public for exposure to the recycled scrap in the following matter. The licensee reports that Co-60 accounts for about 80% of the total concentrations of radionuclides detected in the more highly contaminated surfaces of the heaters. O'Donnell et al ("Potential Radiation Dose to Man from Recycle of Metals Reclaimed from a Decommissioned Nuclear Power Plant," NUREG/CR-0134, ORNL/NUREG/TM-215, December 1978), have estimated the potential doses to individuals and the population from exposure to 100 tons of recycled metal containing 10 pCi/g of Co-60. The maximum dose to an individual and the population from six recycling pathways investigated was estimated to be 14 mrems and 1.1 person-rems, respectively, during the first 30 years after recovery and recycling of the metal (O'Donnell et al (1978)).
The highest annual dose is estimated to be about 2 mrems to an individual and 0.15 person-rems to the population. The average concentrations of radionuclides in the segregated shells of the heaters should be much less than 10 pCi/gm since only surface contamination is of concern and the licensee has committed to cleaning the heater shells prior to recycling. The highest annual dose is estimated to be much less than 2 mrems to an individual and 0.15 person-rem to the population from the proposed recycling of the cleaned heater shells.
-7 Based on the staff's review of the proposed disposal of sections of five feedwater heaters, the staff concludes that:
(1) The licensee has taken appropriate steps to ensure that occupational dose will be maintained as low as is reasonably achievable and within the limits of 10 CFR Part 20; and (2) The estimated doses to the general public from disposal of the heaters and from recycling scrap metal from the heaters are:
(a) well below regulatory limits, and (b) negligible in comparison to the dose members of the public receive each year from exposure to natural background radiation.
Alternatives to the Proposed Action:
An alternative to on-site burial would be to ship and dispose the heaters at Barnwell.
The overall benefit from the proposed method for the disposal of these five slightly contaminated feedwater heaters will be a cost saving of approximately $160,000 and a saving of burial site space of approximately 4525 ft3, which can be used for other radwaste.
Alternative Use of Resources: The principal action involving use of resources not previously considered in connection with the Final Environmental Statement for Operation of Oconee Nuclear Station, Units 1, 2 and 3, is a minor change in land use associated with operating support of the facility. As noted-above, this change in land usage is insignificant. As further noted above, the change also involves a minor addition to the operational radiological monitoring and recordkeeping program during plant operation.
Agencies and Persons Consulted:
The staff reviewed the licensee's request and has not consulted other agencies or persons.
FINDING OF NO SIGNIFICANT IMPACT The Commission has determined not to prepare an environmental impact statement for the proposed action.
Based upon this environmental assessment, the Commission concludes that the proposed action will not have a significant effect on the quality of the human environment.
For further details with respect to this action, see the request for approval dated September 18, 1984, with its November 28, 1984 supplement, which is available for public inspection at the Commission's Public Document Room, 1717 H Street, N.W., Washington, D.C., and at the Oconee County Library 501 West Southbroad Street, Walhalla, South Carolina.
Dated at Bethesda, Maryland, this 22nd day of March 1985.
FOR THE NUCLEAR REGULATORY COMMISSION Gus C. Lainas, Assistant Director for Operating Reactors Division of Licensing