ML16138A831
| ML16138A831 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/19/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16138A830 | List: |
| References | |
| NUDOCS 9702250279 | |
| Download: ML16138A831 (6) | |
Text
,SREG UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 221 TO FACILITY OPERATING LICENSE DPR-38, AMENDMENT NO. 221 TO FACILITY OPERATING LICENSE DPR-47, AND AMENDMENT NO. 218 TO FACILITY OPERATING LICENSE DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1. 2 AND 3 DOCKET NOS. 50-269, 50-270 AND 50-287
1.0 INTRODUCTION
By letter dated February 20, 1996, as supplemented October 16, 1996, Duke Power Company (the licensee), submitted a request for changes to the Oconee Nuclear Station (ONS), Units 1,,
2, and 3,' Technical Specifications (TS). The requested changes would revise TS Table 4.1-3 and TS 3.1.5, 3.1.10, and 4.1.
The TS changes would: (1) reduce the frequency of the concentrated boric acid storage tank boron concentration surveillance for boron concentration from twice weekly to weekly; (2) delete the chemical and radiochemical surveillance requirements for the reactor coolant for Sr89 and Sr, gross beta activity, gross alpha activity, dissolved gas concentration in the reactor coolant, and gross beta activity in the steam generator feedwater; (3) relocate the surveillance requirements for tritium, chloride, fluoride and oxygen to the Selected Licensee Commitments (SLC) Manual; and (4) delete TS 3.1.10 and TS Figure 3.1.10-1 related to temperature and pressure requirements for control rod operation.
Guidance for the evaluation of the proposed amendments is provided by Regulatory Guide (RG) 1.97, by the Commission's Final Policy Statement dated July 16, 1993, on the scope and purpose of the TS, and by the Improved Standard Technical Specifications for Babcock and Wilcox nuclear plants, revised April 7, 1995.
The supplementary information supplied by letter dated October 16, 1996, did not affect the proposed no.significant hazards consideration determination and the initial scope of the February 20, 1996, application.
9702250279 970219 PDR ADOCK 05000269 P
-2 2.0 EVALUATION 2.1 Concentrated Boric Acid Storage Tank (CBAST) Surveillance The concentrated boric acid solution in the CBAST is used to adjust the boron concentration in the reactor coolant.system. Item 6 of TS Table 4.1-3 requires that the CBAST boric acid concentration be determined twice weekly.
However, the only parameters that could affect the boric acid concentration in the CBAST are the temperature of the CBAST and associated piping (which is automatically maintained at preset elevated values to prevent precipitation of boric acid), and the level of the CBAST (which is monitored on instruments.
located in the control room). Also, the operator aided computer (0AC) provides alarms for the operator if the temperatures of the CBAST and associated piping vary from the preset values. Plant operational procedures require evaluation of the CBAST boron concentration within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after completing any volume transfers.
These operational procedure requirements, the 0AC alarms and the remote level monitoring instrumentation provide assurance that any sudden changes in the boron concentration in the CBAST from the TS value will be detected, the effect on the concentration addressed, and the cause determined. Therefore, reduction of the surveillance frequency to determine the CBAST boric acid concentration from twice weekly to weekly is acceptable (Item 6 in TS Table 4.1-3, Minimum Sampling Frequency and Analysis Program).
2.2 Radiochemical Analysis for Sr89 and Sr90 IteP 1 of TS Table 4.1-3 requires that the radiochemical analysis for Sr89 and Sr9 in the reactor coolant be determined monthly when fuel is in the core.
It was originally included since these fission products could be biological hazards and are relatively long-lived. These activities are included in the calculation of Ebar, which is the average beta and gamma energy per disintegration in MeV, weighted in proportion to the measured activity of the radionuclides in reactor coolant samples. This quantity, in turn, is used in TS 3.1.4, which requires that the total activity of the reactor coolant due to nuclides with half-lives longer than 30 minutes shall not exceed 224/Ebar microcuries per milliliter whenever the reactor is critical.
The Bases of TS 3.1.4 state that the specification is based on limiting the consequences of a postulated accident involving the double-ended steam generator tube rupture (SGTR).
The licensee has determined, however, that in two decades of strontium data trending, the strontium activity remained within a range of 1.OE-5 to 1.OE-7 microcuries per milliliter during normal operation. This amounts to less than 2.OE-3 percent of the total reactor coolant activity and, therefore, would not impact the calculation of Ebar. Correspondingly, the low strontium activities during normal operation would not contribute significantly to the consequences of an SGTR accident.
-3 Further, any abnormal increases in reactor coolant activities, including the strontium activities, will be detected in the required twice weekly gamma spectrometer analyses. Also, the current technology for evaluating the SGTR doses provides a more conservative SGTR accident dose estimate, which is tied to a TS requirement that puts a specific limit on the radioactive iodine concentration in the reactor coolant. It should be noted that Note 2 to TS Table 4.1-3 will be retained, requiring an Ebar determination whenever the.
gross gamma concentration exceeds 10 microcuries per milliliter, and the redetermination of Ebar for each additional 10 microcurie per milliliter increase in gross gamma concentration.
In light of the low strontium activities historically observed in the reactor coolant, the ability of the daily gamma spectral analyses to measure increases in strontium, iodine and the other activities, the conservative approach in evaluating the SGTR accident doses, and the additional requirement to perform an Ebar determination when the gross gamma activity exceeds the acceptable limits, the licensee's proposal to eliminate the radiochemical analyses for strontium activities is acceptable.
2.3 Gross Beta and Gamma Analyses The objective of the, gross beta and gamma radiochemical analyses required by Items Id, Ig, and 5a of TS Table 4.1-3 was to monitor the fuel cladding integrity and the concentration of fission products in the reactor coolant and steam generator. Since the time when these requirements were instituted in the early 1970's, there have been significant advances in multichannel gamma
.isotopic analyzer technology as applied in the radiochemistry program at the ONS. The improved analysis permits the precise identification of individual isotopes, including beta and alpha emitting fission products from their coincident gamma emissions.
The results of the gamma spectral analyses for selected isotopes are scrutinized for deviations from normal behavior. Long-term plots of the data are reviewed by ONS staff monthly, with additional reviews 3 times per year.
Any adverse trends are investigated to determine the cause.
In view of the capability of the improved multichannel gamma isotopic analyzer to determine the concentrations of the important fission products in the reactor coolant system, and the provisions for reviewing the short-term and long-term behavior of these isotopes, the licensee's proposal to delete the requirements for radiochemical gross beta and gross gamma analyses (Items Id, Ig, and 5a) from TS Table 4.1-3 is acceptable.
2.4 Tritium Analysis In reactors, tritium is produced by ternary fission and by the reaction of fast neutrons with the Li6 content of the' reactor coolant. The rate of production can be calculated from the known ternary fission yield and the known cross section of Li6 for reactor neutron reactions. To minimize the
-4 contribution of the latter reaction, 99.9 percent pure Li7 is used in the LiOH added to the reactor coolant to control pH level.
The requirement for the surveillance of tritium concentration in reactor coolant was included as Item Ic of TS Table 4.1-3 because tritium is a known biological hazard, as a beta emitter with a half-life of 12.4 years.
The proposed amendments would delete Item Ic from TS Table 4.1-3, and relocate the tritium surveillance requirements to the.Selected Licensee Commitment (SLC) manual, with a quarterly surveillance frequency in place of the monthly frequency specified in TS Table 4.1-3. In addition to this measurement of tritium in the reactor coolant, ONS has programs in place to monitor all effluents leaving the site for tritium content, including the chemical treatment pond discharge and the site groundwater. Containment air is monitored for tritium whenever the reactor building is entered.
The change in surveillance frequency for tritium in the reactor coolant from monthly to quarterly is justified because the known tritium production rate during reactor operation results in slow and predictable changes in the tritium content of the reactor coolant. The relocation of this surveillance requirement to the SLC manual is acceptable, because it is consistent with the Improved Standard Babcock & Wilcox Owners' Group (BWOG) TS and the requirement does not meet any of the four criteria listed in 10 CFR 50.36 for inclusion in the TS. Because the SLC manual is a part of the Updated Final Safety Analysis Report (UFSAR), any changes to the surveillance requirement could only be made in accordance with the 10 CFR 50.59 process. The staff considers this process adequate to ensure that the surveillance program for the tritium content of the reactor coolant will be adequately controlled. In addition, since implementation of the change to the SLC manual will coincide with the change to the TS, the surveillance requirements will remain in effect and adequately controlled during the change process.
In view of the provisions for continued surveillance of the coolant, the effluent monitoring programs and the use of Li7 to reduce the rate of generation of tritium, the proposed amendments regarding tritium surveillance are acceptable.
2.5 Oxygen, Chloride, and Fluoride Analyses The rate of stress corrosion cracking of reactor components is strongly influenced by the levels of dissolved oxygen, chloride and fluoride in the reactor coolant. Therefore, in TS 3.1.4, the concentrations of these species are required to be very low. Item le of TS Table 4.1-3 specifies a frequency of 5 times per week for measuring the concentrations of these species.
However, during normal operation, changes in the concentrations of oxygen and halide ions in the reactor coolant are slow. Therefore, the licensee has proposed to reduce the frequency of these analyses to 3 times per week.
Further, the licensee has proposed to relocate the chemistry specifications to the SLC manual.
-5 Because of the slow rate at which oxygen and halide concentrations change in the reactor coolant, the reduced analysis frequency of 3 times per week is acceptable. Also, the relocation of the chemistry specifications to the SLC manual is acceptable because they do not meet any of the four criteria listed in 10 CFR Part 50.36. Also, the chemistry.specifications are not included in the BWOG Improved Standard TS. Because the SLC manual is a part of the UFSAR, any changes to the specifications could only be made in accordance with the 10 CFR 50.59 process. The staff considers this process adequate to control the surveillance program for the oxygen, chloride, and fluoride concentrations in the reactor coolant. In addition, since implementation of the change to the SLC manual will coincide with the change to the TS, the specifications will remain in effect and adequately controlled during the change process. The related shutdown requirements will be in accordance with the EPRI guidelines.
Based on the previous discussion, the licensee's proposed amendments of TS 4.1.5 and TS Table 4.1-3 related to the chemical specifications are acceptable.
2.6 Dissolved Gas Concentration Analysis The requirement to measure the concentration of dissolved gas in reactor coolant, TS 3.1.10, was placed in the Oconee TS following an incident during the initial testing of ONS Unit 1 in 1971. A nitrogen overpressure of 400 psig had been established for the pressurizer for operation of the reactor coolant pump,-which results in a dissolved nitrogen concentration of 300 standard cubic centimeters of nitrogen per liter of water in the pressurizer.
The failure of a pressurizer valve caused a sudden depressurization to 60 psig, which resulted in the formation of nitrogen gas pockets in the reactor vessel and some of the control rod dri.ve mechanisms. During a subsequent control rod drop test, several of the control rods were damaged because of the absence of water above the snubbing springs for proper dampening action.
The requirement in TS 3.1.10.2 that dissolved gas concentration remains below 100 standard cubic centimeters per liter was designed to preclude the formation of gas bubbles in significant amounts following depressurization.
The restrictions of TS 3.1.10.2 and Figure 3.1.10-1 also limit the dissolved gas concentration. However, during the operational history of ONS the dissolved gas concentration has not exceeded the TS limit, and is normally less than 50 standard cubic centimeters per liter.
During startup, power operation, and cooldown, the gas content of the coolant is controlled through operation practices such as venting. At ONS, instrumentation and procedures are in place to ensure that the appropriate actions are taken to preclude conditions that would result in a "gas-out" problem. Therefore, the licensee proposes to delete TS 3.1.10 and Figure 3.1.10-1 from the Oconee TS.
-6 In view of the low dissolved gas concentrations observed during the operational history of ONS, the unlikelihood that the 1971 gas bubble incident would be repeated, and the instrumentation and-procedures in place at ONS to avoid conditions leading to a "gas-out" problem, the staff finds that the amendments to delete TS 3.1.10 and Figure 3.1.10-1 are acceptable.
2.7 Spent Fuel Pool Sampling Footnote Deletion The third footnote to TS Table 4.1-3 (current page 4.1-10), "Applicable only when fuel is in the wet storage in the spent fuel pool," was originally inserted to prevent excessive monitoring prior to storing fuel in the pool.
The proposed amendments would delete this footnote.
The staff finds the deletion acceptable because fuel will always be present in the spent fuel pool for wet storage. The footnote, therefore, is outdated and unnecessary.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released.
offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (61 FR 13523 dated March 27, 1996).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: S. S. Kirslis Date:
February 19, 1997