ML20235V274
| ML20235V274 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 09/28/1987 |
| From: | Musolf D NORTHERN STATES POWER CO. |
| To: | |
| Shared Package | |
| ML20235V263 | List: |
| References | |
| NUDOCS 8710150072 | |
| Download: ML20235V274 (4) | |
Text
{{#Wiki_filter:- _ _ - - _ _ _ _ - UNITEG STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET NO. 50-282 50-306 REQUEST FOR AMENDMENT TO OPERATING LICENSE DPR-42 & DPR-60 LICENSE AMENDMENT REQUEST DATED September 28, 1987 Northern States Power Company, a Minnesota corporation, requests authorization for changes to Appendix A of the Prairie Island Operating h License cs shown on the attachments labeled Exhibits A, B, C, and D. Exhibit A describes the proposed changes, describes the reasons for the changes, and contains a significant hazards evaluation. Exhibits B and C are copies of the Prairie Island Technical Specifications incorporating the proposed changes. Exhibit D is a topical report supporting the requested changes This letter contains no restricted or other defense information. NCRTHERN STATES POWER COMPANY By b... O h w. N David Muscif ) Manager-Nuclear Support Services On thi deday of A d a' > [ before me a notary public in and for said County, personally appeared a id Musolf, Manager - Nuclear Support l Services, and being first duly sworn acknowledged that he is authorized to l execute this document on behalf of Northern States Power Company, that he l knows the contents there of, and that to the best of his knowledge, i information, and belief the statements made in it are true and that it is not interposed for delay. Q'2M' .,=== :=
==,l l JUDY L KLAPPERICK NOTARY PUDtlC--MINNESOTA h AM0KA COUNTY d My Commusen Dpnes Sept 29.19914 n::. : ^: ^ ^::=:::=:::== :=;* B710150072 870920 PDR ADOCK 050002B2 p PDR I
EXHIBIT A Prairie Island Nuclear Generating Plant License Amendment Request Dated September 28, 1987 Evaluation of Proposed Changes to the Technical Specifications Appendix A of Operation License DPR-42 and DPR-60 Pursuant to 10 CFR Part 50, Sections 50.59 and 50.90, the holders of Operating Licenses DPR-42 and DPR-60 hereby propose the following changes to Appendix A, Technical Specifications: . Turbine Valve Testinn Frecuency Chances l Pronosed Changes (Table TS.4.1-2A) I In place of a specific turbine valve test frequency, it is proposed that i the Technical Specifications allow the use of a turbine valve testing frequency determined by the methodology presented in WCAP-11525 "Probabilistic Evaluation of Reduction in Turbine Valve Test Frequency", and in accordance with the established NRC acceptance criteria for the probability of a missile ejection incident of 1,0x10~ per year,
- a. Replace the specified frequency for point all. Turbine stop valves,..." with a reference to Note 1.
- b. Change Note 1 to read:
(1) Turbine stop valves, governor valves, and intercept valves are to be tested.ar a frequency consistent with the methodology presented in WCAP-ll525 "Probabilistic Evaluation of Reduction in Turbine Valve Test Frequency", and in accordance with the established NRC acceptance criteria missile ejection incident of 1.0x10-{or the probability of a per year. In no case shall the turbine valve test interval exceed one year. Reason For Chance f 1 Current restrictions on turbine valve test intervals are e result of ] applying test intervals generated for fossil plants to early nuclear plants. As nuclear plants have developed their own operating history, design and operations have improved making the applicability of the fossil turbine valve test interval restrictions inappropriate. ] Evaluations of turbine valve test intervals have shown that significant relaxation of turbine valve testing frequency is warranted (reference WCAP-11525, "Probabilistic Evaluation of Reduction in Turbine Valve Test 1 Frequency"). The evaluations have shown that with extended testing ) intervals the probability of generating a turbine missile i lowerthantheestablishedNRCacceptancecriteria(1.0x10" significantly i per year). l Longer valve test intervals will result in improved plant performance, less j i radioactive waste and lower occupational radiation exposures. I I A-1
______--___-_--_---_b
EXHIBIT A currently turbine valve testing is' conducted on a monthly basis, y Conducting a test of the turbine valves requires a significant reduction in i power output. The plant's power level is dropped to approximately 55% of j maximum for the conduct of the turbine valve tests. This power reduction places unnecessary thermal and pressure cycles on plant equipment which may carry an accompanying reduction in overall plant safety and reliability. The power level reduction is completed by adding boron to the reactor coolant system. At the completion of the turbine valve tests the boron concentration in the primary loop must be returned to the pre-test level. The boron concentration is reduced by adding clean reactor grade water to the reactor coolant system. This dilution process results in contaminated water that must be processed as radioactive waste. Reduced frequency of turbine valve testing will reduce the amount of liquid radioactive waste and solid radioactive waste produced. Reduction in the generation of radioactive waste would also result in a reduction in personnel exposure thus helping to keep personnel exposures as low as reasonably achievable. -Egfety Evaluation and Determination of Significant Hazards Considerations i The proposed change to the Operating License has been evaluated to determine whether it constitutes a significant hazards consideration as required by 10 CFR Part 50, Section 50.91 using standards provided in Section 50.92. This analysis is provided below: 1. The proposed amendment will not involve a significant increase in the probability or consequences of an accident previously evaluated. The referenced analysis as reported in WCAP-11525 provides an evaluation of the probability of turbine missile ejection for the purpose of justifying a reduction in the frequency of turbine valve testing. In a letter to Westinghouse Electric Corporation dated February 2, 1987 (C E Rossi, USNRC to J A Martin, Westinghouse), the commission established acceptable criteria for the probability of generatingaturbinemissilefromanunfavorablyorientgdturbine (acceptable probability of missile generation < l.0x10' ). The evaluation in WCAP-11525 shows that the probability of a missile ejection incident for turbine valve test intervals of up to one year is significantly less than the established acceptance criteria. The small change in the probability of generating a turbine missile with longer turbine valve testing intervals does not represent a significant increase in the probability or consequences of an accident previously evaluated. 2. The proposed amendment will not create the possibility of a new or different kind of accident from any accident previously analyzed. The proposed amendment decreases the frequency at which turbine valves are tested. The proposed amendment does not change the kind, number or type of overspeed protection components available. Changing the frequency of turbine valve testing does not result in a significant change in the failure rate or change failure modes for the turbine A-2
EXHIBIT A valves. Therefore, the proposed amendment does not create the l possibility of a new or different kind of accident from any accident previously evaluated. l 3. The proposed amendment will not involve a significant reduction in the margin of safety. As noted above and as shown in the attached WCAP-11525, this change to the Prairie Island Technical Specification will not result in a significant reduetion in the margin of safety for missile ejection. The probability of missile ejection remains acceptubly small and within guidelines established by the NRC Staff. The Commission has provided guidance (March 6, 1986 Federal Register) concerning the application of the standard in 10 CFR 50.92 for determining whether a significant hazards consideration exists by providing certain examples of amendments that will likely be found to involve no significant hazards considerations. The changes to the Prairie Island Technical Specifications proposed in this amendment request are similar to NRC examples (iv) and (vi). Example (iv) relates to the granting of a relief from an operating restriction upon demonstration of acceptable means of operation. This assume. that acceptable operating criteria have been established and that it is satisfactorily shown that the criteria have been met. Example (vi) relates to a change which either may result in some increase to the probability or consequences of a previously analyzed accident or may reduce in some way a margin to safety, but where the results of the change are clearly within all transient analysis acceptance criteria and within the limits'of 10 CFR Part 50.46 and Appendix K to Part 50. The Commission has established missileejectionaccidentof1.0x10"gnacceptancecriteriafortheturbine The probabilities of a turbin missileejectionincidentpresentedinWCAP-11525rangefrom1.86x10~g with j a turbine valve inspection interval of one month to 8.82x10~7 with a turbine valve inspection interval of one year. This demonstrates that the probability of a turbine missile ejection accident at the Prairie Island plant is well within accepted NRC criteria. Based on this guidance and the reasons discussed above, we have concluded that the proposed changes do not involve a significant hazards consideration. l J A-3 L__-_-____ k}}