ML16138A761
| ML16138A761 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/18/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A760 | List: |
| References | |
| NUDOCS 9305240161 | |
| Download: ML16138A761 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 200TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO. 200TO FACILITY OPERATING LICENSE DPR-47 AND AMENDMENT NO.197 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 May 5, 1993, Duke Power Company (the licensee) submitted a request for changes to the Oconee Nuclear Station, Units 1, 2, and 3 Technical Specifications (TS). The amendments would provide an interim acceptance criteria for control rod drop time on Oconee Unit 1. These modifications would change the current acceptance criteria of 1.66 seconds from the fully withdrawn to 3/4 insertion for the control rod drop time specified in TS 4.7.1, "Control Rod Trip Insertion Time Test."
This request is a result of recent testing of control rod drop times, which, in some cases, required multiple drops of the same rod in order to meet the TS acceptance criterion of 1.66 seconds. Although control rod drop time testing is only required during beginning-of-cycle (BOC) startup tests, a test was recently performed on Unit 2 at end-of-cycle (EOC) for a rod which was slow at BOC. The rod did not meet the 1.66 second criterion. This result raised a concern regarding other control rods which tested slow, the concern being that the drop time may have lengthened during the fuel cycle. For Unit 1, Cycle 15, Control Rod 8 in Group 1 and Rod 5 in Group 2 were slow at BOC.
Specifically, for the remainder of Cycle 15, the maximum control rod trip insertion time from the fully withdrawn position to 3/4 insertion (104 inches travel) for Group 1, Rod 8, and Group 2, Rod 5, shall not exceed 2.0 seconds at reactor coolant full flow-conditions with the following provisions:
- 1.
The average insertion time for the remaining rods in Groups 1 and 2 is less than or equal to 1.50 seconds, and
- 2.
The core average negative reactivity insertion rate is within the assumption of the safety margin.
2.0 EVALUATION Although the rod drop times for the two control rods mentioned above were slightly outside the current TS test acceptance criterion, there is a high level of confidence that the rods will trip into the core if required by the 9305240161 930518 PDR ADOCK 05000269 PPDR
-2 reactor protection system. There are several reasons for this high level of confidence. First, although the trend from trip time testing has shown a reduction in speed, there has been no indication that these two rods are being mechanically bound. Secondly, there has been no drastic change in rod drop time over the last several cycles.
Finally, the required TS monthly control rod movement surveillance will continue to verify the rods are not bound. The licensee has evaluated each accident described in the Oconee Final Safety Analysis Report (FSAR) with respect to the proposed changes to the rod drop time criteria. As a result, they have confirmed that the revised test acceptance criteria still assures that the negative reactivity insertion rate is within the assumptions of the safety analysis. In addition, the licensee has verified that Rod 8 of Group 1 and Rod 5 of Group 2, plus the highest worth control rod, could remain fully withdrawn from the core (stuck out) without impacting the required shutdown margin.
The NRC staff finds the proposed TS changes to the Oconee Unit 1 control rod drop time criteria acceptable for the remainder of Cycle 15. Since the negative reactivity insertion rate will remain within the assumptions of the safety analysis, the staff concludes that all safety margins will be maintained. Rod 8 of Group 1 and Rod 5 of Group 2 will be required to meet a 2.0 second drop time, while the average rod drop times for the remaining rods in Group 1 and Group 2 must meet a 1.5 second drop time. The staff, however, requires these two subject rods to be tested at the next available opportunity and changes made to the control rod drive mechanisms, if necessary.
3.0 EMERGENCY CIRCUMSTANCES The licensee's application for the TS change has been timely. Prior to the Oconee Unit 2 outage in March 1992, the licensee had used a computer program for testing control rod drop times in which, due to the program, the rod drop time was not recorded if the time exceeded 1.381 seconds, which was still well below the criteria of 1.66 seconds. If a rod was slower than 1.381 seconds, it was dropped several times until it fell below that time. Thus, it was not known whether the drop time met the test criteria or not, but only that it was slower than the computer program cutoff time. The deficiency in this program was identified in early 1992, and it was determined that "as-found" testing of rods which had previously indicated degraded rod drop times should be performed. The first opportunity to perform this testing was on Oconee Unit 2 after shutdown on April 29, 1993. On May 4, 1993, after reviewing the results of rod drop testing on Oconee Unit 2, the licensee reevaluated rod drop tests conducted on Oconee Unit 1 during the last outage in which two rods required repeated tests before meeting the test acceptance criteria. Based on this reevaluation, the two rods were declared inoperable.
The NRC staff finds that failure to grant the proposed changes in a timely manner would result in shutdown of Oconee Unit 1. We also find that the licensee has responded in a timely manner, and has not delayed its application to take advantage of the Emergency License Amendment provisions of 10 CFR 50.91. Accordingly, the staff concludes that the licensee has satisfied the requirements of 10 CFR 50.91(a)(5), and that a valid emergency exists.
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4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards considerations, if operation of the facility, in accordance with the amendment would not (1) involve a significant increase in the probability or consequences of any accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
This amendment has been evaluated against the three standards in 10 CFR 50.92(c).
In its analysis of the no significant hazards consideration, the licensee has determined that the operation of the Oconee Unit 1, in accordance with the revised control rod drop time test acceptance criteria, would not:
(1) Involve a significant increase in the probability or consequences of an accident previously evaluated:
Each accident analysis addressed within the Oconee Final Safety Analysis Report (FSAR) has been examined with respect to the changes proposed within this amendment request. There is no significant increase in the probability of any Design Basis Accident (DBA) as a result of this change, nor is there a significant increase in the consequences of a DBA as a result of this change, since the revised test acceptance criteria assure the ability of the control rods to mitigate design basis accidents.
Specifically, the revised test acceptance criteria assures that the negative reactivity insertion rate is within the assumptions of the safety analysis.
(2) Create the possibility of a new or different kind of accident from any accident previously evaluated:
Operation of ONS [Oconee Nuclear Station] in accordance with the revised control rod drop time test acceptance criteria will not create any failure modes not bounded by previously evaluated accidents. Consequently, this change will not create the possibility of a new or different kind of accident from any accident previously evaluated.
(3) Involve a significant reduction in a margin of safety:
The revised control rod drop time test acceptance criteria for Unit 1 Cycle 15 assures that the negative reactivity insertion rate assumed in the accident analysis is met. Thus existing margins of safety are preserved. Therefore, there will be no significant reduction in any margin of safety.
The NRC staff has reviewed the licensee's analysis and, based on this review, it appears that the three standards of 10 CFR 50.92(c) are satisfied.
-4 Therefore, the NRC staff has determined that the amendment request involves no significant hazards consideration.
5.0 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.
6.0 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 made a final no significant hazards consideration finding with respect to the amendments.
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.
7.0 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: L. Kopp Date:
May 18, 1993