ML20207G387
| ML20207G387 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/04/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20207G384 | List: |
| References | |
| NUDOCS 9906110133 | |
| Download: ML20207G387 (4) | |
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4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.168 TO FACILITY OPERATING LICENSE NO. DPR-25 COMMONWEALTH EDISON COMPANY DRESDEN NUCLEAR POWER STATION. UNIT 3 DOCKET NO. 50-249
1.0 INTRODUCTION
By letter dated May 5,1999, Commonwealth Edison Company (Comed, the licensee) proposed changes to the Technical Specifications (TS) for the Dresden Nuclear Power Station, Unit 3. The proposed changes would remove the safety valve function of the Target Rock safety / relief valve (SRV) from TS Section 3.6.E and move the reactor coolant system (RCS) safety valve lift pressure setpoints from TS Section 3.6.E to TS Section 4.6.E.
This request for amendment was submitted under exigent circumstances in accordance with NRC Administrative Letter 95-05, Revision 1, " Revisions to Staff Guidance for implementing NRC Policy on Notices of Enforcement Discretion." The requested amendment will supersede Notice of Enforcement Discretion (NOED) 994-004 which is documented in NRC letter dated May 6,1999. NOED 994-004 was issued in response to Comed's letters dated May 4 and 6, 1999,' requesting enforcement discretion to prevent undue shutdown or dorate of Dresden, e
Unit 3, due to the safety valve function of the Unit 3 Target Rock SRV valve becoming inoperable on May 3,1999.
2.0 BACKGROUND
On May 3,1999, an annunciator in the Dresden, Unit 3, control room indicated a possible pilot valve bellows failure for the Target Rock safety / relief valve (SRV). Dresden, Unit 3, has eight reactor coolant system (RCS) safety valves, four RCS relief valves, and one valve, manufactured by Target Rock, that serves as both a safety valve and as a relief valve. Thus, both TS Section 3/4.6.E concoming RCS safety valves and TS Section 3/4.6.F concoming relief valves 9ovem the operability of the Target Rock SRV. The pilot valve bellows is ossociated with the safety valve function of the Target Rock SRV but does not prevent it from functioning as a relief valve. Therefore, the licensee entered the action statement in TS Seebon 3.6.E which requires that the unit be placed in hot shutdown within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of any of the nine RCS safety valves becoming inoperable.
Transient analysis and design basis documents for Dresden, Unit 3, show that overpressure requirements are met with less than nine RCS safety valves. Although the Target Rock SRV is required to be operable by TS, no credit is taken for this valve in the analysis used to meet the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code. To prevent an unnecessary shutdown Comed requested and was granted NOED 99 004.
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- 3.0 EVALUATION The staff verified that the Dresden, Unit 3, design basis for RCS overpressure protection and accident analysis, which is described in Sections 5.2 and 15.2 of the Dresden Updated Final Safety Analysis Report (UFSAR), does not credit the safety valve function of the Target Rock SRV. If the safety valve function of the Target Rock SRV is removed from the TS, TS Section 3.6.E will continue to specify operability requirements for the other eight RCS safety valves. The eight safety valves still specified in TS Section 3.6.E will provide adequate protection for overpressure transients and accident conditions.
The licensee has also proposed to move the RCS safety valve lift pressure setpoints from TS Section 3.6.E to TS Section 4.6.E. The safety valve lift pressure setpoints are verified by surveillance tests and are more correctly specified under the surveillance section, TS flection 4.6.E, rather than the limiting condition for operation section, TS Section 3.6.E. This rolocation of the RCS safety valve lift pressure setpoints follows the format of the improved Stan: lard Technical Specifications, NUREG-1433. This administrative change to TS does not reduce requirements.
On the basis of the preceding information, the staff has determined that it is not necessary to include the safety valve function of the Target Rock SRV in TS and that the RCS safety valve lift pressure setpoints are more correctly specified in TS Section 4.6.E. There are no negative safety consequences associated with deleting the Target Rock SRV safety valve function or with
. relocating the lift pressure setpoints. The staff thus concludes that it is acceptable to remove the I
safety valve function of the Target Rock SRV from TS and to relocate the RCS safety valve lift
_ pressure setpoints within TS.
4.0 EXIGENT CIRCUMSTANCES
l in its May 5,1999, application, the licensee requested that this amendment be treated as an exigent amendment. In accordance with 10 CFR 50.91(a)(6), the licensee provided the
. following information regarding why this exigent situation occurred and how it could not have been avoided.
The need for a NOED and a subsequent license amendment request was determined upon the recent potential failure of the safety mode of the Target Rock SRV on May 3,1999 Comed had no prior knowledge of this failure and discovered during a review of licensing and design bases that credit for the safety mode of the Target Rock SRV was not used in the evaluation of any design basis accidents or transients. Submittal of this amendment request is consistent with the i
guidance provided in NRC Administrative Letter 95-05, Revision 1 for NOEDs that are granted which also require a license amendment. Comed believes that the circumstances surrounding the request for exigent review were unavoidable and were not created by a failure to make a timely application for a license amendment.
The staff concludes that an exigent condition exists in that failure to act in a timely way would result in an undue shutdown or derate of Dresden. Unit 3. In addition, the staff concludes that the licensee made a timely application for the amendment and did not cause the exigent situation. Thus, the conditions needed to satisfy 10 CFR 50.91(a)(6) exist, and the :mendment is being processed on an exigent basis.
5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission's regulations in 10 CFR 50.92(c) state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in accordance with the amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated, or (2) create the possibility of a new or different kind of accident from any previously evaluated, or (3) involve a significant reduction in a margin of safety.
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The proposed changes do not involve a significant hazards consideration because operation of Dresden, Unit 3, in accordance with the proposed changes would not:
(1)
Involve a significant increase in the probability or consequences of an accident previously evaluated:
The probability of an evaluated accident is derived from the probabilities of the individual precursors to that accident. The consequences of an evaluated accident are determined by the operability of plant systems designed to mitigate those consequences. Limits have been established consistent with NRC-approved methods to ensure that fuel performance during normal, transient, and accident conditions is acceptable. The proposed change to permit operation with the Target Rock safety / relief valve (SRV) safety function out of service (OOS) does not affect the ability of plant systems to adequately mitigate the consequences of an accident previously evaluated.
This conclusion was derived by evaluating all applicable analyses including thermal limit, American Society of Mechanical Engineers (ASME) pressurization events, margin to unpiped safety valve, anticipated transient analysis without scram, loss of coolant accident (LOCA),
station blackout, and Appendix R analyses. Therefore, there is no increase in the probability or consequences of an accident previously evaluated because the analyses support operation with the Target Rock SRV safety function OOS.
(2)
Create the possibility of a new or different kind of accident from any accident previously evaluated:
Since the requested change has been previously evaluated, no new precursors of an accident are created and no new or different kinds of accidents are created. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
This conclusion was derived by evaluating all applicable analyses including thermal limit, ASME pressurization events, margin to unpiped safety valve, anticipated transient analysis without scram events, station blackout, and Appendix R analyses. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated because the analyses support operation with the Target Rock SRV safety function OOS.
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s (3)
Involve a significant reduction in a margin of safety:
Allowing Dresden operation with the Target Rock SRV safety function OOS will not involve any reduction in margin of safety. This conclusion was derived by evaluating all applicable analyses including thermallimit, ASME pressurization events, margin to unpiped safety valve, anticipated transient analysis without scram events, station blackout, and Appendix R 1
analyses. The analyses previously evaluated remain valid and conservative. Thus there is no reduction in the margin of safety, i
Accordingly, the Commission has made a final determination that the amendment involves no significant hazards consideration.
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6.0 STATE CONSULTATION
in accordance with the Commission's regulations, the !!Iinois State official was notified of the
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proposed issuance of the amendment.. The State official had no comments.
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7.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no 1
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 finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (64 FR 27824).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(g). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
8.0 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: L. Rossbach Date: June 4,1999 i
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