ML20211H379

License Change Application for Amend to License NPF-1, Increasing Setpoint Tolerance for Pressurizer & Main Steam Safety Valves from 1% to 2%

ML20211H379
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	02/11/1987
From:	Cockfield D PORTLAND GENERAL ELECTRIC CO.
To:
Shared Package
ML20211H337	List: ML20211H333 ML20211H379 ML20211H402
References
TAC-64803, NUDOCS 8702260157
Download: ML20211H379 (4)

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c' PORTLAND GENERAL ELECTRIC COMPANY L'UGENE WATER & ELECTRIC BOARD AND PACIFIC POWER & LIGHT COMPANY Operating License NPF-1 i

Docket 50-344 License Change Application 148 l

This License Change Application requests modifications to Appendix A of Operating License NPF-1 for the Trojan Nuclear Plant to revise the Trojan Technical Specifications to increase the setpoint tolerance for the l pressurizer and main steam safety valves from il percent to 12 percent.

PORTLAND GENERAL ELECTRIC COMPANY By [

D. W. C kfield Vice esident [

Nuclear 1

l l Subscribed and sworn to before me this lith day of February 1987.

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1 Notary Public of Orej(on My Comission Expires: ru f [

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l 8702260157 DR 870211 ADOCK 05000344 PDR

o . o LCA 148

, Page 1 of 3 DESCRIPTION OF CHANGE This change revises the setpoint tolerance for the pressurizer and main steam safety valves from il percent to 12 percent. Trojan Technical Specifications (TTS) affected by this change are (1) TTS 3/4.4.2, Reactor Coolant System Safety Valves - Shutdown, (2) TTS 3/4.4.3, Reactor Coolant System Safety and Relief Valves - Operating, and (3) TTS 3/4.7.1, Turbine Cycle Safety Valves. The Bases for TTS 3/4.7.1 are also revised. The changes are discussed below and shown in Attachment A.

REASON FOR CHANGE Operating experience has demonstrated that a setpoint tolerance for the pressurizer and main steam safety valves of only il percent results in safety valves frequently failing surveillance tests. This occurs during annual setpoint testing of the valves per TTS 4.4.3 and 4.7.1.1. Failure of the surveillance tests requires that additional safety valves be tested. Since this testing is dono during refueling outages, test failures have the potential for impacting schedules and result in the diversion of resources from other refueling activities.

To remedy this situation, an analysis was performed (Attachment B) to determine if greater setpoint tolerance could be permitted without compromising system integrity. The results of this analysis showed that a setpoint tolerance of +4 percent, -3 percent for both the main steam and pressurizer safety valves is acceptable. Whereas, the reviJed safety analysis demonstrates the acceptability of +4 percent. -3 percent, ASME Section XI specifies an acceptable lift setpoint tolerance of 2 per-cent. Accordingly, the TTS in Attachment A have been revised to specify a setpaint tolerance of t2 percent. This tolerance is within the bounds of the revised safety analysis and also satisfies ASME Section XI requirements.

The Bases for TTS 3/4.7.1 is revised to correct an error in the main steam system design pressure. The correct value is 1185 psig, not 1230 psig. In addition, the limiting pressure for safety valve operation is corrected to 110 percent of design pressure in accordance with the W-STS (NUhEG-0452, Revision 4). Furthermore, the Bases have been expanded for clarification.

l l SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION This change does not involve a significant increase in the probability or l

consequences of an accident. The pressurizer and main steam safety valves are designed to mitigate transients by preventing overpressuriza-tion of the Reactor Coolant System (RCS) and main steam system, respec-tively. The proposed change does not alter this design basis. The increase in setpoint tolerance does increase the range of pressures at which the safety valves may lift and subsequently close. This can result in greater system pressures prior to valve lifting and increased blowdown i

LCA 148 p

pegs 2 of 3 prior to valve seating. This does alter the consequences of an accident from the standpoint that the safety valves may respond differently as far as when the valves open and close. However, the revised analysis clearly demonstrates that the RCS and main steam system are not overpressurized.

Therefore, the conclusions of the accident analysis remain unchanged.

This change does not create a new or different kind of accident. Neither the design nor the operation of the Plant is modified. Any pressurizer cafety valve lifting at the extremes of the proposed tolerance will not result a (1) a low lift setpoint that is less than the pressurizer high-pressure reactor trip, nor (2) a high lift setpoint that allowP RCS overpressurizstion. Any main steam safety valve lifting at the extremes of the proposed tolerance will not result in (1) a low lift setpoint that is less than the normal no-load system pressure, nor (2) a high lift set-point that allows main steam system overpressurization.

This change does not involve a significant reduction in a margin of safety. As discussed in FSAR Section 5.4.11.3, the pressurizer safety valves prevent RCS pressure from exceeding 110 percent of design pressure in accordance with the ASME Code. The RCS design pressure is 2500 psia.

This pressure corresponds to a code limit and TTS safety limit of 2750 psia. The analysis indicates that, for a +4 percent tolerance and 3 percent accumulation, the peak RCS pressure is 2699 psia (refer to Table 3.1 of Attachment B) and the Code limit of 2750 psia is met.

The main steam safety valves prevent the main steam system pressure from exceeding 110 percent of design pressure in accordance with the ASME Code. The main steam system design pressure is 1200 psia. This pressure corresponds to a Code limit of 1320 psia. Since the peak main steam system pressure with a +4 percent tolerance on the main steam safety valves with 3 percent accumulation is 1283 psia, the ASME Code limit of 1320 psia is met.

Extensive conservatisms are used in the revised analysis. No credit is taken for operation of the pressurizer power-operated relief valves (PORVs), pressurizer spray, steam dump system, nor steam generator PORVs. In addition, no credit is taken for direct reactor trip on turbine trip. Furthermore, the analysis assumed that the No. 5 group of main steam safety valves and one pressurizer safety valve are not avail-able. If any other group of main steam safety valves was not available, 110 percent of design would still not be exceeded because only one group of main steam safety valves is required to actuate to relieve the pressure.

While the revised safety analysis demonstrates the acceptability of a lift tolerance of +4 percent, -3 percent, the TTS are being revised to increase the tolerance only to i2 percent. This is because ASME Section XI allows a tolerance of only 2 percent, which includes an allowance for setpoint drift. Since the pressurizer and main steam safety valves are Code valves which are tested to meet ASME Section XI, the more restrictive Code requirements will govern.

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LCA 148 P:ss 3 of 3 During lift testing of safety valves, valves that lift within 2 percent of the lift setpoint will be left as is, with no further adjustment of the lift setpoint required. Any valves that lift outside of the 2 per-cent tolerance will be adjusted to within 12 percent. In addition, for each safety valve that lifts outside of the 12 percent tolerance, an additional 20 percent of the safety valves will be tested. This is in accordance with ASME Section II, Which is referenced by TTS 4.0.5.

The proposed change is similar to changes which have been approved on Calvert Cliffs 1, Yankee Rowe, and LaSalle 1 and 2.

In the April 6, 1983 Federal Retister, the NRC published a list of examples of amendments that are not likely to involve a significant hazards consideration. Example No. 6 of that list applies to the change proposed to the setpoint tolerance and states:

"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 safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan, eg, a change resulting from the application of a small refinement of a previously used calculational model or design method."

Example No. 1 from the list in the April 6, 1983 Federal Retister applies to the change which corrects the error in the Bases for TTS 3/4.7.1 and states:

"A purely administrative change to technical specifications, eg, a j change to achieve consistency throughout the technical specifications, correction of an error, or a change in nomenclature."

Based on the above evaluation, the proposed changes are deemed not to pose a significant hazard.

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