ML20207E393

Safety Evaluation Supporting Amend 114 to License NPF-3

ML20207E393
Person / Time
Site:	Davis Besse
Issue date:	08/02/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20207E391	List: ML20207E386 ML20207E393
References
TAC-65685, NUDOCS 8808180032
Download: ML20207E393 (3)

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UNITED STATES NUCLEAR REGULATORY COMMISSION g

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W ASHING TON, D. C. 20655

%.....l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDHENT NO. 114 TO FACILITY OPERATING LICENSE NO. NPF-3 TOLEDO EDISON COMPANY AND THE CLEVELAND ELECTRIC ILLUMINATING COMPANY DAVIS-BESSE NUCl. EAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-346

1.0 INTRODUCTION

By letters dated August 7, 1987 and March 21 and May 2, 1988, Toledo Edison requested several changes to the plant Technical Specifications (TS) for the delete the Safety Features Actuation System (SFAS) posed changes would (1)

Davis-Besse Nuclear Power Station, Unit 1.

The pro signals from certain valves listed in Table 3.3-5, Safety Features System Response Times, on the secondary side of the steam generators; and (2) delete the containment isolation closure time requirements from Table 3.6-2, Containment Isolation Yalves. The valves involved are the main steam isolation valves (MSIV's, MS 100 and 101), main steam warm-up valves (MS 100-1 and 101-1), main steam warm-up drain valves (MS 375 and 394), atraospheric vent valves (AVV's, ICS 11A and B), main feedwater stop valves (W 601 and 612), and steam generator blowdown valves (MS 603 and 604).

The licensees asserted that the purpose of the proposed changes was to eliminate unnecessary redundancy in containment isolation features, to improve reliability and availability of the main feedwater (MFW) system by reducing inadvertent SFAS actuation, and to minimize challenges to the auxiliary feedwater system.

2.0 EVALUATION 2.1 Proposed change to revise TS Section 3/4.3.2 Table 3.3-5 to delete the reference to the MSIV, MFW stop valves, and main steam warmup valves receiving a high-high containment pressure SFAS automatic signal.

The licensees indicated that the above valves currently receive Steam and Feedwater Rupture Control System (SFRCS) signals which provide sufficient redundancy tn automatically isolate them as necessary in the event of a design basis accident. The high-high containment pressure SFAS signal, which is actuated at 38.4 psia, can be caused only by a large break (greater than 0.5 square f t.) loss of coolant accident (LOCA).

For a large break LOCA, the RCS will rapidly depressurize to a value below the saturation pressure of the water in the secondary side of the steam generator (SG). This depressurization effectively seals the SG as a leakage path from the reactor coolant system (RCS); therefore, radioactive releases are not sensitive to the containment h{%3Oh $

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2 isolation closure time of the valves on the SG secondary side. As the SG secondary side pressure falls to approximately 600 psia, a SFRCS steam line low-pressure trip will occur.

The SFRCS trip causes SG isolation valves associated with the feedwater and main steam system to automatically close on both SG's.

The SFRC system can also detect a main steam line break (MSLB) by sensing a steam line low pressure condition in the faulted SG's steam line. The system senses a feedwater line rupture by detecting a steam line low pressure on the faulted SG or a high reverse differential pressure between the unaffected SG and its feedwater line.

For the accidents discussed above, the valves affected by this change will be closed automatically due to the SFRCS trip, and the closure times do not significantly impact radiological consequences.

Further, these valves can also be closed remote manually from the control room. Due to the duplication of automatic isolation function between SFRCS and SFAS for these valves, the staff finds this proposed change acceptable.

2.2 Proposed change to revise TS 3/4.3.2, Table 3.3-5 to delete reference to MS warmup drain and AVV's receiving a high containment pressuie or low reactor coolant system pressure SFAS automatic signal.

The licensees indicated that the above valves are closed during norwal plant operation and the SFAS signals serve to provide a backup to procedural requirements for maintaining the valves in a closed position. During a steam generator tube rupture (SGTR) event, when the condenser is not available, the AVV's will be used to control the cooldown and to minimize main steam safety valve lifts. The SFAS signal due to low reactor coolant system pressure is counter-productive for the above accident mitigation operation when opening of the AVV's is desired.

For a small break LOCA, it is desirable to make these valves available in conjunction with the auxiliary feedwater system for removing decay heat from the SG secondary side.

For a MSLB and feedwater rupture, the AVY's are automatically isolated by an SFRCS signal, which provides a redundant, automatic function to isolate these valves as described in Section 2.1.

For a large break LOCA, the pressure gradients between the primary and secondary system prevent leakage into the secondary system until isolation is initiated by SFRCS low steam-line pressure. When comparing the safety significance of having a backup to a closed containment isolation valve in the secondary system against the enhanced availability of decay heat removal, the staff finds the latter to be more important and, therefore, finds the proposed change to be acceptable.

2.3 Proposed change to revise TS 3/4.3.2 Table 3.3-5 to delete the reference to the AVV's, MS warmup drain valves MSIV's MFW stop valves, and MS line warmup valves receiving a manual SFAS.

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3-T5e licentces indicated that the capability to operate manually the acove valves is available independent of SFAS, and these valves are listed in TS Section 3/4.6.3, Table 3.6-2, Containment Isolation Valves. The oper6bility of these valves including the manual function, is required by TS 3.6.3.1.

Surveillance of the manual operation capability is required by either TS 4.0.5 Surveillance Requirements for inservice inspection of ASME Class 1, 2 and 3 components, or TS Sections 4.3.2.2.1 through 4.3.2.2.3 which include SFRCS operability requirements.

Because of the above duplication in the TS manual operation function, the staff finds the proposed change acceptable.

2.4 Proposed change to revise TS Section 3/4.3.6 Table 3.6-2 to delete isolation time requirements for MS!V, main steam wannup valves, MFW stop valves, AVV, main steam warmup drain valves, and steam generator blowdown valves.

The licensees indicated that the response times for the MSlY, and MFW Rupture Control System (y specified in TS Table 3.3-13. Steam and Feedwater stop valves are currentl SFRCS)ResponseTimes.

Further, the stroke time performance will be monitored as a part of the in-service inspection and testing program, as required by TS 4.0.5, Surveillance Requirements for inservics *aspection of ASME Class 1, 2 and 3 components.

As discussed previously in Sections 2.1 and 2.2, the valve closure times for these containment isolation valves are not critical from the standpoint of containment isolation and limiting radiological releases. Therefore, the valve closure time requirements from the SFRCS and in-service inspection and testing program are adequate, and the staff finds the proposed change acceptable.

4.0 ENVIRONMENTAL CONSIDERATION

Pursuant to 10 CFR 51.?1. 51.32, and 51.35, an environmental assessment and finding of no significant impact has been prepared and published in the Federal Register on June 16, 1988 (53 FR 22588). Accordingly, based upon the environmental asses; ment, the Consnission has determined that the issuance of this amendment will not have a significant effect on the quality of the human environment.

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5.0 CONCLUSION

I The staff has concluded, based on the considerations discussed above, that:

will not be endangered by operation in the proposed manner, and (2) public (1) there is reasonable assurance that the health and safety of the l

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activities will be conducted in compliance with the Cosmission's regulations, i

and the issuance of this amendment will not be inimical to the comon defense l

and security or to the health and safety of the public.

Principal Contributor: Chang-Yang Li Dated: August 2, 1988 l

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