ML20012C674
| ML20012C674 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 03/19/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20012C672 | List: |
| References | |
| NUDOCS 9003230041 | |
| Download: ML20012C674 (5) | |
Text
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,7 UNITED STATES l
NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20666
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.131 TO FACILITY OPERATING LICENSE NO. DPR-3 YANKEE ATOMIC ELECTRIC COMPANY YANKEE NUCLEAR POWER STATION DOCKET NO.50-029 INTRODUCTION By letter dated January 18, 1990, the Yankee Atomic Electric Company (YAEC or the licensee) requested an amendment to Facility Operating License No. DPR-3 for the Yankee Nuclear Power Station (YNPS or the plant). The proposed amendment would:
1.
Relocate surveillance requirements for Valve CH-MOV-524 from Section 4.5.2.b.1.b to Section 4.5.2.b.4.aa.
i 2.
Revise valve function description in Section 4.5.2.b.4.k for Valve SI-MOV-46 from "High Pressure Safety Injection (HPSI) flow control" to i
"HPSI isolation.d 3.
Add surveillance requirements for new Valves SI-MOV-519, SI-MOV-520, and l
CH-MOV-550, Section 4.5.2.b.4 4.
Add Section 4.5.2.b.9 to verify that redundant HPSI header isolation / flow control valves are aligned to receive electrical power from separate operable buses.
5.
Add Section 4.5.2.b.10 to verify that redundant charging line isolation l
valves are aligned to receive power from separate operable buses.
L 6.
Add Section 4.5.2.b.11 to verify that redundant pressurizer auxiliary spray valves are aligned to receive power from separate operable buses.
' [0 7.
Add Section 4.5.2.g.3 to require flow testing following modifications that alter the flow characteristics of the pressurizer auxiliary spray line.
3No i*8$
EVALUATION 8o8 The changes proposed by the licensee reflect modifications to the Emergency CoreCoolingSystem(ECCS),Chargina)whicharedesignedto:and Volume Control Sy Coolant Pressure Control System (PR oo 8@
1.
Enhance the plant's capability to control Main Coolant System (MCS) pressure Q
by providing redundant safety grade pressurizer auxiliary spray capability, gg and a o.a.
2.
Enhance post-LOCA sump recirculation flow control by providing redundant safety grade safety injection throttling capability.
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pressurizer Auxiliary Spray Redundant motor-operated Pressurizer Auxiliary Spray Valves PR-MOV-548, 549 as 1
shown on the attached sketch will be installed to replace the existing manually-operated valve. This change is being implemented to provide enhanced i
safety grade auxiliary spray capability for periods when normal spray via the main coolant pumps is unavailable.
Initiation of auxiliary spray for MCS depressurization will require isolation of the normal charging line in order to direct the charging flow up to the pressurizer spray nozzle.
For this reason, a secced series redundant Isolation Valve CH-MOV-550, located upstream of the Charging Line Isolation Valve CH-MOV-524, is required. This arrangement will ensure that an auxiliary spray flow path will be available following any single active failure. Currently, CH-MOV-524 receives power via a normally open supply breaker. This breaker is open to preclude inadvertent valve closure during normal plant operation and ensures a flow path for manual charging and post-LOCA hot leg recirculation. Because CH-MOV-524 will require closure to initiate auxiliary spray, its power supply will be relocated, and a second series motor starter will be installed to preclude inadvertent valve closure due to single failure or operator error.
Either the charging pumps or the ECCS pumps can be utilized to provide the necessary flow to the euxiliary spray line. When using the ECCS, flow is L
delivered via the hot leg injection subsystem. This subsystem provides a l
discharge path from the HPSI discharge line to the normal charging line for hot leg recirculation following large cold leg breaks.
The NRC staff concludes that this design change will provide a significant degree of system operating flexibility and enhance lor.p-term reliability of the ECCS pumps and is therefore acceptable.
l High Pressure Safety injection Throttling Capabilities l
The proposed scheme for HPSI throttling is needed to establish flow to the pressurizer steam space for Main Coolant System pressure control when using l
ECCS for euxiliary spray. The existing ECCS alignment during a cold leg recirculation results in injection through the single HPSI discharge line.
SI-MOV-46, located in the common HPSI header, is normally fully open during the injection phase of system operation. The control circuit for this valve is designed to preclude single active failures (closure) ty electrical faults or operator error by incorporation of dual series contactors.
To ensure ECCS throttling capability, two additional Valves SI-MOV-519, 520 are required to accommodate all possible single-active valve failures. The proposed arrangement is shown on the attached Sketch.
An additional benefit from HPSI throttling includes the flexibility to reduce ECCS pump operation to a single HPSI pump during the recirculation phase of operation, thus significantly reducing emergency diesel generator loading.
The decay heat removal requirements durino this period are well within the capacity of a single pump, and redundant safety grade systen flow control will ensure that the pump is operated within its flow / Net Positive Suction Head limitations.
The addition of the new valves has negligible impact on ECCS performance.
ys 4%
The proposed modification will enhance the capability for controlling MCS pressure when the normal spray is unavailable. The charging line will be-isolated by series redundant isolation valves, and spray flow will be l
- initiated through one of two parallel redundant flow control valves located in the spray line piping which branches off the normal charging line. This valve arrangement ensures that spray flow can be initiated following any single active failure.
Redundant safety grade HPSI discharge throttling capability will ensure that the required flow can be delivered to the pressurizer auxiliary spray line when using ECCS. This. capability also provides the flexibility to reduce ECCS pump operation to a single HPSI pump during the ret.irculation phase of operation, thus significantly reducing the emergency diesel generator loading.
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The series reduncont. charging line valves will be provided with dual starter contat. tors to preclude spurious valve closure during normal plant operation.
This feature provides assurance that the normal charging and ECCS hot leg recirculation path remains operable in accordance with existing Technical Specification requirements.
The addition of the new valves has been evaluated and determined to have negligible impact on ECCS performance.
Therefore, this change enhances MCS pressure control capabilities and provides an added degree of flexibility during normal cooldown, while preserving the existing design basis functional capabilities of the affected safety-related sy stems..
' The' proposed auxiliary spray modification incorporates design features which enhance MCS' pressure control capabilities while not adversely impacting operation of any cafety-related system's structures or components. The design ensures that Main Coolant System depressurization can be accomplished in consideration of the limiting single failure and also precludes inadvertent chargirig line isolation during normal plant operation.
Inadvertent activation of auxiliary pressurizer spray would result in depressurization of the Main Coolant System. This is not a credible event since multiple failures are needed to isolate the charging line and initiate auxiliary spray.
The charging line isolation modification is designed consistent with existing Technical Specification requirements which ensure that the charging line flow path remains operable during normal operation.
Based on the staff's evaluation of the licensee's submittal, the staff finds that there is reasonable assurance that operation of the Yankee Rowe plant consistent with the proposed Technical Specifications will not endanger the heslth and safety of the public, and that the change is acceptable.
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4 ENVIRONMENTAL CONSIDERATION e
This amendment involves a change in a requiremen+. with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillana requirements. The staff has determined that the amendment involves 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 occupa.
tional radiation exposure. The Commission has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibility criteria for categoricel exclusion set forth in 10 CFR 51.22(c)(9).-Pursuantto10CFR51.22(b),noenvironmentalimpactstatementor environr. ental assessment need be prepared in cor.nection with the issuance of 1
this emendment.
CONCLUSION 1
The Comission made a proposed determination that the amendment involves no significant ha7ards consideration which was published in the Federal Register (55 FR 4290) on February 7,1993. No public coments were received anc' the State of Massechesetts did not have any coments.
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the p(ublic will not be endangered by operation in the proposed canner, and 2) such activities will be conducted in compliance with the Comission's regulations, and (5) the issuance of ti:is amendment will not be inimical to the common e.d ense and security or to the health and safety of the public.
- Principal Contributor: Patrick M. Sears Dated:
March 19,1990 l
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