ML20058K998
| ML20058K998 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/06/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058K989 | List: |
| References | |
| NUDOCS 9312160092 | |
| Download: ML20058K998 (5) | |
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UNITED STATES i"'
NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. In AND 147 TO FACILITY OPERATING LICENSE NOS. DPR-24 AND DPR-27 WISCONSIN ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-266 AND 50-301
1.0 INTRODUCTION
By letters dated February 21 and April 16, 1992, and March 4,1993, in accordance with the requirements ~of 10 CFR 50.59(c), 50.90, and 50.4, Wisconsin Electric Power Company, licensee for Point Beach Nuclear Plant, Units 1 and 2, requested amendments to Facility Operating Licenses DPR-24 and DPR-27, to incorporate changes into the plant Technical Specifications. The proposed changes included new limiting conditions for operation (LCOs) addressing the main steam stop valves (MSSVs) and the main steam non-return check valves (NRCVs). Also included were changes to the definition of acceptable periodic testing for the MSSVs, a surveillance requirement for the NRCVs, and clarification of the permissible valve testing conditions. The revised surveillance requirements are intended to supplement, or clarify, rather than supersede, the testing requirements of Technical Specification 15.4.2.B and 10 CFR 50.55a relative to ASME Section XI-inservice testing, which requires testing these valves during cold shutdown (reference NRC Safety Evaluation dated April 17,1992). The April 16, 1992, and March 4,1993, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
The subject Technical Specification change request was submitted to fulfill the licensee's commitment in their letter of December 3,1991, as a result of an l
event which occurred September 29, 1991. At that time, Point Beach, Unit 2, was in the process of shutting down for its annual refueling outage. An attempt to close the MSSVs from the control room was ineffective.
By applying mechanical force to the valves, an operator was able to cause the valves to close.
This event was reported in Licensee Event Report 301/91-001. A second similar event occurred May 31, 1992, when an MSSV failed to fully close when an inservice test was performed during startup of Point Beach, Unit 1. Again, mechanical force was required to close the valve. This event was reported in Licensee Event Report 266/92-006.
Technical Specification 15.3.4, " Steam and Power Conversion System," is proposed to be amended to include limiting conditions for operation (LCOs) for the main steam stop valves (MSSVs) and the main steam non-return check valves (NRCVs).
The current technical specifications contain no such limiting conditions. Also proposed are revisions to Specification 15.4.7, " Main Steam Stop Valves," to clarify the definition of acceptable periodic testing for the MSSVs and to propose a surveillance requirement for the NRCVs.
This specification and its bases are also revised to clarify the permissible valve testing conditions.
9312160092 931206 DR ADOCK 05000266 PDR
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Technical Specification 15.3.4, " Steam and Power Conversion System," presently does not address the operability of the MSSVs or the NRCVs.
Specification i
15.3.4.D states that if the reactor is in power operation when one MSSV is discovered to be inoperable, but open, reactor operations may continue, provided the valve is restored to an operable status within four hours. Otherwise, the j
reactor shall be placed in the hot shutdown condition within the following six hours.
The proposed LC0 permits continued operation in the hot shutdown condition provided the inoperable valve or valves r maintained closed.
The specification provides for the MSSVs to be opened wo in hot shutdown for the i
purpose of operability testing. The new LCO for tk sin steam NRCVs proposed f
in this application is the same as that proposed for the MSSVs.
Technical Specification 15.4.7 presently requires periodic testing of the MSSVs to verify the ability of the valves to close upon initiation of a valve closure j
signal. The valves are required to close within five seconds of the initiating i
signal. The licensee is proposing that the specification be revised to read, in i
part, "The five seconds shall be measured from the time of signal initiation l
until the valve indicates closed."
The reference to the dashpot in this t
specification has been removed. This reference was no longer correct, since the
.i dashpots no longer function as an arresting device for the valve disk closure.
The proposed amendment would also clarify when the surveillance testing of the 3
MSSVs is required and when it can be performed.
In addition a surveillance I
specification for the NRCVs is proposed to be added. The function of the NRCVs l
is to shut in the event of reverse steam flow in the main steam line. The NRCVs will be tested for operability during plant outages for major fuel reloading.
l To reflect the more comprehensive nature of this surveillance specification, 15.4.7 has been retitled " Main Steam System Valves."
The applicability and objective statements have been revised to include the NRCVs and the specification organized into twu sections.
The Bases section of the Technical Specifications is changed as necessary tt l
support the new LCO and surveillance procedures.
2.0 EVALUATION The intent of the Technical Specification change is to (1) clarify that the main-steam.stop valves are required to close within five seconds with more accurate i
stroke time measurement methods, (2) define test conditions for the MSSVs, (3) add. testing requirements for the NRCVs, and (4) rename. and rearrange the i
specifications for the main steam system valves.
The MSSVs and NRCVs are not addressed in the Westinghouse Standard Technical Specifications (STS); however, these valves, in combination, provide-a function similar to main steam isolation valves which are addressed in STS. The requested amendment is, then, similar to the STS for the main steam valves.
The MSSVs
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4 centain a swing disc which is normally held out of the main steam flow path by 1
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! an air piston.
These valves are designed to close by a spring when the air supply is shut off by a signal from the steam line break protection system, and the piston is vented by redundant valves actuated by the same signal. The MSSVs are designed to close in less than five seconds in response to a steam line l
break.
The I RCVs prevent reverse flow of steam.
If a steam line ruptures between an MSSV and a steam generator, the affected steam generator will blow down. The NRCV in the line will prevent blowdown (reverse flow) from the other steam generator. Each steam line contains an MSSV and a NRCV in series; hence, a single failure will not permit blowdown of more than one steam generator irrespective of the steam line rupture location.
2.1 Specification 15.3.4.D The proposed specification defines the limiting conditions for operation for the MSSVs and NRCVs.
Power operation is allowed to continue for up to four hours with an inoperable but open (allowing steam flow to the turbine) MSSV or NRCV, i
thereafter within six hours the reactor must be placed in a hot shutdown condition. This period allows the licensee time to return the inoperable valve j
to operable if the condition can be corrected while at power operation.
If the l
licensee determines the condition cannot be corrected, the additional six hours allows for an orderly plant shutdown. Additionally, it does not allow continued operation if more than one MSSV or NRCV is inoperable.
In the event more than one valve is determined to be inoperable, immediate action would be required to place the reactor in a hot shutdown condition within six hours.
With one or more MSSV or NRCV inoperable, subsequent operation in the hot shutdown condition is allowed for an indefinite period provided the inoperable valve or valves are maintained closed.
However, an inoperable valve may be i
opened in the hot shutdown condition for testing to confirm operability.
This is an acceptable allowance in that the safety function of the valves is to close, and this will place the inoperable valve or valves in the safe position. If the inoperability is such that the affected valve or valves cannot be closed, hot shutdown may not continue, but the plant must proceed to cold shutdown.
Additionally, the specification allows only one inoperable valve at a time to be opened for testing; therefore, if the tested valve does not reclose, hot shutdown may not continue, but the plant must proceed to cold shutdown.
The establishment of limiting conditions of operation clarifies actions the operators are required to take when an MSSV and/or a NRCV is determined to be inoperable during power operations and during hot shutdown conditions.
Rather
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than relying on the discretion of the operators to make a determination, these I
limiting conditions provide an additional level of assurance that the appropriate actions will be taken for inoperable safety-related equipment.
The limiting i
conditions are more conservative than the STS for main steam isolation valves.
The staff finds the proposed specification acceptable.
2.2 Specification 15.4.7 i
This specification provides the surveillance requirements, in addition to the requirements of specification 15.4.2.B for inservice testing, for the main steam stop valves and the non-return check valves.
)
. The requested change renames the specification from Nafn Steam Stop Va7ves to
- ain Steam System Valves in recognition that the non-return check valves are now included in the specification.
The applicability statement and the objective sections were changed to include the non-return check valves, as well.
l The surveillance requirements for the MSSVs have been changed to clarify when the valve testing is to be performed.
The revised specification requires MSSV testing during plant start-up following a refueling outage prior to admitting steam to the turbine to assure an acceptable "as-left" condition.
Reactor shutdown was replaced by plant shutdown to allow conduct of the testing with the reactor critical, thereby providing steam for the test. Low flow conditions has been clarified to be 5% steam flow or less for establishing test conditions for the valves.
The basis section has been modified by deleting a reference to static test conditions and valve seating.
The closure time of five seconds is retained in the revised specification, but the closure verification has been modified.
Previously, the specification required measurement of the closure time from the time of signal initiation until the valve disc was brought to a halt by the dashpot.
Because closure can be verified by a shut indication in the control room and by mechanical indication locally at the valve, and because the dashpots no longer function as an arresting device for the valve disc, the measurement of the closure time will now be from the time of signal initiation until the valve indicates closed. This change more accurately reflects the configuration of the valves and the current methods of stroke time measurements.
The revised specification adds the surveillance requirements for the non-return check valves such that they are to be tested during refueling outages. The basis section now includes a description of the function of the non-return valves and the purpose of the surveillance. The licensee has indicated their intention to install position indicators for the NRCVs for verification of disc closure in order to meet the requirements of the revised specification. Currently there is no means to verify that these valves are fully closed.
The revised specification is acceptable to the staff.
The changes include additional requirements and clarify existing requirements. The modifications to the NRCVs to provide position indication will enhance the existing inservice testing required for these valves. The revised surveillance requirements provide an increased level of assurance of the operability of the valves.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Wisconsin State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments change a requirement with respect to the installation or use of i
a facility component located within the restricted area as defined in 10 CFR Part 20 or change an inspection or surveillance requirement. The staff has determined l
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l 5-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, r
and that there is no significant increase in individual or cumulative occupa-tional radiation exposure. The Commission has previously published a proposed finding that these amendments involve no significant hazards consideration and i
there has been no public comment on such finding (57 FR 18181).
Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 551.22(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 these amendments.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not i
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 e
of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Patricia Campbell Date: December 6, 1993 i
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