ML20151L472
| ML20151L472 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/01/1997 |
| From: | Rainsberry J SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9708070011 | |
| Download: ML20151L472 (5) | |
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50Ullu RN CAulORNI A EDISON i
Manager. Plant Licensing An EDISON IV1LRN ATIO%AL~ Compan;r August 1, 1997 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket Nos. 50-361 and 50-362 Appendix R Process Monitoring Instrumentation San Onofre Nuclear Generating Station Units 2 and 3 During 1996, Edison completed a Self Assessment. of the fire protection program and analyses in place for Units 2 and 3.
During this assessment. Edison noted' a discrepancy regarding the instrumentation provided at the Essential Plant Parameters Monitoring (EPPM) panels.
Specifically, narrow range steam i
generator level instrumentation is provided at the Units 2 and 3 EPPM panels versus wide range steam generator level instrumentation as recommended in Information Notice 84-09.
A review of Emergency Operating procedures and validation by use of the plant i
simulator confirmed that operator responses to potential plant conditions would be no different if wide range instrumentation had been provided.
i Consequently, Edison concluded the availability of narrow range steam generator level instrumentation would enable operators to achieve and maintain i
safe shutdown if control room evacuation were required.
Nevertheless, Edison i jj improved the information that would be available.to plant operators during a I
post-fire Alternative Shutdown by installing direct reading pressure gauges at the discharge of each Unit's motor operated AFW pumps.
These gauges will provide indication of AFW flow during the postulated Alternative f
Shutdown / control room evacuation event.
gob The enclosure to this letter provides a discussion of Appendix R requirements as they relate to steam generator level instrumentation at the EPPM panels for Alternative Shutdown.
9708070011 970001 PDR ADOCK 05000361 F
PDR c u. -..<
San Onofre Nuclear Generating Station P. O. Ikw 128 San Clemente, CA 926744128 e
714- % 8-7420
Document Control Desk If you have any questions, please let me know.
- incerely, f
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'J Enclosure cc:
E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 i
4 Enclosure Fire Protection Requirements for San Onofre Units 2 and 3 As indicated in Edison to NRC letter dated October 5, 1992, the Licensing Basis for the Fire Protection Program at Units 2 and 3 is the combined requirements of 10 CFR 50, Appendix R, Sections III.Gl', III.J, and III.0, and the requirements of Appendix A to BTP.APCSB 9.5-1.
Appendix R,Section III.G, " Fire protection of safe shutdown capability," states in part:
1.
Fire protection features shall be provided for structures, systems, and components important to safe shutdown.
These features shall be capable of limiting fire damage so that; a.
One train of systems necessary to achieve and maintain hot shutdown conditions from either the control room or emergency control station (s) is free of fire damage....
Appendix R,Section III.L, " Alternative and dedicated shutdown capability,"
states in part:
2.
The performance goals for the shutdown functions shall be:
d.
The process monitoring function shall be capable of providing direct readings of the process variables necessary to perform and control the above functions.
By letter dated February 14, 1984, theNRCissuedInformationNotice(IN)84-09,
" Lessons Learned from NRC Inspections of Fire Protection Safe Shutdown Systems (10 CFR 50, Appendix R)."
This information notice was provided as guidance for power reactor facilities conducting analyses and/or making modifications to implement requirements of 10 CFR 50, Appendix R.
This information notice also provided.the following list of process parameters the NRC Staff considered to be the minimum monitoring capability necessary to achieve safe shutdown:
a.
Pressurizer pressure and level.
b.
Reactor coolant hot leg temperature or exit core thermocouples, an1 cold leg temperature.
c Steam generator pressure and level (wide ' range).
d.
Source range flux monitor.
i e.-
Diagnostic instrumentation for shutdown systems.
f.
Level indication for all tanks used (e.g., CST).
' The NRC has indicated that by reference, compliance with 10 CFR 50, i
Appendix R,Section III.G requires compliance with Section III.L.
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As can be seen from the following statement from Generic Letter 86-10, the instruments listed in IN 84-09 are acceptable and preferred, act not required:
In I&E Information Notice 84-09, the staff provides a listing of j
instrumentation acceptable to and preferred by the staff to demonstrate compliance with this provision. While this guidance provides an i
acceptable method for compliance with the regulation, it does not exclude other alternative methods of compliance. Accordingly, a licensee may propose to the staff alternative instrumentation to comply with the regulation (e.g.,boronconcentrationindication). While such a submittal is not an exemption request, it must be justified based on a technical l-evaluation.
(emphasisadded)
During design and construction of Units 2 and 3 in the late 1970's, Edison installed narrow range steam generator level instrumentation at the Essential Parameters Monitoring (EPPM) panels. These panels contain Alternative Shutdown instrumentation for use during a postulated fire requiring shutdown from outside j
the control room.
4 A review of the various fire protection related submittals revealed that Edison i
did not specifically indicate whether narrow range or wide range indication of steam generator (SG) level was being provided at the EPPM panels.
d i.
Technical Evaluation of Steam Generator Level Indication I
Appendix R requires licensees to demonstrate that plant operators will be able l
to achieve and maintain safe shutdown in the event a fire were to start and burn unimpeded until all combustible material in the affected fire area is consumed.
j The EPPM panels are used for that subset of postulated fire scenarios which require control room evacuation.
Edison's evaluation of all other postulated fires is unaffected; i.e., wide range Sb level instrumentation is available in the control room and/or SG level can be continuously maintained within the t
narrow range level indication band.
Monitoring SG level during an Appendix R Alternative Shutdown event provides indirect indication of the reactor heat removal function.
The superior resolution of SG narrow range level indication makes it preferred over wide t
range for purposes of SG level control.
Edison has determined by simulator tests that narrow range SG level instrumentation may not be able to display SG 4
water level for a short time period af ter shutdown and control room evacuation, 4
when level shrinks to below 0% on the narrow range instruments.
Consequently, 4
for that short time period, SG narrow range indication would not provide j
indirect indication of the reactor heat removal function.
(Directindication would continue to be provided by reactor coolant system hot and cold leg i
temperatureinstrumentation.)
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SG water level would, however, soon increase to above 0% narrow range level as operators performed their prescribed actions to initiate Auxiliary Feed Water (AFW) flow to the steam generators.
Edison concludes the reactor can be safely shut down, cooled down and mainiained in cold shutdown without having on-scale narrow range SG level indication for the short time period in question.
To enhance the operators' ability to verify adequate AFW flow, Edison has provided indirect indication of AFW flow during the postulated Alternative Shutdown control room evacuation event by installing direct reading pressure gauges at the discharge of each Unit's motor operated AFW pumps.
The new AFW pump discharge pressure gauges, in combination with the pre-existing pump suction pressure gauges, will provide an indirect indication for verification of adequate AFW pump flows, which provides assurance of a.dequate decay heat removal capability and steam generator level recovery until narrow range SG 1evel indication returns on scale.
After noting this discrepancy and before this design change was implemented, i
Edison used hourly fire watch patrols to monitor fire areas crediting alternative shutdown.
These patrols provided added assurance of safe shutdown capability by minimizing the potential for an alternative shutdown fire and control room evacuation.
Edison believes that the instrumentation provided on the EPPM panels, together with the newly installed pressure gauges at the discharge of the AFW pumps, provides adequate process monitoring capability to: 1) ensure the availability of SG 1evel indication (for most of the duration of Alternative Shutdown); and
- 2) ensure the ability to verify adequate AFW flow for SG 1evel recovery and performance of the decay heat removal function.
l 3.