ML13330B468
| ML13330B468 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/01/1989 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-88-17, NUDOCS 8902090101 | |
| Download: ML13330B468 (7) | |
Text
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g Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 F. R. NANDY TELEPHONE MANAGER OF NUCLEAR LICENSING February 1, 1989 (818) 302-1896 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 Loss of Decay Heat Removal (Generic Letter 88-17)
San Onofre Nuclear Generating Station Unit 1
References:
A. Letter dated January 5, 1989, from M. 0. Medford (SCE) to the NRC, Loss of Decay Heat Removal (Generic Letter 88-17)
B. Letter dated September 24, 1987 from F. R. Nandy (SCE) to the NRC, Loss of Residual Heat Removal (RHR) While the Reactor Coolant System (RCS) is Partially Filled (Generic Letter 87-12)
By Reference A, Southern California Edison (SCE) responded to the eight "expeditious actions" of Generic Letter 88-17, dated October 17, 1988, as applicable to San Onofre Unit 1. In that response, actions or enhancements implemented during the present (Cycle X) refueling outage as the result of Generic Letter 88-17 were described.
Enclosed herewith is SCE's response to the six "programmed enhancement" items of the generic letter. This response describes additional enhancements that are planned to be implemented. These will be implemented according to the schedule given below.
Enhancements that depend on hardware installation and/or modification will be implemented by the end of the next (Cycle XI) refueling outage. Enhancements that do not depend on hardware installation and/or modification will be implemented by April 30, 1990.
8902090101 890201 7
PDR ADOCK 05000206 P
'PDR
Document Control Desk
-2 With the implementation of these six programmed enhancements, SCE's previous commitments made in Reference B, in response to Generic Letter 87-12, will not be necessary and, therefore, will no longer be implemented.
If you have any questions, please let me know.
Respectfully submitted, By F. R. Nandy Manager of Nuclea~rlicensing Subscribed and sworn to efore me this
/day of
/
OFFICIAL SEAL AGNES CRABTREE Notary Public-California LOS ANGELES COUNTY My Comm. Exp. Sep. 14. 1990 NotaK Public in and for the County of Los Angeles, State of California Enclosure cc:
- 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3 C. M. Trammell, NRR Project Manager, San Onofre Unit 1
Reference A:
Letter dated January 5, 1989, from M. 0. Medford (SCE) to the NRC, Loss of Decay Heat Removal (Generic Letter 88-17)
Item No. 1 (Instrumentation)
Recommendation Provide reliable indication of parameters that describe the state of the RCS and the performance of systems normally used to cool the RCS for both normal and accident conditions. At a minimum, provide the following in the CR:
(a) Two independent RCS level indications (b) at least two independent temperature measurements representative of the core exit whenever the RV head is located on top of the RV (We suggest that temperature indications be provided at all times.)
(c) the capability of continuously monitoring DHR system performance whenever a DHR system is being used for cooling the RCS.
(d) visible and audible indications of abnormal conditions in temperature, level, and DHR system performance.
Response
By the end of the Cycle XI refueling outage, existing instrumentation will be upgraded to provide the following capabilities (most of which already exist):
a) Two independent continuous wide range RCS water level indications with low level alarm capability in the control room, whenever the RCS is in a reduced inventory condition. The use of Tygon tubing will be discontinued.
b) Two independent temperature indications with high temperature alarm capability in the control room, whenever the reactor vessel (RV) head is located on top of the reactor vessel and the RCS is in a reduced inventory condition.
c) Continuous display of the residual heat removal (RHR) system combined flow rate, temperatures and pump amperage readings in the control room.
(This capability already exists.)
-2 d)
Both visual and audible indication of the following abnormal conditions in the control room:
(i) RCS low level (ii) RCS high temperature (iii)
RHR low flow (iv) RHR low suction pressure Item No. 2 (Procedures)
Recommendation Develop and implement procedures that cover reduced inventory operation and that provide an adequate basis for entry into the reduced inventory condition. These include:
(a) procedures that cover normal operation of the NSSS, the containment, and' supporting systems under conditions for which cooling would normally be provided by DHR systems.
(b) procedures that cover emergency, abnormal, off-normal, or the equivalent operation of the NSSS, the containment, and supporting systems if an off-normal condition occurs while operating under conditions for which cooling would normally be provided by DHR systems.
(c) administrative controls that support and supplement the procedures in Items (a), (b), and all other actions identified in this communication, as appropriate.
Response
The existing procedures and administrative controls, some of which were described in Reference A, are considered adequate and will continue to be implemented until revisions are made necessary by new analyses and/or hardware changes.
Procedural changes that either have been accomplished or will be accomplished by April 30, 1990, include the following:
(i) Improved coordination between the procedures governing operation in a reduced inventory and mid-loop condition and the procedures which directly interface with them.
(ii) Enhanced containment closure procedures to consolidate and clarify containment closure methods and requirements, based on engineering analysis.
(iii)
Separation of surveillance and abnormal event response items from the general plant operating instructions.
-3 Future procedural enhancements as the result of new analyses which do not involve hardware changes will be implemented by April 30, 1990.
Procedural enhancements that involve hardware changes will be implemented by the end of Cycle XI refueling outage.
Item No. 3 (Equipment)
Recommendation (a) Assure that adequate operating, operable, and/or available equipment of high reliability is provided for cooling the RCS and for avoiding a loss of RCS cooling.
(b) Maintain sufficient existing equipment in an operable or available status so as to mitigate loss of DHR or loss of RCS inventory should they occur. This should include at least one high pressure injection pump and one other system. The water addition rate capable of being provided by each equipment item should be at least sufficient to keep the core covered.
(c) Provide adequate equipment for personnel communications that involve activities related to the RCS or systems necessary to maintain the RCS in a stable and controlled condition.
Response
Items (a) and (b)
The existing equipment and the existing prescriptive methods to provide RHR cooling as specified in Reference A are considered adequate and will continue to be used in the long term unless modifications are required by new analyses. These modifications, if any, will be implemented according to the schedule provided in the transmittal letter.
The reliability of pumps and valves in the residual heat removal (RHR) system, component cooling water (CCW) system and saltwater cooling (SWC) system is demonstrated periodically by inservice testing of these components to the ASME Code Section XI requirements. All motor operated valves (MOVs) in the RHR and CCW systems have been MOVAT tested in accordance with IE Bulletin 85-03.
At San Onofre Unit 1, there exists no autoclosure interlock feature associated with the RHR system, such as that described in GL 88-17.
Therefore the risk of loss of RHR due to unplanned activation of this feature does not exist.
-4 Item (c)
Various communication systems are employed to ensure reliable and adequate communication between personnel during all modes of plant operation as well as maintenance under normal and emergency conditions. These communication systems include private telephone, two way UHF radio, radio paging (commercial and local) and a public address system.
Item No. 4 (Analyses)
Recommendation Conduct analyses to supplement existing information and develop a basis for procedures, instrumentation installation and response, and equipment/NSSS interactions and response. The analyses should encompass thermodynamic and physical (configuration) states to which the hardware can be subjected and should provide sufficient depth that the basis is developed. Emphasis should be placed upon obtaining a complete understanding of NSSS behavior under nonpower operation.
Response
This activity will be coordinated with the results obtained from Phase 2 and Phase 3 of the Westinghouse owners group analysis program.
Plant specific analyses completed to date are:
(i) Determination of required hot leg vent path size versus number of days elapsed since plant shutdown.
(ii) Determination of makeup water flow requirements versus number of days elapsed since plant shutdown.
Additional plant specific analyses planned to be completed are:
(i) Determination of RCS heatup rate and containment pressurization rate due to a postulated loss of RHR.
(ii) Determination of minimum RHR flow requirements versus number of days elapsed since plant shutdown.
(iii)
Confirmation that flooding the RCS lower cavity provides an adequate water seal of the fuel transfer tube in order to maintain containment integrity.
(iv) Re-evaluation of the earlier analyses as may be required by the subsequent analyses, in the items enumerated above.
-5 These planned analyses will be completed in sufficient time to permit any procedural enhancements and hardware changes required by the analyses to be completed by the due dates of April 30, 1990, and end of Cycle XI refueling outage, respectively.
Item No. 5 (Technical Specifications)
Recommendation Technical specifications (TS's) that restrict or limit the safety benefit of the actions identified in this letter should be identified and appropriate changes should be submitted.
Response
Pending results of new analyses (Item 4 above), revised TS's will be proposed, if and as required. Any new requirements and restrictions related to the concerns of Generic Letter 88-17 will be implemented by means of plant operating procedures and will not be proposed as new TS's.
Item No. 6 (RCS Perturbations)
Recommendation Item (5) of the expeditious actions should be reexamined and operations refined as necessary to reasonably minimize the likelihood of loss of DHR.
Response
Item (5) of the expeditious actions, as submitted by Reference A, has been reexamined. The procedures and administrative controls described in Reference A are considered adequate to reasonably minimize the likelihood of loss of DHR.
As a further long term improvement, permanent tags which uniquely identify the first isolation valve off the RCS/RHR systems will be installed.
The existence of these tags will be incorporated in plant operating procedures and the significance of these tags will be taught to Maintenance and other support personnel prior to entering a reduced inventory condition.
The above actions will be completed by the end of Cycle XI refueling.
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