IR 05000206/1991017
| ML13316A078 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/28/1991 |
| From: | Johnson P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML13316A076 | List: |
| References | |
| 50-206-91-17-EC, NUDOCS 9106180203 | |
| Download: ML13316A078 (10) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION REGIGN V Report N /91-17 Docket N License N DPR-13 Licensee:
Southern California Edison Company Irvine Operations Center 23 Parker Street Irvine, California 92718 Facility Name:
San Onofre Unit 1 Enforcement Con-Region V Office, Walnut Creek, California ference at:
Conference Date:
May 3, 1991 Prepared by:
C. D. Townsend, Resident Inspector, SONGS 1 C. W. Caldwell, Senior Resident Inspector Approved By:
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_q P. H Johnson, Chief Date Signed Reac or Projects Section 3 Summary An enforcement conference was held on May 3, 1991, to discuss the signifi cance of the misalignment of the containment spray flow limiter valve, S1-CRS-CV-518, and the implications on plant safet Violations One violation was identified concerning the misalignment of CV-518 (Paragraph 2).
9106180203 910530 PDR ADOCK 05000206 Q
DETAILS 1. Meeting Participants Nuclear Requlatory Commission J. B. Martin, Regional Administrator R. P. Zimmerman, Director, Division of Reactor Safety and Projects S. A. Richards, Chief, Reactor Projects Branch A. D. Johnson, Enforcement Officer P. J. Johnson, Chief, Reactor Projects Section 3 C. W. Caldwell, Senior Resident Inspector, San Onofre C. D. Townsend, Resident Inspector, San Onofre Unit 1 Southern California Edison Company H. B. Ray, Senior Vice President, Nuclear R. M. Rosenblum, Manager, Nuclear Regulatory Affairs J. T. Reilly, Manager, Nuclear Engineering and Construction B. Katz, Manager, Nuclear Oversight R. W. Waldo, Operations Manager L. D. Brevig, Supervisor, Onsite Nuclear Licensing 2. Background On May 3, 1991, an enforcement conference was held at the Region V office in Walnut Creek, California. The purpose of the meeting was to discuss the significance of the misalignment of a containment spray flow limiter valve on the overall capability of the containment spray system to perform its intended safety function following a postulated acciden A copy of the slides used during the licensee's presentation is included as an attachment to this repor Two refueling water pumps (RWPs) are provided as part of the Unit 1 safety injection system. During the injection phase following a loss of coolant accident (LOCA), the RWPs pump water from the refueling water storage tank into the containment spray headers. During the subsequent recirculation phase, the recirculation pumps take suction from the containment sump and provide water to the charging pumps (for injection into the reactor coolant system (RCS)) and to the RWPs (for continuing containment spray flow, at a reduced rate).
The reduced rate of spray flow is provided by closing the normally open spray flow limiter ball valves, S1-CRS-CV-517 and CV-518, which are installed in parallel around an orifice in the containment spray supply lin On February 13, 1989, with Unit 1 in its Cycle X refueling outage, maintenance personnel removed the actuator from valve S1-CRS-CV-518 to perform maintenance. While the actuator was removed, Operations personnel manually repositioned the valve to the open position to support a leak rate test. However, Operations did not reclose the valve after completion of the test, and maintenance personnel reinstalled the actuator with the valve misaligned (CV-518 is a ball valve, and rotates
-2 90 degrees when changing from the open to the closed position). A simi lar misalignment of the companion valve, CV-517, had been experienced previously. The Maintenance Incident Investigation Report (MIIR) which addressed the misalignment of CV-517 was issued on February 13, 1989, but did not assess the problem in sufficient depth to preclude or identify the misalignment of CV-51 On December 23, 1990, with Unit 1 in its Cycle XI refueling outage, operations personnel identified during an RWP performance evaluation that flow limiter ball valve S1-CRS-CV-518 was actually closed when the position indicator associated with its valve operator showed it to be open. (The parallel spray flow limiter valve, CV-517, was verified to be properly aligned.) A root cause assessment performed by the Safety Engineering organization subsequently determined that CV-518 had been misaligned on February 13, 1989. This valve misalignment appeared to affect the ability of the containment spray system to perform its safety function and was contrary to TS 3.3.1.A(3), which requires that all valves and interlocks associated with the containment spray system be operabl This issue was discussed in Special Inspection Report No. 50-206/91-1 In that report, questions were raised concerning the ability of plant operators to recognize and correct this condition during a loss of coolant accident (LOCA) scenario. The NRC concluded that, while the operators might have been able to successfully diagnose the misalign ment, their ability to do so in a post-LOCA situation could not be assured. Although the licensee noted that emergency response personnel would be available to assist in diagnosis and correction of the mis alignment, the NRC noted that the injection phase of the worst-case LOCA (design basis accident) would last only about 10 minutes. Depending on the time of day, the accident scenario could proceed into the recircula tion phase before emergency response personnel could provide assistanc Since the instrument air system is -not safety related, there is also no assurance that it would have been available to permit repositioning of CV-518, even if its incorrect position had been properly diagnosed following an accident. The NRC therefore concluded that the containment spray system would apparently have been unable, under certain circum stances (loss of instrument air, or no credit allowed for operator diagnosis and manual actions), to fulfill its safety function of limiting peak containment pressure following a design basis LOC As discussed in inspection report 50-206/91-11, containment spray flow limiter valve S1-CRS-CV-518 appears to have been inoperable, in violation of Unit 1 TS 3.3.1(3), while the unit was operating in Modes 1 and 2 during Cycle X (May 1989 through June 1990).
3. Introduction Mr. Richards opened the discussion by presenting the NRC's conclusions, as summarized above. He noted that the instrument air system was non-safety related, and therefore could not be counted upon during troubleshooting and realignment of the containment spray flow limiter
-3 valve following a postulated accident. He also stated that the operators would have to perform beyond their previously considered duties during a postulated even. Discussion Mr. Ray opened SCE's portion of the discussion by stating that the instrument air system would be required in order to allow for operator corrective actions, which did not appear consistent with the NRC's view on the availability of that system under certain conditions. He also stated, however, that Southern California Edison (SCE) had performed an analysis of the containment response with CV-518 misaligned. This analysis concluded that the misalignment would have been corrected by the operators. However, even if operator action did not correct the misalignment and both refueling water pumps became inoperable, contain ment spray flow (provided by the recirculation pumps pumping through the idle refueling water pumps) would have been within design requirement Mr. Ray also stated that the root cause programs in place today would prevent SCE from now taking such a narrow focus on an issue such as this one. In particular, all MIIRs and other departmental incident reports are now examined by the Safety Engineering group, with a broad perspec tive, to ensure that appropriate specific and generic corrective actions have been identifie Mr. Reilly then presented the results of the analysis that was performed to address the NRC's concerns, as shown in the attached presentation notes. Mr. Reilly pointed out that the expected flow from the containment spray header during the recirculation phase (with CV-518 misaligned, both recirculation pumps running normally, and both RWPs idle) was calculated to be 815 gpm, or roughly twice the normal recirculation phase containment spray flow rate (with both CV-517 and CV-518 closed). He mentioned that containment spray flow during the recirculation phase acts to limit the second pressure peak (the first containment pressure peak occurs before the injection phase), which is also significantly affected by decay heat and the recirculation system heat exchanger capabilit Mr. Reilly noted that because of conserva tisms in the design of Unit 1, the second containment pressure peak has been calculated to remain below the containment design pressure, even considering containment spray flows as low as 200 gpm in the recircula tion phas Mr. Rosenblum then commented that without any containment spray flow in the recirculation phase, the peak pressure would not have exceeded the containment yield strength. He also pointed out that in the event of a LOCA with a concurrent loss of instrument air, and with the spray flow limiter valve misaligned, sufficient containment spray flow would still have been provided. The air-operated containment spray isolation valves, CV-'82 and CV-114, would have failed open, providing a contain ment spray flow path from either or both of the recirculation pump Mr. Zimmerman then asked if this analysis was performed considering other recent problems affecting the containment spray system (e.g.,
-4 buildup of corrosion products in the spray headers). Mr. Ray stated that they would consider the various conditions that may affect the outcome of this analysis. Mr. Waldo then presented the corrective actions as described in Licensee Event Report (LER) 91-01, Revision Mr. Katz commented that the new root cause organization was implemented in October 1989 and that the misalignment of CV-518 occurred prior to this time. He stated that the root cause program is more comprehensive now and that they review all Division Investigation Reports with a broad focus in mind. He also stated that the quality oversight organization will be conducting training for various divisions so that SCE will not have to rely solely on the root cause organization for this type of broad view perspectiv Mr. Martin stated that this issue points out an apparent weakness at the working level in recognizing and troubleshooting potential common cause failures. For instance, if one component fails for some reason, the condition of other similar components should be questioned. He stated that an effort appears needed to instill these instincts at the lower levels of the organization and to make safety consciousness more a part of the day-to-day attitude. In this instance, CV-518 was misaligned just as CV-517 had been misaligned only days before. However, this was not discovered until 22 months later. The safety instinct was clearly not exhibited in this exampl Mr. Ray stated that he would personally look into the concept of developing a safety instinct at all levels. He also committed to provide Revision 3 to LER 91-01, discussing the recent analysis of spray flow and containment performance and addressing other concurrent problems, within 10 days (in the absence of further discussions between SCE and the NRC).
5. Closing Remarks Mr. Martin thanked everyone and adjourned the meetin Attachment:
Copy of slides used during the licensee's presentatio LER 1-91-001, CONTAINMENT SPRAY FLOW VALVE ACTUATOR INCORRECTLY COUPLED STATUS OF PLANNED CORRECTIVE ACTIONS COMMITMENT STATUS ORGANIZATION ACTION TAKEN Procedural controls for valve Open Operations Procedure S0123 alignments will be revised to ensure that changes to plant 0-23e "Con configuration which could ments" will affect other maintenance revised to activities are properly incorporate tracked, additional requi rement Maintenance procedures will be Open Maintenance S01-1-6.61, revised to clearly and strictly
"Valves-Efcomatic define the reassembly-of ball Ball-Valve & Paul valves which can not be Munroe Actuator permanently and positively Overhaul" has marked to verify valve position been revised and is currently in the approval cycl The population of both manual Closed NE&C FCNs were issued and motor operated ball valves to modify at Unit 1 has been identifie automatic ball Manufacturers of these valves valves and have been contacted and design install a documents reviewed to determine permanent if other ball valves and positive local actuators could be assembled indicatio The such that the position of the physical work has valve was indeterminat been completed, Automatic valves for which a the valves were design change can provide tested and the permanent and positive local FCNs have been visual position indications are being modified. Valves which cannot be similarly modified will be addressed through appropriate maintenance procedure revisions (see above).
COMMITMENT STATUS ORGANIZATION ACTION TAKEN Maintenance procedures will be Open Maintenance Maintenance is revised to include permanent currently match-marking of all ball reviewing all valves prior to disassembly and procedures that post maintenance verification work on ball of correct valve positio valves & will enhance as necessar Target Date for completion is
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9/1/9 This event will be reviewed Open Operations & Operations target with appropriate Operations and Maintenance date is 5/28/9 Maintenance personnel, and will emphasize the understanding of Maintenance work scope and component review in function. Additionally, the event will be included inn the annual requalification program Requalificatiorr for Operations and Maintenance program will Mpersonne nextend into 199 Original Assumptions in LER Instrument Air System available No flow occurred in CS header when RWP's tripped Operator Action Concurrent Single Failure (loss of one safety train)
Current AssumDtions No operator action Instrument Air unavailable RWP's are not mechanically locked as result of overcurrent trip No concurrent single failure
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Enclosure 1 ENFORCEMENT CONFERENCE SOUTHERN CALIFORNIA EDISON COMPANY NRC Region V Office May 3, 1991 AGENDA 1. Opening Remarks, Purpose of Conference -- J. B. Martin, Regional Administrator, and H. B. Ray, Senior Vice President, Nuclear 2. Discussion of Apparent Violation of Technical Specification Requirements Regarding Containment Spray Flow Limiter Valve CV-518 -- P. H. Johnson, Chief, Reactor Projects Section 3 3. Response by Edison Staff 4. NRC Comments and Additional Discussion 5. Review of Enforcement Policy -- A. D. Johnson, Enforcement Officer 6. Closing Remarks -- J. B. Martin, Regional Administrator, and H. B. Ray, Senior Vice President, Nuclear