ML19351A455

LER 89-020-00:on 891113,determined That Some Solenoid Valves & Valve Power Supplies for Saltwater Sys May Not Be Able to Perform Design Function After Design Basis Seismic Event. Cause Undetermined.Power Supplies upgraded.W/891213 Ltr

ML19351A455
Person / Time
Site:	Calvert Cliffs
Issue date:	12/13/1989
From:	Russell L, Sly C BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-020, LER-89-20, NUDOCS 8912180020
Download: ML19351A455 (10)

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• SALTIMORE l OAS AND  ;

ELECTRIC CHARLES CENTER

• P.O. BOX 1475 e BALTIMORE, MARYLAND 21203 1475 j i

CALVERT Clifft NUCLEAR POWER PLANT DEPARTMENT

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December 13, 1989 U. S. Nuclear Regulatory Commission Docket No. 50-317 '

Document Control Desk License No. DPR 53 Washington, D. C. 20555 t

Dear Sirs:

The attached LER 89 020 is being sent to you as required under 10 CPR 50.73. i Please note that this is a partial'LER and a supplement will be issued by February 7,1990. The supplement will list a more complete descriptionco f the root cause analysis, and corrective actions for this event.

Should you have any questions regarding this report, we would be pleased to discuss them with you.

Very truly yours, ,

La L. B. Russell Manager Calvert Cliffs Nuclear Power Plant Department LBR:CDS:sdw cc: William T. Russell Director, Office of Management Information and Program Control Messrs: G. C. Creel C. H. Cruse R. E. Denton J. R. Lemons l

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On November 13, 1989, a condition was discovered at Calvert Cliffs Units 1 and 2 which was concluded to be outside the design basis of the plant as described in the Updated Final Safety Analysis Report (UFSAR). Certain solenoid valves (SV) and some SV power supplies associated with our Saltwater System may not have been able to perform their intended design function after a design basis seismic event.

At the time of the discovery, Unit I was in cold shutdown with reactor pressure and temperature at atmospheric and 116 F, respectively. Unit 2 Reactor Coolant System was at atmospheric pressure with the core off-loaded.

The root cause of the event is still under investigation.

Short term corrective actions have been initiated to upgrade the deficient SV power supplies and replace the non seismic SVs with SVs that are built to withstand a seismic event.

Additional corrective actions shall be submitted in a supplement to this LER.

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ol o of2 0' o 19 text u . <,,,. , m cr , = uon I. DESCRIPTION OF EVENTS On November 13, 1989, a condition was discovered at Calvert Cliffs Units 1 and 2 which was concluded to be outside the design basis of the plant as described in the . Updated Final Safety Analysis Report (UFSAR). Certain solenoid valves (SV) and some SV power supplies associated with our Saltwater System may not have been able to perform their intended design function after a design basis seismic event.

At the time of the discovery, Unit I was in cold shutdown with reactor pr6ssure and temperature at atmospheric and 116 F, rer.pectively. Unit 2 Reactor Coolant 1 Syctem was at atmospheric pressure with the core off-loaded.

The UFSAR Section SA.2, " Classes of Structures Systems and Equipments," states, in part; "Throughout the context of this section, Class I shall mean Category 1 (Seismic) structures, systems 6 equipment. Class I structures, systems, and equipment are those whose failure could cause uncontrolled release of radioactivity or those essential for immediate and long term operation following a loss of coolant incident."

Contrary to the above statement, it was discovered that portions of the electrical supplies to five SVs in Class 1 applications may not have been able to withstand a seismic event. It was also discovered that four solenoid valves in Class 1 applications were not built to withstand a seismic event. The condition was discovered during a re'riew to determine the ability of Saltwater System instrument air components to withstand a seismic event. Upon discovery of the condition, the Control Room notified the NRC at 1614 hours0.0187 days <br />0.448 hours <br />0.00267 weeks <br />6.14127e-4 months <br /> on November 13, 1989.

The investigation started on November 13, 1989 when it was discovered that several SVs were listed in the Calvert Cliffs Q. List as safety related (SR), but were listed on the electrical schematic diagrams as non-safety related (NSR). A walkdown was later performed to ascertain if the SVs are actually provided power from a SR source. It was determined that the power sources were indeed SR, but that the cables were not routed through a fully seismically qualified path. The SV's power sources were found to satisfy all other requirements of SR cabling with the exception of the incomplete seismically-qualified cable paths. The af fected SVs are listed in Table 1.

During the review of the Saltwater System instrument air supply, four SVs were found which were not built to withstand a seismic event. As part of the review, analyses were performed to determine if the SVs could survive a seismic event.

These analyses included design reviews and destructive examination of the solenoid valves.

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0l0 0l3 0F 0 l9 nxw - ., . , 4 ., mc w w nn The analyses showed that this type of_SV could be compromised during a seismic event because the core tube could "crin:p. " This valve type was intended for use in commercial design and not intended by the vendor for nucicar service. The valves are listed in Table 2.

These issues are the responsibility of the project team previously established to address several outstanding Facility Change Requests (FCRs) and the air accumulator failures discussed in LER 317/89-018. The proj ect team was established to assure that corrective actions to associated with these issues are coordinated and implemented in manner which will ensure the safe operation of the Units. The efforts of this project team are currently underway.

11, CAUSE OF EVENTS We are currently conducting a root cause investigation of those events. The results of the investigation will be provided in a supplement to this LER.

III. ANALYSIS OF EVENTS The Saltwater System is designed to provide cooling water for the Service Water and Component Cooling Water Heat Exchangers, and ECCS Pump Room Coolers. The Component Cooling and Service Water Systems are designed to remove heat from the plants' varjous auxiliary systems during normal and shutdown conditions and remove heat during a LOCA. (Figure 1)

During the recirculation mode after a LOCA, should a piping rupture occur in the common discharge header of the Saltwater System, the alternate (overboard)

Saltwater System flow path to the bay would be employed. (Figure 2) The valves used to position this lineup are air operated with accumulators supplied by the Instrument Air System. Most of the valves would have to be repositioned from their failed position for the alternate discharge path lineup. Some of these valves cannot be manually operated after a LOCA because they would be located in a ,

very high radiation area.

Table 1 shows a list of SVs having an incomplete scismically supported path for their power cables. All of these valves are associated with the Saltwater System Alternate Discharge Path. Failure of the SVs would result in a loss of air pressure to the associated CVs. The CVs would fail to the closed position.

Failure of these valves to open during a LOCA and concurrent piping rupture of the Saltwater System normal discharge header would have resulted in the loss of the plants' ultimate heat sink. We believe that this event has a very low probability of occurring. A PRA is currently underway to help evaluate the significance of such a scenario.

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• Outlet Throttle Valves. Failure of these SVs after a seismic event could have a wide range of effects on the ability of the Saltwater System to removo residual  ;

heat from the Service Water System Heat Exchangers. If the throttle valves were to fail open, there is a danger of saltwater pump failure due to pump runout. If the throttle valves failed to the closed position, no cooling water would be available to the Service Water Heat Exchangers.

Operators are trained to maintain Saltwater Pump discharge pressure greater than 13 psig at all times to prevent damage or losa of the Saltwater Pumps. Although this would normally be done by throttling CVs $210 and 5212, steps exist in various operating procedures that direct the throttling of the Saltwater Pump discharge valves to maintain proper discharge pressure. Therefore, had the failure of the Service Water Heat Exchanger throttle valves occurred, causing them to open, operators would have been dispatched to throttle the Saltwater Pump discharge valves.

The Saltwater Pump Discharge Valves are cecessible to operators after a LOCA.

Thus, we believe that the consequences of the failure of the CVs to the open position would be mitigated by manual control of these throttle valves. The consequences of the failure of the CVs to the closed position will be addressed in the supplement to this LER.

This event is considered reportable per 10 CFR 50.73(a)(2)(ii)(B), "Any event or condition that resulted in the nuclear power plant being in a condition that was outside the design basis of the plant,"

IV. CORRECTIVE ACTIONS FCR 89-0180 was initiated to upgrade the electrical circuits of the SVs in Table 1 to SR.

FCR 89 95 was initiated to replace the SVs in Table 2 with seismically qualified SVs.

Additional corrective actions will be provided in a supplement to this LER.

IV. ADDITIONAL INFVRMATION There has been one previous similar event involving Saltwater System components being outside the design basis. The event is discussed in LER 317/89 008. The root cause of that event was poor maintenance practices.

There has been one previous similar events involving a potential loss of instrument air to Saltwater System components. The event is currently being investigated and is discussed in LER 317/89 018. The root cause of the event is still under investigation.

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-Instrument Air N/A LD Component Cooling System N/A CC Service Water System N/A BI ECCS N/A BP, BQ, BE Heat Exchanger HX N/A Solenoid Valve PSV N/A Control Valve Air Operated V N/A l

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CV No. Function Related Position Position Comments SV 5149 Saltwater Alternate Closed Closed Must Open for CV-5149 Discharge Valve Alternate Discharge Lineup SV 5155 SRW Hx 12 Outlet Closed Closed Must Open for CV-5155 to Alternate Alternate Discharge Path (1st) Discharge Lineup SV-5156 GRW Hx 12 Outlet Closed Closed Must Open for to Alternate Alternate Discharge Path (2nd) Discharge Lineup SV-5165 Component Cooling Hx 12 Closed Closed Must Open for Outlet to Alternate Alternate Discharge Path (1st) Discharge Lineup SV 5166 Component Cooling Hx 12 Closed Closed Must Open for Outlet to Alternate Alternate Discharge Path (2nd) Discharge Lineup

• Alternate discharge lineup is required during the recirculation mode after a LOCA only if a piping rupture should occur in the common normal discharge header of the saltwater system.

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