05000341/LER-1998-003, :on 980317,noted That Potential Drain Path to Hotwell or Condensate Return Tank Could Reduce CST Level. Caused by Inadequate Review of Dedicated Shutdown Sys. Completed Spurious Component Actuation Review of CST Piping
| ML20236W806 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/31/1998 |
| From: | Peterson N DETROIT EDISON CO. |
| To: | |
| Shared Package | |
| ML20236W799 | List:
|
| References | |
| LER-98-003, LER-98-3, NUDOCS 9808060222 | |
| Download: ML20236W806 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3411998003R00 - NRC Website | |
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Licensee Event Report (LER) No.96-019 addressed the inoperabilityof the Standby Feedwater (SBFW) system now l
path as required by Technical Specification 3.7.11," Appendix R Alternative Shutdown Auxiliary Systems." During the 1996 LER investigationit was discovered that a combination of multiple hot shorts could potentiallyopen a drain path to the hotwell and cause a loss of Condensate Storage Tank (CST) [KA][TK] inventory required for dedicated shutdewn.
Temporary Change Notice (TCN) T09897 was written to revise Abnormal Operating Procedure (AOP) 20.000.18 to i
isolate the CST from the hotwell[SG) and from the Condensate Return Tank (CRT)[KA)[TK). The TCN was subsequently incorporated into the AOP; however, difTerent valves were used to isolate the CST. This new configuration would isolate the CST from the hotwell, but not from the CRT, and did not prevent the closed valves from reopeningdue to hot shorts during a postulated fire. This potential drain path to the hotwell or CRT could reduce CST level and may result in not meeting the CST inventory requirements of Technical SpeciHeation(TS) 3.7.11.vhen using the Standby i
Feedwater System. This condition is reportable under Operating License Paragraph 2.F, not meeting License Condition 2.C(9). On March 17,1998 at 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br />,the NRC was notified of this event. The ineffective corrective actions have existed from December 19,1996 to March 17,1998 w hen TCN 10339 was implemented. The NRC notiHeation cited that the event was being additionallyreported under 10CFR50.73(a)(2)(i)(B). This was in error and is retracted herewith as a reporting criteria. The CST level was always maintained within the requirements of TS 3.7.11.
j 1mmediate actions were to enter the Limiting Condition for Operation (LCO) for TS 3.7.11. A temporarychange to the l
AOP was initiated which would deenergize and close appropriate valves during a dedicated shutdown to ensure a hot short does not create the potential for draining CST inventory required to achieve shutdown. When the temporary change was completed,an operabilitydeterminationwas made and the LCO was exited. As stated above,the CST level was always maintained within the requirements of the LCO.
9808060222 980731 ~'
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INITI AL PLANTCONDITIONS:
OperationalCondition:
1 PowerOperation ReactorPower:
96 Percent ReactorPressure:
1030 psig ReactorTemperature:
540 degrees Fahrenheit DESCRIPTIONOF THE EVENT:
Detroit Edison submitted Licensee Event Report (LER) No.96-019 on December 19,1996. This LER addressed the inoperabilityof the Standby Feedwater (SBFW) [SJ] System flow path as required by Technical Specification 3.7.11," Appendix R Alternative Shutdown Auxiliary Systems." During the investigationof that LER, it was discovered that a hot short could potentially cause the N2000F636 valve [SD][ISV] to open. This hot short, as well as other hot shorts, could cause loss of Condensate Storage Tank (CST) [KA][TK] inventory required for cold shutdown, via a drain path to the hotwell [SG], or equalize wi.h the Condensate Return Tank (CRT) [KA][TK], which does not have a minimum specified level. Deviation Event Report (DER) 96-1662 was written to document and track corrective actions.
Approximately20 corrective actions were developed to address issues identified during the investigation.
These actions included issuing Temporary Change Notice (TCN) T09897 to revise Abnormal Operating l
Procedure (AOP) 20.000.18," Control of the Plant from the Dedicated Shutdown Panel," to deenergize valves P1100F603 and P1100F604 [SD][ISV] and close them manually. When AOP 20.000.18 was subsequently revised to incorporate outstanding TCNs and other comments, the revision resulted in replacing the recommended valves, P1100F603 and P1100F604 [SD][ISV], for isolating the CST by closing i
other valves that only isolated the hotwell and failed to prevent subsequent reopening due to hot shorts. The rationale for selection of alternate valves was to provide isolation of the CST for the dedicated shutdown situation consistent with the CST isolation used in other AOPs, e.g., Station Blackout. A recent engineering review of the new configuration concluded that closing these valves did not adequately isolate the CST to prevent the potential for a drain path on a hot short. The omission of P1100F604 from the AOP revision also left the plant susceptible to gravity draining of the CST to the CRT assuming a hot short condition.
Condition Assessment Resolution Document (CARD) 98-11773 was initiated a document the finding and to track corrective actions. The dedicated shutdown system does not have the ability to transfer water from the hotwell back to the CST; therefore,the diverted water would have reduced the CST inventory required by SBFW to maintain core coverage during this event.
This condition is reportable under Operating License Paragraph 2.F, not meeting License Condition 2.C(9).
i On March 17,1998 at 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br />, the NRC was notified of this event. The ineffective correctiveactions have existed from December 19,1996 to March 17,1998 when TCN 10339 was implemented. The NRC notification cited that the event was being additionally reported under 10CFR50.73(a)(2)(i)(B). This was in error and is retracted herewith as a reporting criteria. The CST level was always maintained within the requirementsofTS 3.7.11.
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During the investigation of the issues identified in CARD 98-11773, the normal supply to the High Pressure Coolant Injection (HPCI) System [BJJ and the Reactor Core Isolation Cooling (RCIC) System [BN] were identified as another potential CST drain path. This potential drain path had previously been reviewed as t
part of the Fire Hazards Analysis and had been determined not to be subject to hot short induced failures.
This determination was based on the assumption that when the HPCI pump was shutdown (it is not assumed to be available in dedicated shutdown) flow tarough the pump would stop. However, this assumption is now considered to be invalid. Additionally,it was not recognized that a RCIC gravity drain path could be l
opened to the suppression pool [BT] by a hot short. These conditions have existed since the initial dedicated shutdown design was implemented.
The absence of emergency eight hour battery pack lights [FH] was also identified as a non-confonning condition during the review of AOP 20.000.18 for CARD 98-11773. Emergencylighting fbr operator l
access to manually operate the CST, llPCI, and RCIC valves is required to meet 10 CFR 50 Appendix R, Sectionlil.J.
CAUSE OF THE EVENT
DER 96-1662 was initiated to document the corrective actions required to address the potential for loss of inventory in the CST. TCN T09897 was issued to revise the AOP to require specific actions during an App.:ndix R fire. The operator would deenergize a bus which removed the power to Pl 100F603 and P1100F604,and then manually close them.
At the time this TCN was in effect, the pending revision for AOP 20.000.18 included several changes and l
other comments to be processed concurrently for the formal procedure revision. During the 1996 review of the composite revision package, accessibility concerns regarding the manual operation of the deenergized valves were identified. Manual operation of these valves would require sending the operator outside the l
building and into a confined space, a pit under the CST, to take local action. Additionally,this method of I
isolating the condenser from the CST was different from the way it is done in other AOPs such as for Station Blackout. It was believed that consistency was important to success because it would reduce confusion.
The procedure author, therefore, directed that valves different than those identified in the TCN, be identified for manipulationin the procedure. He believed these valves would accomplish the same purpose of preventing drain down of the CST. It is not uncommon for the permanent change to differ slightly from the fCN. In this instance,the permanent change which should have addressed the intent of the tempormy i
change was not adequately incorporated to address the potential for hot shorts.
The archived documents were reviewed during the 1998 investigationand they indicate that the procedure change process was followed properly; however, it was not noticed nor evaluated during the revision process that the changed configuration did not ensure that a hot short could potentially cause the loss of CST inventory.
Corrective actions for CARD 98-11773 included a review for other potential CST leakage paths. During this review the concerns with the HPCI and RCIC systems were identified. it was subsequently determined L__._______________________
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that a contributing factor to the cauce of this concern is that the cross disciplinary review of the original design may not have been adequate. As indicated in LER 96-019, when the dedicated shutdown method was c'eveloped in 1984 and 1985, the cross disciplinary review process was not yet fomialized in the design verificationprocess. Certain assumptions were made by the electrical engineers which were not subject to a mechanical or other cross discipline review. Apparently,the unfamiliarity of the electrical engineers with i
mechanical failure modes, i.e., that gravity flow could continue through the shutdown pump, was a j
contributing factor to the error. As stated in LER 96-019, a reliance on consultant work for preparation of l
the Appendix R design without a detailed review by Detroit Edison employees was identified as a l
contributing factor. It was assumed that the contractor's QA program was sufficient to ensure the adequacy l
of the design calculations and a detailed Detroit Edison review was not considered necessary.
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ANALYSIS OF THE EVENT
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A review of the sequence of steps in AOP 20.000.18 indicates that N2000F636 is closed before power is removed. This out-of-step sequence,i.e., positioning the valve prior to removing power, leaves the motor operated butterfly valve N2000F636 susceptible to a spurious opening. If a hot short were to open the valve after the step to close it in AOP 20.000.18, the valve would remain open even after power was removed l
because the valve fails"as-is."
Valve N2000F636 is an eight inch motor-operated valve in the condensate transfer piping. The open valve j
provides a direct pathway from the CST through the emergency hotwell pump to the condenser hotwell.
I-In the event a fire causes sufficient damage to require entry into AOP 20.000.18, certain plant equipment is transferred over to local control and is locally operated to recover reactor coolant inventory and maintain hot shutdown, establish torus and drywell cooling, and initiate the shutdown cooling mode of the Residual lleat Removal System [BO] within ten hours. If a loss of offsite power occurs, the Combustion Turbine Generator (CTG) I l-1 is started from the local Dedicated Shutdown Panel and the breakers are lined up to power the SBFW pumps. The CST provides the water inventory for operation of the SBFW system in the Dedicated Shutdown scenario.
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l In the unlikely event of an Appendix R fire which induced hot shorts and repositioned one of the closed l
valves such that the CST began to lose inventory, the Dedicated Shutdown Panel would provide the appropriateindications to apprise the operators of the CST level. The operators would have sufficient time to recognize the potentialloss ofinventory and to take actions to make up the amount of water needed to remotely shutdown the reactor and allow it to cooldown to a point when shutdown cooling could be initiated. Steps to address actions to makeup water were proposed and reviewed by Operations during the investigation subsequent to LER 96-019. These included means to makeup water to the CST from the CRT or the hotwell; however, these actions were not proceduralized.
Therefore, based on the above discussion,the health and safety of the public is not adversely affected by this condition.
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CORRECTIVE ACTIONS
l The potential drain path to the CST via the normal supply to HPCI and RCIC and the potential for a RCIC gravity drain were evaluated and determined not to be a significant flow path. The review of the CST piping for spurious component actuation is complete. No additional valves were identified which are susceptible to l
flic induced spuriousoperation.
l Subsequent to that review, the valves proposed to isolate the CST during a postulated Appendix R fire, were reviewed by engineering and have been approved for incorporationinto AOP 20.000.18. Access routes to these manually operated valves were reviewed and emergency battery pack lighting will be provided where needed by June 30,1999. In the interim, until permanent emergency lighting can be installed, portable l
lights will be made available. A Temporary Change Notice (TCN) was issued to revise the procedure to indicate that portable lights may be required. The AOP will be revised by August 30,1998, to incorporate j
the results of the engineering walkdown and the need for portable lights.
l The ongoing 10 CFR 50 Appendix R reassessmentwill continue and will be completed by June 30,1999.
i ADDITIONALINFORMATION:
i A. Failed Components:
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None 1
A. Previous LERs on Similar Problems:
LER 96-008 l
Following a plant housekeepingtour, a concern was raised about the fire wrap in the Auxiliary Building Basement, elevations 551 feet and 562 feet. This prompted a reviewof the 10CFR50, Appendix R assumptions used for this area. This review which was completed on May 13,1996 revealed an incorrect assumption used in the Appendix R Fire Hazards Analysis. Furtherinvestigationidentified a portion of Division 2 cable trays which were not fire-wrapped in their entirety and were located near equipment which can be considered intervening combustibles,i.e., combustible material withir4 20 feet of redundant shutdown divisions. An engineering design modificationwas installed to bring this area into compliance with 10CFR50, Appendix R.
LER 96-019 On November 15,1996 a Deviation Event Report (DER) was initiated to investigate the adequacy of the water supply for the Standby Feedwater(SBFW) system to meet Appendix R requirements. The water supply for SBFW is from a nine foot standpipe in the Condensate Storage Tank (CST). Technical Specification (TS) 3.7.11 requires an operable SBFW system consisting of two operable SBFW pumps and an operable flow path L____-_-_-_____-
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6 from the CST to the reactor vessel. The cause of this event was an inadequate design review of the Appendix R Dedicated Shutdown Method during design developmentin 1984. Appropriate Operating procedures were j
revised to maintain the required volume of water in the CST at greater than 22 feet.
i LER 97-005 On March 7,1997, during an engineering review of Emergency Equipment Cooling Water (EECW) it was discovered that the Reactor Building Closed Cooling Water (RBCCW) to EECW return and supply isolation valve interlocks are not bypassed when the valve is in local control at the dedicated shutdown panel. These l
valves cannot be operated from the dedicated shutdown panel; therefore there was no assurance that the EECW l
makeup tank isolation valve could be operated properly from the dedicated shutdown panel if the RBCCW and i
EECW supply and return valves could not be verified to be closed. The cause of this event was an inadequate I
design review and inadequate post modification testing.
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