05000305/LER-2002-001
| Docket Number | |
| Event date: | 01-10-2002 |
|---|---|
| Report date: | 03-11-2002 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| Initial Reporting | |
| 3052002001R00 - NRC Website | |
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3)
DESCRIPTION
operation at 100 percent power, Nuclear Management certain operating conditions, the 'A' Component Cooling the 'B' CCW pump. Consequently, with both "dead-headed" against the unopened discharge check eventually caused the "dead-headed" pump to fail, a have resulted in a complete loss of CCW. Thus, NMC the ability of safety related components to perform their Report (USAR) Section 9.3, the CCW system consists a CCW surge tank [TK], cooling lines to various valves, and instrumentation. CCW piping to various normal operation, the CCW pumps and heat the heat removal loads. One pump and one heat during normal operation. Two pumps and two heat sensible heat during plant shutdown. If one of the pumps shutdown of the plant is not affected; however, the time and a discharge isolation valve into a common header automatically start on a Safety Injection (SI) signal or a loss if the discharge head capacity of the operating CCW the stand-by pump's discharge check valve may not flow rates, both pumps will share the load and this reported this condition to the NRC (EN 38621) in that results in the plant being in an unanalyzed since original plant construction. � It is apparent that the interaction. Although single pump testing was is routine to date, dual pump testing was not performed to flow conditions.
pump-to-pump interaction. However, the Kewaunee as being a concern with the Kewaunee CCW system.
evaluation. Efforts to date show the need to modify the for the pumps is always available. However, because cause or causes are more difficult to determine.
On January 10, 2002, while the plant was in normal Company (NMC) personnel determined that under Water (CCW) [CC] pump [P] discharge capacity overpowered pumps operating in parallel, the 'B' CCW pump was valve [V], CC-3A. Because this condition could have single failure in the opposite, or strong, train would concluded that this condition could have impacted intended function.
As stated in the Kewaunee Updated Safety Analysis of two CCW pumps, two CCW heat exchangers [HX], components to be cooled, and associated piping, components is arranged in parallel flow circuits. During exchangers are operated as needed to accommodate exchanger can provide 100% heat removal capability exchangers are used to remove the residual and or one of the heat exchangers is not operative, safe for cool-down is extended.
Each CCW pump discharges through a check valve (see Figure 1). At Kewaunee, both CCW pumps of offsite power. Because of the common header, pump is greater than that of the stand-by CCW pump, open when the stand-by pump starts. At higher CCW "dead-heading" condition is not a concern.
At 1601 CST, on January 10, 2002, NMC conservatively accordance with 10CFR50.72(b)(3)(ii)(B) as a condition condition that significantly degrades plant safety.
CAUSE OF THE EVENT
The design of the CCW system has been in place original designers failed to realize this potential design performed following the system's installation and assure pump performance under low to moderate NRC Bulletin 88-04 provided additional insights to response to Bulletin 88-04 did not identify this issue (see Additional Information).
Kewaunee is continuing to complete a full root cause system design to assure minimum flow requirements of the time that the condition has existed, the root FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3)
ANALYSIS OF THE EVENT
Probabilistic Risk Assessment (PRA). As a result an incremental core damage frequency of 8.5E-7, which trains of CCW being inoperable. Therefore, this condition under 10CFR50.73(a)(2)(v). However, because this inoperable, it is being reported in accordance with that significantly degraded plant safety.
out in Kewaunee's response to Bulletin 88-04 show heading concerns.
controls requiring Operators to stop one CCW pump in during low CCW system demand.
why this condition exists and why it was not systems to ensure this condition does not exist elsewhere.
this pump-to-pump interaction.
for additional administrative corrective actions, NMC to the Kewaunee corrective action program.
three years.
Safety-Related Pump Loss". The purpose stated and correct as applicable two miniflow design concerns.
dead-heading of one or more pumps in safety-related two or more pumps or other piping configurations that do miniflow operation. The second concern pertained to is adequate for even a single pump in operation.
NMC has evaluated the risk-insights from the site-specific of this evaluation, this condition was assessed with corresponds to a very low risk significance.
This design issue alone did not result in redundant is not reportable as a Safety System Functional Failure event did result in one train of CCW being considered 10CFR50.73(a)(2)(ii)(B) as a unanalyzed condition
CORRECTIVE ACTIONS
NMC has completed the following corrective actions:
- Preliminary reviews of the other systems called adequate mini-flows are assured and no dead
- NMC initiated a root cause evaluation to determine recognized sooner.
NMC plans to perform the following corrective actions:
- NMC plans to perform further reviews of plant
- NMC plans to implement a design change to prevent Should the root cause evaluation determine the need will include them as additional corrective actions according
SIMILAR EVENTS
There have been no similar events within the last
ADDITIONAL INFORMATION
On May 5, 1988, the NRC issued Bulletin 88-04, "Potential in the Bulletin was:
"The purpose of this bulletin is to investigate The first concern involved the potential for the systems that have a miniflow line common to not preclude pump-to-pump interaction during whether or not the installed miniflow capacity FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 Kewaunee Nuclear Power Plant 05000305 YEAR SEQUENTIAL I REVISION NUMBER � NUMBER The Kewaunee response to NRC Bulletin 88-04 stated, in part, "The component cooling pumps do not have miniflow recirculation lines. System design and normal operating practices are such that the pumps are always supplying the main component cooling loads; therefore, recirculation flow to the pumps is not required, and pump-to-pump interaction is not a concern.
"The component cooling pumps do not have miniflow recirculation lines. System design and normal operating practices are such that when a pump is operating, it is sufficiently loaded to component cooling loads. Pump damage due to low flow conditions is not a concern for the component cooling pumps.
ENS notification 38621 provided on January 10, 2002 stated that the Kewaunee response to NRC Bulletin 88-04 "indicated that the CCW system was not vulnerable to this particular type of system failure." As such, the ENS notification provided the NRC with a report in accordance with 10CFR50.9. However, as described in the Bulletin, the interaction between the CCW pumps is not during miniflow recirculation operation, per se.
Rather, the interaction reported in this LER occurs under normal system steady state flow conditions which could be the same during the initial stages of an SI condition or a loss of offsite power. It is unclear whether this distinction was used during the review of NRC Bulletin 88-04, resulting in dismissing the CCW system from further evaluation of possible pump-to-pump interaction.
Under normal operating conditions, flow in the CCW system is around 1000 gpm. It seems that the evaluation for the response to the Bulletin did not recognize this as a low flow condition that could result in a dead-heading condition.
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