05000382/LER-2005-002
| Docket Numbersequential Revmonth Day Year Year Month Day Year N/Anumber No. 05000 | |
| Event date: | 06-09-2005 |
|---|---|
| Report date: | 01-12-2006 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3822005002R01 - NRC Website | |
switches were unable to perform their specified safety function of detecting a leakage rate of 1 gallon per minute (GPM) as required by Technical Specification (TS) 3.4.5.1. This condition existed under the original TS LCO and TS Amendment 197, implemented on August 2, 2004.
The original TS 3.4.5.1 specified that the following leakage detection systems shall be operable:
a. a containment atmosphere particulate radioactivity monitoring system, b.the containment sump level and flow monitoring system, and c. either the CFC condensate flow switches on at least three coolers or a containment atmosphere gaseous radioactivity monitoring system.
Amendment 197 changed the Reactor Coolant System (RCS) Leak Detection TS 3.4.5.1 to specify that one CFC condensate flow switch shall be operable in Modes 1-4. TS LCO 3.4.5.1 action statement c.
specified that with the required CFC condensate flow switch inoperable, a channel check will be performed on the containment atmosphere particulate radioactivity monitor once per eight hours or a reactor coolant system inventory balance will be performed once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or if unable to comply with the action, a plant shutdown is required. Since the CFC condensate flow switches were not identified as being not able to detect 1 GPM RCS leakage within one hour, the requirements of Action c.
were not met during certain periods from August 2, 2004 through April 17, 2005.
For the period prior to the amendment, the TS LCO 3.4.5.1 action statement specified that with only two of the required leakage detection systems operable, operation may continue for up to thirty days otherwise, be in at least Hot Standby within the next six hours and in Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Since the CFC condensate flow switches were not identified as not being able to detect 1 GPM RCS leakage within one hour, the requirements of the RCS leakage detection TS LCO action regarding having two required leakage detection systems operable were not met during certain periods.
On November 17, 2005, an evaluation determined that TS 3.4.5.1 did not meet R.G. 1.45, Regulatory Position C.9, requirement for the CFC condensate flow monitoring leakage detection method. Per Regulatory Position C.9, TSs should include limiting conditions for leakage to address the CFC condensate flow monitoring leakage detection. TS 3.4.5.1 did not adequately address CFC condensate flow monitoring leakage detection method since the CFC condensate flow switches are collectively incapable of detecting a 1 GPM RCS leak in all cases. Each CFC condensate flow switch is configured to detect 1 GPM of water flow, therefore more than 1 GPM of RCS leakage is necessary for detection by each flow switch due to the distribution of RCS leakage to the running CFCs.
This condition is reported in accordance with the 60-day written reporting requirements of 10CFR50.73 (a)(2)(i)(B) as a condition prohibited by the TS.
INITIAL CONDITIONS
At the time of discovery of this condition the plant was in power ascension subsequent to Refueling Outage 13 and operating in Mode 3. There were no procedures being implemented specific to this condition. There was no TS LCO specific to this condition in effect. There was no equipment out of service specific to this condition.
Event Description:
On May 25, 2005, during performance of the channel functional test of the CFC condensate flow switches [IJ] to comply with the 18 month RCS leakage detection TS surveillance requirement 4.4.5.1.c, five of the six flow switches did not respond when flowing 1 GPM of water into the flow switch drain lines. Each of the flow switches was adjusted to actuate at 1 GPM of water flow.
On June 9, 2005, Engineering completed a past operability evaluation and determined that none of the six flow switches would have performed their specified safety function of detecting a collective RCS leakage rate of 1 GPM as required in the detector sensitivity section of Regulatory Guide 1.45, Reactor Coolant Pressure Boundary Leakage Detection Systems, based on the as-found flow switch settings.
On August 8, 2005, LER 2005 002-00 was submitted to the NRC.
On November 17, 2005, an evaluation determined that the CFC condensate flow switches did not have the capability to perform a TS CFC condensate flow monitoring specified safety function of detecting a collective leakage rate of 1 GPM of RCS leakage. TS 3.4.5.1 was determined to be inadequate, and the inadequacy had existed since the original configuration of TS 3.4.5.1.
The TS inadequacy was previously unrecognized, and the time of discovery of the TS inadequacy was based on the completion of the November 17, 2005 engineering evaluation which confirmed the CFC condensate flow switches collectively did not have the capability to detect 1 GPM RCS leakage.
BACKGROUND
The original TS Surveillance Requirement and implementing procedure did not incorporate the R.G. 1.45 detector sensitivity requirement in the functional testing of the CFC condensate flow switches even though CFC condensate flow switch monitoring was part of the original configuration of TS 3.4.5.1. The original RCS leakage detection TS LCO specified that the CFC condensate flow switches were one part of one of the three required leak detection systems with the other part being the Containment Atmosphere Gaseous Radioactivity Monitoring System (CAGRMS) [1.1]. The other two required systems were the containment sump level and flow monitoring system [1,1] and the containment atmosphere particulate radioactivity monitoring system [1.1].
BACKGROUND (Continued) On August 2, 2004, the implementation of Amendment 197 revised the RCS leakage detection TS LCO by removing the CAGRMS from the group of required systems, crediting either the containment sump level instrumentation or the containment sump flow monitor instrumentation as the "one containment sump monitor, and allowing one CFC condensate flow switch as the third leakage detection system. Additionally, the RCS leakage detection TS Bases was revised and specified that the CFC condensate flow switches were instrumented to alarm for increases of 0.5 to 1.0 GPM in the normal flow rates.
On June 9, 2005, an engineering determination was made that none of the six flow switches would have performed their specified leakage detection safety function to the detector sensitivity requirements of R.G.
1.45. A review of the plant's station log was conducted for the period from June 9, 2002 to August 2, 2004 to identify any instances where any other leakage detection system was inoperable and credit was being taken for the CFC condensate flow switch leakage detection system to meet the original RCS leakage detection TS LCO Action requirement. During this period, multiple occasions were identified wherein TS 3.4.5.1 Action was not met. On August 8, 2005, LER 2005-002-00 was submitted to the NRC.
On November 17, 2005, an evaluation determined that, even though the CFC condensate flow switches functioned as designed, TS 3.4.5.1 did not meet R.G. 1.45 Regulatory Position C.9 requirement for RCS leak detection. The TS should have included limiting conditions for leakage to address CFC condensate flow monitoring leakage detection with the capability of detecting a 1 GPM RCS leak in all cases. The CFC condensate flow switches did not have capability to detect a RCS leak rate of 1 GPM within one hour. TS 3.4.5.1 did not meet the RCS leakage requirements of R.G. 1.45 since the original configuration of TS 3.4.5.1.
Causal Factors:
The cause of this event is a historical error in the original configuration of TS 3.4.5.1. The CFC condensate flow switches were incorrectly included in TS 3.4.5.1. A contributing cause of this event is that plant personnel did not have an adequate understanding of R.G. 1.45 requirements associated with CFC condensate flow leakage detection monitoring.
Corrective Actions:
Waterford 3 established administrative controls for TS 3.4.5.1 by taking credit for already existing containment sump weir (CSW) leakage detection instrumentation to satisfy the CFC condensate flow monitoring system leakage method. A TS change request will be submitted to the NRC which accurately describes the leakage method instrumentation which assure R.G. 1.45 requirements are met. This action is being tracked in the corrective action program.
Safety Significance:
Redundant indications of RCS leakage are necessary to promptly and quantifiably identify Reactor Coolant Pressure Boundary leakage.
5 Safety Significance (Continued):
During the past three years, occasions were identified wherein Waterford 3 was operating with only one leakage detection method specified in TS 3.4.5.1; however, during these periods, other non-R.G. 1.45 RCS leakage indicators were available (e.g. containment temperature, containment humidity and Volume Control Tank level).
During the time interval when the CFC condensate flow switches were incorrectly included as an RCS leakage detection system for TS 3.4.5.1 CFC condensate flow monitoring, there was always at least one R.G. 1.45 qualified RCS leakage detection system operable. In addition, TS Surveillance Requirement 4.4.5.2.1, Reactor Coolant System inventory balance, was being performed at least once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and provided Reactor Coolant Pressure Boundary leakage detection capability at less than a 1 GPM leakage rate.
The requirement for leakage detection is also contained in the leak-before-break" analysis. This analysis is contained in CEN-367-A, "Leak-Before-Break Evaluation of Primary Coolant Loop Piping in Combustion Engineering Designed Nuclear Steam Supply Systems." This analysis assumes a Reactor Coolant Pressure Boundary leakage of 10 GPM and is based on a safety factor of 10 on R.G. 1.45 leakage detection capability requirements. Therefore, safety significance for the "leak-before-break" analysis is minimal since the plant maintained at least one leakage detection method at the capability specified in R.G. 1.45.
The RCS leakage detection system is not modeled in the PRA. The PRA LOCA initiator frequencies are from NUREG/CR-5750, "Rates of Initiating Events at U.S. Nuclear Power Plants: 1987 - 1995." These PRA LOCA initiator frequencies would remain valid while in this condition. Qualitatively, the low LOCA initiator frequencies and alternative leak detection methods indicate a negligible impact in Core Damage Frequency (CDF) and Large Early Release Frequency (LERF).
The leak detection methods and indicators that were available, "leak before break" analysis, and PRA insights provide reasonable assurance that the condition is of low safety significance.
This condition is not a Safety System Functional Failure. Per 10 CFR 50.73, there are four safety system functions: ability to shut down the reactor and maintain it in a safe shutdown condition, ability to remove residual heat, ability to control the release of radioactive material, and ability to mitigate the consequences of an accident. The R.G. 1.45 RCS leakage detection system is a monitoring system that provides Reactor Coolant Pressure Boundary leakage detection monitoring that does not provide a mitigating function as defined in 10 CFR 50.73.
SIMILAR EVENTS
There were no previous similar reportable events identified that involved CFC condensate flow switches or Regulatory Guide 1.45 design basis requirements.
ADDITIONAL INFORMATION
Energy Industry Identification System (EIIS) codes are identified in the text within brackets a.