ENS 46327
ENS Event | |
|---|---|
18:05 Oct 11, 2010 | |
| Title | Technical Specification Does Not Account for Power Uprate |
| Event Description | On October 11, 2010 at 1305 CDT it was identified that the analysis of record for the Technical Specification 3.3.5.1, Table 3.3.5.1-1 function 1e and 2e, Reactor Steam Dome Pressure Permissive-Bypass timer (Pump Permissive) did not reflect current plant conditions. Specifically, the analysis was not updated to account for any increase in plant licensed power and a change to the RWCU (Reactor Water Cleanup System) isolation for enhanced ability to isolate RWCU on a line break on critical crack. The allowable value for these function is greater than or equal to 18 minutes and less than or equal to 22 minutes.
All equipment associated with emergency core cooling function are unaffected. Discussion with General Electric indicates that a margin exists to accommodate the higher power level. Additionally, the changes to the RWCU isolation logic added leak detection instruments that will isolate RWCU earlier for the majority of pipe leaks. This discovery is being reported as an unanalyzed condition solely due to the lack of a formal analysis of current plant conditions. The NRC Resident Inspector has been notified.
Under NUREG-0737, Item II.K.3.18 is a regulatory requirement to implement a modification to extend the ADS [Automatic Depressurization System] to a unique event sequence that involves multiple failures including HPCI [High Pressure Coolant Injection] plus no operator action after 10 minutes. According to Item II.K.3.18, the bypass timer logic complements, but does not replace, the existing ADS actuation logic. This requirement is not associated with any design basis accident mitigation sequence at MNGP [Monticello Nuclear Generating Plant]. The plant has performed an evaluation that addresses the changes in plant thermal power and RWCU (Reactor Water Cleanup System) enhanced isolation capabilities to the analysis of record. This evaluation concluded that Peak Clad Temperature (PCT) will remain under the 2200 ?F acceptance limit with the current Technical Specification allowable value, current plant configuration and current licensed thermal power. GEH [General Electric] did an independent evaluation that concluded that based on use of limiting scenarios analyzed for MNGP, this condition is only a lack of formal analysis of current plant conditions and that no Substantial Safety Hazard exists. It is judged that the maximum Reactor Steam Dome Pressure Permissive-Bypass timer (Pump Permissive) setting of 22 minutes will not result in a predicted PCT higher than 2200?F with consideration of the RWCU pipe break isolation instrumentation modification. Since the timers with their current setpoint will protect the fuel cladding, this event does not significantly degrade safety. Therefore, the event notification made on October 11, 2010 is being retracted. The licensee has notified the NRC Resident Inspector. Notified R3DO (Skokowski) |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+4 h0.167 days <br />0.0238 weeks <br />0.00548 months <br />) | |
| Opened: | Mark Pikus 22:05 Oct 11, 2010 |
| NRC Officer: | Charles Teal |
| Last Updated: | Oct 29, 2010 |
| 46327 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (95 %) |
| After | Power Operation (95 %) |