ENS 46699
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ENS Event | |
|---|---|
15:53 Mar 25, 2011 | |
| Title | Potential Unanalyzed Condition Due to Power Level Greater than Limit |
| Event Description | During performance of maintenance to troubleshoot the B feedwater regulating bypass valve, the Thermal Power Monitor (TPM) indication exceeded the maximum thermal power assumed in the Safety Analysis Report. Operators were maintaining 12 Steam Generator (SG) water level in a band from 40 to 48 percent by controlling the B Feed Regulating Valve (FRV) in manual from the Control Room. Operators noted a power increase; adjustments were made via the FRV to reduce SG water level, however the valve response was sluggish and thermal power exceeded 100%. Immediate steps were taken to reduce power to below 100% by reducing 1st stage turbine pressure and inserting Bank D control rods 7 steps.
The TPM indication was above the maximum thermal power limit of 100.36% for 1.68 minutes. The TPM indication peak was 100.39%. No concurrent increase in power was observed by the nuclear indication system. NRC Resident had been informed.
An eight hour report (EN#46699) per 10 CFR 50.72(b)(3)(ii)(B) was conservatively reported on March 25, 2011 for Thermal Power Monitor indication above the maximum thermal power limit of 100.36% for 1.68 minutes. Subsequent engineering investigation has determined that this specific transient had been previously analyzed. The transient was within the bounds of the safety analysis. The 10 CFR 50.72(b)(3)(ii)(8) report (EN#46699) is retracted. NRC Resident has been informed. Notified R3DO (Peterson). |
| Where | |
|---|---|
Prairie Island  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+1.57 h0.0654 days <br />0.00935 weeks <br />0.00215 months <br />) | |
| Opened: | Terry Bacon 17:27 Mar 25, 2011 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Mar 29, 2011 |
| 46699 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (99 %) |
| After | Power Operation (98 %) |
WEEKMONTHYEARENS 526382017-03-20T21:39:00020 March 2017 21:39:00
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