ENS 43750
ENS Event | |
|---|---|
00:30 Oct 26, 2007 | |
| Title | Both Low Temperature Overpressure Protection Systems Out of Service |
| Event Description | This 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report is being made pursuant to 10 CFR 50.72(b)(3)(v). On 10/25/2007 at 1930 CDT Point Beach Nuclear Plant (PBNP) Unit 1 and Unit 2 low temperature overpressure protection systems (LTOP) were declared inoperable as a result of the determination that the current LTOP actuation setpoint was non-conservative based on updated calculations. Specifically,
1) The mass input from the Safety Injection Pumps has significantly increased based on the use of a Point Beach Nuclear Plant specific system flow model. 2) The setpoint calculation does not consider instrument delay times during (PORV) Pilot Operated Relief Valve actuation. 3) The updated Calculation changes instrument uncertainties. LCO 3.4.12 for the LTOP system is not applicable at this time for either unit (both units in Mode 1/100% power). LCO 3.4.12 is only applicable in Mode 5, Mode 6 when the reactor vessel head is on, and Mode 4 when any cold leg temperature is at or below the temperature specified in the Pressure Temperature Limits Report (270 deg F). Changes to operating procedures to delineate operation of reactor coolant pumps and charging pumps during low temperature conditions are in progress. Implementation of these procedure changes will permit LTOP to be returned to service. The licensee stated that this issue was discovered as part of the on going calculation reconstitution initiative at the plant. The licensee notified the NRC Resident Inspector.
The following is an update to the 8 hr report made to the NRC via EN#43750: On 10/26/07 at 17:51 procedure changes which identify requirements for operation of reactor coolant pumps and charging pumps during low temperature conditions have been made. These procedures provide the guidance required to ensure that the current LTOP setpoints remain conservative. Based on the issuance of these procedures with the required guidance, LTOP is returned to service for both Unit-1 and Unit-2. The licensee notified the NRC Resident Inspector. Notified R3DO (Hills). |
| Where | |
|---|---|
Point Beach  Wisconsin (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| LER: | 05000266/LER-2007-008 |
| Time - Person (Reporting Time:+13.82 h0.576 days <br />0.0823 weeks <br />0.0189 months <br />) | |
| Opened: | Robert Brock 14:19 Oct 26, 2007 |
| NRC Officer: | Jason Kozal |
| Last Updated: | Oct 26, 2007 |
| 43750 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |