ENS 48541
ENS Event | |
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04:38 Nov 28, 2012 | |
Title | Control Room Ventilation System Will Not Automatically Start in Pressurization Mode |
Event Description | The control room ventilation system (CRVS) pressurization mode is required to be actuated by a safety injection signal, control room radiation atmosphere air intake, and operator manual actuation in accordance with Technical Specification (TS) 3.3.7.
On November 27, 2012 at 2038 hrs. PST, Pacific Gas and Electric Company (PG&E) identified that none of the CRVS four pressurization fans would operate continuously if they started in response to a safety injection or control room radiation atmosphere intake actuation signal. All of the pressurization fans remain capable of continuous operation via manual actuation. At 2050 PST the Unit 2 CRVS was manually placed in pressurization mode in accordance with TS 3.3.7, ACTION B.1.1. This was determined to be caused by a recent flow balancing of the CRVS that raised the static air pressure. The increased system static pressure actuates the fan-run pressure switches for each of the four associated pressurization fans, when only a single pressurization fan is operated. This results in the system logic securing all pressurization fans started by the CRVS automatic actuation signals. If all pressure switches actuate, automatically started pressurization fans will be secured until air pressure decays below the fan-run switch setpoint, at which time the pressurization fan would restart. This would result in cyclic operation of the pressurization fan. The fan-run pressure switches are not part of the manual actuation circuitry for the pressurization fans. Diablo Canyon (DCPP) is making this 8-hour, non-emergency notification under 10 CFR 50.72(b)(3)(v)(D). Plant personnel notified the NRC Resident Inspector. |
Where | |
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Diablo Canyon California (NRC Region 4) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
Time - Person (Reporting Time:+-2 h-0.0833 days <br />-0.0119 weeks <br />-0.00274 months <br />) | |
Opened: | Michael Kennedy 02:38 Nov 28, 2012 |
NRC Officer: | Howie Crouch |
Last Updated: | Nov 28, 2012 |
48541 - NRC Website
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Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
Unit 2 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |