05000293/LER-2017-009

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LER-2017-009, Supplement to Potential Primary Containment System Inoperability Due to Relay Concerns
Event date: 05-17-2017
Report date: 11-15-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat
2932017009R01 - NRC Website
LER 17-009-00 for Pilgrim Nuclear Power Station Regarding Potential Primary Containment System lnoperability Due to Relay Concerns
ML17220A063
Person / Time
Site: Pilgrim Entergy icon.png
Issue date: 07/17/2017
From: Perkins E P
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.050
Download: ML17220A063 (6)


comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

2017

BACKGROUND

The safety objective of the Primary Containment System (PCS) is to provide the capability in conjunction with other safeguards features to:

  • Limit the release of fission products in the event of a postulated design basis accident so that offsite doses would not exceed the guideline values set forth in 10 CFR 100.
  • To prevent excessive fuel cladding temperatures.

Group 3 Isolation isolates the Shutdown Cooling (SDC) mode of the Residual Heat Removal (RHR) system from the reactor vessel, when conditions indicate a system breach or over pressurization. Relay 16A-K54 gets an initiation signal on high reactor pressure and provides a signal to relay 16A-K30 to energize to close MO-1001-47 (RHR SDC outboard isolation valve). This 16A-K30 relay also isolates the RHR shutdown cooling valve on any one of the following conditions:

a. Reactor low water level (+12 inches) b. High drywell pressure (+2.2 psig) c. High reactor pressure (76 psig) The high reactor pressure isolation setpoint prevents over pressurizing the RHR low pressure piping.

EVENT DESCRIPTION

On May 17, 2017, during Refueling Outage 21 while performing an extent of condition review it was discovered that the contact indicating tabs of relays 16A-K29, 16A-K30, 16A-K53 and 16A-K54 of the Pilgrim Nuclear Power Station (PNPS) Primary Containment System, were visually hanging in the mid- position (partial travel).

CAUSE OF THE EVENT

The relays were sent to an offsite vendor for further testing and analysis. The results of the testing proved that the relays would have made the associated isolation valves go closed, which satisfies the safety function of isolating the valves on a Group 3 isolation signal.

CORRECTIVE ACTIONS

The relays were replaced, ensuring the capability of the Group 3 Isolation of the SDC mode of RHR.

Forensic testing was performed on the removed relays proving that the relays would have made the associated isolation valves go closed, which satisfies the safety function of isolating the valves on a Group 3 isolation signal.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Pilgrim Nuclear Power Station 05000-293 2017 -01

SAFETY CONSEQUENCES

The function of 16A-K29 is to energize and isolate MO-1001-50 upon a Primary Containment Isolation System Group 3 Isolation signal. Once the Group 3 signal is manually cleared by Operations, 16A-K29 de-energizes to provide a permissive to re-open MO-1001-50. Field troubleshooting and the offsite vendor analysis demonstrated that 16A-K29 would consistently provide the isolation signal to close MO-1001-50 during testing, which satisfies the safety related function of the relay.

The engineering analysis that was performed concluded that this event did not constitute a Safety System Functional Failure (SSFF). (Reference NEI 99-02, Revision 7, Regulatory Assessment Performance Indicator Guideline, Section 2.2, Mitigating Systems Cornerstone, Safety System Functional Failures, Clarifying Notes, Engineering analyses.) As such, this event will not be reported in the NRC Performance Indicator (PI) for safety system functional failures since an engineering analysis was performed which determined that even though the isolation valves would have required a manual reset to reopen, the relays would have performed as required to close the valves on a Group 3 isolation signal, thereby proving that they were capable of performing the safety function during this event.

This condition was discovered during the refueling outage when conditions were such that the equipment normally energized/activated by these relays was not required to be operable.

There are no consequences to the general safety of the public, nuclear safety, industrial safety and radiological safety from this event. No actions to reduce the frequency or consequence are necessary.

REPORTABILITY

PNPS stated at the time that this event was reportable under 10 CFR 50.73(a)(2)(i)(B) — Operation or condition prohibited by Technical Specifications; and potentially in accordance with 10 CFR 50.73(a)(2)(v)(B), (C) and (D) — Any condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat, control the release of radioactive material and mitigate the consequences of an accident. However, additional information provided by our offsite vendor and an engineering evaluation, support the conclusion that there was never a loss of safety function. Therefore, this event was not reportable under 10 CFR 50.73(a)(2)(i)(B) nor under 10 CFR 50.73 (a)(2)(v)(B), (C) or (D).

PREVIOUS EVENTS

A review of PNPS LERs for the past five years did not identify any other LERs that were submitted for the same reason as this submittal.

REFERENCES:

CR-PNP-2017-5390 CR-PNP-2017- 5396