05000293/LER-2017-010

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LER-2017-000, Air Accumulation Creates Small Void in Core Spray Discharge Piping
Event date: 06-07-2017
Report date: 08-03-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2932017000R00 - NRC Website
LER 17-010-00 for Pilgrim re Air Accumulation Creates Small Void in Core Spray Discharge Piping
ML17227A130
Person / Time
Site: Pilgrim Entergy icon.png
Issue date: 08/07/2017
From: Perkins E P
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.054
Download: ML17227A130 (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.

Pilgrim Nuclear Power Station 05000-293 2017 - 00

BACKGROUND

Air/gas in discharge piping can be an indicator of potential back-leakage from high-pressure sources such as accumulators or the Reactor Coolant System, and the gas may have moved into the pumps and the pump suction piping. Such gas may have flowed through multiple closed in-series valves. For this reason, it is important to reassess air/gas accumulation conditions following system operations and valve manipulations.

(Reference NRC Generic Letter 2008-01).

EVENT DESCRIPTION

While performing Ultrasonic testing (UT) examination on Core Spray A high point piping in the A Residual Heat Removal Quad to ensure this piping was water solid, it was identified that the horizontal pipe had an air void internally. This piping goes through the concrete wall at this location and into the Torus room. A high point vent line with valves is located in the area of the UT exam. It was found that the top 2 inches of the 10 inch core spray pump discharge line had accumulated an air void within the known inverted loop in Core Spray Loop-A discharge line.

CAUSE OF THE EVENT

The air volume was likely introduced into the system as a consequence of inadequate guidance in procedure 2.2.20, Core Spray, which does not provide task specific directions for fill and vent of the Core Spray system to restore from a draindown.

The information for filling and venting the system was contained in one Section of the procedure and in two Attachments, but it was not compiled in one place that was readily accessible to the Operator performing the procedure. The lack of guidance provided an error trap when system restoration was being performed.

CORRECTIVE ACTIONS

The immediate corrective action was to vent the air from the 10 inch Core Spray Pump discharge line that had accumulated an air void within the known inverted loop in Core Spray Loop-A Discharge Line.

The follow-up UT exam was performed and determined that the Core Spray Loop-A discharge piping was water solid with no evidence of air present. Core Spray Loop-A is OPERABLE.

Procedure 2.2.20, Core Spray, will be revised to provide specific guidance to fill and vent the Core Spray system following maintenance requiring a system draindown, or any activity requiring a system breach.

- 010 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 - 00 - 010

SAFETY CONSEQUENCES

There were no consequences to the safety of the general public, nuclear safety, industrial safety, or radiological safety due to this event. For the purpose of evaluating the potential consequences of the as-found void volume, the measured void volume was compared to the Maximum Allowable Void Criteria that was established for this purpose. These criteria are used only for functionality determinations if voids are detected. The void volume did not exceed the maximum allowable void criteria. Therefore, the Core Spray system would have been capable of performing all of it specified safety functions.

No actions to reduce the frequency or consequence are necessary.

REPORTABILITY

Pilgrim Nuclear Power Station (PNPS) is reporting this event pursuant to 10 CFR 50.73(a)(2)(i)(B), as a condition prohibited by Technical Specifications (TS). Although upon discovery the proper Limiting Condition for Operation Action Statement was entered and the void was filled immediately to correct the issue, it is believed that this condition existed before the time of discovery for a period of time longer than that allowed by TS.

PREVIOUS EVENTS

A review of PNPS LERs since NRC Generic Letter 2008-01 was issued did not identify any other LERs that have been written regarding line voids of air or gas accumulation in discharge piping.

REFERENCES

CR- PNP-2017-06029