05000293/LER-2017-006

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LER-2017-006, Source Range Monitor Inoperable During Fuel Movement
Pilgrim Nuclear Power Station
Event date: 04-14-2017
Report date: 06-13-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2932017006R00 - NRC Website
LER 17-006-00 for Pilgrim Nuclear Power Station Regarding Source Range Monitor Inoperable During Fuel Movement
ML17171A231
Person / Time
Site: Pilgrim Entergy icon.png
Issue date: 06/13/2017
From: Perkins E P
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.044
Download: ML17171A231 (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:

The Source Range Monitors (SRMSs) provide neutron flux information during reactor startup and low flux level operations. There are four SRM channels, each of which includes one detector that can be remotely positioned in the core from the control room. The detectors are inserted into the core for a reactor startup and may be withdrawn if the indicated count rate is above preset limits or if the Intermediate Range Monitors (IRMs) are on the third range or above.

EVENT DESCRIPTION:

During fuel movements (core alterations) conducted on April 14th and April 15th in reactor quadrant B, SRM channel B was inoperable due to not meeting the signal to noise ratio of no less than 2 to 1 required by FSAR section 7.5.4.1. This was a condition prohibited by Technical Specification 3.10.B.

CAUSE OF THE EVENT:

The cause of the event was that SRM B had faulty or dirty pre amp connectors which led to the signal to noise ratio margin degrading to less than the minimum required 2 to 1 ratio. This condition was not recognized as being required or validated by the stations procedures.

CORRECTIVE ACTIONS:

The following corrective actions to reduce the probability of similar events occurring in the future were performed:

  • The SRM B detector was replaced.
  • The SRM cables and connectors were cleaned.
  • A ground path between the preamplifier and the cabinet frame was cleared.

(After the ground path was cleared, the noise was significantly reduced.)

  • SRM calibration test procedure was revised to include determinations of signal to noise ratio.
  • SRM discriminator setting procedure was revised to include determinations of signal to noise ratio.

SAFETY CONSEQUENCES:

There are no consequences to the general safety of the public, nuclear safety, industrial safety and radiological safety from this event. The inoperability of SRM B had no significant impact on the public other than not being able to monitor an inadvertent criticality at a very low level in one quadrant of the core.

No actions to reduce the frequency or consequence are necessary.

- 006 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 Infocallects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, 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

REPORTABILITY:

On April 15, 2017, after moving fuel during the current Refueling Outage, it was discovered that Source Range Monitor (SRM) B was inoperable. The SRM B was located in a core quadrant in which fuel was moved. This situation created an event that is reportable under 10 CFR 50.73(a)(2)(i)(B), a condition prohibited by the plant's Technical Specifications.

PREVIOUS EVENTS:

A review of PNPS LERs for the last ten years did not find a similar event as described in this LER.

REFERENCES:

CR-PN P-2017-3541 CR-PNP-2017-3659 CR-PNP-2017-3660 CR-PN P-2017-3773 CR-PNP-2017-3952 CR-PN P-2017-5294