ML23068A099

Special Report 2023-01 PAM Report

ML23068A099
Person / Time
Site:	Callaway
Issue date:	03/09/2023
From:	Ameren Missouri, Union Electric Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
Shared Package
ML23068A097	List: ML23068A099 ULNRC-06802, Special Report 2023-01 (PAM Report); Non-Functionality of a Post-Accident Monitoring Instrument
References
ULNRC-06802 2023-01
Download: ML23068A099 (1)

Text

Enclosure to ULNRC-06802 Page 1 of 3 Enclosure Special Report 2023-01 PAM Report

Enclosure to ULNRC-06802 Page 2 of 3 Special Report 2023-01 PAM Report Requirement:

GTRE0021B is the unit vent high range noble gas monitor discussed in Section 16.3.3.4 of the Callaway Plant Final Safety Analysis Report (FSAR). FSAR 16.3.3.4, "Accident Monitoring Instrumentation Limiting Condition for Operation," in particular, requires the unit vent high range noble gas monitor channel to be functional during MODES 1, 2, and 3. If the monitor is declared non-functional during those Modes, Action c of FSAR 16.3.3.4 applies, which states:

With the number of FUNCTIONAL channels for the unit vent-high range noble gas monitor less than the Minimum Channels FUNCTIONAL requirement of Table 16.3-7, initiate the preplanned alternate method of monitoring the appropriate parameter(s) within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and either restore the non-functional channel to FUNCTIONAL status within 7 days, or prepare and submit a Special Report to the Commission within the following 14 days outlining the preplanned alternate method of monitoring, the cause of the non-functionality, and the plans and schedule for restoring the channel to FUNCTIONAL status.

Per these requirements, and due to the extended non-functionality of GTRE0021B, Callaway is submitting this Special Report to the U.S. Nuclear Regulatory Commission (NRC).

Background:

The affected radioactive gaseous effluent monitor, GTRE0021B, has several monitoring functions. However, only the unit vent high range noble gas monitor channel performs the post-accident monitoring (PAM) function of FSAR 16.3.3.4, which is the section of concern for this Special Report.

Callaway Plant declared the unit vent high range noble gas monitor (GTRE0021B) non-functional on February 16, 2023, due to a loss of process flow (process flow displaying zero).

The monitor was not able to be restored to functional status within 7 days (i.e., by February 23, 2023), and thus, this Special Report is required to be submitted within 14 days from that date, i.e., by March 9, 2023.

Preplanned Alternate Method of Monitoring:

An alternate means of monitoring, as required per Action c of FSAR 16.3.3.4, "Accident Monitoring Instrumentation Limiting Condition for Operation," is being performed in accordance with the following procedures:

Alternate sampling cart and calculated unit vent flow:

HTP-ZZ-04150, OPERATIONS OF THE G.A. PROCESS MONITOR SYSTEM This procedure provides instructions for the operation of the General Atomics (GA) process monitor system relating to Radiation Protection activities.

Enclosure to ULNRC-06802 Page 3 of 3 HOA-ZZ-00100, VENTILATION FLOW RATES This reference document provides ventilation flow rates for the unit vent, radwaste vent, and laundry decontamination facility in a series of tables denoting system, fan and the associated ventilation flow rates.

Grab samples:

HTP-ZZ-03006, USE OF AIRBORNE SAMPLING CART This procedure provides the methods to be used in the collection of samples radioactive gaseous effluent, and airborne radioactivity, using the airborne sampling cart.

The plant's Count Room will determine Unit Vent Flow Rate in accordance with HTP-ZZ-04150 on a shiftly basis. The compensatory measures per procedure KDP-ZZ-00013 Appendix 1, EQUIPMENT IMPORTANT TO EMERGENCY RESPONSE MATRIX, are to obtain a grab sample in accordance with HTP-ZZ-03006 and analyze. A backup to grab sampling is the use of Field Team Surveys performed by the on-shift Radiation Protection Technician or Field Monitoring Team. Increased sampling frequency is implemented if there is an indication of increased activity.

Cause of the Non-functionality:

Unit vent flow indication was lost at 16:54 on 2/16/2023. At 21:28 on 2/16/2023 the Count Room Technician reported that flow on GTFI5032, Unit Vent Low Range Flowmeter, was reading zero.

This indicates a loss of process flow to GTRE0021B. A filter train swap was attempted but did not improve flow indications. Since the cause of the loss of flow indication could not immediately be determined, the sample pump was stopped to prevent damage and the monitor was taken out of communication with the RM-11, which is the radiation monitor display system in the Control Room. GTRE0021B was declared non-functional. Action c of FSAR 16.3.3.4 was entered, and procedure HSP-ZZ-00014, Rad Monitor Non-functionality, was initiated to document FSAR compliance with unit vent radiation monitors out of service. The Count Room Technician was contacted to ensure alternate sampling and grab samples were taken to comply with Action c.

Plans and Schedule for Restoring the Instrumentation Channel to Functional Status:

This instrument channel (GTRE0021B) was restored to functional status at 13:50 on 03/03/2023. The Unit Vent Flow Rate indication was restored by cycling power to the mass flow meter processor, which is a sub-system that feeds into the radiation monitor. Alarms continued to be received, however, so time was taken to investigate their cause and get them cleared.

Once proper functioning of the Unit Vent Flow monitor was confirmed, GTRE0021B was declared functional.