ML21335A160

Special Report 2021-02: Accident Monitoring Instrumentation Non-Functional for Greater than 7 Days

ML21335A160
Person / Time
Site:	Callaway
Issue date:	12/01/2021
From:	Ameren Missouri, Union Electric Co
To:	Office of Nuclear Reactor Regulation
Shared Package
ML21335A158	List: ML21335A160 ULNRC-06703, Submittal of Special Report 2021-02: Accident Monitoring Instrumentation Non-Functional for Greater than 7 Days
References
ULNRC-06703
Download: ML21335A160 (1)

Text

Enclosure to ULNRC-06703 Page 1 of 1 Special Report 2021-02 Requirement Chapter 16 of Callaway Plants Final Safety Analysis Report (FSAR) contains requirements relocated from the Technical Specifications. In particular, FSAR Section 16.3.3.4 specifies requirements for accident monitoring instrumentation, which includes the unit vent - high range noble gas radiation monitor (GTRE0021B). The Limiting Condition for Operation (LCO) specified per FSAR 16.3.3.4 requires the accident monitoring instrumentation to be Functional in MODES 1, 2, and 3. With GTRE0021B non-functional, Action "c" applies. It 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."

Preplanned Alternate Method of Monitoring There are two preplanned alternate methods: obtaining grab samples of the unit vent activity and/or gathering data from field monitoring. The alternate method of monitoring currently in place is the first one, i.e., utilizing manual grab samples from the unit vent per procedure HSP-ZZ-00014, "Rad Monitor Non-functionality." If an emergency were to occur, the second method would be applied and accomplished by the field monitoring team in accordance with the Emergency Plan implementing procedures.

Cause of the Non-functional Unit Vent - High Range Noble Gas Monitor During the performance of Job 20503223.500 to perform a channel calibration for the unit vent thermal mass flow transmitter associated with GTRE0021B (i.e., GTFT0021BA), the display screen was found to be non-functional and indicative of a failure of the transmitter function. The cause of the non-functional transmitter was identified to be a failed power supply. As a result, GTRE0021B has been non-functional since 0900 on 11/10/2021. Job 21004207 was generated to initiate repairs.

Plans and Schedule for Restoring the Instrument to FUNCTIONAL status The delay in the return to service for this radiation monitor is due to unavailability of a replacement power supply. The faulty power supply has been sent to a vendor for repair. GTRE0021B will be returned to FUNCTIONAL status when the repaired power supply has been received and installed.

The estimated restoration date for the monitor is 1/7/2022. In parallel, approval of an alternate part for the power supply is being pursued.