ML033440301

MB8939, Draft RAIs for Tle-Conf. Discussion

ML033440301
Person / Time
Site:	Grand Gulf
Issue date:	10/08/2003
From:	Bhalchandra Vaidya NRC/NRR/DLPM/LPD4
To:	Byrd R Entergy Operations
vaidya B, NRR/DLPM, 415-3308
References
TAC MB8939
Download: ML033440301 (2)

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Grand Gulf, MB8939, Draft RAIs for Tle-Conf. discussion.

10/8/03 9:28AM Bhalchandra Vaidya BKV@nrc.gov Recipients entergy.com RBYRD (RBYRD@entergy.com)

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Bhalchandra Vaidya - Grand Gulf, MB8939, Draft RAls for Tle-Conf. discussion.

Page 1 From:

Bhalchandra Vaidya To:

RBYRD@entergy.com Date:

10/8/03 9:28AM

Subject:

Grand Gulf, MB8939, Draft RAls for Tle-Conf. discussion.

Draft RAls from SPSB( PRA) and SRXB ( Reactor Systems) are listed below. I am trying to set a call with Grand Gulf next week. Let me know your convenient dates and times. I am on leave on Tuesday, 10-14-2003.

FROM MARIE POHIDA - SPSB:

The licensee did not provide any risk assessment that justifies why eliminating the RHR Automatic Isolation on Low RCS Level (Level 3) when the Cavity is flooded and the transfer canal gates are removed is acceptable.

Based on assessment of past events, the staff has found the automatic isolation of RHR on low RCS level to significantly reduce the risk of loss of RCS inventory events in BWRs.

In summary, the licensee considered the worst case drain down event - loss of RCS through the RHR mini flow line to the suppression pool. This worst case drain down scenario would reduce the pool level to the reactor flange in approximately 4 /2 hours. The licensee is arguing that sufficient time is available before reaching the automatic isolation set point for the operator to take action.

To ensure that the risk of removing the automatic isolation is acceptable, the staff needs to ensure that the likelihood that the operator fails to take appropriate action following a draindown event is minimized Therefore, The licensee needs to document:

(1) the sources of RCS level instrumentation that will be operable during this time period (2) the RCS level alarms that will be operable during this time period (3) the frequency that the operators will be directed by procedures to check these alarms during this period (4) the time to drain to the RCS to the reactor flange based on the worst case drain down path AFTER the first available RCS level alarms would be received.

(5) Items one and two should be added in Technical Specifications to ensure compliance.

FROM TANYA FORD - SRXB:

1. The licensee stated that the purpose of the proposed change is to allow certain outage-related activities to be performed efficiently without an undue burden on operations personnel resources and to minimize the risk of spurious or unintended shutdown cooling isolations. What outage-related activities are to be performed during this time? What activities, if any, are to be performed below the reactor vessel?

2. How would maintenance staff performing the above activities under the reactor vessel be protected in the case of a drain down event or a leakage from the botton of the reactor vessel without the automatic isolation function operable. What current procedures, training of staff, and/or instrumentation controls are used to detect leakage under the reactor vessel? Will additional training of staff be required and/or current procedures revised to compensate for the elimination of the automatic isolation function to protect maintenance staff from excess exposure if a draindown event was to occur?

Thanks.

Bhalchandra Vaidya NRR/DLPM Licensing Project Manager, PDIV-1 Grand Gulf Nuclear Station, Unit 1 301-415-3308 M/S: 0-7D1