ML20116K704
| ML20116K704 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 07/15/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20116K705 | List: |
| References | |
| NUDOCS 9608150184 | |
| Download: ML20116K704 (1) | |
Text
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o j discussed in Section 3.1 above for the LOCA signal.
This design was reviewed and approved by the Staff as documented in Section 8.3.1 of the Safety Evaluation Report, NUREG-0831, dated September 1981, for GGNS.
The licensee stated that, in accordance with the GGNS system design, it is possible that an EDG started as a result of a LOOP signal could trip due to some engine or generator protective trip because, as previously noted, protective EDG trips are not bypassed by a LOOP signal.
It is also possible that this trip could result in the actuation of a generator lockout.
In this instance, local operator action would be required (i.e., resetting lockout) prior to the EDG restarting and/or resequencing onto the bus following a subsequent signal (either emergency or non-emergency).
For emergency starts, a
local operator action would only be required if a generator lockout protective y
trip had previously actuated.
The staff has also been concerned that a possible fault on the offsite system could cause a lockout of the ESF bus or could trip the EDG itself, which would delay the EDG's response to an emergency condition.
The licensee stated that while one could postulate a grid or bus fault that could actuate an EDG protective trip or lockout, any delay in the EDG response time should be considered acceptable because of the:
less critical nature of EDG start / load times for LOOP, low probability of subsequent events occurring following the initial i
LOOP, and procedural requirements that would tend to minimize EDG response times as discussed in the licensee's application.
The procedure for testing EDGs i
has an operator in the room where the local EDG parel is during the test and this would minimize the operator response time to EDG trip or lockout.
The licensee stated that it has not done an exhaustive review of relay l
actuation for an almost unlimited number of possible sequence of events and/or scenarios. The approach taken by the licensee was to confirm the possibility that an EDG lockout could occur, assume that the lockout actuated, and then determine whether this resulted in an unacceptable condition.
The licensee l
also did not attempt to quantify the frequency of the actuation of the lockout relay; however, the licensee stated, based on its experience of operating the EDGs in a similar configuration when performing SR 3.8.1.3 on at least a monthly basis, that the likelihood of such an event is low.
The licensee also stated that a LOOP, unlike a LOCA, does not present an immediate challenge to fuel cladding integrity, reactor water level control, or to the containment, as demonstrated by the bounding 4-hour Station Blackout coping analysis contained in UFSAR Appendix 8-A.
The licensee further stated that, if there has only been the loss of offsite power or an individual bus fault, an LOCA has also not occurred, it is not necessary that the EDG respond in the same manner as for the LOCA; therefore, there would be sufficient time for the operator to recover an EDG from a lockout or trip if plant conditions warranted such action.
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