ML19247A451
| ML19247A451 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/18/1979 |
| From: | Swanson D NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Buck J, Mike Farrar, Rosenthal A NRC ATOMIC SAFETY & LICENSING APPEAL PANEL (ASLAP) |
| Shared Package | |
| ML19247A452 | List: |
| References | |
| NUDOCS 7907310566 | |
| Download: ML19247A451 (2) | |
Text
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May 18, 1979 it
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Atomic Safety and Licensing Appeal Atomic Safety and Licensing Appeal Board Board U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Washington, D.C.
20555 Dr. John Buck Atomic Safety and Licensing Appeal Board U.S. Nuclear Regulatory Commission Washington, D.C.
20555 In the Matter of Virginia Electric and Power Company (North Anna Nuclear Power Station, Units 1 and 2)
Docket Nos. 50-338 OL and 50-339 OL Gentlemen:
The attached Boar.1 notification material regarding the analysis of a single rod drop event in Westinghouse three loop plants is being pro-vided for your information.
This single rod drop is a DNB-liaited transient considered to be a moderate frequency event.
The calculated consequences of this transient, as discussed in the attached memoranda, are dependent upon whether the reactor is being operated in the automatic or manual control mode.
This notification pertains to the analysis of a single rod drop event with the reactor in the automatic control mode.
The consequence of the event as now analyzed by Westinghouse is that the single rod drop could, if the reactor did not trip, create a nominal increase in the overall power level of the reactor (i.e. by a few per-cent). This slight it. crease in power would not be expected to create a turbine overspeed situation, due to the increase in power level of only a few percent over normal power levels, and the existence of two sets of pressure relief valve" and three sets of redundant overspeed control systems that would prevent an overspeed situation.
Nevertheless, there exists a theoretical relationship between the single rod drop event and turbine overspeed, which in turn is a factor in the generation of turbine missiles.
Accordingly, the Board notification information is being 488 275 0%
'g 907 31
. provided because of the potential relationship between the inforcation and one of the issues in the referenced procc.eding.
As noted in the memoranda, the Staff has recommended that for operating reactors, such as North Anna Unit 1, a change be made to tl'e set-point and rate-lag time constant in the negative flux rate trip feature,i:hich would eliminate the referenced consequence of the single rod drop event.
The Appeal Board will be notified when a resolution of the natter has been accomplished.
Sincerely,
/f u
'7/ /
- C 7 Daniel T.
Swanson Counsel for NRC Staff
Enclosure:
As stated cc w/ enclosure:
Service List 488 275