ML19207B492
| ML19207B492 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/12/1979 |
| From: | Ippolito T Office of Nuclear Reactor Regulation |
| To: | Parris H TENNESSEE VALLEY AUTHORITY |
| References | |
| NUDOCS 7908300054 | |
| Download: ML19207B492 (3) | |
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( (,g NUCLEAR REGULATORY COMMISSION A E W ASHINGTON, D. C. 20555
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JULY 1 2 1979 Docket Nos. 50-259 50-260 and 50-296 Mr. Hugh G. Parris Manager of Power Ternessee Valley Authority 500 A Chestnut Street, Tower II Chattanooga, Tennessee 37401
Dear Mr. Parris:
Reference is made to your letters of February 23, 1979 and March 9,1979, and to the conference call with members of your staff on May 17, 1979 regarding stem-mounted limit switches installed on the MSIVs on Browns Ferry Units Nos.
1, 2 and 3.
You have stated that these limit switches need not be environmen-tally qualified for an accident enviroment for the following reasons and, therefore, will not be replaced with qualified switches.
1.
The switches are not needed to mitigata any accident or transient including a fast closure of the MSIV's. No credit has been taken for these limit switches in the analyses provided in the FSAR.
2.
The switches do not have any control function and are isolated fran all control circuits and the RPS by an interposing relay.
3.
The only possible deleterious effect of a failure would be a loss of the position indication derived from the limit switches.
We have reviewed the infonnation which you have provided and have concluded that the following conditions must be satisfied if the unqualified limit switches are not replaced.
1.
An analysis must be provided (or a reference if it has previously been provided) to show that the MSLIV closure input to the RPS is not required to mitigate the consequences of a closure of three or more MSLIV's. Such an analysis does not appear to be included in the FSAR.
2.
Schematic diagrams must be provided which show all circuits with inputs from the unqualified limit switches and the interposing relay isolating the limit switches from the RPS so that we can verify that the switches do not have any safety function and that they are adequately isolated fran the RPS.
(Note: The isolation relay and circuit must be Class IE).
7 90'830 oosi 852 049
Mr. Hugh G. Parris 3.
An environmentally qualified method of detemining MSLIV position fra the control room must be provided and the indication devices with input signals derived from the unqualified litnit switches must be clearly identified with a pennanent tag which:
(1) states that they should not be relied on for position indication except during normal operation; and (?) provides a reference to an instrument located in the control room which should be relied on during transient or accident conditions.
Please advise us by August 1,1979 when you will submit the infonnation requested in 1 and 2 above and your schedule for empleting the action deteribed in 3 above.
Sincerely, I
h, W
Thomas Ippolito, Chief Operating Reactors Branch #3 Division of Operating Reactors cc:
see next page 852 050
'Mr. Hugh G. Parris Tennessee Valley Authority 3-cc:
H. S. Sanger, Jr., Esquire General Counsel Tennessee Valley Authority 400 Commerce Avenue E 11B 33 C Knoxville, Tennessee 37902 Mr. Dennis McCloud Tennessee Valley Authority 400 Chestnut Street, Tower II Chattanooga, Tennessee 37401 Mr. E. G. Beasley Tennessee Valley Authority 400 Comerce Avenue W 10C 131C Knoxville, Tennessee 37902 i
Rcbert F. Sullivan U. S. Nuclear Regulatory Commission P. O. Box 1863 Decatur, Alabama 35602 Athens Public Library South and Forrest Athens, Alabama 35611 852 C\\eI D