ML17174A009
| ML17174A009 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Browns Ferry  |
| Issue date: | 06/06/1979 |
| From: | Lainas G Office of Nuclear Reactor Regulation |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17174A010 | List: |
| References | |
| NUDOCS 7909130067 | |
| Download: ML17174A009 (2) | |
Text
MEMORANDUM FOR:
- FROM:
SUBJECT:
ENCLos92 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. ZOM5 T. Ippolito, Chief, Operating Reactors Branch #3, Division of Operating Reactors G. Lainas, Chief, Plant Systems Branch, Division of Operating Reactors BROWNS FERRY UNITS 1, 2 AND 3 - ENVIRONMENTAL QUALIFICATION OF STEAM ~UNTED LIMIT SWITOiES ON MSLIV's {IE BULLETIN 79-01)
In connection with their response to IE Bulletin 79-01, TVA has reported that the stem mounted limit switches on the MSLIV's which provide input to the RPS are not qualified for an accident {e.g. LOCA) environrrent.
(Ref. TVA letters dated February 23, 1979 and March 9, 1979 and Telecon dated May 17, 1979).
TVA has stated that these limit switches need not be en vi ronmenta l ly qualified for an accident en vi romren t for the f o-11 owing
.reasons and, therefore, will not be replaced with qualified switches.
- 1. The switches are not needed to mitigate 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 from 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 provided by TVA and have concluded that the following conditions must be satisfied if the unqualified limit switches are not replaced.
1: An ar.a1ys1s must be provided (or a reference if it has previously been provided) to show that the MSLIV closure input to the P.PS is not -
required to mitigate the consequences of a closure of three or m:>re
- MSLIV's.
Such an analysis does not appear to be included in the FSAR.
7909190()~7*
2
- 2. Schematic diagrams must be provided which show all circuits with inputs from the unqualified limit switches andti'e interposing reloy 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 from the RPS.
{Note:
The isolation relay and circuit must be Class IE).
- 3.
An environmentally qualified method of detennining MSLIV position from the control room must be provided and the indication devices with input signals derived from the unqualified limit switches must be clearly identified with a pennanent tag which:
(l) states that they should not be relied on for position indication except during nonnal operation; and {2) provides a reference to an instrument located in the control room which should be relied on.during transient or accident conditions.* ---
. Please* infonn. the licensee of our position and request that they provide
. the information identified above and make any modifications necessary to satisfy these conditions if they do not elect to replace the unqualified limit switches.
(J _4-;-
~; 'Lainas, Chief
~
- Pl ant Sys terns Branch Division of Operating Reactors
Contact:
E. Butcher, X28077 cc: v. Stello
- 0. Eisenhut R. Vollmer P. Check R. Satterfield G. Lainas
- o. Ton di M. Chi ramal J. Burdo in
~
R. Clark E. Butcher