ML18031A764
| ML18031A764 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/09/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18031A762 | List: |
| References | |
| GL-84-09, GL-84-9, TAC-R00098, TAC-R00099, TAC-R00100, TAC-R100, TAC-R98, TAC-R99, NUDOCS 8609150075 | |
| Download: ML18031A764 (4) | |
Text
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t UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION BROMNS FERRY NUCLEAR PLANT, UNITS I, 2 AND 3 RELATING TO RESPONSES TO GENERIC LETTER 84-09 ON HYDROGEN RECONBINER CAPABILITY
- 1. 0 INTRODUCTION DOCKET NO. 50-259, 260 AND 296 By letters dated July 2, 1984 and Nay 13, 1986, the licensee provided information to demonstrate that Browns Ferry does not require hydrogen recombiners to control combustible gases inside containment after an accident.
The bases provided were in response to the guidelines suggested in Generic Letter 84-09.
In order to justify that recombiners are unnecessary, the licensee provided an assessment indicating that the only post-accident oxygen generation would be due to radiolysis of reactor coolant, and that such radiolysis would not produce sufficient oxygen to provide a combustible mixture inside containment.
The post-accident oxygen concentration would be maintained below the combustible limit for more than 30 days after the accident.
Additionally, in accordance with Generic Letter 84-09, the following measures have been taken by the licensee:
a.
The Technical Specifications require the plant to shut down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if the containment oxygen concentration exceeds 4 percent; b.
Nitrogen, or the containment atmosphere, is used in all containment pneumatic control systems.
c.
The pneumatic control system inside containment will be modified to eliminate the need for the backup instrument air system when containment integrity is required.
The three units are presently shut down and this modification wi 11 be completed before each unit is returned to power.
d.
A redundant, safety grade Nitrogen Containment Atmosphere Dilution (NCAD) System has been provided to maintain the oxygen concentration below the combustible limit following a LOCA.
It is possible to supply air with the backup air system to the pneumatic control systems inside containment when the nitrogen supply system is unavailable.
As a result of a design modification, an alternate supply of nitrogen to the pneumatic control systems will be provided.
This modification will eliminate the need to use air as a backup pneumatic supply when primary containment integrity is required and, therefore, will eliminate the backup air system as a potential oxygen source.
The 8b09150075 8b0909 PDR ADOCK 05000259 P
backup air supply system is isolated from the pneumatic control system by two check valves in series.
These check valves are held closed by the backpressure exerted in the pneumatic control system.
The pressure is maintained by the fully redundant safety grade nitrogen supply which is considered essential and, therefore',
is considered available throughout a
design basis LOCA event.
The use of check valves to isolate influent lines was within the Browns Ferry original licensing basis
- and, therefore, was not reconsidered as part of this review.
In order to demonstrate complete compliance with the guidance to remove all potential oxygen sources, the licensee should also provide Technical Specifications that limit operation when the nitrogen supply systems to the pneumatic control system are disabled.
These Technical Specifications should be similar to the Technical Specifications that limit operations when the Nitrogen Containment Atmosphere Dilution System is disabled.
Principal Contributor:
P.
Hearn Dated:
September 9,
1986
Re uest for Additional Information Related to Res onses to Generic Letter 84-09 On H dro en Recombiner Ca abi lit for the Browns Ferr Nuclear Plant Units 1
2 and 3
Please prepare Technical Specifications that limit operation when the nitrogen supply systems to the pneumatic control system are disabled.
These Technical Specifications should be similar to the Technical Specifications that limit operations when the Nitrogen Containment Atmosphere Dilutions System is disabled.
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