ML20028C433

Responds to IE Bulletin 78-03, Potential Explosive Gas Mixture Accumulations Associated W/Bwr Offgas Sys Operations. Operation & Maint Procedures Adequate to Ensure Proper Operation within Sys Design Parameters

ML20028C433
Person / Time
Site:	Cooper, 05000000
Issue date:	03/23/1978
From:	Pilant J NEBRASKA PUBLIC POWER DISTRICT
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20027A594	List: ML20028C411 ML20028C420 ML20028C424 ML20028C428 ML20028C431 ML20028C433 ML20028C435 ML20028C437 ML20028C443 ML20028C446 ML20028C449 ML20028C451
References
FOIA-82-545, REF-SSINS-6820 IEB-78-03, NUDOCS 8301100135
Download: ML20028C433 (2)

Text

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March 23, 1978 U~ i Mr. E. Morris Howard, Director U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011 Subj ect : IE Bulletin No. 78-03 Fotential Explosive Gas Mixture Accumulations Associated With BWR Off Gas System Operations

Dear Mr. Howard:

The subject bulletin has been reviewed and the following response ad-dresses each of the five (5) items re'ferenced in the bulletin.

1. A review of the operation and maintenance procedures has been completed and the subject procedures are considered adequate to insure proper operation within the design parameters of the systed and to prevent inadvertent actions which might cause ignition of the mixture of gases in the off gas piping.

2. The ventilation systems associated with the spaces and areas through which the off gas system piping containing an explosive mixture of gases pass have been evaluated. All areas, with the exception of one (1) piping chase, are large volumes and in the event of a total loss of ventilatio,n, natural circulation of the air within the space would mitigate an off gas leak long enough for station operation personnel to provide corrective action. In the event of low dilution steam flow, the off gas system will auto-matica11y isolate.

3. A review is being conducted of the piping chase identified in item 2 to determine if changes should be made. There are monitors in the other areas identified which will indicate the presence of off gas containing hydrogen. This monitoring equipment has proven acceptable in detecting previous off gas system leakage.

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' Mar'ch 23, 1978 Page Two

4. The installed loop seals associated with the off gas piping drain to a sealed sump which is vented to the elevated release point. In the event of a high off gas radiation alarm and/or a no flow alarm from the off gas dilution fans, the total loop seal drain system is isolated. A surveillance procedure provides a semi-annual check to insure the loop seals are not plugged.and a monthly surveillance procedure adds water to the loop seals. After a pressure transient in the off gas system, the loop seals are filled.

5. The operation, instrumentation, surveillance and abnormal proce-dures have been reviewed and are considered sufficient to provide adequate guidance to the operating staff to respond promptly to off gas system explosions.

We feel we are very conscious of potential problems with explosive gas mixture accumulations as we have previously sustained two occurrences at our station. These occurrences were reported under reports RO-50-298-75-32 and RD-50-298-76-1. The actions taken after these occurrences are also included in these reports.

If you have any further questions on this subject, please contact us.

Sincerely, ,

M J. $ . Pilant Director of Licensing and Quality Assurance *

/db cc: U.S. Nuclear Regulatory Commission Of fice of Inspection and Enforcement, Division of Reactor Operationc Inspection ,

Washington, D.C. 20555 s

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