IR 05000409/1984009

Safety Evaluation Supporting Util 850208 Proposed Installation of Two Check Valves in Series in Sample Line to Improve Capability to Isolate Containment Atmosphere from Environ,Per Insp Rept 50-409/84-09

ML20154M808
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	03/10/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20154M800	List: IR 05000409/1984009 ML20154M796
References
NUDOCS 8603140491
Download: ML20154M808 (2)

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SAFETY EVALUATION BY THE ,

0FFICE OF NUCLEAR REACTOR REGULATION LACROSSE BOILING WATER REACTOR (LACBWR)  :

DOCKET NO. 50-409 t SHUTDOWN CONDENSER SAMPLE LINE

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, Introduction i As a result of the SEP review of containment isolation systems at LACBWR, i several corrective actions concerning administrative controls, procedures .

l and locking devices for valves were identified (NUREG-0827 Section 4.21). '

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During the region's verification of the licensee's actions, the staff

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identified an additional containment isolation issue, which is discussed in Inspection Report 50-409/84-09 dated October 5, 1984. The licensee ,

proposed corrective actions in a letter dated February 8, 198 (

Discussion I The shutdown condenser, located inside containment, provides a heat sink ,

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, when the reactor is isolated from the main condenser. Steam from the i main steam line passes through the tube side of the shutdown condenser where it is condensed by evaporating water on the shell side. The steam t

generated in the shell is exhausted to atmosphere, through a non-isolable vent line. A sampling line (1/2") is connected to the shell side to allow the water to be sampled. Two manual valves are provided on this Ifne,

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which are locked closed (with independent verification) except when a

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sample is in progress. The sample is taken inside containment and the

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manual valves can only be cot. trolled locally. The shutdown condenser is sampled twice per month and after use to ensure maintenance of high i purity water such that the tube heat transfer characteristics are not

! degrade Should an event occur that releases steam to the containment while a sample is in progress, the individual perfoming the sampling may be unable to reclose the manual valves before leaving the containment. If the containment

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pressure exceeds the head of water in the sample line, a direct path from the .L

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1 containment atmosphere to the shell side of the shutdown condenser and thus -

to the environment would exis Evaluation .

In response to the staff's concern, Dairyland Power Cooperative (DPC)

proposed to install two check valves in series in the sample line. This'

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arranqement would permit samples to be drawn, by opening of the two (existing) ,

manua' valves, but the check valves would prevent backflow of air through i the line even if the manual valves are not close , 1 As noted above, the two manual valves would normally provide the isolation

function. The check valves will enhance the capability to isolate the  ;

containment from the environment by providing additional barriers. The i l modifications proposed by the licensee will provide an isolation boundary

between the containment atmosphere and the environment should an accident ,

occur during the limited time periods while sampling is in progrc.. ,

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Conclusion The staff concludes that the proposed modifications, in conjunction with the existing valving and administrative controls, provide acceptable isolation for the shutdown condenser sample lin Principal Contributors: E. McKenn Dated: March 10, 198 .

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