ML20204B968
| ML20204B968 | |
| Person / Time | |
|---|---|
| Issue date: | 10/26/1978 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| Shared Package | |
| ML19246A285 | List: |
| References | |
| TASK-OS, TASK-RS-604-5 REGGD-01.128, REGGD-1.128, NUDOCS 7811150215 | |
| Download: ML20204B968 (4) | |
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BACKGROUT1D Ai10 VALUE/ IMPACT ASSESSMEtlT 0F PROPOSED REVISI0tt 1 TO REGULATORY GUIDE 1.128 (RS 604-5),
"INSTALLATI0fl DESIGN AtlD IflSTALLATI0tl 0F LARGE LEAD STORAGE BATTER FOR fiUCLEAR POWER PLANTS"
Background
Regulatory Guide 1.128, " Installation Design and Installation of Large Lead Storage Batteries for Nuclear Power Plants," is being revised to respond to cements received on the guide.
General All of the changes made in the revision to the guide, except for the following, were made to clarify the intent and do not involve a substan-tial change frcm the previous version.
Significant Change with Basis and Value/Imoact' a.
Change Regulatory Position C.5, item' f, has been changed by replacing
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" hydrogen detectcr sensor (s) and instruments" with " ventilation air flow sensor (s) and alarm (s) in the control recm".
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Basis Coments received during the public coment period indicated that the use of hydrogen detectors in battery rooms was not necessary.
The ressons given were that the ventilation system is required to maintain the ' ydrogen concentrations below 2% by volume at n
any location in the battery area and because R.G.1.120 has deleted the recuirements for hydrogen detectors and has included a requirement for an alarm in the control rocm for indicating a loss of ventilation in the batt.ery recm.
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Value/ Impact, R.G. 1.128 -
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Basis -(continued) 1 The scope of R.G.1.120 (" Fire Protection Guidelines for Nuclear Power Plants") includes, as part of its coverage, fire protection in the battery rocm.
However, in, addition to requiring fire pro-
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tection, the IEEE Standard, Section 4.2 (" Nuclear Power Generating Station Class 1E Batteries") requires that the Class 1E battery be protected in part, from "... explosions..."
The basis for requiring the detection of hydrogen accumulation, even with the requirement for alarming in the control room due to loss of ventilation (motor-
' trip), is still valid regarding an undetected malfunctioning venti-lation system.
A reduction in air flow due to partial vent blockage
. or reduction in motor RPM due to mechanical (defective bearings) or electrical (partially shunted field winding) defects would allow a potentially hazardous condition to exist.
Therefore, air flow supervision, such as an air flow detector (s) in the battery venti-lation exhaust duct with control rocm alann would provide continuous surveillance of a potentially hazardous batte,y byproduct (hydrogen) as a result of mai.ntaining the required level of battery capacity to power the Class 1E DC system.
Therefore, the neec for hydrogen accumulation detection represents a surveillance criterion for.the Class 1E DC power. sources.
In addition, based on I&E reports of six operating plants, hydrogen monitoring was found to be nonexistent.
Some plants performed, at the request of the NRC, hydrogen measurements using portable survey
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Value/ Impact, R.G. 1.128 b.
Basis _ (continued)
' meters (hydrogen detector explosameter) and reported the findings were negative.
In addition, there was no actual hydrogen measurement data. recorded for review or reference at any of the six plants.
Further, there were no records indicating concentration levels during plant start-up to verify the adequacy of the design of the ventilation sy. stem to keep the hydrogen accumulation below the 2%
j limit as required.
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Based on the above it appears that there is a need to prevent hydrogen accumulation; the need to monitor hydrogen accumulation is less apparent.
Since the ventilatign system is required to
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prevent hydrogen accumulation from reaching 2% by volume at any-location in the battery area, then monitoring the air flow of the l
ventilation system, such as by with alarms in the control room would I'
provide a more direct means of detecting a malfunctioning ventilation i
system and potentially hazardous hydrogen buildup.
This along with the initial hydrogen survey during installation (Freshening charge)
I should be performed to verify that the ventilation design for the installation meets the design criteri acth initially and throughout its operation.
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- Value/ Impact, R.G. =1.128.
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Value/Imoaet-I, This change.is an improvement in the regulatory position in that o
it provides a more practical means of monitoring hydrogen accumu-l-
lation.and-brings the guide into agreement with current regulatory practice.
Therefore, no impact in cost, schedule delay or other aspec'a of. the Regulatory process is anticipated.as; a. result of including. this revised regulatory position.
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Backfitting Recomendations i
No additional backfitting is recommended on this guide since the above provisions are presently being required of all operating plants.
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