ML20127D346
| ML20127D346 | |
| Person / Time | |
|---|---|
| Issue date: | 08/14/1992 |
| From: | Ward D Advisory Committee on Reactor Safeguards |
| To: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| References | |
| REF-GTECI-106, REF-GTECI-NI, TASK-106, TASK-OR ACRS-R-1485, NUDOCS 9209140253 | |
| Download: ML20127D346 (3) | |
Text
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!I NUCLEAR REGULATORY COMMISSION ACRSR-1485 t
n-I ADVISORY COMMITTEE ON REACTOR SAFEGUARDS PDR 8
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r August 14, 1992 i
Mr. James M. Taylor Executive Director for Operations U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Taylor:
' SUBJECT.
PROPOSED RESOLUTION OF GENERIC SAFETY ISSUE 106, " PIPING AND THE USE OF HIGHLY COMBUSTIBLE GASES IN VITAL AREAS" During the 387th and=388th meetings of the Advisory Committee on Reactor Safeguards, July 9-11 and August 6-8, 1992, we reviewed the NRC staff's-preposed resolution of Generic Safety Issue 106 (GI--
.106), _" Piping and - the.Use of Highly combustible Gases in Vital Areas." ;Our Subcommittee on. Auxiliary and Secondary Systems also
-reviewed this~' matter during its meeting on July 8, 1992.
During this-review, we had the benefit of discussions with representatives of the_ NRC staff and its contractor and of the documents referenced.
-The: proposed-resolution deals-with the piping and use of combustible gases, principally hydrogen, within nuclear power plant buildings. ' _ Storage : facilities l external to plant buildings are lbeing dealt with.by.a new separate licensing issue.
Hydrogen is stored usually in large quantities, and used in both boiling water reactor (BWR) _ and pressurized. water reactor (PWR) units.
The
-concern is that a large release-of hydrogen may-lead-to fires _or explosions that could_ jeopardize safety. Although scoping analyses
- reported _in the Regul'atory Analysis (NUREG-1364) indicate that the rink is generally small, detailed analyses fer some PWRs have shown tnat certain corrective measures may be justifiable under the
.Backfit Rule.
For the selected BWRs' the analyses showed that corrective measures were not necessary.
The~ -staf f isl intending to ; implement the proposed resolution by
- issuing a generic-letter to inform all licensees and applicants of.
the-findings. _Only-affected PWR' licensees'and applicants (i.e.,
!those-who find: corrective measures are necessary) are requested to respond,-but no new -staff requirements or-positions are being
. imposed.
The response will-require an evaluation which may be performed separately or as a-part-of the IPE or IPEEE.
The staff resolutiondoes not cover. hydrogen water chemistry' installations
.for__BWR1 units _or. liquified petroleum gas installations for PWR-or BWR~ plants..These are being treated as a separato Licensing Issue identified.as LI-136.
l 9209140253 920814 b
PDRO ACRS l
!R-1485-
'PDR-3
t Mr. James M. Taylor 2
August 14, 1992 We have the following comments concerning the proposed generic letter:
1.
The letter should apply to both BWR and PWR units.
Otherwise, the hydrogen distribution system for a BWR main generator will
-net receive an evaluation.
Further, a BWR turbine building may contain safety-related equipment.
2.
The letter should point out that-the turbine building evaluation should include consideration of the effects of hydrogen detonations on the physical separation barrier wall (including penetrations such as doors) between the turbine building and adjoining
- reactor, control, or auxiliary buildings.
It is not clear that this (:onsideration was included by the NRC staff in deciding to exclude BWR units from the evaluation and response requirements of the letter.
A similar detonation vulnerability consideration should apply to separation barriors (e.g.,
fire barriers) within PWR auxiliary buildings.-
- 3.
The letter should indicate what preoperational and periodic testing provisions and requirements should apply when the
-evaluation takes credit for the functioning of excess flow-check valves or other active isolation provisions.
4.
The letter'should provide-guidance on dealing with hydrogen fires.
Our concern is that extinguishing a hydrogen fire could result in the accumulation and possible detonation of the hydrogen.
If thesp ::omments are appropriately addressed in the generic letter, we would agree with the NRC staff that-NUREG-1364 provides a satisfactory basis for the resolution of GI-106 and that the proposed generic letter constitutes-a suitable implementation of the resolution.
We would like to review the final revision of the generic letter before it is issued.
As part.of the GI-106 effort to arrive at resolution, a study of hydregen combustion and detonation was done by INEL.
This study is currently in draft form and is under peer review.
The study yielded the shock loadings on concreto-walls as a function of distance from.the ignition point and amount of hydrogen involved.
- The. shock loading was used by INEL and its contractor, RPK Structural Mechanics consulting, to establish separation distances needed to prevent unacceptable damage to the walls.
The staff and its contractors are to be commended for a fine analysis of a difficult problem.
We recommend that the draft report describing the effort be released as soon as possible so that it can benefit
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r Mr. James M. Taylor 3
August 14, 1992 those who must make decisions about severe accident containment loading.
Sincerely, i
David A. Ward Chairman
Reference:
Memorandum. dated April 3,-1992, from Warren Minners, Office of Nuclear Regulatory
- Research, for Raymond F.
- Fraley, ACRS, transmitting resolution package for review,Lincluding:
(a)
U.C.
Nuclear Regulatory Commission, NUREG-1364, " Regulatory Analysis for the Resolution of Generic-Issue J.06:
Piping and the Use of Highly Combustible Gases in Vital Areas" (b)
Generic Letter to Licencees and Applicants,
Subject:
Request for Information Related to the Resolution of Generic Issue 106, " Piping and the Use of Highly Combustible Gases in Vital Generic Letter 29-XX.
Areas, _" Pursuant to 10 CFR 50.54 (f) l (c)-
W. W. Madsen,'D.
H'.
Van Haaften, EG&G Idaho, Inc., and R. P.
I-Kr.nnedy, RPK Structural Mechanics consulting, EGG-SSRE-9747,
" Improved Estimates of Separation Distances to Prevant Unacceptable Damage to Nuclear Power Plant ~ Structures from Hydrogen Detonation for Gaseous' Hydrogen Storagei" December-1991 I
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