ML20031D678
| ML20031D678 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 10/09/1981 |
| From: | Fields M Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20031D662 | List: |
| References | |
| NUDOCS 8110140012 | |
| Download: ML20031D678 (3) | |
Text
10/09/81 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICEhSING BOARD In the Matter of HOUSTON LIGHTING & POWER COMPANY
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Docket No. 50-466
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(Allens Creek Nuclear Generating
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Station, Unit 1)
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NRC STAFF TESTIMONY OF.MEL B. FIELDS RELATIVE TO SUPPRESSION P00L SWELL
[Doherty Contention 5]
Q.
Please state your name and position with the NRC.
A.
My name is Mel B. Fields.
I am employed at the U. S. Nuclear Regulatory Connission as a Containment Systems Engineer in the Contain-ment Systems Branch.
I have testified previously in this hearing on Board Question 48, Compliance with GDC 50; Board Question 9, Bypass Leakage; and Board Question 4A, Combustible Gas Control.
l Q.
What is the purpose of this testimony?
A.
The purpose of this testimony is to respond to Doherty Conter.-
tion 4.
Q.
What does Doherby Contention 5 allege?
l A.
Doherty Contention 5 states as follows:
l' In the event of blowdown, loss of Loolant, reactivity initiated or other accident, the location of the Control Rod Drive Mechanism Hydraulic Unit as plannes in ACNGS, as well as the Traversing In-Core Probe makes these two systems vulnerable to suppression pool uplift. There are no Mark-III containment systems in operation today, and no full-scale tests l
have been done to guard against this possibility.
Petitioners contend plant is endangered in the event such accidents destroy these systems when they are needed.
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.. Q.
Is the nature and behavior of pool swell phenomena well enough understood and quantified to the extent that conservative pool dynamic load criteria can be defined for the control rod drive hydraulic control units (HCUs) and the transversing incore probe (TIP)?
A.
Yes. The pool dynamic load criteria for Mark III containments at the construction permit (CP) st.19: were reviewed at the GESSAR Prelmini-nary Design Approval (PDA) stage (SER published in December,1975; last Supplement published in June,1977).
The staff concluded at that time that the pool snell loads were sufficiently defined for plants at the CP stage.
Q.
Has the staff been actively reviewing the Park III pool dynamic load definitions since the conclusion of GESSAR PDA review?
A.
Yes. Afditional tests were performed by GE since the review of GESSAR PDA to better define certain pool load phenomena (chugging, conden-sation oscillation and multi-vent effects). Tests were also conducted to better define the safety / relief valve (SRV) loads. The staff has been reviewing the revised pool dynamic loads under two generic approaches.
Task Action Plan A-39, " Determination of Safety / Relief Valve (SRV) Pool Dy-namic Loads and Temperature Limits" was established to review the discharge phenomena of SRVs for all BWR containments. This review examined the am-plitude reduction and Monte Carlo phasing techniques proposed by GE to re-duce the SRV load definition and concluded that these proposed methodologies are acceptable. A NUREG on this topic (NUREG-0802) will be issued in Novem-ber of this year.
Pool swell loads, which is the issue of concern in this contention, are a result of a design basis Loss of Coolant Accident (1.0CA).
The LOCA-related pool dynamic loads are being reviewed under Task Action
e Plan B-10, " Behavior of BWR hark III Containments" for which I am the task manager. Our review of the finalized load definitions is not complete at this time although most of the generic Mark III design specifications for the LOCA-related pool dynamic loads have been accepted by the staff. A 3
NUREG on this topic will be issued in February of 1982. The staff's basic concern is with the pool swell velocity specification and its effect on the impact loads on structures above the pool. Although our evaluation is not yet completed, the staff is confident that the changes, if any, to the de-sigi load criteria will be minor and easily accommodated by plants at the CP stage.
Q.
Are SRV loads combined with pool swell loads for structural analy-sis of components that couid be iraacted by the rising pool?
A.
No. Although GE specifies that structures are to be analyzed for dynamic loads associated with a safe shutdown earthquake simultaneous with a LOCA and the actuation of an SRV for conservatism, SRV actuation concurrent with pool swell is not specified for components that
- uld be affected by pool swell. To justify this assumption, GE has provided analysis to the staff that shows there are no mechanisms whereby one or more SRVs can actuate fol-i lowing onset of a LOCA and has provided arguments to show the single fai?ure criterion should not be applief for this situation because lof the extremely
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low probability (less than 10 per year) of an SRV actuating during the pool swell loads. The staff has examined GE's arguments and concurs that there
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are no mechanistic considerations that could cause an SRV to actuate because of a LOCA and also agrees that the required time interval (about 1 second) for an SRV to accidently open is so small as to remove from consideration of a l
single active failure of a SRV roncurrent with pool swell.
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