ML20031D716
| ML20031D716 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 10/09/1981 |
| From: | Litton F NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| Shared Package | |
| ML20031D662 | List: |
| References | |
| NUDOCS 8110140054 | |
| Download: ML20031D716 (7) | |
Text
10/09/81 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the flatter of
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HUUSTON LIGHTING AND POWER COMPANY Docket No. 50-466 (Allens Creek Nuclear Generating Station, Unit 1)
HRC STAFF TESTIMONY OF FELIX B. LITTON REGARDING IGSCC/ WATER HAMMER
[Doherty Contention 44]
Q.
Please state your name and position with the NRC.
A.
My name is Felix B. Litton.
't am a Senior Materials Engineer, Materials Engineering Branch, Division of Engineering, Office of Nuclear Regulation, U.S. Nuclear Regulatory Commission.
I have previously sub-mitted a statement of my professional qualifications and have testified in connection with other contentions in this proceeding.
Q.
Please state the scope of your responsibilities for the review of the Allens Creek application for a construction permit.
j A.
I am responsible for the review and evaluation of _a 2 sections of the Applicant's Preliminary Safety Analysis Report for which the Materials Application Section of the Materials Engineering Branch has primary review responsibility. This responsibility includes a review of the materials specified for fabricating Class 1, 2 and 3 components and the procedures which will be used to preserve the integrity of the compo-l nents.
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Q. What is the purpMe of your. testimony?
A.
The purpose of qy testimony is to address the Doherty Contention No. 44 which states:
Intervenor contends the ACNGS design is unsafe against pipe break accidents at pipe cracks initiated by water hammer.
Further, analysis of such an event is required to indicate what must be done to cope with accidents caused by large deep cracks in the recirculation pipes such as those discovered at the Duane Arnold Energy Center in 1978. According to the 1978 NRC Annual Report, 100 incidents involving water hammer have occurred in both PWR's and BWR's. A recent Advisory Connittee on Reactor Safeguards (ACRS) report to the Commission (August 16,1979), indicates there is need for more adequate inservice inspection of piping including feedwater and steam supply piping, residuai heat removal system, ECCS, containment sprr.y system, and service water systems in nuclear plants such as ACNGS.
Intervenor contends:
a.
Applicant should be required to analyze and determine what additional measures may be taken to mitigate the consequences of water hammer on system piping listed above, and b.
Applicant should be required to analyze and determine what additional measures may be taken to mitigate the consequences of water hammer on system piping listed above which has suffered the various types of cracking ob-served in NUREG-0531, and NUREG-75/067, and c.
Applicant should be required to analyze and determine what additional measures can reduce the probability of an event where water hammer causes a cracked pipe to break.
Q.
Have you read the Applicant's Motion for Summary Disposition on Intervenor Doherty's Contention No. 44, relating to intergranular stress corrosion cracking and water hammer, and the documents attached thereto, including the affidavits of Louis A. Gunther and' Walter F. Maleo?
l A.
Yes. The affidavits of Mr. Gunther and Mr. Malic identify the materials specified for the construction of the piping systems of reference in the contention.
The identified materials are not sus-ceptible to intergranular stress corrosion cracking. Hence, the Allens Creek facility will be cons.tructed to minimize the occurrences of intergranular stress corrosion cracking in the systems referred to by Mr. Doherty.
Q.
Is the information submitted by the Applicant consistent with the Staff recommendations to minimize the occurrence of intergranular stress corrosion cracking in stainless steel piping systems?
A.
Leaks and cracks in the heat-affer zones (HAZ) of welds that join stainless steel piping and associated components in boiling water reactors (BWR) have been observed during the past several years. As a result two Task Action Plan activities were identified as Unresolved Safety Issues:
A-10. "BWR Hozzle Cracks" and A-42, " Pipe Cracks in Boiling.;ater Reactors." Both of the issues identified in the Task Action Plans have been resolved by the Staff.
Q.
Will you describe the resolution of these issues?
A.
The occurrences and potential resolutions of the pipe cracking issues were published in 14UREG-75/067, " Technical Report - Investigation and Evaluation of Cracking in Austenitic Stainless Steel Piping of Boiling Water Reactor Plants" and NUREG-0531 " Investigation and Evaluation of Stress-Corrosion Cracking in Piping of Light Water Reactor Plants." The implementation of the recommendations for resolution of Task Action Plan A-10 and A-42 were published in NUREG-0619 and NUREG-0313, Revision 1, respectively.
i,
Q.
Is the Applicant in compliance to the recommendations of NUREG-0619 and NUREG-0313. Revision I?
i A.
Yes. The Applicant is in canpliance with the recommendations of eluREG-0619 and 14UREG-0313, Revision 1, for the Allens Creek facility.
NUREG-0619, "BWR Feedwater Nozzle and Control Rod Drive Return Line Nozzle Cracking," April, 1980, recommends the redesign and inservice inspection of feedwater nozzles to reduce the occurrence of thermal fatigue. The new GE triple-sleeve-sparger design has been adopted by the Applicant for
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the Allens Creek facility for the feedwater nozzles. NUREG-0313. Revision 1, October,1979, recommends the use of materials in the BWR piping systems which are not susceptible to intergranular stres3 corrosion cracking.
In the event susceptible materials are used, an augmented inservice inspection program is required. The Applicant has specified materials not susceptible to intergranular stress corrosion cracking in the Feedwater, Main Steam, I
Residual Heat Removal, Emergency Coolin2 Wuter Systems. The Applicant has also agreed to conduct an augmented inservice inspection progra'.n in compliance with tne recommendation of NUREG-0313, Revision 1, on the piping systems not fabricated with material susceptible to intersreaular stress corrorson cracking.
Q.
Contention 44 postulates the force of water hammer superimposed on a piping system already structurally weakened by intergranular stress corrosion cracking. What is the Staff's position regarding water hammer?
A.
In 1977 the Staff initiated a review of the occurrences of water hammer events in all the fluid systems that could have an impact on plant safety. The objective of th', review was to identify the cause of the i
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.I water hammer event and recommend the action needed to reduce the likeli-hood of the event.
HUREG-0582, " Water Hammer in Nuclear Power Plants,"
July,1979, describe the results of this review.
After this study was initiated and prior to the publication of NUREG-0582, water hanmer was incorporated in Task Action Plan A-1, " Water Hammer" as an unresolved Safety Issue, which is described in NUREG-0371,
" Approved Task Action Plans for Category A Generic Activities." Task Action Plan A-1 is scheduled for resolution by December,1982, prict to the issuance of an Operating License to the Allens Creek facility.
Should the resolution of the Task Action Plan A-1 identify either design factors or operating conditions not incorporated in the Allens Creek facility, the Staff will require implementation of the recommendations to reduce the frequency and minimize the severity of the event.
The Staff's current position on the water hammer event is described in HUREG-0582 and Section 3.9.2 of the Standard Review Plan. The recom-mended approach at the design stage to minimize the impact of water hammer include (1) increase valve closure time, (2) piping layout to pr;clude formation of water slugs in the steam lines and vapor pockets 11 water lines, (3) snubber and pipe hanger usage, and (4) system desigr to judicial use of vents and drains. The Standard Review Plan specifies that vibrational and dynamic effects testing should be conducted during the initial startup and preoperational test program.
The ASME Boiler and Pressure Vessel and ANSI Pressure Piping Codes require the designer to consider impact forces caused by either external or internal conditions. These Codes do not provide guidance as to the f
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load type, magnitude pulse shape or the type analysis tnat should be performed.
y.
Are water hammer events continuing to occur in operating BWRs?
A.
It is my understanding that water hammer events are continuing to occur, but that damage is principally damage to pipe hangers and snubbers.
4 Even though the Applicant is and will be taking appropriate measuret to reduce the likelihood of the occurrence of water hammer events and is complying with Staff requirements to reduce the occurrence of IGSCC, is not water hammer nore likely to cause a pipe break if a large deep crack should exist?
A.
Possibly. However, the occurrence would also depend on the location of the crack relative to the loadings resulting from the water hammer event.
Q.
Why then does the Staff conclude that licensing of plants su '1 as ACHGS can be continued?
A.
We stated in Appendix C, Section C-5, of the Supplement No. 2 to the Safety Evaluation Report, NUREG-0515, March 1979, that since the probability of failure due to water hammer is low and the consequences of postulated water hammer induced accidents would be adequately limited by currently installed redundant engineered safety features, continued operation and licensing of plants can proceed with reasonable assurance that the health and safety of the public is protected while task A.1, Water Hammer, is being conducted.
Subsequent implementation of the resolutions of Tasks A.10 and A.42 is expected to further reduce the likelihood of IGSCC. Water hammer events continue to occur and may occur
even after implementation of the resolution of Task A.1 However, a net reduction in probability of a water hammer induced failure of a pipe with preexisting crack due to IGSCC is expected L';.esolution of these three tasks.
Finally, since Supplement No. 2 to the SER was published in March,1979 there has been no change in the Staff's conclusion that the consequences of water hammer induced accidents would be limited by re-dundant engineered safety features.
Q.
In summary, are you in support of the Applicant's program?
A.
The program initiated by the Applicant is basea on an accurate understanding of the cause of intergranular stress corrosion cracking and the prevention of the water hammer event. The implementation of the actions comply with the recommendations of the Staff to minimize the occurences of other phenomena addressed by the Doherty Contention 44.
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