ML20133A667

Summary of 961219 Meeting W/Nuclear Energy Institute in Rockville,Md Re Industry Responses to GL 96-06.List of Attendees Encl

ML20133A667
Person / Time
Issue date:	12/26/1996
From:	Stewart Magruder NRC (Affiliation Not Assigned)
To:	Matthews D NRC (Affiliation Not Assigned)
References
PROJECT-689 GL-96-06, GL-96-6, NUDOCS 9701020021
Download: ML20133A667 (23)

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UNITED STATES g

j NUCLEAR REGULATORY COMMISSION C

WASHINGTON, D.C. 20555-0001 o

December 26, 1996 MEMORANDUM T0:

David B. Matthews, Chief Generic Issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation Stewart L. Magruder, Project Manager b tl FROM:

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Generic Issues and Environmental Projects Branch 9

Division of Reactor Program Management Office of Nuclear Reactor Regulation

SUMMARY

OF DECEMBER 19, 1996, MEETING WITH THE NUCLEAR i

ENERGY INSTITUTE (NEI) REGARDING INDUSTRY RESPONSES TO GENERIC LETTER 96-06 On December 19, 1996, representatives of NEI, the Electric Power Research Institute (EPRI), and several utilities met with representatives of the Nuclear Regulatory Commission (NRC) at the NRC's offices in Rockville, Maryland. Attachment 1 provides a list of meeting attendees.

The purpose of the meeting was to discuss (1) the status of industry responses to Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," (2) the NRC responses to questions asked at a meeting with NEI on the same subject on October 29, 1996, and (3) potential long-term acceptance criteria.

During opening remarks by NRC staff representatives, it was noted that copies of several relevant documents were available for reference by the meeting attendees.

These documents included: GL 96-06; Generic Safety Issue (GSI) 150, Rev. 1 (excerpted from NUREG-0933, June 30, 1995); a letter to Mr. Ashok Thadani dated November 8, 1996, from Mr. Roger Reedy; a letter from Mr.

Thadani responding to Mr. Reedy dated December 4, 1996; and a summary of the October 29, 1996, meeting dated November 22, 1996. All of these documents are available to the public.

The NEI representatives began their remarks by stating that licensees are working hard on their responses to the GL.

They stated that some licensees are working tcgether and with EPRI as they develop their operability evaluations.

The NEI presentation material is included as Attachment 2.

The first topic of discussion was a request by NEI for a clarification of tiie answer to a question asked by the industry during the October 29, 1996, meeting. The questior was related to non-safety systems, which penetrate containment that are not required post-accident, and whether it is acceptable y

to allow overstressing and potential pipe yielding in these systems caused by Uy-0 2c, trapped fluid expansion, while declaring containment integrity (Question 11 of I

October 29, 1996, meeting summary). The staff's response to Question 11

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i December 26, 1996 D. Matthews l l

stated that overstressing and potential pipe yielding may be acceptable for such systems as long as containment integrity is assured in accordance with the plant design basis. During the meeting, the staff questioned the reference to non-safety related systems which penetrate containment and 1

whether they are reclassified in the segments penetrating the containment boundary and between the isolation valves.

NEI representatives affirmed that piping in such systems is typically reclassified as safety-related in the segments between the isolation valves.

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The next topic of discussion was the applicable acceptance criteria for piping between containment isolation valves which contains fluid that is subject to thermal expansion.

The industry noted that they believed that the majority of the cases will involve American Society of Mechanical Engineers (ASME) Level D events. The NEI representative asserted that no acceptance criteria exist for this situation and presented an ASME Code Interpretation NI 96-32, dated December 17, 1996, to bolster their argument.

The letter from ASME is included as Attachment 3.

The NEI representative next stated that, based on the response to the ASME Code Interpretation, the industry believes that a strain-based acceptance criteria should be considered by the staff. NEI and EPRI representatives suggested a strain-based criteria equal to approximately one half the uniaxial i

failure strains for carbon and stainless steels. They suggested that piping operability could be maintained with a strain of 10 percent for carbon steel and 25 percent for stainless steel. The staff indicated that it was not prepared to respond during the meeting regarding the acceptability of the NEI/EPRI proposal.

In a teleconference wit'. NEI on December 23, 1996, the staff indicated that there is no regulatory precedent or technical oasis for approving the proposed strain criteria. The staff noted that ASME Code Interpretation NI 96-32 contains language indicating that Section III of the ASME Code does not provide criteria for pipe deformation resulting from exposing isolated sections of ASME Class 1, 2, or 3 piping, containing liquid, which is exposed to an external heat source that causes thermal expansion of the trapped liquid during a postulated Level D event. The staff notes that the ASME Code contains a pressure stress limit for a postulated Level D event. The ASME Code Interpretation NI 96-32 did not address this pressure stress limit.

On the basis of the ASME Code Interpretation NI 96-32, NEI argued that a definition of the acceptance criteria for evaluating the event is necessary.

NEI requested the staff endorsement of the use of strain criteria to evaluate the piping for the thermal expansion of the trapped fluid.

As stated above, the staff believes that the ASME Code does contain criteria that is applicable to the stress produced by internal pressure due to a Level D event. The staff further believes that most licensees have specific load combination criteria specified in the facility FSAR that is applicable to the Loss-of-Coolant Accident (LOCA) or Main Steam Line Break (MSLB) scenarios.

Consequently, the staff is not prepared to endorse a generic strain limit for the GL 96-06 evaluation.

4 December 26, 1996 D. Matthews stated that overstressing and potential pipe yielding may be acceptable for such systems as long as containment integrity is assured in accordance with the plant design basis. During the meeting, the staff questioned the reference to non-safety related systems which penetrate containment and whether they are reclassified in the segments penetrating the containment boundary and between the isolation valves. NEI representatives affirmed that piping in such systems is typically reclassified as safety-related in the segments between the isolation valves.

The next topic of discussion was the applicable acceptance criteria for piping.

between containment isolation valves which contains fluid that is subject to thermal expansion. The industry noted that they believed that the majority of the cases will involve American Society of Mechanical Engineers (ASME)' Level D events. The NEI representative asserted that no acceptance criteria exist for this situation and presented an ASME Code-Interpretation NI 96-32, dated December 17, 1996, to bolster their argument. The letter from ASME is included as Attachment 3.

The NEI representative next stated that, based on the response to the ASME Code Interpretation, the industry believes that a strain-based acceptance.

criteria should be considered by the staff.

• LEI and EPRI representatives.

suggested a strain-based criteria equal to approximately one half the uniaxial failure strains for carbon and stainless steels. They suggested that piping operability could.be maintained with a strain of 10 percent for carbon steel and 25 percent for stainless steel. The staff indicated that it was not prepared to respond during the meeting regarding the acceptability of the NEI/EPRI proposal.

In'a teleconference with NEI on December 23, 1996, the staff indicated that there is no regulatory precedent or technical basis for. approving the proposed strain criteria. The staff noted that ASME Code Interpretation NI 96-32 contains language indicating that Section III of the ASME Code does not provide criteria for pipe deformation resulting from exposing isolated sections of ASME Class'1, 2, or 3 piping, containing liquid, which is exposed to an external heat source that causes thermal expansion of the trapped liquid during a postulated Level D event. The staff notes that the ASME Code contains a pressure stress limit for a postulated Level D event. The ASME Code Interpretation NI 96-32 did not address this pressure stress limit.

On the basis of the ASME Code Interpretation NI 96-32, NEI argued that a definition of the acceptance criteria for evaluating the event is necessary.

NEI requested the staff endorsement of the use of strain criteria to evaluate the piping for the thermal expansion of the trapped fluid. As stated above, the staff believes that the ASME Code does contain criteria that is applicable to-the stress produced by internal pressure due to a Level D event.

The staff

'further believes that most licensees have specific load combination criteria specified in the facility FSAR that is applicable to the Loss-of-Coolant Accident (LOCA) or Main Steam Line Break (MSLB) scenarios.

Consequently, the staff is not prepared to endorse a generic strain limit for the GL 96-06 evaluation.

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a D. Matthews December 26, 1996 a

The staff notes that nonmandatory Appendix F to Section III of the ASME Code contains criteria for inelastic analysis of components for Level D events.

Depending on the licensee's load criteria and the facility code of record, the provisions of Appendix F may be appropriate; however, each licensee may need to assess their situation to determine if a licensa amendment would be necessary.

During the December 19, 1996, meeting, in response to a question from the staff, an industry representative stated that for the vast majority of cases, there are no thermal reliefs in the piping between containment isolation valves.

It was also stated that, regardless of whether thermal expansion of fluid between containment isolation valves was considered in the design of a plant, the industry agrees that it is a safety issue which must be adequately dispositioned.

A short discussion followed regarding whether the thermal stress should be classified as a primary or secondary stress. An industry representative stated that they have been using the bulk containment pressure-temperature curves following a loss of coolant accident as the input to the piping stress calculations.

The industry argued that since the containment temperature peaks within a few hours of the postulated accident and then ramps down, the 4

stress should be considered self-limiting and therefore a secondary stress.

The staff stated that this was not the correct interpretation of the term i

sel f-limiting. After further discussion, it was agreed that the stress is a primary stress.

The next topic of discussion was GSI-150, "0verpressurization of Containment Penetrations." The NEI representative asked the staff to explain the relevance of GSI-150 to the issues raised in GL 96-06. The NEI representative noted that GSI-150 had been placed in the " DROP" category in 1991 by the NRC Office of Research, leading some in the industry to believe that the issue had been resolved. The NRC representatives explained that GSIs are prioritized based on probabilistic risk insights and staff resources. The staff stated that GSIs placed in the DROP category are sometimes reopened based on new information. The NRC staff is considering reopening GSI-150. There was general agreement that the short term resolution of the issues in GL 96-06 should not be tied to GSI-150.

The EPRI representative next presented a sumary of current EPRI efforts to support resolution of the containment fan cooler waterhamer issue and proposed EPRI efforts related to overpressurization of isolated piping sections.

The presentation materials are provided as Attachments 4 and 5.

1 The EPRI representative stated that EPRI is attempting to prove the hypothesis

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that the effect of waterhamer may be mitigated in this situation since the piping is subject to continuous heating and the cold water entering the pipe will be heated to some extent before it contacts the steam voids. The EPRI 1

representative stated that the~ efforts are just getting underway and that it J

appears that the waternamer analysis will be very plant-specific. With regard to the piping overpressurization issue, the EPRI representative stated I

that the presentation material provides very preliminary thoughts and that any j

follow-up work must be approved by the industry. The NRC staff stated that i

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December 26, 1996 D. Matthews the EPRI efforts were interesting but cautioned the industry not to rely on them until they have been fully developed and reviewed.

l The meeting closed with a short discussion of the industry responses to GL 96-06. The industry representatives stated that they expected that all of the responses would be submitted by the 120-day deadline and that some of the responses would probably contain commitments for additional work. The staff l

encouraged the industry to coordinate with each other as much as possible.

l The staff also noted that the responses to the GL should include evaluations of non-safety related systems as well as safety related systems.

i Project No. 689 Attachments: As stated cc:

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i D. Matthews the EPRI efforts were interesting but cautioned the industry not to rely on them until they have been fully developed and reviewed.

The meeting closed with a short discussion of the industry responses to GL 96-06.

The industry representatives stated that they expected that all of the responses would be submitted by the 120-day deadline and that some of the responses would probably contain commitments for additional work.

The staff encouraged the industry to coordinate with each other as much as possible.

The staff also noted that the responses to the GL should include evaluations of non-safety related systems as well as safety related systems.

Project No. 689 Attachments: As stated cc: See next page DISTRIBUTION:

See attached page Document Name: G:\\SLM1\\MSUM1219.961 To receive a copy of this document, indicate in the box:

"C" - Copy without attachment / enclosure "E" - Copy with attachment / enclosure "N" - No co)y 0FFICE PM:PGEB l

C:EMEB C:SPLB.._,l

'SC:PGEB(m Ml1 C:RGIA dor NAME SMagruder*:sw RWessman*

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FAkstulewici~'

DMatthews DATE 12/26/96 12/26/96 124Ed/96 /

12/90/96 12/SQ/96

• See previous concurrence 0FFICIAL RECORD COPY

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l Distribution: Mtg. Summary w/NEI Re Industry Responses to GL 96-06 Dated December 26. 1996 Hard Cony.

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Docket File PUBLIC 1

PGEB R/F OGC ACRS SMagruder j

E-Mail FMiraglia AThadani BSheron TMartin j

RZimmerman GHolahan Glainas JStrosnider RWessman TMarsh DMatthews SMagruder FAkstulewicz GHubbard WLefave 1

CWu GHammer JFair JTatum BWetzel KManoly WLong CBerlinger MMarkley, ACRS I

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NRC/NEI MEETING ON GENERIC LETTER 96-06 LIST 0F ATTENDEES December 19, 1996 l LAM _E ORGANIZATION David Murphy Bechtel Bob Hammersley FAI Roger Hayes Southern Nuclear William Birely New York Power Authority Thomas Wroblewski Wisconsin Electric John Anciaux Wisconsin Electric James Hallenbeck PECO Energy Bill Peebles Sargent & Lundy Skip Denny PEC0 Nuclear John McCann Maine Yankee Jorge del Mazo Pacific Gas & Electric Subhash Khurana Florida Power & Light Glenn Adams Wisconsin Electric Steven Greco Wisconsin Electric Eric May Virginia Power i

David Stellfox McGraw-Hill Nancy Chapman Bechtel/SERCH Barry Sullivan NUS Dave Modeen NEI Kurt Cozens NEI Avtar Singh EPRI William LeFave NRC/NRR James Tatum NRC/NRR Cheng-Ih Wu NRC/NRR John Fair NRC/NRR Gary Hammer NRC/NRR Beth Wetzel NRC/NRR Kamal Manoly NRC/NRR Dick Wessman NRC/NRR Tad Marsh NRC/NRR George Hubbard NRC/NRR Bill Long NRC/NRR Stu Magruder NRC/NRR i

Michael Markley NkC/ACRS l

Attachment I

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GL 96-06 k

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i Presented by Kurt Cozens e

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OBJECTIVES i

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j Industry s'. Js Obtain clarification of NRC 0

response to question asked at the l

Dallas meeting Define long-term acceptance criteria

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INDUSTRY STATUS i

Licensees are developing j

operability evaluations Typical 120 day responses j

- Describe basis for operability

- Discuss actions that will extend past 120 days Evaluation of acceptance criteria (code and regulatory)

Evaluation of need to make modifications EPRI efforts to support GL responses h

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CLARIFICATION REQUEST I

Question 11 (page 6) states, "Over stressing and potential yie! ding may be acceptable for this system as long as containment integrity is assured..."

- Does this mean a system's containment penetration between the two isolation valves can be subjected to an over stress and potential yielding caused by trapped fluid expansion as long as containment integrity and post accident functionality are maintained?

Marginal strain above yield does not impact integrity of the piping system.

i ASME CODE CRITERIA i

i NC-3612.4(a)(3)(e)

" Adequate consiceration shall be given to the control of fluid pressure caused by heating of the trapped fluid between two valves."

ASME Code Interpretation NI 96-32

- Question: Does the ASME Section Ill, Division 1, Code provide criteria for evaluating pipe deformation resulting from exposing isolated sections of ASME class 1, 2, and 3 piping, containing liquid, which is exposed to an external heat source, that causes thermal expansion of trapped liquid during a postulated Level D event.

- Response: No.

l ASME CODE CRITERIA l

(Continued) f l

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l Definition of acceptance criteria is needed l

- A strain based criteria is appropriate l

- Precedence exist ASME Section lil, Appendix F GSI-150 l

Definition of ASME Level D event l

assumed distortion occurs and j

replacement is likely l

SRP, NUREG 0927 (functionality)

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l ANSI B31.1 CRITERIA i

l Acceptance criteria for accident i

conditions are not clear Design pressure is defined as

" maximum sustained operating j

pressure" l

Definition of acceptance criteria is j

needed

- A strain based criteria is appropriate e

i GENERIC SAFETY ISSUE RELEVANT TO GL 96-06 GSI - 150, "Over Pressurization of l

Containment Penetrations"

- Resolved 1995 Priority -- DROPPED

- NRC staff letter dated December 4,1996 Local strains near penetrations may be higher j

NRC staff reassessing GSI-150 technical j

evaluation l

- NRC staff requested to discuss l

Relationship to GL 96-06 i

GSI-150 action plan

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Status of GSI-150 reassessment Basis to use GSI -150 for resolution of GL i

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i CONCLUSION 1

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j A strain basec' acceotance criteria is l

appro ariate for GL 96-06 long-term l

resolution j

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how we, arr tomt December 17,1996 i

Mr. Jack R. Cole Mail Drop PE24 P.0, Box 968 Richland, WA 99552 J

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Subject:

Section M, Division L NC/ND-M21.2; &id Expansion Effects (1995 Edition)

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Your letter dated December 3,1996 1

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File:

N196-32 i

Our understanding of the question and our reply are as follows:

i Quesbon:

Does tfee ASME sostwn III. Division L Code provide criteria for l

evaluating pipe deformation resultin5 roni % isolaW estions of f

i ASME class 1,2, or 3 piping, containing liquid, which is exposed to an external heat source that cauess thermal expenolon of the trapped liquid during a postulated W D cvent?

i Reply:

No.

i RespectfuHy, l

Nathan Lane

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Section mTechnicalInquiry Committee (212) 705 7005 I

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TOTAL P.02

I, EPRl/NPG Proposed EPRl/ Industry Collaborative Efforts to Support Resolution of GL 96-06 Technicalissues Avtr Singh Nuclear Power Group EPRI

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NRC/NEl/ Industry Meeting on GL 96-06 Rockville, MD December 19,1996 j

EPRl/NPG j

Topics i

Current EPRI efforts to support resolution of the Containment Fan Cooler system waterhammer issue Proposed plan to support resolution of the GL 96-06 long term technicalissues SARA 1977VrAbt IDI1 to 3

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EPRl/NPG Current EPRI Efforts Thermal hydraulic analyses of CFCU boiloff during LOCA / LOOP events (GOTHIC and RETRAN).

- timing and extent of voiding

- thermal stratification in the headers

- reduced potential for waterhammer EPRI project on Waterhammer Prevention, Mitigation and Accommodation

- Potential waterhammer mechanisms

- EPRI reports: TR 106438 and NP 6766 k

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SARA i

l EPRl/NPG Generic versus Plant Specific Aspects Prejiminary information indicates vast variability in 3

design and operational characteristics

- Issue resolution is expected to be mostly plant i

specific However, certain CFCU performance related aspects may be oeneric

- Two phase flow and voiding

- Potential waterhammer phenomena SARA So!7VdAH 131995 e i

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i EPRl/NPG Generic Technical Tasks to Support Resolution

1. Gather input data on plant specific design, configuration, and operational characteristics

2. Develop guidelines for realistic assessment of boiling potential and voiding for waterhammer evaluation

3. Perform scaled experiments to generate test data on

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expeded two phase phenomena

4. Validation of analysis tools via experimental data SARA i

EPRl/NPG Summary and Conclusions i

Generic tools exist to analyze and assess the impact of issues identified in GL 96-06 Containment fan cooler systems have plant specific designs Generic phenomena investigations can help plant specific reso!ution Effective resolution can be achieved via industry collaborative effoits SARA

EPRI NPG Overpressurization ofisolated Piping Sections H.T. Tang Avtar Singh Electric Power Research Institute

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NRC/NEl/ industry Meeting on GL 96-06 Washington D.C.

December 19,1996 g- -,,

EPRI NPG Overpressurization ofIsolated Piping Sections Physical Behavior Isolated piping under internal pressure is stressed both in the hoop and axial direction Overpressurization may stress the pipe into plastic state The pipe will expand in the hoop direction along the pipe a short distance away from the two isolated ends Depending on the state of strain and geometric nonuniformity (e.g., boundary ccnditions, thickness variations, etc.), the pipe might balloon at a particular section

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l EPRINPG Overpressurization of Isolated Piping Sections Physical Behavior (continued)

Finite plastic expansion of pipe will lead to pressure reduction The reduced pressure interaction will reach a state of convergence whereby the pipe will likely be stressed without further plastic deformation Nuclear piping is ductile and thus its ultimate behavior is controlled by strain i

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EPRINPG Overpressurization of isolated Piping Sections Strain Criteria Piping performance under overpressurization should a

be evaluated using strain criteria Uniaxial strain limit of carbon steelis > 20% and stainless steel > 50%

- Depending on the state of stress blaxiality/triaxiality, the uniarlal strain limit may be reduced by 40 to 50%

- Piping operability should be maintained with a strain of >10% for carbon steel and > 25% for stainless steel Depending on the state of strain and geometric nonuniformity (e.g., boundary conditions, thickness variations, etc.), the pipe might balloon at a particular section GSI-150 uses strain criteria for evaluation l

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NEI Project No. 689 cc:

Mr. Ralph Beedle Mr. Thomas Tipton, Vice President Senior Vice President Operations and Chief Nuclear Officer Nuclear Energy Institute Nuclear Energy Institute Suite 400 Suite 400 1776 I Street, NW 1776 I Street, NW Washinton, DC 20006-3708 Washington, DC 20006-3708 Mr. Alex Marion, Director Mr. Jim Davis, Director Programs Operations Nuclear Energy Institute Nuclear Energy Institute Suite 400 Suite 400

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1776 I Street, NW 1776 I Street, NW i

Washington, DC 20006-3708 Washington, DC 20006-3708 Mr. David Modeen, Director Ms. Lynnette Hendricks, Director Engineering Plant Support Nuclear Energy Institute Nuclear Energy Institute Suite 400 Suite 400 1776 I Street, NW 1776 I Street, NW 4

Washington, DC 20006-3708 Washington, DC 20006-3708 Mr. Anthony Pietrangelo, Director Licensing Nuclear Energy Institute Suite'400 l

1776 I Street, NW Washington, DC 20006-3708 Mr. Ronald Simard, Director i

Advanced Technology Nuclear Energy Institute Suite 400 1776 I Street, NW Washington, DC 20006-3708 1

Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, Pennsylvania 15230 J

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