ML20206S275

Summary of 980218 ACRS Thermal Hydraulic & Severe Accident Phenomena Subcommittee Open Meeting in Rockville,Md Re Review of RES Program in Area of thermal-hydraulic Phenomena in Support of ACRS Planned Rept to Commission

ML20206S275
Person / Time
Issue date:	03/09/1998
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-3095, NUDOCS 9905210086
Download: ML20206S275 (8)

Text

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. PTE F ILTJ 20  % db' 1 %i l ii (Q2 CERTIFIED BY:

hs.{NOidlibSd Date Issued: 3/9/98 T. S. Kress - 3/31/98 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS THERMAL HYDRAULIC AND SEVERE ACCIDENT PHENOMENA SUBCOMMITTEE SUBCOMMITTEE MEETING MINUTES

-NRC OFFICE OF NUCLEAR REGULATORY RESEARCH THERMAL-HYDRAULIC RESEARCH PROGRAMS j FEBRUARY 18, 1998 '

ROCKVILLE, MARYLAND INTRODUCTION The ACRS Subcommittee on Thermal Hydraulic Phenomena held a meeting on  !

February 18, 1998 with representatives of the NRC Office of Nuclear Regulatory Research. The purpose of this meeting was for the Subcommittee to review the Office of Nuclear Regulatory Research's (RES) program in the area of thermal-hydraulic (T/H) phenomena in support of the ACRS planned report to the Commission on the NRC safety research program. The entire meeting was cpen to  ;

public attendance. Mr. P. Boehnert was the cognizant ACRS staff engineer and l Designated Federal Official (DF0) for this meeting. There were no written  ;

comments or requests.for time to make oral statements received from members of  ;

the public. The meeting was convened by the Subcommittee Chairman at 8:30 am,  ;

December 18, 1997, and adjourned at 6:17 pm that day.  !

i ATTENDEES ACRS Members /ACRS Consultants:  !

T. Kress, Chairman I. Catton, Consultant M. Fontana. Member V. Schrock, Consultant D. Powers, Member N. Zuber, Consultant R. Seale, Member P. Boehnert DF0 G. Wallis, Member Princioal NRC-RES sneakers:

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F. Eltawila' S. Smith J. Uhle J. Kelly V. Housseau Opr[ g l

There were about 5-10 other members of the public in attendance at this meeting. A listing of those attendees who registered is available in the ACRS office files, Public participation during this meeting was limited to the

. presentations by the 'above named industry representatives.

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T/H;and S;A. Sub.,Mtg. .2 Febr'uary 18.-1998 L iThe presentation slides and handouts _.used during the meeting are attached to l <the 0ffice Copy of these Minutes. The presentations to the Subcommittee are

. Summarized below. ,

. INTRODUCTORY PRESENTATIONS - OPEN SESSION Chairman's Comments

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T. Kress,. Subcommittee' Chairman convened the meeting and asked that the.

L y Consultants provide commentsL on the items to be discussed during this meeting.

' Consultants' C e nts s' * -Dr? Catton. . A number of lessons learned with regard to the use of TRAC and RELAPS for modeling of AP600 accident analyses leads to the L ' conclusion that RES needs to' perform a critical and focused evaluation

.of the' Agency's user needs with. regard to code development. Reliance on one code for all T/H evaluations is a mistake. The ACRS recommended L formation of a NRC Code Users Group: I cannot find evidence that the l Group exists..or has met with RES. Its.not clear that-TRAC will meet the

.needs'for a. modular code. Agrees.that a T/H systems code is necessary, i .but certain issues may require use of a CFD-type code (s).

l s Dr.' 7uber - Asked of RES has a. User Need request from NRR to develop the L TRAC updated code. Questioned'whether TRAC will have a user constituency. Concerned that RES's priorities are askew. As an example he opined that neither NRC, nor the industry, has an adequate containment systems code to support T/H analyses of the AP600 Passive

' Containn:ent' System.

L 's . Mr. Schrock Disappointed that RES has elected to go forward with a L

short-term fix to the T/H code. Believes that there should be a.long-range code' development plan.

s-  : Dr. Wallis.- The TRAC and RELAP5 codes are dinosaurs. " Cross-breeding" L- them to produce a new species of dinosaur is not productive.

m Dr. Seale - With regard to the concerns of Drs. Catton and Zuber on containment code deficiencies, the issues of stratification and fluid  :

mixing will be of concern for the future. Analysis of severe accident phenomenaLinvolves examination of competing natural driving forces.  ;

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T/H and S.A. Sub. Mtg. 3 )

February 18, 1998 These type of analyses don't' lend themselves to adequate evaluation by i

" fixed up" one-dimensional T/H codes.

Dr. Eltawila indicated that the above comments have merit. He said that he needs time to correct the errors of the past with regard to the management of the RES T/H research Program. I NRC-RES PRESENTATIONS 1

Discussion Tonics '

1 The Office of Nuclear Regulatory Research made the following presentations as ,

noted below:

.A. Overview of Rx and Plant  !

Systems Branch Research i

+ F. Eltawila. NRC-RES B. Thermal-Hvdraulic Code Consolidation l

Update

+ J. Uhle. RES C. Code Unarades and Thermal-Hydraulic-Research

+ J. - Uhle l

0. Status of Graohical User Interface (GUI) Develooment i

+ S. Smith. RES E. Couo11no of 3-D Soatial l Kinetics Code to T/H Code l

+ V. Housseau, RES

-F. Rod Bundle Heat Transfer Research- ,

+ J. Kelly RES G. Concludino Remarks

+ F. Eltawila The centerpiece of the RES T/H program effort is the code consolidation / code improvement effort. Subcommittee discussion centered on RES plans to consolidate the capabilities of its T/H codes into one code (making use of the-TRAC-P platform), and to make some short-term improvements, e.g., modernize

-the architecture, minimize the " User Effect", upgrade to near real-time performance.-and add ~3-D" kinetic capability. Other major T/H research activities noted included development and addition to the NRC (T/H) Data Bank.

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T/H and S.A. Sub. Mtg. 4 February 18, 1998 and initiation of a Rod Bundle Heat Transfer Program to improve the reflood modeling capability of the upgraded TRAC code.

SUBCOMMITTEE COMMENTS AND CONCERNS L

Subcommittee Members and Consultants noted the following significant comments l and raised the following concerns during the meeting discussions

i a With regard to the capability of RES .to model Flow-Accelerated l

Corrosion, the Subcommittee indicated that there is a problem here. Mr.

Eltawila said he would pass this concern along to the appropriate RES

! Division (Division of Engineering).

m Professor Schrock opined that RES needs to take a broader look at the capabilities existing in the university community with regard to seeking solutions to pressing problems.

m Dr. Wallis indicated that RES should provide a statement of the goals and uses_for the new revised TRAC-H code. He also urged RES to explore installation of a more flexible or advanced form of modularity into  !

TRAC-M than seems to be currently envisioned.

i a- Dr. Wallis recommended that the Subcommittee hold a meeting to review i the results of RES's first attempt to modularize TRAC-M. Dr. Uhle  !

indicated that the RES schedule calls for the first BWR module component I (jet pump) to be completed in approximately four months.

a With regard to the Institute of Thermal-Hydraulics. RES noted that peer i review of the projects, as necessary, is performed by members of the i

Institute. Dr. Zuber indicated that such peer review should be performed by individuals not affiliated with the Institute to avoid concerns with conflict of interest. .

a The Subcommittee expressed skepticism that RES's approach to revising the interfacial area transport equation will be of much use. RES indicated that this is a difficult problem, but the effort being l expended is of low level; further, if the tack being pursued is not l bringing results, it will be abandoned.

m Mr. Schrock stated that RES should not make use of so-called " modified correlations" for its code modernization program. Use of such L

' 3 T/H and S.A. Sub. Mtg. 5 i Februarylb.1998 i.

correlations is wrong from both a scientific and ethical standpoint.

RES agreed, and noted that such correlations will not be used.  !

e In response to Drs. Catton and Zuber. RES noted that a new reflood model is needed for the following reasons: (1) licensees are moving to higher i peak power levels which will result in plants becoming reflood limited with regard to the ECCS models:-(2) NRC needs a more accurate code to be able to perform confirmatory analyses of licensee's best-estimate LOCA codes; and, (3) the reflood model in TRAC is poor and needs to be replaced.

m In response to Dr. Zuber. RES noted that a report detailing completion

.of the first nine of 16 tasks (including the top /down and bottom /up scaling analyses for the test facility) associated with the Rod Bundle Heat Transfer Program will be available for peer review by the first of September, 1998.

SUBCDMMITTEE CAUCUS - DPEN The following comments were made relative to the meeting discussions:

Dr.: Catton - RES seems to be lacking a top-down approach to the code modification program. He is still looking for a convincing argument that a single T/H code will address all issues of concern to the NRC.

Dr. Zuber - His chief concern is the need for RES to address the issue of developing a code.that will adequately address T/H modeling for containments.

He also would like to see one person put in charge of the code development

~ activities. He also questioned the need for large T/H system codes: what is needed are fast-running flexible codes.

Mr. Schrock - Will provide his comments in his written report to the Subcommittee.

Dr. Powers -'Believe the RES Program is technically suburb. It is well organized and dovetails with the Commission's charge to develop the technical expertise of the staff.

o Dr. Seale - Agrees with Dr. Power's comments. Impressed with the knowledge I and composure of the newer RES staff Members. He has more confidence in the quality of.the issue analysis, based on today's presentations.

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February 18, 1998 Dr. Fontana - Work is of high quality. RES should focus the work on developing'an ability to analyze a spectrum of accidents, not just the large-break LOCA given the move to a risk-based reactor safety approach.

Dr. Kress - RES's approach for code consolidation appears reasonable and appropriate. A full top /down approach was not performed relative to the code modeling needs, but RES did a listing of issues that they believe need to be addressed.

The Chairman requested that the Consultants provide written reports to the Sub committee in 3-4 weeks time.

SUBCOMMITTEE FOLLOW ON ACTIONS The Subcommittee will hold a meeting in 4-5 months time to track the progress of the RES code consolidation program. The information obtained at this meeting will be factored into the Committee's discussion of a planned Report to the Commission on the Agency's safety research program - to be held during its 450th Heeting. March 5-7. 1998.

FOLLOW UP ACTIONS RES Action Items RES took the following action items as a result of discussions during the above-noted agenda items:

a RES will provide the Subcommittee copies of the Minutes of the Agency Code Users' Group meetings.

m In response to Dr. Wallis's request for a delineation of success criteria with regard to the T/H code consolidation and improvement  !

t.ffort, RES will provide a letter listing these criteria.

m RES will provide a listing of the shortcomings in its current T/H code suite and how the consolidation effort will address these shortcomings.

s RES will provide a document that details its approach to the code modularity issue.

m RES will provide the results of its literature search associated with development of an improved model for phase separation at Tees.

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LT/H and S.A. Sub.'Mtg. 7 February-18.,1998

.m' Dr. J.' Kelly will provide a copy of his Paper on development of a near-wall subcooled boiling model that was presented at-last year's CSNI Meeting.

• a: In response-to Drf Catton's' request, RES will provide model. development

Letter Reports.for. the four areas of the TRAC-M code that are being upgraded: interfacial area transport, subcooled boiling at low ,

' pressures.- phase separation at Tees, and, rod bundle heat transfer.

a RES will provide a copy of the Proceedings of the 1997 WRSM Information

Meeting-(which contains Papers on the RES Code Consolidation Plan and the incorporation of.~3-D" neutron kinetics into the TRAC and RELAP5 f

codes) to Mrh P. Boehnert for transmittalito the Subcommittee.

= RACKGROUND MATERIAL PROVIDED TO THE SUBCOMITTEE PRIOR TO THIS MEETING 4

IL Memorandum to the Commission from J. Taylor, EDO.' Subject. Thermal-

_ Hydraulic Research Plan, dated September 6, 1996..

2. Memorandum to T. Kress. ACRS, from I. Catton,.ACRS Consultant. Comments

, on'Dr.:L. Shotkin Report: " Lessons Learned from the NRC T/H Computer Code Development and Application", unpublished report, July 1997.

3. Memorandum to M. W. Hodges. RES, from L. Shotkin, RES. dated December 16,11997,

Subject:

Report on Lessons Learned: Final Version,.

4. SCIENTECH Report: " Code Consolidation Issues Related to the Numerics of the TRAC-B~and TRAC-P Codes B. Aktas and'S. Lucas, dated September 11, 1997..

L5 SCIENTECH Report: "BWR Stability Modeling with NRC Current Generation Thermal Hydraulic System Codes", S. Lucas. B. Aktas. M. Straka, L.

Ward,' dated October 9.-1997.

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. 6. Memorandum, dated February 4, 1998, from L. Ward, SCIENTECH, to D.

L :Ebert..NRC,1 transmitting SCIENTECH Report: "A Plan for Consolidation of TRAC Codes", B.;Aktas, dated August 11, 1997.

7. . Purdue University Report, "The Implementation of Three-Dimerisional Spatial; Kinetics 1n the TRAC-B Code". T.J. Downar and P. Turinsky. dated January 31, 1997.

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T/H and S.,A. Sub. Mtg., 8 February 18.:1998

'8; Purdue University Report - to be added.

9. . Los Alamos National Laboratory Report. TRAC-P Validation Test Matrix

.(Draft). E.D. Hughes and B.E. Boyack dated September 5. 1997. Revision 1.0.

10. Report. " Application Program Interface Document for the Modernized i Transient Reactor Analysis Code (TRAC)". J. Mahaffy. Pennsylvania State University and B. Boyack. Los Alamos National Laboratory, Draft, dated Detober 13. 1997. I

11. Los Alamos National Laboratory Report. LA-UR-97-3026. " Software Design Implementation Document for TRAC-H Data Structures". S. Jolly-Woodruff.

0gden Environmental and Energy Services. J. Mahaffy, Pennsylvania State l University. P. Giguere. J. Dearing. B. Boyack. Los Alamos National Laboratory, dated July 1997.

NOTE: Additional details of this meeting can be obtained from a transcript of this meeting available in the NRC Public Document Room. 2120 L Street.

Washington, D.C. 20006. (202) 634-3274, or can be purchased from Ann Riley &' Associates. LTD., 1250'I. Street. Suite 300. Washington. D.C.  !

20005. (202)842-0034.  !

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