ML20043D800

Comments on ACRS Subcommittee on Thermal Hydraulics Meeting on 900424 Re BWR Flow Instability Issues.Nrr Needs to Review Instability Envelope Proposed by BWR Owners Group,Evaluate Containment Bypass & Potential for Fuel Damage

ML20043D800
Person / Time
Site:	LaSalle
Issue date:	05/07/1990
From:	Lisa Sullivan LOS ALAMOS NATIONAL LABORATORY
To:	Catton I Advisory Committee on Reactor Safeguards
References
ACRS-CT-1971, N-6-90-678, NUDOCS 9006110183
Download: ML20043D800 (3)

Text

. - __ _. __ _ _ - . . - . . _- . ___ _

lN S&//@f i

@b bbhh Los Alamos National Laboratory c=: M 7,1990

==m=mm N 90-678 Los Alamoen.hmuaxico. A7 SAL..>..... mmm MS K557 ,

mmc = (505)reptace ,

FIS: replace  :

l l

Engineering & Safety Analysis r ~ ~ ~t ' ' ., , , ,

7 .. . , .

p Dr.1. Catton g 1 0 1996 l

US Nuclear Regu'.atory Commission ,

1 Advisory Committee on Reactor Safeguards  % . :. .

e. e e "'"

Washington, DC 20555

SUBJECT:

Consultant Report for BWR Flow Instability Meeting On April 24,1990, the Advisory Committee on Reactor Safeguard's (ACRS) '

subcommittee on Thermal Hydraulles met on boiling water reactor (BWR) flow instability issues. Below are my major conclusions and recommendations developed from this meeting.

BWR Flow Instability Analytical Capability ,

The current code capability developed by NRC research is contained in about five computer programs. No single code has all the models that have been identified as being important to accurate prediction. The method being used is to add correction terms to the HIPA code based on calculated results from more complex codes. These corrections include such items as 3D neutronics effects and multiple channel effects, i If NRC feels this is an important problem, Research should select a code or codes to do  :

these analyses, and a complete set of analytical models should be included. I believe that this is warranted. NRR needs to review the instability envelope being proposed by the BWR owners' group, evaluate containment bypass, evaluate the potential of L effects on ATWS analysis, and evaluate the potential for fuel damage. Independent assessment of these issues should be performed using an integrated code.

La Salle.2 Plant Calculation Results were presented from the BNL Plant Analyzer, GE's TRACG, and the La Salle 2 data My conclusions were that both ce;ia need to be reviewed because of l 9006110183 900U0 DESIONATED ORIGINE

" fb EC199I" au= 3, M3974- k"

' Dr. Catton May 7,1990  !

N 6-90-678  !

their lack of agreement with data. Again, this should not be considered as a chance to do code development but should be in context as it relates to the licensing issues such as potential fuel damage, effects on ATWS, and the BWR Owners' Group plant i operation modifications. -l l

BWR Owners' Group Long-Term Solutiona 1 in the BWR Owners' Group's Stability Committee report titled " Licensing Basis for Long-Term Solutions," three solutions were developed with a fourth presented in the meeting. I did not completely review this document but did develop some  !

comments as I read it, which follow. ,

• It appears that no hardware modifications were considered as "permaneni" l solutions. Although these would potentially be more expensive, they also  ;

could be better long term solutions and cover other issues than operations.

l'lant classes have been defined for the possible solutions From discussion in the meeting, operating procedures, balance of plant and other plant-specific items were defined as being important. Considering these dcves it make the on set prediction plant-speelfic? .

It was not apparent what the conse:vatisms are in the approach and how much has been included. 'Ihis approaches uses only code and data to form  !

the limits of the instability region. Therefore, I believe it is important to know the limitations of both.

Suggested approaches used an operator warning leading to a scram. I believe it is critical to know what the overall effect and trip frequency of this system could be. '

Proposed solutions use several methods to determine the regional or local power. Specifically, how the power is determined and responsiveness are critical information. From the details provided, how the power is  :

determined is not known.

Probabillstic Risk Assessment (PRA)

{

The BWR Owners' Group report suggested several long-term solutions,(these plans were discussed in the meeting). I believe a PRA should be performed, including the proposed solution, and the benefits it offers and potential difficulties should be '

examined. It should be clear that the benefits outweigh the difficulties before the

~

'. Dr. Cctton 3- May 7,1990

~

N-6 90-678 long term solutions are implemented. A concern is what effects are there of the automatic scram be implemented vs providing a clear warning to the operator with no automatic scram. l LAPUR and FABLE Comparisons -

Oak Ridge . National Laboratory (ORNL) is performing a comparison of the  ;

LAPUR (NRC) and FAULE (GE) computer codes. I believe this is important work because of the reliance on codes in the BWR Owners' Group long term solutions in determining the boundaries. This work should be extended in comparison to ,

experimental data and determimng the uncertainties. It also will be important to know the accuracy that FABLE offers in setting the boundaries.

If you have any questions or comments on my comments and recommendations, please call me.

Sincerely, "kad )b. fluo L. H. Sullivan LHS/js l Cy: CMR-4, MS A150 N 6 File l

l j

t i

. , . . - .