ML19345E094
| ML19345E094 | |
| Person / Time | |
|---|---|
| Issue date: | 11/20/1980 |
| From: | Jensen W Office of Nuclear Reactor Regulation |
| To: | Speis T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19345E096 | List: |
| References | |
| NUDOCS 8012230109 | |
| Download: ML19345E094 (4) | |
Text
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UNITED STATES
[?c, 'i NUCLEAR REGULATORY COMMISSION W ASHINGTON, D. C. 20555
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NOV 2 01930 MEMORANDUM FOR:
T. P. Speis, Chief, Reactor Systems Branch, DSI FROM:
W. L. Jensen, Reactor Systems Branch, DSI THRU:
G. R. Mazetis, Section Leader, Reactor Systems Branch, DSI
SUBJECT:
MEETING MINUTES, ODYN CODE REVIEW
Reference:
Letter from R. Denise (NRC) to General Electric dated January 23, 1980.
Backaround On April 18, 1980, the NRC staff met with representatives of General Electric Co. to discuss our review of the ODYN code summarized in the above letter.
General Electric requested the meeting to appeal the staff positions.
ODYN is the computer code used by General Electric for analysis of certain anticipated transients. The staff Safety Evaluation for ODYN is in draft form and will be issued in about or;a month.
The summary letter presented the staff positions from the draft Safety Evaluation Report which provide for two acceptable prescriptions for the determination of the operating Initial Critical Power Ratio (ICPR). The ICPR is obtained by adding a aCPR value to the GETAB Safety Limit to ensure that in the event of an anticipated transient, a critical power ratio less than the GETAB safety limit will not be obtained. The critical power ratio is tne power at which boiling in the limiting bundle would change from nucleate boiling to film boiling divided by the reactor power.
The GETAB Safety Limit is the critical power ratio for which it is expected that less than 0.1% of the rods in the core will be in film boiling. The GETAB safety limit contains a margin to reflect the uncertainties in the calculations. ODYN is used in conjunction with the SCAT code to calculate aCPR in the method presented by GE.
In the staff's summary letter, Option A provides an interim penalty to be added to the calculatad aCPR to calculate a new higher value of ICPR.
Option B is a statistical approach for the reduction or elimination of margin penalty. The statistical approach would utilize plant data such as control rod scram time data, code uncertainties, power uncertainties and actual transient test data to assure that the GETAB safety limit would not be exceeded with a 955 probability at a 951 confidence level.
GE Presentations GE stated that 't is their belief the above options would lead to excessive additional work and conservatisms that might prevent operating plants from 0U12230 f
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achieving full power.
They cited the conservatisms that are already built into their model for determining the GETAB Safety Limit. They also cited data from sample fuel rods in test reactors indicating that no fuel damage would occur during operation in the film boiling regime for an extended period of time.
The slides from these preseatations are attached.
They requested that the GE prescription for use of ODYN be accepted and suggested that as an alternative they might drop ODYN and instead use the older REDY code for transient analysis.
NRC Resconse The staff stated that the purpose of the meeting was to discuss ODYN and not conservatisms in the GETAB Safety Limit.
The staff then stated six conclusions as follows:
1.
The staff has requested additional transient tests at GE plants over the last two years and to date only the tests at Peach Bottom have been performed.
There is a possibility that the ODYN code has been tuned to match the Peach Bottom tests and additional tests are desirable to confirm the code.
It was noted that the Peach Bottom tests were relatively mild in comparison to the anticipated transients analyzed in Chapter 15 of FSAR's.
Even one additional test would enhance code verification and would perhaps remove some of the penalty of Option A and would enhance the data base for Option B.
2.
In the future the staff will deal more directly with the utilities tc discuss future tests and required changes in Technical Specifications.
3.
We believe Option B in the staff summary letter is clearly defined but we will carefully review the staff safety evaluation before issuance to ensure there is no misunderstanding.
The staff's safety evaluation will also be sent to the utilities for comment with a reference to this meeting.
4.
We believe little additional staff work will be required in the implementation of ODYN and we foresee no enforcement problems.
If requested we will meet with station engineers for each of the affected OL's to get their opinion on enforcing Option B.
Option A requires even less enforcement problems.
5.
In a separate letter we will inform General Electric of a time table for switching from the REDY code to the ODYN code.
6.
After the above time period, the results of the REDY code will no longer be accepted.*
- Unless reviewed for this analysis and appropriate margin is added.
T. P. Speis A discussion followed on the implementation of Option B providing clarification to General Electric.
It was stated that the staff would accept existing data for scram times obtained with existing instrumentation. Each plant would have to show compliance with the data base used in Option B as group rod tests were performed. These tests are already a required procedure.
It was also stated that GE could use nominal values with measured distributions for other ODYN inputs as long as plants can show that there is no basis for rejecting the hypothesis that the data belong to the -same population.
GE Concludina Statements After these clarifications, G.E. outlined the following course of future action, l.
They will re-evaluate Option B with hope of reducing the ICPR and the need for derating certain operating plants.
2.
They will provide a schedule for implementing Technical Specifications revisions 3.
Revised draft Technical Specifications will be provided to the NRC for comment.
4 The impact of Option A on plant operation will be evaluated to determine if an appeal will be made.
5.
G.E. sees no value in future full scale tests without a definite commitmenc by the staff to reduce the Option A penalty.
6.
G.E. believes results obtained using the REDY code are still valid.
The representative from TVA requested more interchange between the NRC and GE on implementation of Option B and future Technical Specification changes.
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Walton Jensen
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Reactor Systems Branch Division of Systems Integration Enclosures 1.
Attendee List 2.
Slide Presentation
ATTENDANCE LIST Name Oraanization Walton Jensen NRC/AB Paul Norian NRC/AB D. W. Radcliffe GE B. C. Morris TVA/Div, Nuc. Pwr.
R. E. Rogers TVA/ Regulatory Suff J. W. Heard YAEC J. W. Goswell Boston Edison J. M. Holzen YAEC J. A. Silady Commonwealth Edison H. J. Diamond Philadelphia Electric Company l
L. F. Rubino Philadelphia Electric Company H. C. Pfefferlen GE Carl G. Ofarrill Southern Company Services J. F. Schardt GE Kris Chitkara Cincinnati Gas & Electric Company G. J. Scatena GE D. F. Ross NRC/DPM T. P. Speis NRC/DPM R. B. Lee GPU Service Corporation G. M. Holahan URC/ DSS H. H. Klopfer GE R. H. Bucholz GE J. W. Wood GE D. F. Fieno NRC/ DSS F. Odar NRC/RES t