ML20054E620
| ML20054E620 | |
| Person / Time | |
|---|---|
| Issue date: | 06/28/1982 |
| From: | Palladino N NRC COMMISSION (OCM) |
| To: | Udall M HOUSE OF REP., INTERIOR & INSULAR AFFAIRS |
| Shared Package | |
| ML20054E621 | List: |
| References | |
| NUDOCS 8206130066 | |
| Download: ML20054E620 (2) | |
Text
.
, ga cq UNITED STATES
+
[
"o NUCLEAR REGULATORY COMMISSION O
f WASHINGTON, D.C. 20656
\\...../
C']
[T June 28, 1982 c
The Honorable Morris K. Udall Chairman, Comittee on Interior and Insular Affairs United States House of Representatives Washington, D.C.
20515
Dear Mr. Chairman:
In response to your letter of May 26, 1982 concerning the U.S. Nuclear Regulatory Commission's (NRC) press release covering the Loss of Fluid Test (LOFT) Anticipated Transient Without Scram (ATWS) test, I would like to provide the following supplemental information.
Since LOFT is only a small, partially-scaled pressurized water reactor (PWR), the results from LOFT experiments cannot be applied directly to a commer-cially sized PWR (or a boiling water reactor (BWR)).
Because of these atypicalities and scaling effects in LOFT, the data from LOFT are used in assessment of computer codes used by the NRC and the regulated indus-try; the codes are then scaled up for application to a large PWR.
For the ATWS test performed on LOFT, the pressurizer relief valve and plant safety relief valves, which are responsible for overexposure control, were sized to provide the scaled flow rate expected in a generic PWR. Howdver, the NRC staff has not drawn the conclusion that the LOFT ATWS test demonstrates that for all plants opening of the pressure relief valves will provide adequate pressure control.
For example, I
licensing assumptions may require the assumption of nuclear core param-l eters (e.g., moderator temperature coefficient) more conservative than that actually present during the LOFT test.
~'
Since the complex computer codes used to predict reactor response to transient conditions are a collection of models developed from separate experiments, their operation as a whole needs to be evaluated against a systems test.
Programs like LOFT are important because they provide a data base for the evaluation of these computer codes.
Throughout the LOFT program the NRC has been careful to point out that LOFT is not a demonstration plant. Unique ' atypical features of LOFT prevent us from making generalized statements based on LOFT test results about how all PWRs would respond to an ATWS event. An accurate predic-tion with computer codes of the response of LOFT to a transient condition can develop confidence in the predictions made by the same codes for large PWR response.
8206130066 }
NJ
The Honorable Morris K. Udall.
Since LOFT is a scaled PWR, the results of the ATWS test are not directly applicable to a BWR.
Detailed and quantitative studies using facilities representative of BWR designs are needed. We have a trilateral program with the General Electric Company and the Electric Power Research Institute for the study of BWR ATWS events in the scaled BWR Full Integral Systems Test Facility during the next two years.
The ATWS event has been under study for many years. LOFT provides an important tool for addressing the ATWS questions concerning procedures for dealing with the event and the ability to predict the system conditions, should the event occur. Specific to the latter, all PWR vendors and PWR owners groups have been invited to demonstrate their predictive capabilities by calculating the second LOFT ATWS test, L9-4, scheduled for September of this year. After the test has been performed, the code predictions will be compared with the test data. The procedures which will be followed will provide a valid method of assessing computer code capabilities.
Further information on the implications of the LOFT ATWS tests will be available later this year.
~ We hope that this response clarifies the record. While we believe the press release is factually correct, we understand your concern and regret any erroneous impression that might have resulted from the press release on that test.
In the future, all press releases covering LOFT test results will reiterate the point that LOFT is not a demonstration reactor and that unique atypical features of LOFT prevent us from making generalized statements, based on the results of a LOFT test alone, about how all PWR's would respond to a tested event.
Please let us know if you have further needs for information in this area.
Sincerely, gggf:'
1 --
Nunzio J. Palladino Chairman cc: Manuel Lujan, Jr.
k f
9