ML20207A367
| ML20207A367 | |
| Person / Time | |
|---|---|
| Issue date: | 08/06/1986 |
| From: | Hopenfeld J Office of Nuclear Reactor Regulation |
| To: | Allen C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20207A169 | List:
|
| References | |
| FOIA-86-678 NUDOCS 8611100237 | |
| Download: ML20207A367 (2) | |
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MEMORANDUM T0: Cardis Allen G)45' Safety Program Evaluation Branch l
Division of Safety Review I and Oversight FROM: Joram Hopenfeld Reactor Systems Branch Division of Reactor System Safety
SUBJECT:
REVIEW 0F ALPHA-MODE FAILURE STUDY, JULY 22, 1986 '
This is in response to your requests for comments regarding the subject meeting.
GENERAL The analysis presented by Professor Theofanous is based on numerous arbitrary assumptions which in several significant instances are inconsistent with experimental observations and industrial experience.
The papers preserted are at best useful as an educational tool for the ellucidation of scFe of the complexities cf steam explosions. Considerable additiorici technical justification and peer reviews would be reovired however, to render this study sufficient credibility to support any NRC policies invc1ving steam explosions:
SPECIFIC
- 1. It was net clear that the flow chart (Part 1) employed in this study would yielo results which are different and better than the old methodologies employec six years ago by Corradini and Swenson and two years ago by Berman. One cannot help but ask the question why Professor Theofanous is reinventing the wheel.
- 2. Insufficient justification or rationale was provided for the premise that the geometry, and initial conditions employed bound all other physically i possible or experimentally observed conditions (e. g., multiple explosions, delayed explosions, stratified contact, different particle diameter, distorted core barrel geometry etc.)
- 3. No justification was provided that coarse initial prer.ixing is the necessary condition for steam explosions. Professor Theofanous stated that the stratified contact mode is not credible.
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- 4. Fragmentation and mixing during the explosion and expansion process were recognized for over twenty years as the major problem in predicting the energy partition from steam explosions. The study ignores this issue ,
completely without providing any technical justification.
- 5. During the short term expansion the model neglects the variation in dersity of the non participating water . This assumption is physically incorrect considering the high bubble pressures (1000 MPa).
- 6. Professor Theofanous stated that the compressibility of the slug was not important. In other words inertia loading would give the same results as acoustic leadings. Considering the fact that in acoustic loading the bubble liquid interface would move as soon as the pressure is applied while its motier would be relatively slow in inertia loading, it is reasonable to expect different time constants for the two cases. As a minimum .an explanation should be provided why the energy partition in Figure 18 is insensitive to compressibility.
- 7. Professor Theofarous statea that large-scale steam explosion experiments are needed. He also stated that his premixing calculations could be used in reverse to establish the required experimental initial conditions.
The stated purpose of these experiments was to remove any doubts about his prer.ixing calculations. The calculations to date using 2, 5 and 10cm melt drops are not sufficient to bound the experimental initial conditions.
CONCLUSIONS A brief review cf the proposec study has been conducted and was found to be war. ting.
A peer review, similar to the one assembled for the LANL study, should be conducted to provide a more detailed technical evaluation of this work.
Joram Hopenfeld Reactor Systems Branch Division of Reactor System Safety DISTRIEUl:0N:
SUBJ CIRC CHRON BRANCH R/F LShotkin BMorris MErnst Dross JHopTiffeTd DSolberg
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