ML20038B738
| ML20038B738 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/30/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8112090064 | |
| Download: ML20038B738 (4) | |
Text
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o TENNESSEE VALLEY AUTHORITY CHATTANOOGA..?ENNESSEE 374ot 1100 Chestnut Street Tower II November 30, 1981 8 ((
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Director,of Nuclear Reactor Regulation 4
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Att,antion:
Ms. E. Adensam, Chief
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Licensing Branch No. 4 8
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i Division of Licensing 43 U.S. Nuclear Regulatory Commission
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Dear Ms. Adensam:
l In the Matter of
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Docket.Nos. 50-327 l
Tennessee Valley _ Authority
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50-328
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In your October 29, 1981 letter to H. G._Parris, you requested that we provide comments on the August 17, 1981 report by Dr. Roger A. Strehlow
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regarding hydrogen combustion and control. Enclosed is our response to Dr. Strehlow's August 17, 1981 report on TVA's Quarterly Progress-Report No. 3, "Research Program on Hydrogen Combustion and Control,"
dated June 16, 1981 for the Sequoyah Nuclear Plant and the' July 23, 1981 Progress Report Meeting.
If you have any questions regarding this subject, please call Jerry Wills at FTS 858-2683 at your earliest convenience.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety to d subsc ibed efore me Swor O g-day of' ev1981 thi 1
Notary Public g
My commission expires 7-5 -8jr-Enclosure i
ksi 8112090064 811130 PUR ADOCK 05000327 P-POR-An Equal Opportunity Employer s
RESPONSE TO DR. ROGER A. STREHLOW'S EVALUATION REPORT ON TVA'S HYDROGEN COMBUSTION AND CONTROL QUARTERLY REPORT NO. 3 AND THE JULY 23, 1981 PROGRESS REPORT MEETING We have reviewed Dr. Strehlow's comments in the subject evaluation report and have the following responses to those unresolved issues contained in the report.
Item 3 - Dr. Strehlow maintains that the laminar spherical deflagration tests (Whiteshell) are unnecessary because they repeat basic experiments and results could be predicted theoretically.
Response
The EPRI Whiteshell test plan, which was established in early March 1981 after extensive discussions among EPRI, AEP-Duke-TVA, Whiteshell-AECL and Ontario Hydro, reflects the several objectives that the group set out to realize. The details of the Whiteshell program have been related to the NRC through quarterly research reports and discussed with the staff in person on different occasions. Here, the key elements of the research program which are pertinent to the issue of hydrogen combustion are summarized.
The laminar spherical deflagration tests at Whiteshell are being performed by EPRI and the utilities for two major reasons. First, the tests will serve as a baseline to aid in the comparison of results from other experiments. For instance, the effects of scaling from earlier, smaller tests will be investigated. Second, the tests are only one phase of a comprehensive hydrogen combustion research program that was already underway at Whiteshell when EPRI contracted to participate. In this regard, these basic combustion tests will function as checkout tests to characterize the new vessel responas, instrumentation, and test procedures.
Items h and 5 - These tests study the effects of forced and obstacle-induced turbulence, flame propagation between compartments, and th3 potential for transition to detonation (Whiteshell).
Dr. Strehlow maintains that they are facility-specific end results cannot be extrapolated.
Response
The principal thrust of the Whiteshell effort is focused on providing confirmatory information in suppor t of our selection and implementation of a distributed ignition system and in augmenting the current understanding of hydrogen combustion phenomena which are pertinent to the application of that system. We have maintained, based on the recommendations of Dr. B.
Lewis and Mr. B. Karlovitz and on careful evaluations of plant geometries, current literature and accident parameters, that the existing experimental data on transition from deflagration to detonation do not support, as_ credible, the possibility of its occurrence in an ice-condenser plant. It is within this reference frame that the Whiteshell pipe-sphere test configuration was conceived, that is with the intention of investigating flame acceleration and propagation in general at various concentrations of hydrogen.
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The modeling of an ice-condenser geometry for the transition from deflagration to detonation phenomenon was found to be complex and impractical. There is a general consensus in the technical community that data collected from reduced scale models or models which do not reproduce the exact configuration, including material surface roughness, initial temperature, etc., of an ice condenser would not be conclusive.
In view of this situation, a commitment was made to utilize the pipe-sphere configuration at Whiteshell as a best effort to acquire more fundamental knowledge on the phenomenon of transition to detonation as a function of hydrogen concentration and not to model the ice-condenser geometry specifically.
As another part of the experimental effort at Whiteshell, the utilities have undertaken to study the effects of physical phenomena which result from the presence of obstacles in the event of hydrogen combustion. A series of experiments are being concluded in which effects of turbulence generated by either a fan or the presence of gratings are beinc investigated.
It is our belief that under conditions which are prototypic of an S,D type event, the aforementioned Whiteshell turbulent axperiments will adequately address conditions similar to thr e in an ice-condenser plant.
Moreover, in calculations pertinent to the hydrogen mitigation and control system, conservative assumptions have consistantly been applied which would correspond to the existence of turbulent effects upon the overall safety evaluation of the plant. The forthcoming results from Whiteshell should confirm the validity of assumptions used.
Item 7 - Dr. Strehlow believes the lower compartment distribution / mixing tests (Hanford) are not necessary because the region of interest is the ice condenser itself.
Response
The lower compartment distribution / mixing tests at Hanford are being performed by EPRI and the utilities to investigate the potential for
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nonuniformity or maldistribution of hydrogen in that region. Concerns have been expressed that extreme maldistribution anywhere in the containment could create a potential for local detonations. A concern also was expressed that localized concentrations of hydrogen in the lower compartment could lead to localized burnthrough in the ice bed since the combusting mixture flows from the lower compartment directly into the ice condenser. This potential was investigated quite some time ago for design basis events and also has been addressed for hydrogen-producing events in recent submittals. In addition, the Hanford tests should furnish information as to whether the assumptions of using single volumes to represent the lower compartment and the ice condenser are valid for containment hydrogen combustion analysis.
Overall Comment - Dr. Strehlow believes the overall question of flame acceleration in an ice condencar configuration has not been addressed.
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Response
Refer to our response to items 4 and 5 on the applicability of the
-Whiteshell flame propagation tests to an ice condenser geometry.- Further, as stated in earlier submittals, the operation of the distributed ignition system will maintain the hydrogen concentration in the lower compartment below 8 v/o. Burning at such low concentrations would produce weak flames with very little potential for flame acceleration. Hence, based on the lack of one-dimensional confinement in the ice bed flow channels and the maintenance of low concentrations of hydrogen, we believe that combustion initiated in the lower compartment and propagating through the ice condenser is not expected to be substantially different from that occurring in other parts of the containment.
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