ML19350B590
| ML19350B590 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah, McGuire  |
| Issue date: | 01/22/1981 |
| From: | Hanrahan E NRC OFFICE OF POLICY EVALUATIONS (OPE) |
| To: | Ahearne J, Gilinsky V, Hendrie J NRC COMMISSION (OCM) |
| Shared Package | |
| ML19247D089 | List: |
| References | |
| NUDOCS 8103230079 | |
| Download: ML19350B590 (2) | |
Text
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. UNITED STATES q
NUCLEAR REGULATORY COMMISSION y
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\\.,,,8 January 22, 1981 MEMORANDUM FOR:
Chairman Ahearne Comissioner Gilinsky Commissioner Hendrie Commissioner Bradford a/
FROM:
Edward J. Hanraha F
SUBJECT:
OPE REVIEW OF HYCROGEN CONTROL MEASURES FOR SEQUOYAH f
Shortly, the staff will brief the Comission with regard to whether the January 31, 1981 license condition for Sequoyah has been satisfied, i.e.,
"TVA shall by testing and analysis show to the satisfaction of the NRC staff that an interim hydrogen control system will provide with reasonable assurance protection against breach of containment in the event that a suostantial quantity of hydrogen is generated" (emphasis added).
OPE comments with regard to a Ccenission decision on this license condition are provided below.
P The immediate decision facing the NRC is whether " reasonable assurance of protection" required by the January 31, 1981 license condition has been obtained through use of the IDIS.
In this regard, two principal aspects should be considered:
. Reasonable assurance against breach of containment due to direct over-pressure from hydrogen combustion, irrespective of equipment survivability.
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. Reasonable assurance against breac5-of containment due to failure of essential equipment to survive the affects of hydrogen ccabustion with the subsequent inability to maintain core integrity, possibly leading to eventual containment failure.
Given the clcse connection of ice condenser containment plants and the potentially significance of hydrogen effects, whatever decision is reached on Sequoyah should be applied to all ice condenser containment plants.
In compliance with its license conditions, TVA submitted to NRR on December 1, 1980 its first quarterly report cn the research program for hydrogen control and a revised Volume 2 of the Sequoyah Core Degradation Program Report which provides information on TVA's proposed Interim Distributed Ignition System (IDIS) as well as longer term efforts for a " final hydrogen control system."
In early January, the staff prepared a draft " Supplement No. 4 to the Sequoyah Safety Evaluation Report (SER)" containing a preliminary evaluation of the TVA submittals.
CONTACT:
Jim Milhoan (OPE) 634-3295 R1032300 7u
For the Commission i OPE Review OP'- '.2s reviewed the above documents with the assistance of Dr. Roger S*.rehlow, a nationally recognized expert in gas dynamics with particular expertise in hydrogen combustion.
Dr. Strehlow's evaluation report is attached.
Dr. Strehlow concluded that a well designed and maintained glow plug igniter system which is energized only for testing or during an event which has the potential of generating.hydrr. gen is an effectir my to protect the Sequoyah nuclear plants-frcT'the possibility of br
.hing the containment vessel due to inadvertent combustion of accumulated hyJ ogen.
(Dr. Strehlow also identified additional research needs and providec comments on combustion dynamics.)
f Dr. Strehlow's review was related primarily to the question of reasonable assurance against breach of containment due to direct overpressure from hydrogen ccmbus: ion.
In this regard, Dr. Strehlow has identified mechanisms which could lead to explosion if a continuous flame is able to propagate in an ice condenser type containment.
Even though he concluded the glow plugs will virtually eliminate the possibility of detonation in the contain-ment vessel, he recomended further research be accomplished.
I recommend the staff address Dr. Strehlow's comments before reaching a decision on
" final hydrogen control measures."
With regard to the second questiori (equipment survivability), Dr. Strehlow indicated that glow plug initiated burns.will.be much less dangerous.than-spark initiated burns because glow plugs will initiate burns at lower concentrations than sparks of,the type that undoubtedly initiated the TMI burn. 'It appears that the lower the concentration at which hydrogen burns, the better chance of equipment survivability because of reduced flame propagation at low hydrogen concentrations. Thus, glow plugs should be an improvement with respect to equipment"' survivability.
Based upon our own review and that of Dr. Strehlow, I believe operation of the IDIS will reduce further any probability of breach of containment in the event that a substantial quantity of hydrogen is generated. The question of whether the " reasonable assurance" criterion has been satisfied appears'to hinge on the question of equipment survivability.
(Equipment survivability is certainly improved by use of glow plug. igniters.) Equip-ment survivability will be addressed further in the next Supplement to the Sequoyah SER.
Enclosure:
As stated L. Bickwit
-cc:
S.'Chilk
. Fraley
. Dircks H. Denton R. Tedesco
.W. Butler C. Tinkler C. Stahle L