ML20003G884
| ML20003G884 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/25/1981 |
| From: | Bender M, Lawroski S, Mark J Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-1811, NUDOCS 8105040127 | |
| Download: ML20003G884 (5) | |
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hlNUTES OF THE ACRS SUBCOMM8TTEE h h/
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SEQUOYAH NUCLEAR POWER PLANT I
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[jg ASHINGTON, D.C., JANUARY 6, 1981 The principal attendees were:
NRC STAFF TVA ACRS C. Stable Dr. Lau TT. Mark, Chairman C. Tinkler
- eilim, S. Lawroski, Member S. Israel
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co M. Bender, Member Z. Rosztoczy 7
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C. Siess, Member H. Polk y
M. Sichel, Consultant N
H. Dance 27 a
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W. Lipinski, Consultant I. Catton, Consultant 2 S fgg
"#' g'*D'C's d[6 Z. Zudans, Consultant g
G. Quittschreiber, ACRS Staff
- R. Savio, ACRS Staff (partial mtg coverage) t INTRODUCTION-C. Stahle, NRC Staf_f, The NRC Staff requested that the ACRS write a letter with regard to h'yBro'-
gen control measure - Condition ~ 1, of the Sequoyah License which require TVA, shall by testing and analysis, satisfy the NRC Staff by January 31, 1981, that an interim hydrogen control system provides, with reasonable assurance, protection against breach of contairiment in the event that a substantial The NRC Staff currently believes this quantity of hydrogen is generated.
9 condition is satisfied.
STATUS OF SEQUOYAH START'JP TEST PROGRAM - H. Dance, NRC Staff The Sequoyah startup program has been in progress for about three months.
Several shutdowns have been required for numerous reasons, most of which are I&E feels that the, low power associated wit, the steam / feed related systems.
test program did help the startup program and that most problems have been associated with the steam / feed portions of the plant which were not tes During December the plant has been critical 522 the low power test program.
hours out of a possible 744 hours0.00861 days <br />0.207 hours <br />0.00123 weeks <br />2.83092e-4 months <br />.
- Designated Federal Employee 8105 0 d 0 l3.7 S
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. January 6,1981 Sequoyah PROBABILITY OF CORE DAMAGE EVENT-S. Israel, NRC Staff The NRC Staff, using Sandia, TVA studies, and th'e MARCH Code has determined that about 50% of the core melt events are rectifiable, which if corrected, would lead to a degraded core instead of full core melt. H control measures 2
would be effective during degraded core events but would not be adequate for full core melt events. Even though 50% of the core melt events are rectifiable, only 10% of these events are likely to be turned into degraded core events due to the short time windows for which components must be repaired, e.g., it takes longer than four hours to repair 90% of the diesel failures.
EFFICACY OF INTERIM DISTRIBUTION IGNITION SYSTEM DESIGN - C. Tinkler, NRC Staff TVA has decided to add 13 ignitors to the upper containment area in addition to the three ignitors previously proposed for this area.
The TVA Fenwall tests are consistent with published data showing there is limited combustion with H2 concentratins of 6-8% and complete combustion with H concentrations of 10-12%. Steam concentrations up to 40% steam 2
Water fractions do not hinder the igniters' ability to initiate combustion.
J ll sprays had no discernible effect on combustion. Pressures reached during the l
Fenwall tests were as high as 70 psi at H2 concentrations of about 12%.
The NRC Staff's tests performed at Livermore also showed results consis-i tent with the literature with steam concentrations up to 40% steam fractions; however, steam inerting occurred at 50% concentration and when reduccd by.
condensation, ignition did not apparently occur even though the literature indicates combustion should have occurred. This may have been caused by fogging and is an area requiring further investigation to see what effect this may have in an ice condense, plant.
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. January 7,1981 Sequoyah Subemte Mtg s.
Sandia has reviewed the 1015 and has concluded that for moderate H 2
release rates deliberate ignition is beneficial. Sandia has recommended that igniters in the upper plenum be removed based on concern over detona-The NRC Staff and TVA do not presently agree with this recommendation.
tions.
The NRC Staff has concluded that deliberate ignition in the Sequoyah containment is beneficial for degraded core accidents and that the IDIS is a reliable means for initiating combustion. The NRC Staff pointed out several topics for review over the January 1981 to January 1982 period.
SURVIVABILITY OF ESSENTIAL EQUIPMENT - Dr. Lau, TVA Representatives of TVA discussed the survivability of essential components TVA has recuired to operate during a degraded core hydrogen burn event.
looked at all equipment needed during such an event and has tested representa-in a hydrogen burn atmosphere in a test chamber at Fenwall.
tive componens:
TVA has determined that all necessary equipment would function following such Several actual components which were tested in the a hydrogen burn event.
burn atmosphere were shown to the Subcommittee, minor scorch marks and oxida-tion were visible.
SURVIVABILITY OF ESSENTIAL EQUIPMENT - Z. Rosztoczy TVA calcula-The NRC analysis of equipment survivability was discussed.
tions indicate peak temperatures of 2000 F (less than 1 second duration) 0 and, under the assumption of no heat transfer, average temperatures of about Realistic estimates of the sustained temperature level is not yet 0
800 F.
Surface scorching, the melting of teflon insulation and soldered available.
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. S:quoyah Subemte ntg Surface scorching and solder connectior.s was observed in the Fenwall tests.
The relationship melting was also observed inside of protective housings.
between the test environment and the actual containment environment ha The NRC is proposing requiring TVA to perform further been established.
TVA has not yet concurred.
analysis and tests to be submitted by May 1, 1981.
STRUCTURAL RESPONSE - H. Polk, NRC Staff The loading resulting from the detonation of a spherical hydrogen cloud 6 ft. in diameter was considered. A 180 psi peak pressure, one-half milli-The dynamic analysis performed by Ames yielded second loading pulse resulted.
an effective pressure of 7.1 psi. Dynamic analysis performed by the NRC, using two methods, yielded effective pressures of 12.1 psi and 13.3 psi.
CLOSING REMARKS Dr. Mark, Subcommittee Chairman, informed the NRC Staff and Applicant that 8-10, 1981 meeting this matter would be brought before the ACRS at the January It was the opinion of the Subcom-for a brief presentation by the NRC Staff.
mittee members that if there is hydrogen in the containment in sufficient The quantity it wil. be ignited, and the IDIS would likely be beneficial.
1 It was felt question of equipment survivability still remains an issue.
that there was a better likelihood of survivability with the IDIS in the l
l event that an unlikely accident should occur, since with planned ignition hydrogen would burn in relatively small amounts and less damage to > quip-ment would occur than if the hydrogen were to accumulate to larger amounts
. before it should be ignited.
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t For additional details, a complete transcript of the meeting is available in the N Public Document Room,1717 H Street, NW., Washington, D.C, 20555 or from Alder Reporting, Inc., 300 7th Street, SW, Washington, D.C., (202/554-2345).
--m eo
Sequoyah 1/6/81 Meeting List of Documents 1.
NRC - 48 slides 2.
Charlie Tinkler, NRC - 25 slides 3.
Letter from V. L. Conrad to J. C. Mark, dated 1/19/81 concerning colloquy between ACRS member Ebersole and two attendees at 249th Meeting 1/9/81.
4.
Letter w/ attach from L. M. Mills to A. Schwencer, dated 12/24/B0 on hydrogen issue on 12/18/80.
5.
Memo from J. C. Mark to ACRS Members, dated 1/2/81,
Subject:
Comments on NUREG/CR-1762 (12/1/80, Draft) " Analysis of Hydrogen Mitigation for Degraded Core Accidents in the Sequoyah Nuclear Power Plant".
6.
L. W. Lau, TVA - 9 slides l'
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