ML19326C677
| ML19326C677 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/02/1977 |
| From: | Snaider R Office of Nuclear Reactor Regulation |
| To: | Desiree Davis Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19326C675 | List: |
| References | |
| NUDOCS 8004250492 | |
| Download: ML19326C677 (6) | |
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UNITED STATES V'
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NUCLEAR REGULATORY COMMisslON E
W ASHING TON. D. C. 20555 OCT 2 1977 Docket No. 50-313 l
MEMORANDUM FOR: Don K. Davis, Acting Chief, Operating Reactors Branch #2, D0R FROM:
R. P. Snaider, Project Manager, Operating Reactors Branch #2, D,
SUBJECT:
DESIGN ERROR AT ARKANSAS NUCLEAR ONE - UNIT 1 (ANO-1) AND
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SUMMARY
OF 9/13/77 MEETING WITH ARKANSAS POWER & LIGHT COMPANY l (AP&L) AND BECHTEL BACKGROUND On Tuesday, September 6, 1977,, I&E Region IV-tnformed D0R of an ANO-1 design error which could possibly have sicnificant safety implications.
The error was discovered by AP&L and Bechtel personnel wilile performing studies related to impact of ANO-2 upon maximum temperature rating for the future (upon ANO-2 licensing) joint use of the emergency cooling pond.
Upon the re-rating of the pond from 120*F to 129'F, it was found i
that greater capacity would be necessary for emergency cooling systems utilized to cool electrical equipment rooms vital to plant safety in the event or either a Loss-of-Coolant-Accident (LOCA) concurrent with a loss of offsite power or a sustained loss of offsite power. When this situation was examined at ANO-1, 't was found that there were no emergency safety-grade cooling systems for the areas in question, which are:
(1) South electrical equipment room (2) North electrical equipment rocm (3) South charger room (4) North charger room Equipment contained in these rooms includes the followinn: statiun emeraency batteries, battery chargers, inverters (instrumentation power supply), ~
Motor Control Centers (MCC) for ECCS motor-operated valves, and MCCs for other motors important to safety.
An initial, very conservative analysis by AP&L and Bechtel indicated that little time would be available to take corrective action if power to the existing non-safety-grade chillers, powered frem off-site (or station generator) power through the auxiliary and/or start-up transformers, were lost for an extended period of time. AP&L requested until Friday September 9 to perform a refined analysis which, unlike the calculatiens mentioned above, would take into account available heat sinks and would 8gg4 g
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o Mtg Summary for AP&L & Bechtel also provide a more realistic assessment of equipment actually energized in the affected recms under postulated initiating event conditions.
ISE allowed them this time for a new analysis, based upon the icw probability of an initiating event occuring.in the short inte.rin) petri:od.
On September 9, DOR, which had taken responsibility for the review effort, called AP&L to receive and discuss the revised analysis.
This analysis, as expected, shcwed results vastly different frem previous cursery examination, with calculated delays of apcroximately 2 days prior to the limiting area exceeding the design maximum continuous duty ambient air temperature rating for the equipment.
Hcwever, AP&L requested, and the NRC staff agreed to, additional time to quantify heat loads, temperature profiles and ventilation capabilities.
This decision was based on icw initiation event probability, the revised analysis noted above, the realization that operation for a limited period of time at temperatures above the manufacturer's recommended maximum continucus duty rating would not be detrimental to the equipment in question,
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and the availability of large ventilation fans, at a minimum, frcm the immediately adjacent ANO-2 constructier. site.
A meeting was scheduled to take place in Bethesda en Tuesday, September 13, 1977, at which rep esentatives of AP&L and Sechtel were 1
to cresent the results of the latest analysis and were to provide plans for the proposed interim and long-term repair programs.
The summary of the meeting is presented below.
MEETING
SUMMARY
A list of attendees is attached (Attachment 1 ).
AP&L provided drawings of the affectes recms, showing major equipment and ventilation equipment. provides calculated results of the in-depth analysis, which took into acccunt heat loads through walls from adjacent recms and heat loads frem cable losses., recm lighting and panel lighting.
The North and Scuth switchgear rooms are included because the se"vice water cooler capacity will be affected by the decreased emergency cooling pond capahility when ANO-2 becomes operaticnal.
AP&L will address this study later.
Although the air temperature of the North and Scuth charger rooms will exceed the manufacturer's reccmmended maximum continucus duty ambient rating, the NRC staff feels that the equipment will continue to function in the interval untii pcwer to the chillers is restored, especially since the maximum temperature increase will be only 9*F above the reccmmended (South charger recm).
AF&L has been asked to provide infomation with regard to equipment cacability to withstand higher temperature.
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Mtg Summary for AP&L & Bechtel A major portion.of the discussion was devoted to the. methods by which Bechtel calculated room heat loads and temperature increases.
The analysis appeared to have Been very thorough, with such diverse inputs as heat transfer through thick concrete walls and increased ventilation supply air temperature because of operating diesels, having been considered. The NRC staff was generally satisfied with
.i the analysis, with exceptions, in the form of requested additional infonnation, stated below.
AP&L and Bechtel discussed their preliminary plans for interim and long-term solutions. The interim plan is to provide one seven-ton capacity, non-safety-grade, direct expansion cooling unit.
This would be housci in the turbine building with cooling lines directed to individual coolers located in the North and South Charger rooms.
It would be powered from a swing MCC (capable of being powered frca either the red or green safety pcwer divisions) located in the South charger room.
Actual unit startup would be manual.
The present estimate is that approxmately three months would be recuired for obtaining and installing this equip-ment.
AP&L is also investigating the use of circulating fans in electrical equipment rooms to prevent air stagnation. As noted on, these rooms will reach the maximum continuous ambient temperature rating after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The fans would be continuously running and would be pcwered from emergency power sources.
It was determined by AP&L that nothing being proposed for the interim fix would interfere with compliance with either the security or fire protection plans.
The permanent solution presently proposed by AP&L involves the addition of two fully qualified chiller packages, each supplying only rooms of one division of emergency power and each therefore pcwered by *: hat division._ Projected lead time to equipment delivery is one year, with i stallation additional.
The NRC staff stressed that necessary tie-ins should be accomplished whenever an opportunity existed.
AP&L noted that the ANO-1 diesels have sufficient spare capacity to handle the additional chillers.
The following commitments were made:
(1) AP&L will provide five copies of each drawing used.
(2) As part of report to be completed by 9/20/77, AP&L will 3
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Mtg Summary for AP&L & Bechtel
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identify that equipment which would be most limiting if run at higher than recommended maximum continuous duty air temperature limits. The NRC desires either a time limit at maximum expected temperatures or an intermittent rating for the most limiting equipment.
(3) AP&L will investigate the addition of permanent temperature monitoring systems in the affected areas.
(4)
In response to an NRC request for more background on the cause of the design error, AP&L will, by 9/20/77, provide an expected date for submittal of such data.
(5) AP&L will verify the minimum allowable temperature for the affected areas.
(6) AP&L will provide specific surveillance for use during the periods between now and the implementation of the interim solution and between the interim solution and final solution. The NRC staff stated that AP&L should, at a minimum, monitor temperatures in the affected areas and prepare procedures defining specific actions to be taken if designated maximum temperatures are exceeded.
(7) AP&L will submit detailed information on the proposed interim and final solutions to the NRC for review.
M Richarc P. Snaider, Project Manager Operating Reactors Branch #2 Division of Operating Reactors Attachments 1.
List of Attendees 2.
Calcolation Sheet ce; See next page yee 2
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i ATTENDEES LIST NRC R. Snaider-D. Tondi
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S. Rhow J Burdoin W. Butler-M. Chiramal F. Nolan (I&E)
AP&L 4
e D. Crabtree D. Morgan i
R. Lane D. Rueter Bechtel Pcwer Coro.
J. Grill G. Borsteins E. Smith H. Hall G. Smith 1
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MEETING
SUMMARY
DISTRIBUTION r.
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-NRC POR Local PDR OR8 #2 Reading NRR Reading B. C. Rusche E. G. Case V. Stello K
R. Goller D. Eisenhut T. J. Carter A. Schwencer G. Lear R.'Reid W. Butler B. Grimes R. Baer L. Shao Project Manager -
Attorney, OELD -
OI&E (3)
R. Diggs NRC Participants '(Major)
R. Fraley, ACRS (16)
T. B. Abernathy, DTIE J. B. Buchanan
' Licensee
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