ML20148T341
| ML20148T341 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/07/1978 |
| From: | Treby S NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Kelley J NRC OFFICE OF THE GENERAL COUNSEL (OGC) |
| References | |
| NUDOCS 7812040371 | |
| Download: ML20148T341 (14) | |
Text
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James L. Kelley pi V .g% ,
g Acting General Counsel D; U .S. Nuclear Regulatory Commission //p f,') Ap g*{f{$, -
gM Washington, D . C . 20555 C; jp/ v In the Matter of Virginia Electric and Power Company (North Anna Nuclear Power Station, Units 1 and 2) 1 Docket Nos. 50-338 OL and 50-339 OL l
Dear Mr. Kelley:
Enclosed is a memorandum from the Director of the Office of Nuclear Reactor Regulation to the Commissioners dated September 29, 1978 discussing the results of a recently conducted fire protection research test by the Under- .
writen Laboratory for the Commission as part of the NRC's fire protection research program.
j If the Commission wishes any additional infornmtion, please let us know.
Sincerely,
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ff'( ? ~,ll~ 'l/{j'/, /j l Stuart A . Treby j Assistant Chief IIcaring Counsel for NRC Staff
Enclosure:
As stated cc w/ enclosure:
Dr. Paul W . Purdom Mr . James M . Torson Mr . R . B . Briggs Richard Foster, Esq.
Michael W . Maupin , Esq . Mr. Bradford Whitman Dr. Kenneth A . McCollom Mrs . James C . Arnold Anthony Gambardella , Esq. Mr. Warren Warren Mrs. June Allen Atomic Safety and Licensing l Mrs. Margaret Dietrich Board Panel Mr Dean P. Agee Atomic Safety and Licensing William 11. Rodgers, Jr . , Esq. Appeal Panel John J. Runzer, Esq. Docketing and Service Section 78 3 2 9 4 g 3,, p
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, .8 fJUCLEAn REGULATORY COMMisslOfJ WASHINGTON, D, C. 20055 k, w, I o 18,M, 5 , ..
9gw % / j',E September 29, 1978
- o f4EliORAf!DUM FOR: Chairman Hendrie Commissioner Gilinsky .
Commissioner Kennedy l Commissioner Bradford N Commissioner Ahearne \ v, j THRU:
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Executive Director for Operati:ns hh d
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l FROM: Harold R. Denton, Director l Office of Nuclear Reactor Regulation l l
SUBJECT:
liRC FIRE PROTECTION RESEARCH TEST l On September 15, 1978, a fire test of a full-scale vertical cable tray array was conducted at the Underwriters'. Laboratory near Chicago, .
Illinois. It was part of the NRC-expedited fire protection research program requested in the Commission's Order of April 13, 1978. The purpose of the test was to demonstrate the effectiveness of area sprinklers and mineral wool blanket type cable tray fire barriers in
/ prevenLing damage to cables as a result of an exposure fire created by igniting two callons of heptane. l The configurat'on of cables and fire protection features in the test did not simulato any particular nuclear power plant. There are plants in operation and under construction for which the electrical cable tray configuration of the test was typical. Ilowever, based on the staff's ongoing fire protection reviews, we know of no operating plants with the configuration of fire protection features used in the test, although features of this type have been proposed for installation and are currently under review by the staff.
The test resulted in damage to some of the electrical cables. Prelim inary analysis (see Enclosure 1) indicates that the configuration of fire protection features used in the test would not be acceptable for application in nuclear power plants. In particular, it appears that fire barriers for vertical trays in some configurations may need to be designed to prevent entry of flarynable fluids. A uick effect may also need to be considered in the design of fire barriers. The response of the fusible link sprinklers used in the test is also under further study. -
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. . . . . . . - . . . . . . - - - . ..- - = , _ .
lThe Commissioners , 3 The test results are still being analyzed and it would be premature !
to_ establish firm conclusions at this time; however, the results now available suggest that modifications to certain of the staff's fire protection criteria may be necessary. The staff is continuing its ;
review and will meet with the test contractors (Sandia and VL) on October 3,'1978'to further study the preliminary findings and results. A quick lcok report is expected to be completed by UL within the next several days and will be issued by Sandia shortly-thereafter. The schedule and nature of further testing under this program are under review.*
I Ue will keep the Commission informed of significant results and possible impacts on operating reactors as information becomes available.
A circular or bulletin will be issued by IE to inform l'censees of the results of the test. Its preparation will follow the October 3 meeting with the contractors. Plants currently in operation remain subject to administrative procedures aimed at minimizing the sources of ignition and continue to maintain manual fire fighting capability.
He will inform the Commission of any action deemed necessary as .
a result of our continuing review of the test results. The public announcement provided in Enclosure 2 is planned for release by the Office of Public Affairs on October 2. We are in the process of informing the ACRS and llearing Boards where this information is
/ relevant.
/ho#A A .
Harold R. Denton, Director -
Office of Nuclear Reactor Regulation
Enclosures:
- 1. Preliminary Analyses
- 2. Public Announcement cc: (w/encls.) '
Union of Concerned Scientists Office of the Secretary NRC Public Document Room l
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SEP 2 71973 y l MEMORAf!DUM FOR: Robert L._Tedesco, Assistant Director 1
. for Plant Systems l Division of Systems Saf ety 1 i
FROM: Grepv A. Harrison J Auxi r Systems Branch Divi of Systems Safety Philip R. Matthews, .Section Leader Auxiliary Systems Branch Division of Systems Safety TilRU: Victor Benaroya, Chief Auxiliary Systems Branch ()
Division of Systems Safety .
SUBJECT:
UL FIRE PROTECT 1071 TESTS i
(fn September 15, 1978, Undentriters Laboratory conducted a full scale vertical cable tray fire test including fire barriers 7'ad sprinklers.
The source of the fire was two gal'ons of heptane liquid. This test was part of the expedited fire protection research pregram as requested in the Cammission's order of April 13, 1978. The purpose of the test was to cemonstrate the effectiveness of area sprinklers and cable tray fire barriers in preventing damage of safety significance to the cable circuits due to exposure fire conditions.
The configuration of the fire test was selected to simulate a section of a plant. area with vertical cable trays containing redundant safety divisions arranged such that the redundant divisions could be simul-taneously exposed to a potential fire resulting from an inadvertent spill of flamable liquid in the area. The arrangement of the cabic trays and the designation of the redundant tray divisions is shown in Figure 1 taken from the User Request Memorandum.1/ Figure 2 shows the location of the fire detectors and the three groups of sprinklers. )
Each of the five cable trays was enclosed in a separate mineral wool blanket fire barrier from floor to ceiling in accordance with the manu-facturers specifications currently recommended to their customers.
The sprinher and detector arrangement was as permitted by liFPA Code.
' l 1/ l
~ User Request Memorandum dated June 1,1978, from E.G. Case, NRR j
to S. Levine, RES l Enclosure 1 8*M8D
Robttrt L. Tedesco SEP 2 ? 39m i
Each sprinkler _ location contained three nominally identical tempera-ture sensing sprinkler heads with fusible links adjacent to an open sprinkler head which was connected to a manual water supply valve.
The temperature sensing heads were wired to signal when their links fused. After all three temperature sensing heads at a given location activated, then the water supply for the open head was to be manually admitted. The sprinklers were of a type which actuate at the slow end of acceptance for reaction time. The test procedure required that all '
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three temperature sensing hecids had to activate before water would be turned on. In this way it was expected to get some' A data on variability detailed description in the response time of identical sprinklers.
of the test set up and precedure will be in the UL test report which ';
will be issued later. It was agreed that the demonstration would be considered to have no safety significance if the electrical circuits did not fail in more than one tray.2/
The following sucmary of the test results is based on direct observa-tion of the test by 11RC staff. Test data are still being correlated .
by UL and will be included in their Quick Look Report to be issued to Sandia for its review shortly.
The test was started by igniting the two gallons of heptane that was
/ poured into the floor pan. A fully developed fire occurred almost inmediately. The ceiling smoke detector alarmed in Ebout 15 seconds.
In about 50-60 seconds, two of the three temperature sensing sprinklers located between the wall and cable trays 1 and 2 activated. The fire l between cable trays 1, 2, 3, and 4 appeared most intense apparently because of a chimney effect between the four trays. The flames between cable trays 3 and 5 did not appear to be so intense. The mineral ,
blankr L absorbed some of the heptane so that after the heptane in the pan turned, most of the flame seemed to come from the bottom outside surface of the' mineral blanket, llo additional temperature sensing sprinkler heads at any location activated; thus, the sprinkler water supply was not turned on for any of the three sprinkler loca-The apparent tions. tio water was used at any time during the test.
slow response of the third temperature sensing sprinkler is being investigated. ,
1 l
l Uriemorandum dated September 13, 1978, from V. Benaroya and G. Lainas to i
G. Bennett l 1
j
Robert L. Tedesco. SEP 2 71970 At about 3 minutes there was an indication of a short circuit in cable trays 3, and after 7 minutes indication of a short in tray 1.
After 5-7 minutes the height of the flames appeared to subside; however, residual flames continued for about 40 minutes. It was reported that apparently the highest measured temperature inside any cable bundle was less than 150 F; however, damage to the cables indicates that higher temperatures were reached in the trays at the bottom regions, below the location of the thermocouples.
Test results are still being analyzed and no firm conclusions can be drawn at this time. Preliminary information received from RES subse-quent to the test indicates that the flamnable liquid or flames pene-trated an opening in the protective barriers at the bottom of the vertical trays and caused fire damage to the pVC cables in four of the five trays. The electrical short to ground that occurred in l cable tray 3 probably was caused by the fire. The second electrical short in tray l apparently was caund by a broken instrument connec-
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tion, and is not considered to be related directly to the firc. On subsequent 500-volt megger tests, it was found that another cable ~
in tray 2 had also experienced sme damage.
The most probable cause of the fire damage in certain cable trays j appears to be related to the absorption and/or seepage of heptane under the mineral wool blanket at the jucture with the floor. Once :
the heptane entered the interior regions of the cable tray, then l ignition apparently occurred via the small opening at the fleor or !
through a vapor / air path within the joints. It is believed that this type of failure made could be prevented by using a seal material that would prevent the. absorption or the seepage of heptane under' the nineral wool blanket. There is some indication that some cable damage was caused by absorption of the inside of the barrier (wicking effect) which heated a cable tray ladder, causing damage to a cable in contact with the ring. The investigation of the results is still underway, and while no definitive findings can be stated, damage did occur to cables in several trays due to the fire. The slow response of the sprinkler system was not predicted. The ingress of the heptane into the mineral wool needs to be further evaluated since this appears to be the most significant failure mode.
The test results are still being analyzed and it would be premature to establish firm conclusions at this time; however, the results now available indicate: (a) fire detectors located approximately 15 feet away from the fire promptly (al5 sec) detected the fire; (b) some small fires may not actuate sprinkler heads; and (c) protective barriers should be designed to prevent the entry of flamable liquids.
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._.7 4- # u .. wm e w- -w --w- --- p e --. e.s SEP27 g Robert L. Te'desco The staff plans to meet with personnel from Sandia and UL during A Quick Look Test Report is expected the first week of October.
to be released in early October, it does appear that;further evaluation of the results may lead to the formulation of suppicmental fire protection In view requirements of this, itconcerning is 1 seals and types of sprinkler heads to be used.
appropriate to notify the ACRS, the Commission, Weand any Boards, where will continue this issue is relevant, as 'to the current situation.our d by the evaluation tests to be Office ofconducted. A Enclosure Public Affairs (public to be released September
- 3) andconouncement has been prepare
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29, 1978.
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- ja 6 liarrison Gret Auxi ry/y ia Systems Branch Division of Systems Safety
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Philip R. Matthews, Section Leader l' Auxiliary Systems Branch !
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PUBLIC Af1NOUNCD4ENT llRC Staff Evaluating Results of Test of Fire Protection Systems -
The staff of the fluclear Regulatory Commission (NRC) is evaluating the results of a recent test of fire suppression systems to determine whether changes should be made in llRC fire protection criteria for nuclear power plants.
As part of f;RC's research program, the test was conducted at Underwriters' Laboratory (UL) near Chicago on Sept ember 35, 1978.
The test involved electrical cables in five vertical trays and included fire barriers and unter sprinklers. The test resulted in danuge to some of the electrical cables. Preliminary analyses indicate that
/ the fire barrier and sprinkler configuration used in the test would not by itself be acceptable fire protection in nuclear power plants.
As a result of the fire at the Browns Ferry I'uclear Plant in Alabama in 1975, the !!RC has imposed strict administrative controls over fire ignition sources at all nuclear power plants, and nanur' firefighting capability has been strengthened. Fire suppression systems of the type tested at Underwriters' Laboratory are among those being reviewed for further strengthening of fire protection in these plants. Although some plants already have sprinkler systems, and many rely on various types of fire barriers, the 11RC staff knows of no present use of the system tested at Underwriters.' Laboratory.
Enclosure 2
A configuration of five, full-scale vertical cable trays containing electrical cables simulating redundant safety systems was used in the test. Each of the cable trays was enclosed, from floor to ceiling, in a separate fire barrier of mineral uool. Three groups of sensing sprinkler heads were wired to signal when their heat sensitive links fused'from the heat of the fire. The manually operated sprinkler then was to be actuated. In actual plant appli-cations, each fusible link would actuate one sprinkler head.
A fire was started in a pan on the floor and an alarm was sounded by a ceiling detector about 15 seconds later. During the test two of three links in one sprinkler location fused; none of the other links fused and, censequently, no water was used to extinguish the
/
fire. In addition, it appears that some of the flamable liquid used as the fire source seeped under the blanket and was absorbed, resulting in damage to the cables at the bottom of the cable trays.
Preliminary analysis indicates there was some fire damage to cables in four of the five trays. Addition of a seal material might have prevented the damage resulting from the absorption or seepage of flammable liquids under or into the mineral blankets.
However, the tests appear to have confirmed that blankets can be an effective heat barrier. The performance of the sprinkler links is still being analyzed. Upon completion of the analyses, the NRC staff will inform licensees of the results.
These analyses may lead to new requirements for the type of fusible links which can be used in sprinkler heads, as well as for sealants for fire barriers. In the interim, the NRC staff believes existing fire protection requirements--including administrative controls over ignition sotirces and the presence of fire brigades et the plants--provide adequate protection.
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lid 1DRAI!DUM FOR-->Tho:ios F. Engelhardt, Acting Hearing Division Dircctor and Chief Counsel, OLLD FROM: D. B. Vassallo, Assistarit Director for 1ight Water Reactors Division of Project fianag ment, f!RR SulJECT: BOARD l'OTIFICAT10N - UL FJRE TEST (Bl!-78-20)
The two enclosed staff memoranda concerning UL Fire Protection Tests are sel f-expla na tory.
I reconmend that these be sent to all Boards since the natter is generic and could be applicable to all nuclear f acilities.
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Lnclosures:
- 1. 11emo, H. Denton to Co:amissioners 9/29/78 w/ enclosures
- 2. 1'.emo, R. Tedesco to D. Vassallo 1/2/78 cc w/ enclosures:
}l, Dcnton V. Benaroya D. Case G. Lainas J. Davis R. Tedesco R. Doyd R. !bttson V. Stello .
R. DeYoung D. Eisenhut L. flichols B. Grimes J. Stolz R. Baer
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11El10RANDUM FOR: Domenic B. Vassallo, Assistant Director for Light Water Reactors, DPM FROM: Robert L. Tedesco, i\ssistant Director for Plant Systems, DSS SUBJECf: UL FIRE TEST On September 15,19/8, a fire test of a full-scale vertical cable tray array uith cable protected by fire barricrs and sprinklers was conducted at the Underwriters' Laboratory near Chicago, Illinois. It was part of the ID:C-expedited fire protection research program requested in the Co:nmission's Order of April 13, 1978. lhe purpose of the test was to dwonstrate the elf ectiveness of area sprinklers and mineral wool blanket type cable tray fire barriers in preventing dan sge to cables as a result ,
of an e>.posure iire created by igniting two gallons of heptane.
The CoTmissioners have i'een inforocd by the enclosed separate me.norandum It is rippropriate that the ACRS and Boards also lie notii-ied where this
/ issue is relevant. We will continun our evaluntion of the test results and considerations of new additional tests to be conducted.
t n s -f]tN.(?ELR';c.1-o d Robert L. Tedesco, Assistant Director for Plant Systens Division of System Safety
Enclosure:
As stated cc: R. J. Idttaon R. S. Doyd V. Stello '
V. Den 3foyd G. Lainas D. Eisenhut B. Grimes 9
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