ML20148G184
| ML20148G184 | |
| Person / Time | |
|---|---|
| Site: | 05000452, 05000453 |
| Issue date: | 10/30/1978 |
| From: | Sohinki S NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Bowers E, Cole R, Jordan W AFFILIATION NOT ASSIGNED, Atomic Safety and Licensing Board Panel |
| References | |
| NUDOCS 7811100171 | |
| Download: ML20148G184 (1) | |
Text
[pa at%, UNITED STATES y ' v, .? , NUCLEAR RF.GULATORY COMMISslON
- g WAST slNGTON, D. C. 20055
$ s ' . ' j I K ? M, 'E October 30, 1978
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NRC PUP;LIC DOCUAIENT ROOM Elizabetn S. Bowers, Esq., Chairman Dr. Richard F. Cole Atomic Safety and Licensing Board Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission Washington, DC 20555 Washington, DC 20S55 Dr. Walter H. Jordan f {sp s 881 W. Outer Drive .(f Oak Ridge, TN 37830 g , /
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In the Matter of -
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The Detroit Edison Company (Greenwood Energy Center, Units 2 and 3)C.,
G t @ p h *%d. 3 e
Docket Nos. 50-452, 50-453 /
Dear Chairman and Members of the Board:
M Enclosed is a memorandum from the Director of the Office of Nuclear Reactor Regulation to the Commissioners da'ted September 29, 1978, discussing the results of a recently conducted fire protection research test by the Underwriters Laboratory for the Commission as part of the NRC's fire protection research program.
If the Board or the parties wish any additional information, please let us know.
Sincerely, ,
[
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Stephen M. Schinki r
Counsel for NRC Staff
Enclosure:
As Stated ,
cc w/ encl: Frank G. Giambrone Dr. Robert G. Asperger Peter A. Marquardt, Esq. Mr. Robert F. Philip Harry H? Voigt, Esq. Atomic Safety and Licensing Dr. Robert Magnuson Board Panel Mr. Arthur Robertson Atomic Safety and Licensing Ms. Bertha Daubendiek Appeal Board Docketing and Service Section 7R1110017\* .
4 UNITED STATES
. *yN f ,S NUCLEAR REGULATORY COMMtsslON
- I WASHINGTON, D. C. 205$5 k* ' s.
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\.'..../ September 29, 1978 MEMORANDUM FOR: Chairman Hendrie Commissioner Gilinsky
- ~
Commissioner Kennedy Commissioner Bradford N
. Commissioner Ahearne THRU:
l Executive Director for Operations ^
b f~m FROM: Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
NRC FIRE PROTECTION RESEARCH TEST 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 -
preventing damage to cables as a result of an exposure fire created -
by igniting two gallons of heptane.
The configuration of cables and fire protection features in the test did not simulate 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. However, 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 flarmable fluids. A wick 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. -
The Commissioners 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 UL) on
. October 3,1978'to further study the preliminary findings and results. A quick look 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.
We 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 licensees 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.
We 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 Hearing Boards where this information is relevant.
/6fS 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
. HRC Public Document Room 9
g.pn Mcg'o UNITED STATES 3\, 4 NUCLEAR REGULATORY COMMISslON f ;- h WASHINGTON, D. C. 20555 si !
%..w...y SEP 2 71978 ?
MEMORANDUM FOR: Robert L. Tedesco, Assistant Director for Plant Systems Division of Systems safety FROM: Gregory A. Harrison Auxiliary Systems Branch Division of Systems Safety Philip R. Matthews, Section Leader Auxiliary Systems Branch Division of Systems Safety THRU: Victor Benaroya, Chief Auxiliary Systems Branch Division of Systems Safety
SUBJECT:
UL FIRE PROTECTION TESTS On September 1E, 1978, Underwriters Laboratory conducted a full scale vertical cable tray fire test including fire barriers and sprinklers.
The source of the fire was two gallons of heptane liquid. This test was part of the expedited fire protection research program as requested in the Commission's order of April 13, 1978. The purpose of the test was to demonstrate 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-
. teneously exposed to a poten,tial fire resulting from an inadvertent spill of flamable liquid in the area. The arrangement of the cable 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 l
blanket fire barrier from floor to ceiling in accordance with the manu-facturers specifications currently recommended to their customers.
The sprinker and detector arrangement was as permitted by NFPA Code.
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~ User Request Memorandum dated June 1, 1978, from E.G. Case, NRR to S. Levine, RES x-- .- - - . _ _ _ - - - _ _ __ _ _ _ _ _ _ _ _ _ _ - - - . _ . _ __ _ _ _ _
Enclosure 1
Robert L. Tedesco SEP 2 71973 Each sprinkler location contained three nominally idential tempera-ture sensing sprinkler heads with fusible links adjacent to an open sprinkler head which was connected to a manual water suppl" 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 three temperature sensing heads had to activate before water would be turned on. In this way it was expected to get some data on variability A detailed description in the response time of identical sprinklers.
of the test set up and procedure 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 su$ mary of the test results is based on direct observa-tion of the test by HRC 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 innediately. The ceiling smoke detector alarmed in about 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 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 blanket absorbed some of the heptane so that after the heptane in the pan burned, most of the flame seemed to come from the bottom outside surface of the mineral blanket. No 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-tions. No water was used at any time during the test. The apparent slow response of the third temperature sensing sprinkler is being investigated. ,
1 U norandum Me dated September 13, 1978, from V. Benaroya and G. Lainas to G. Bennett
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- 1 P,obert L. Tedesco SEP 2 71978 -
L At about 3 minutes there was an indication of a shor; pircuit in cable trays 3, and after 7 minutes indication of a s g t in tray 1.
After 5-7 minutes the height of the flames appeared 9 subside; '
however, residual flames continued for about 40 minu.pp. It was reportedthatapparentlythehighestmeasuredtemperapreinside any cable bundle was less than 150 F; however, damage to the cables indicates that higher temperaturns were reached in the trays at the bottom regions, below the location of the thermocouplps.
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 flamable liquid pr 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 cabic tray 3 probably was caused by the fire. The second electrical short in tray 1 apparently was caused by a broken instrument connec-tion, and is not considered to be related directly to the fire. On subsequent 500-volt megger tests, it was found that another cable
- in tray 2 had also experienced some damage.
The most probable cause of the fire damage in certain cable trays appears to be related to the absorption and/or seepage of heptane under the mineral wool blanket at the juncture with t$ floor. Once the heptane entered the interior regions of the cable tray, then ignition apparently occurred via the small opening at the floor or through a vapor / air path within the joints. It is believed that this type of failure mode could be prevented by using a seal material that ,
under the would prevent mineral wool blanket. the absorption There isorsome the seepage ofthat indication heptanp$ome cable damage '
was caused by absorption of the inside of the barrier?(wicking effect) which heated a cable tray ladder, causing damage to a' pable in contact -
with the ring. The investigation of the results is s while ne definitive findings can be stated, damagef di{ill occurunderway, to cables and in several trays due to the fire. The slow response g# the sprinkler system was not predicted. The ingress of the heptanerinto the mineral wool needs to be further evaluated since this appearg' :o'be the most significant failure mode. 3 Thetestresultsarestillbeinganalyzedanditwou]j be premature to establish firm conclusions at this time; however, thg fesults now available indicate: (a) fire detectors located apprbimately 15 feet away from the fire promptly (evl5 sec) detected the' M e;'(b) some small fires may not actuate sprinkler heads; and ((, a opective barriers should be designed to prevent the entry of. Imable liquids.
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Robert L. Tedesco SEP 2 7 g
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The staff plans to meet with personnel from Sandia and LL during the first week of October. A Quick Look Test Report is expected to be released in early October.
It does appear that further evaluation of the results may lead to the formulation of supplemental fire protection requirements concerning seals and types of sprinkler heads to be used. In view of this, it is appropriate to notify the ACRS, the Commission, and any Boards, where
- this issue is relevant, as 'to the current situation. We will continue our evaluation of the test results and consideration of new additional tests to be conducted. A Office of Public Affairs (public announcement Enclosure 3) and ' to behas beenSeptember released prepared by the 29, 1978.
.3 .
W N-Greg y f. Harrison Aux iary Systems Branch Division of Systems Safety l
Philip R. Matthews, Section Leader Auxiliary Systems Branch Division of Systems Safety cc: R. Mattson V. Stello it. Moseley ,
T. Murley -
J. Fouchard J. Scinto l 0. Eisenhut G. Bennett G. Lainas R. Feit ,
R. Ferguson E. Sylvester
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PUBLIC ANNOUNCEMENT NRC Staff Evaluating Results of Test of Fire Protection Systems -
The staff of the Nuclear Regulatory Commission (NRC) is evaluating the results of a recent test of fire suppression systems to determine whether changes should be made in NRC fire protect'on criteria for nuclear power plants.
As part of NRC's research program, the test was conducted at Underwriters' Laboratory (UL) near Chicago on September 15, 1978.
The test involved electrical cables in five vertical trays and included fire barriers and water sprinklers. The test resulted in damage 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 Nuclear Plant in Alabama in 1975, the NRC has imposed strict administrative controls over fire ignition sources at all nuclear power plants, and manual firefighting capability has been strengthened. Fire suppression systems of the type tested at Underwriters' Laboratory are amor.g those being reviewec 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 NRC staff knows of no present use of the system tested at Underwriters' Laboratory.
Enclosure 2
, . 2 A configuration of five, full-scale vertical cable trays containing electrical cables sinulating 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 wool. Three a
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, consequently, no water was used to extinguish the fire. In addition, it appears that some of the flammable 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 scepage 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 comp 1 nlon of the analyses, the NRC staff will inform licensees of tne 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 i
scalants 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 at the plants--provide adequate protection.
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