ML20148M730

Forwards IE Circular#78-18,UL Fire Test. W/Encl ANO:7811150002

ML20148M730
Person / Time
Site:	Fort Calhoun
Issue date:	11/06/1978
From:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	Short T OMAHA PUBLIC POWER DISTRICT
References
NUDOCS 7811220119
Download: ML20148M730 (1)

Text

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UNITED STATES

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[' ,.. g HEGION IV l! ., a-A ,.g Gil HYAN PLA2A DRIVE, SUITE 1000 6 AR LINGTON, T E X AS 76011

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• • • a' flovember 6, 1978 Docket flo. 50-285 THIS DOCUMENT CONTAINS POOR QUAUTY PAGES Omaha Public Power District ATTil: Mr. T. E. Short, Division f4anager Production Operations l 1623 llarney Street l Omaha,fiebraska 68102 Gentlemen :

The enclosed IE Circular 78-18 is forwarded to you for information. flo specific action is requested and no written response is required. If you desire additional information regarding this matter, please contact this office.

Sinceraly, f

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t Karl 1. 'Sey fri t Director

Enclosures:

1. IE Circular 78-18

2. List of IE Circulars Issued in 1978 4

7811220\\9 1

UNITED STATES fiUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND EfiFORCEMENT WASHINGTON, D. C. 20555 IE Circular 78-18 Date: flovember 6,1978 Page 1 of 3 UNDERWRITERS LABORATORY FIRE TEST

Background:

On September 15, 1978, a fire test of a full-scale vertical cable tray array was conducted at the Underwriters Laboratory (UL) near Chicago, Illinois. It was part of the fire protection research program managed by Sandia Laboratories under NRC contract. The purpose of the test was to demonstrate the ef fectiveness of area sprinklers and cable tray fire barriers constructed of ceramic fiber blankets in preventing damage to cables as a result of an exposure to a flammable liquid fire. The test resul ted in damage to some electrical cables.

> Discussion: ,

1 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 cable trays and the designation of the redundant tray divisions is shown in Figure 1.

Figure 2 shows the location of the fire detectors and the three groups of sprinklers. Each of the five cable trays contained cable insulated with polyvinyl chloride and was enclosed in a separated ceramic fiber blanket fire barrier from floor to ceiling in accordance with the manu-facturer's reconmendations. The sprinkler and detector arrangement wn as permitted by NFPA Code. However, no water was actually used at any time during this test due to the failure of some sprinkler heads to actuate, as explained below.

Each sprinkler location in the test arrargement contained three nominally identical temperature sensing sprinkler hwJ.; 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. Af ter all three temperature sensing heads at a given loca-tion activated, then the water supply for the open head was to be manually admitted. The sprinklers were of a type which activate 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 the variability in the response time of identical sprinkler heads.

IE Circular 78-13 Date: fiovember 6, 1978 Page 2 of 3 Test Dati ils:

The test was started by igniting the two gallons of heptane that were poured into the floor pan. A fully developed fire occurred almost immedia tely. 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 acHvated. The fire between cable trays 1, 2, 3, and 4 appeared most intense, apparently because of a chimney ef fect between the four trays. The flames between cable trays 3 and 5 did not appear to be so intense. The ceramic fiber blanket absorbed some of the heptane so that after the heptane in the pan burned, most of the flama seemed to come from the bottom outside surface of the ceramic fiber blanket, fio additional temperature sensing sprinkler heads at any location activated; thus, the sprinkler water supply v;as not turned on for any of the three sprinkler locations.

The apparent slow response of the third temperature sensing sprinkler is  !

i being investigated, since this was not intended to be a slod response l l

sprinkler.

l l At about 3 minutes into the test there was an indication of a short I circuit in cable tray 3, which was probably caused by the fire. After S-7 minutes the height of the flames appeared to subside; however, residual flames cont inued for about 40 minutes.

Preliminary Resul t; and Analyses:

Preliminary information indicates that the flammable liquid or flames penetrated the protective barriers at the bottom of the vertical trays and caused fire damge to the polyvinyl chloride insulation on cables in four of the five trays.

On subsequent 500-volt megger tests, it was found that another cable in tray 2 had also experienced some damage, as evidenced by a conductor to ground short circuit.

The most probable cause of the fire damage in certain cable trays appears to be related to the absorption or seepage of heptane under the ceramic I fiber blanket at the juncture with the 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. There is some indication that some cable damage was caused by absorption of heptane on the inside of the barrier (wicking effect) and its ignition which heated a cable tray ladder rung, causing damage to a cable in contact with the rung. The ingress of the heptane into the ceramic fiber needs to be further evaluated since this appears to be the nast significant failure mode.

a IE Circular 78-18 Date: Movember 6, 1978 Page 3 of 3 Tentative Conclusions The test results are still being analyzed, and it would be premature to establish firm conclusions at this time; ho'. lever, the results no.i available indicate that the follo'. ling areas of the fire protection program need close consideration:

1. To protect against spills of flamable liquids, barriers or curbs may be needed to prevent entry of the flammable liquid behind fire barriers. A wick ef fect may also need to be considered in the design of fire barriers.

2. Some small fires may not actuate sprinkler heads. To reduce this possibility in sprinkler systems to be installed, fast response sprinkler heads should be considered (less than approximately 3 minutes in the UL Standard 199 " Automatic Sprinklers for Fire Protection Service").

3. The location of the fire detection devices and the sprinkler heads relative to the fire and components being protected is of great

{ importance. The path of the air movement in the area influences the actuation of such devices and should be considered in the system layout.

The final results of this test will be issued when the analysis of the test is complete.

This circular is being issued for information only.

No specific action is requested and no written response is required. If you desire addi-tional information regarding this matter, contact the Director of the appropriate MRC Regional Of fice.

Attachments:

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• 9 IE Circular flo. 78-18 fiovember 6, 1918 LISTItlG F IE CIRCULARS ISSUED Irl 1978 Circular Subject Fi rs t Da te Issued To flo. Of Issue 78-01 Loss of Well Logging 4/5/78 All Holders of Source Well Logging Source Licenses 78-02 Proper Lubricating 4/20/78 All Holders of Oil for Terry Reactor Operating Turbines Licenses (OL) or Cons truc tion Permits (CP) 78-03 Packaging Greater 5/12/78 All Holders of Than Type A Reactor Operator Quantities of Low Licenses (OL),

l Specific Activity Construction Radioactive liaterial Permits (CP), Fuel for Transport Cycle, Priority I flaterial and Waste Disposal Licenses 78-04 Installation Error S/15/78 All Holders of That Could Prevent Reactor Operating Closing of Fire Doors Licenses (OL) or Construction Permits (CP) 78-05 Inadvertent Safety 5/23/78 All Holders of injection During Reactor Operating Cooldown Licenses (OL) or Construction Permits (CP) 78-06 Potential Common 5/25/78 All Holders of Mode Flooding of Reactor Operating ECCS Eouipment Licenses (OL) or Rooms at irWR Construction Facilit ies Permits (CP) 78-07 Damaged Components 5/31/78 All Holders of Of a Bergen-Paterson Reactor Operating Series 25000 Hydrau- Licenses (OL) or lic Test Stand Construction l Permits (CP)

Enclosure Page 1 of 3

IE Circular ?!o. 78-18 tiovember 6, 1978 78-08 Environmental Quali- 5/31/78 All Holders of fication of Safety- Reactor Operating Related Equipment Licenses (OL) or at Nuclear Power Construction Plants Permits (CP) 78-09 Arcing of General 6/5/78 All Holders of Electric Company Reactor Operating Size 2 Contactors Licenses (OL) or Construction Permits (CP) 78-10 Control of Sealed 6/14/78 All Medical Sources Used in Licensees in Radiation Therapy Categories G and G1 78 11 Recirculation M-G , 6/15/78 All Holders of Set Overspeed Stop BWR Operating Licenses (OL) or Construction Permits (CP) 78-12 HPCI Turbine Control 6/30/78 All Holders of Valve Li f t Red BWR Operating Bending Licenses (0L) or Cons truc tion Permits (CP) with Similar HPCI Design 78-13 Inoperability of 7/10/78 All Holders of Service Water Pumps Reactor Operating Licenses (OL) or Construction l

I Permits (CP) except for plants located in: AL, AK, CA, FL, GA, LA, MS, SC Enclosure L _ ._ .

IE Circular tio. 78-18 flovember 6,1978 78-14 HPCI Turbine Reversing 7/12/78 All Holders of Chamber Hold Down BWR Oparating Bolting Licenses (OL) or Construction Permits (CP) for plants with a HPCI Terry Turbine excepting Duane Arnold and Monticello 78-15 Tilting Disc Check 7/20/78 All Holdars of Valves Fail to Close Reactor Operating With Cravity in Licenses (OL) or Vertical Position Cons truc tion Permi ts (CP) 78-16 Limitorque Valve 7/26/78 All Holciers of Actuators Reactor Operating Licenses (OL) or Construction Permits (CP) 78-17 Inadequate Guard 10/13/78 All Holders of Tra ining/ Qual i fica- and applicants tion and Falsified for Reactor Training Records Operating Licenses (OL).

Enclosure Page 3 of 3

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