ML20148H796

Forwards IE Circular 78-18

ML20148H796
Person / Time
Site:	Palo Verde
Issue date:	11/06/1978
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Vanbrunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
References
NUDOCS 7811150009
Download: ML20148H796 (1)

Text

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% 9 0 1990 N. C ALiFOR NI A 00VLEVA RD

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Docket Nos. 50-528 50-529 50-530 ._

Arizona Public Service Company P. O. Box 21666 Phoenix, Arizona 85036 Attention: Mr. E. E. Van Brunt, Jr.

Vice President, Construction Projects Gentl emen:

The enclosed IE Circular No. 78-18, is forwarded to you for information.

No specific action is requested and no written response is required. If you desire additional information regarding this matter, please contact this office.

Sincerely, '~..

[bkMk R. H. Engelken Director

Enclosures:

1. IE Circular No. 78-18

2. List of IE Circulars '

Issued in 1978 ,

l cc: R. W. Kramer, APS l

l 7 81115 0 Od 7 m

IE Circular No. 78-18 November 6,1978 Page 1 of 3 UL 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 effectiveness 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 resulted in damage to some electrical cables.

Discussion 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 flammable 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 recommendations. The sprinkler and detector arrangement was 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 arrangement contained three nominally identical temperature 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 1.ignal when their links fused. After all three temperature sensing heads at a given lot a-tion 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 tu med on. In this way, it was expected to get some data on variabilit3 in the response time of identical sprinklers.

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IE Circular tio. 78-18 flovember 6,1978 Page 2 of 3 Test Details The test was started by igniting the two gallons of heptane that was poured into the ficar p n. A fully developed fire occurred almost immediately. The ceili g smoke detector alarmed in about 15 seconds.

In about 50-60 seconc's, 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 eff 3ct between the four trays. The flames between cable trays 3 and 5 did not appear to be so intense. The ceramic fiber bleiket absorbed some ofl 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 ceramic fiber 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 locations.

The apparent slow response of the third temperature sensing sprinkler is being investigated, since this was not intended to be a slow response sprinkler.

At about 3 minutes into :1e test there was an indication of a short circuit in cable tray 3, which was probably caused by the fire. After 5-7 minutes the height of the flames appeared to subside; however, residual flames continued for about 40 minutes.

Preliminary Results 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 damage to the polyvinyl chloride insulation on cables in four of the five trays..

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

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 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 most significant failure mode.

IE Circular No. 78-18 November 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; however, the results now available indicate that the following areas of the fire protection program need close consideration:

1. To protect against spills of flammable liquids, barriers or curbs may be needed to prevent entry of the flammable liquid behind fire barriers. A wick effect 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 NRC Regional Office.

Attachments:

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. IE Circular No. 78-18 November 6,1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subject Date Issued To No. of Issue 78-01 Loss of Well Logging 4/5/78 All Holders of Source Well Logging Source Licenses 78-02 Proper Lubricating 011 4/20/78 All Holders of for Terry Turbines Reactor OLs or cps 78-03 Packaging Greater Than 5/12/78 All Holders of Type A Quantities of Reactor OLs, cps, Low Specific Activity Fuel Cycle, Radioactive Material Priority I Material for Transport and Waste Disposal Licenses 78-04 Installation Error That 5/15/78 All Holders of Could Prevent Closing of Reactor OLs or Fire Doors cps 78-05 Inadvertent Safety Injection 5/23/78 All Holders of During Cooldown Reactor OLs or cps 78-06 Potential Common Mode 5/23/78 All Holders of Flooding of ECCS Equipment Reactor OLs or Rooms at BWR Facilities cps 78-07 Damaged Components of a 5/31/78 All Holders of Bergen-Paterson Series Reactor OLs or 25000 Hydraulic Test cps Stand 78-08 Environmental Qualification 5/31/78 All Holders of of Safety Related Equipment Reactor OLs or at Nuclear Power Plants cps 78-09 Arcing of General ~ Electric 6/5/78 All Holders of Company Size 2 Contactors cps Enclosure 2 Page 1 of 2 1

. IE Circular No. 78-18 November 6,1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subject Date of Issued to No. Issue 78-10 Control of Sealed 6/14/78 All Medical Sources Used in Licensees in Radiation Therapy Categories G end G1 78-11 Recirculation M-G 6/15/78 All Holders of Set Overspeed Stops BWR OLs or cps 78-12 HPCI Turbine Control 6/30/78 All Holders of Valve Lift Rod Bending BWR OLs or cps for plants with HPCI Terry Turbine 78-13 Inoperability of Multiple 7/10/78 All Holders of Service Water Pumps Reactor OLs and cps except for plants located in: AL, AK, CA, FL, GA, LA, MS, SC 78-14 HPCI Turbine Reversing 7/12/78 All Holders of BWR Chamber Hold Down Bolting OLs or cps for plants with a HPCI Terry Turbine excepting Duane Arnold and Monticello 78-15 Checkvalves Fail to 7/20/78 All Holders of Close In Vertical Reactor OLs or cps Position 78-16 Limitorque Valve 7/26/78 All Holders of Actuators Reactor OLs or cps 78-17 Inadequate Guard Training / 10/13/78 All Holders of Qualification and Falsified and applicants Training Records for Reactor OLs.

Enclosure 2 Page 2 of 2 6

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