ML20062C870
| ML20062C870 | |
| Person / Time | |
|---|---|
| Site: | 05000484 |
| Issue date: | 11/06/1978 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dienhart A NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7811150048 | |
| Download: ML20062C870 (1) | |
Text
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. o yor W4 UNITED STATES
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- "0 ;\ NUCLEAR REGULATORY COMMISSION
[ ,'l (f; yt j REGION lli 799 ROOSEVELT ROAD g . s,,4 to OLEN ELLYN. lLLINOIS 60137 Docket No. 50-484 NOV 6197T ~.
r Northern States Power Company -
ATTN: Mr. A. V. Dienhart
- Vice President - Tyrone Energy Park 100 North Barstow Street i Eau Claire, WI 54701 --
Gentlemen:
The enclosed IE C,ircular No. 78-18 is forwarded to you for infor-mation. No specific action is requested and no written response is required. If you desire additional information regarding this matter, please contact this office.
Sincerely, E hy ek _
g' James G. Keppler
. Director
Enclosures:
- 1. IE Circular No. 78-18
- 2. List of IE Circulars
(,? Issued in 1978
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Central Files Director, NRR/DP!: !
Director, NRR/ DOR PDR Local PDR NSIC TIC Regions I & IV
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! i s' 1 U.S. NUCLEAR REGULATORY C0m!ISSION OFFICE OF INSPECTION AND ENFORCE!! EFT
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REGION III -
P IE Circular No. 78-18 November 6, 1978 UL FIRE TEST
Background
On September 15, 1978, a fire test of a full-scale vertical cable tray array was conducted at the Underwriters Laberatory (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 demenstrate the effectivenerr of area sprinklers and cable tray fire barriers constructed of ceramic liber blankets in preventing damage to cables as a result of an exposure to a flammable liquid fire. The test resulted in damage to 'seme 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 flac=able 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 shews the locatien 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.
i Each sprinkler location in the test arrangement contained three nominally identical tecperature sensing sprinkler heads with fusible links adjacent ,
to an open sprinkler head which was connected to a manual water supply i valve. The temperature sensing heads were wired to signal when their links fused. After 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 sprinkler = 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 in the respense time of identical sprinklers. I i !
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IE Circular Mo. 78-18 November 6, 1978 I
Test Details i 4
The test was started by igniting the two gallons of heptane that was ;
poured into the floor pan. A fully dev61oped fire occurred almost immediately. The ceiling smoke detector alarmed in about 15 seconds.
In about 50-60 seconds, two cf 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 ceracic fiber 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 surf ace 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 the 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 flam=able liquid or fla=es !
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.
' 5 s 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.
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 l 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 j oints . There is some indication that some cable damage was caused by absorption of heptane on the inside of the barrier (vieking effect) and its ignition which heated a cable tray ladder rung causing damage i to a cable in contact with the rung. The ingress of the heptane into i the ceramic fiber needs to be further evaluated since this appears to be the most significant failure mode. ,
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I IE Circular No. 78-18 November 6,1978 Tentative Conclusions The test results are still being analyzed, and it would be pre =ature to establish firm conclusions at this time; however, the results now available indicate that the following areas of the fire protection progra: need close consideration:
- 1. To protect against spills of flec=able liquids, br.riers or curbs may be needed to prevent entry of the fla==able liquid behind fire barriers. A vick 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
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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.
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l IE Circular No. 76-18 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 CPa 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 I 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 l
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4 IE Circular No. 78-18 November 6, 1978
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LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subj ect Date of Issued to No. Issue 78-10 Control of Sealed 6/14/78 All Medical Sources Used in Licensecs in Radiation Therapy Categories G and 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 EPCI 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 Eciders of BWR Chamber Hold Down Bolting OLs or cps for plants with a HPCI Terry Turbine excepting Duane Arnold and Monticelle 78-15 Checkvalves Fail to 7/20/78 All Bolders of Close In Vertical Reactor OLs or cps Position 78-16 timitorque Valve 7/26/7,8 All Holders of Actuators Reactor OLs or cps 78-17 Insdequate Guard Training / 10/13/78 All Holders of Qualification and Falsified '
and applicants Training Records '
for Reactor OLs.
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