ML20034D586
| ML20034D586 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/30/1992 |
| From: | Gagliardo J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Collins S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML082410566 | List: |
| References | |
| NUDOCS 9302170359 | |
| Download: ML20034D586 (9) | |
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ENCLOSURE 11 aA Rf C UNITED STATES f,
Jg NUCLEAR REGULATORY COMMISSION E
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REGION IV -
$b : /[I sii nv AN etAzr oRivE. susTE r.o0 k 'T @
AR LINGTON, TEXAS 760114064 SEP 301982 1
MEMORANDUM FOR:
Samuel J. Collins, Director Division of Reactor Safety -
FROM:
J. E. Gagliardo, Chief Test Programs Section Division of Reactor Safety
SUBJECT:
CONFIRMATORY TESTS OF CPSES THERM 0-LAG INSTALLATIONS In a letter dated August 7,1992 (TXX-92381), Mr. ' Bill Cahill of TU Electric -
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invited the NRC to witness an_ additional series of confirmatory fire tests of the CPSES Thermo-Lag 330-1 installations. The licensee's contractor, Omega Point Laboratories in San Antonio, conducted the testing of the test assemblies which were fabricated by TU craftsmen using CPSES specifications.
l The testing was performed during the period of August 19-22, 1992.
l The tests were witnessed by.a team of TU personnel, representatives of other-l utilities, a representative of NUMARC, a representative of the Thermo-Lag manufacturer, and by a number of NRC personnel. -The NRC representatives for the tests on August 19-20 were Ashok Thadani (NRR), Pat Mhdden (NRR), Isabel Moghissi (NRR), and Jim Gagliardo (RIV).- The test conducted on August 21 and
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disassembled on August 22 was witnessed by Isabel Moghissi (NRR) and Jim Gagliardo (RIV).
The results of the tests, our observations of the test process, and my i
conclusions are documented in the attached report.
If you have any questions-regarding these testing activities or my conclusions, I would be pleased to
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discuss them with you.
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- 3. E. Ga liardo, Chief fest Pro rams Section cc:
A. Thadani, NRR (0WFN BE2)
R. Architzel, NRR (0WFN BD1)
P. Madden, NRR (0WFN BD1) i 9302170359 930210 PDR-COMPfS NRCC CORRESPONDENCE PDR
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OBSERVATIONS OF THE FIRE ENDURANCE TESTS
.OF 1
i COMANCHE PEAK STEAM ELECTRIC STATION
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THERMO-LAG INSTALLATION l
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BY
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JAMES E. GAGLIARDO i
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-i EXECUTIVE SUPMARY t
In August 1992, TU Electric performed a second series of fire endurance tests for their existing and planned Thermo-Lag installations in CPSES Units 1&2.
'The tests were performed to assure that the CPSES installations met the requirements of the applicable codes and standards. This series of tests was.
performed because of the failures in the original tests performed in June 1992.
The tests were performed at the Omega Point Laboratories in San Antonio, Texas. Three test assemblies which had been constructed by TU site personnel using CPSES installation procedures and CPSES stock Thermo-Lag material were tested. The first test assembly included three runs of conduit (1%",
2",
and 3") which had been covered by a single layer of the standard %"-thick pre-formed Thermo-Lag covering. The assembly also included two %" conduits, which had been covered by four different enhancement designs. This test was to establish the upper bound of conduit size below which the enhanced design would be required. The test was also designed to determine which of the j
enhanced conduit cover designs would be preferred.
1 The second test assembly was constructed with a 24" ladderback cable tray with i
a tee connection. The cable tray had been covered with the standard design Thermo-Lag enclosure for cable trays.
The third test assembly was constructed of a 30" wide ladderback cable tray installed in a U-shape. This cable tray was also covered with the standard design Thermo-Lag enclosure for cable trays. The cable tray tests were designed to determine the upper bound in cable tray size above which the previously tested enhanced design would be j
required.
l The test assemblies were instrumented with temperature monitors and with circuit integrity monitors. The test assemblies were tested'in the e
laboratory's furnace for the 1-hour period required by the ASTM standard. The two cable tray assemblies were subjected to a hose stream test immediately after being removed from the furnace. The conduit assembly was not subjected to a hose stream test, but was cooled with water spray at low pressure from a garden hose. The cables in each of the assemblies were.also megger tested l
after the assemblies had been initially cooled by water spray and also the next day when the assembly had fully cooled.
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The testing results showed that the 1%" and 2" conduits experienced internal cable damage and apparent Thermo-Lag burn-through. These size conduits will have to be covered by the enhanced design to assure fire barrier qualification. The cables within the 3" conduit were free of apparent damage except in the area of the LBD box enclosures. The LBD box enclosures for all size conduits tested shifted (slumped) because of their weight and the seam i
between the enclosure and the vertical conduit cover opened exposing the LBD to furnace temperatures. This resulted in cable degradation in the areas of essentially all of the LBDs in the test assembly. The licensee will have to enhance the supports of the LBD box enclosures for all sizes of conduit.
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Both of the cable tray assemblies experienced breaks in the vertical joints (seams) of the assemtJies. A butt joint seam on the 24" tee section and a lateral seam on the 30" cable tray failed and opened the internal cables to the furnace temperatures.
The cables near the seam breaks showed obvious signs of degradation and the megger tests indicated insulation breakdown for a number of these cables. These test demonstrated that both of the test sizes of cable tray, and larger, will require the enhancements being considered for CPSES cable trays.
Although burn-through of the Thermo-Lag was obvious at the seam breaks, there were no noted burn-throughs in other areas, and the Thermo-Lag material did not appear to be fully consumed by the fire. The hose stream tests for the two cable tray assemblies demonstrated that the fog nozzles used at CPSES do not result in the type of damage to the Thermo-Lag material as that experienced in the June 1992 hose stream tests.
In conclusion, the Thermo-Lag fire barrier material appears to be an I
acceptable form of fire barrier material, but installations using this 3
material must be constructed under well defined configuration controls to assure that the barrier integrity can be maintained under fire conditions.
Licensees will have to perform qualification tests of the configurations being used in their plants, and they will have to exercise effective controls over barrier construction activities to assure that the installed configurations conform to those that have been qualified.
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l The test assembly was instrumented with 24 temperature monitors (thermocouples) on the cable tray rails, and 45 temperature monitors on the cables within the barrier. (pages 3-7 of Enclosure 2)
The cables within the assembly were also interconnected at the top of the assembly (outside of the furnace region) to monitor circuit integrity during the 1-hour test in the furnace. The cable connections were also used to perform the megger tests after the assembly had been removed from the furnace.
30" Wide Cable Tray - Scheme 8 This assembly, which is shown on pages 1 and 2 of Enclosure 3 and.in the photographs of Attachments 27 & 28, was constructed of a 30" wide and 4" deep ladderback tray. The assembly was supported by two trapeze type supports.
The channels of the supports were protected with %"-thick Thermo-Lag board to a distance of approximately 9 inches away from the conduits. The struts were uncovered beyond that distance.
The test assembly was instrumented with 25 temperature monitors (thermocouples) on the cable tray rails, and 39 temperature monitors on the cables within the barrier. (pages 3-8 of Enclosure 3)
The cables within the assembly were also interconnected at the top of the assembly (outside of the furnace region) to monitor circuit integrity during the one hour test in the furnace. The cable connections were also used to perform the_megger tests _after the assembly had been removed from the furnace.
TEST RESULTS The test results and observations are summarized below for each of the tests performed.
Conduit Assembly - Scheme 7 (Tested on August 19)
The test was conducted for the ASTM specified one hour. The licensee had decided to megger the cables in the assembly immediately after the fires were extinguished. The laboratory staff decided to disconnect the circuit integrity monitors and megger the cabling while the assembly was still in the furnace. This evolution took much longer than expected, and the result was that the assembly remained in the hot furnace for approximately 15 minutes before it was removed and cooled with water. At the request of the NRC (Reactor Systems Branch), the licensee did not perform the hose stream test, but used a garden hose to cool the assembly with a low pressure spray of water.
The assembly had remained intact, but the Thermo-Lag enclosures over all of the LBD boxes had slumped and opened the seams between the enclosure and the Thermo-Lag on the vertical portion of the conduit (see the photographs in 1
Attachments 5, 9, and 11). These seam breaks resulted in hot spots, as measured by the temperature monitors within the barrier, but-the circuit-
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- integrity data and subsequent megger testing indicated that there were no shorts or open circuits in the cable within the barrier.
1 The data from the temperature monitors had indicated the seam breaks at the LBD boxes before the assembly was even removed from the furnace. The monitors attached to the LBD fittings had peak temperatures in excess of 1000'F in several locations (pages 10-14 of Enclosure 1). The cables within the 3" conduit had a maximum indicated temperaturi of 399'F, but most of the temperatures were much lower (pages 15-17 of Enclosure 1). The licensee reported that the average cable temperature in the 3" conduit was 200*F, which appears reasonable from the above data. The cable within the %" conduit with enhancement A (see above description) experiented a maximum temperature of 409'F (page 18 of Enclosure 1) and an average temperature of 380'F (as reported by the licensee). The remaining temperature indications are shown below in tabular form:
Conduit Size Enhancement Max Temp Ave Temp (from licensee)
B 380*F 352*F C
409'F 378'F D
305'F (Note) 289'F i
1%"
N/A 388'F 318*F 2"
N/A 445'F 303*F Note: The licensee reported a max temperature of 346*F On the morning of August 20 the assembly was disassembled and an inspection of the cables within the LBD boxes for all sizes of conduit indicated significant degradation (cracks, blistering, and hardening) of the outer jackets of the cables (see the photographs in Attachments 3, 4, 5, 9A, and 12). There was evidence of burn-through of the Thermo-Lag material covering on the horizontal and vertical sections of the conduit runs of %",1%", and 2" (see the photographs in Attachments 2, 3, 5, 11, and 12). The Thermo-Lag on the 3" conduit, with the exception of that around the LBD boxes did not appear to have experienced burn-through (see the photograph in Attachment 9).
In addition to the cable degradation noted in the LBD box areas, the cables in the 1%", 2", and three of the %" conduit sections showed signs of jacket degradation (see the photographs in Attachments 4, 7, and 13) within the conduit runs. The cabling in the horizontal section of the 2" conduit was stuck in the conduit and had to be pulled out with a "come-a-long" (see photographs in Attachment 6). Although the cable jackets had been degraded, the conductors within the cable did not appear to have experienced any degradation, and the circuit integrity was maintained in these cables. The cable in the %" conduit with the %"-thick pre-shaped Thermo-Lag cover and the
%"-thick overlay had essentially no degradation (see the bottom-right photograph in Attachment 13) except at the LBD box areas.
The cables in the 3" conduit showed no evidence of jacket or conductor degradation except in the LSD box area (see the photographs in Attachment 98).
b t 24" Wide Cable Tray w/ Tee - Scheme 6 (Tested on Auoust 20)
The test was conducted for the ASTM specified one hour time period.
Temperature ino'ications during the test, and visual observations of the assembly in the furnace indicated that a number of seams had opened on the test assembly. Circuit integrity measurements during the test run and following the hose stream test did not indicate any shorts or open circuits within the assembly.
There were indications of high temperatures within the Thermo-Lag barrier.
The maximum temperature within the fire barrier was 484'F at two tray rail locations near the seam breaks (pages 11 & 17 of Enclosure 2). The maximum cable temperature was 434'F on an instrument cable near one of the seam breaks 1
(pages 28 of Enclosure 2).
The licensee reported an average cable temperature of 317'F.
The licensee decided to perform the hose stream test using the guidance provided for penetration seals in Branch Technical Position (BTP) 9.5.1.
This test involved a 5-minute spray with a fog nozzle set at 30' and a nozzle pressure of 75 psi (see the photograph in Attachment 16).
The assembly remained intact and very little of the Thermo-Lag or char material was removed from the assembly by the spray. Megger testing after the' hose stream test indicated that one of the cables had indications of degradation.
Visual inspections after the spray test showed that three seams (Thermo-Lag joints) had failed during the test (see the photographs in Attachments 16 &
17). The assembly was further cooled by spraying water through the seam breaks with a garden hose.
The essembly was then allowed to cool overnight.
The assembly was disassembled 5t! the morning of August 21, and the cables within the assembly were inspected. The Thermo-Lag boards had slumped during the fire test, but appeared to be supported by the stainless steel bands (see the photographs in Attachments 15, 17, 18, 19, and 20). With exception of the damage and burn-through in the areas of se&m breaks, the Thermo-Lag material appeared to withstand the fire and did not burn-through (see the photographs in Attachments 21, 24, 25, and 26). The bottom photograph in Attachment 25 shows a seam that had not failed. This photograph shows the char layer, a 1
thickness of unaffected Thermo-Lag material and a layer of Thermo-Lag on the interior surface that had been stained by the fumes entering the enclosure through the seam break, but is otherwise unaffected.
There were numerous indications of cable damage or degradation within the assembly in the vicinity of the seam breaks (see the photographs in Attachments 20, 21, 22, 23, and 26). The cables within the enclosure and away from the seam breaks showed no indications of degradation (see the photographs in Attachment 24).
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30" Wide Cable Tray - Scheme 8 (Tested on August 211 The test was conducted for the ASTM'specified one hour time period.
Temperature indications, and visual observations of the assembly in the j
furnace indicated that at about 30 minutes into the test a bottom seam at the mid-span of the assembly had opened. The licensee had decided to continue the i
test until circuit integrity was lost, but circuit integrity was maintained throughout the test run and after the hose stream test. There were indications of high temperatures within the Thermo-Lag barrier. The maximum l
temperature within the fire barrier was 764*F at a tray rail locations near the seam break (page 4 of Enclosure 3). The maximum cable temperature was 703*F on a control cable near the mid-span seam break (page 7 of Enclosure 3).
Other temperatures in this area were also very high (pages 6 & 8 of l ).
The licensee performed the hose stream test with the 30' fog nozzle using the f
guidance provided for penetration seals in BTP 9.5.1.
This test involved a 5-l minute spray with a fog nozzle set at 30* and a nozzle pressure of 75 psi.
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The assembly remained intact and very little of the Thermo-Lag or char material was removed from the assembly by the spray. Megger testing after the hose stream test indicated that many of the cables had indications of t
degradation.
i Visual inspections after the spray test showed that the outside vertical seams (Thermo-Lag joints) had also failed during the test. The assembly was further cooled by spraying water through the seam breaks with a garden hose. The assembly was then allowed to cool overnight.
The assembly was disassembled on the morning of August 22, and the cables within the assembly were inspected. The Thermo-Lag boards had slumped during the fire test, but appeared to have been supported by the stainless steel bands (see the photographs in Attachments 15, 17, 18, 19, and 20). With the exception of the damage and burn-through in the areas of the seam breaks, the Thermo-Lag material appeared to withstand the fire and did not burn-through (see the photographs in Attachments 29, 30, and 31).
There were numerous indications of cable damage or degradation within the assembly in the vicinity of the seam breaks (see the photographs in i
Attachments 29, 30, and 31). The cables within the enclosure and away from t
the seam breaks showed no indications of degradation (see the photographs in Attachments 31 & 32).
CONCLUSIONS The results of this testing appeared to demonstrate that Thermo-Lag installations can be configured to meet the design function of a fire barrier.
The tests of the conduits present the greatest concern.
It is apparent that i
conduit sizes below 3" will have to be enhanced. The tests of the %"
conduits also show that the type of enhancement is very critical. The l
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l licensee has argued that:the extra 15 minutes the' assembly' spent in the i
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. furnace to. perform the megger test contributed to the failures!.It can be argued that the amount of cable degradation may have been lessened if the -
assembly had been immediately removed from the furnace. The temperature-data, f
however, would. indicate that degradation was already present when the 1-hour.
y test was complete.
I Clearly the need to better support the LBD box enclosures is needed.- I have some reservations, however, regarding the types of supports that the licensee' diameter LBD box enclosures, but the 3" and 5" enclosures are so massive that.
i is proposing to fix the problem. This proposed fix may work for the-small.
1 I fear they will not hold up in the October tests.
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1 The tests of the 24" and the 30" cable tray assemblies demonstrated that the Thermo-Lag material can be used in these applications provided the appropriate; j
measures are taken in sealing and reinforcing the seams between adjoining section of the Thermo-Lag. The tests also indicate that'the Thermo-LagL
- f material can remain free of burn-through provided that it is adequately
.i supported. The stainless steel bands sagged early in the test. because of i
thermal expansion. The Thermo-Lag sheets also sagged during the test,: but at a much1 slower rate. The result was that the stainless-steel bands ultimately i
provided support for the Thermo-Lag material and very likily prevented further' damage to the barrier.
It is the author's belief that_this support prevented the burn-through that-has been seen in other; tests such:as those performed for.
1 the NRC.
l The utility will perform additional testing to prove an acceptable design for j
the small diameter conduits, the LBD box enclosures, and horizontal cable'
- i trays.
The Omega Point Laboratory's testing process appeared to'be acceptable _ for j
testing the Thermo-Lag material and _its configurations in the power plants.
i The test assemblies were well instrumented and' the laboratory's-instrumentation appeared to be appropriate for the testing.
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