ML20056F034
| ML20056F034 | |
| Person / Time | |
|---|---|
| Issue date: | 08/06/1993 |
| From: | Mccracken C Office of Nuclear Reactor Regulation |
| To: | Marion A NUCLEAR ENERGY INSTITUTE (FORMERLY NUCLEAR MGMT & |
| References | |
| NUDOCS 9308250449 | |
| Download: ML20056F034 (8) | |
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UNITED STATES n
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WASHINGTON, D.C. 20555 l
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August 6. 1993 l
t Mr. Alex Marion Manager, Technical Division Nuclear Management and Resources Council 1776 Eye Street, N.W., Suite 300 Washington, D.C. 2006-3706
Dear Mr. Marion:
i During the June 3, 1993 meeting, to address the concerns raised by Mr. James i
M. Taylor, Executive Director of Operation in his letter dated May 4, 1993, Mr. Joseph Colvin, President and Chief Executive Officer of Nuclear Management and Resources Council (NUMARC), indicated that they have developed a program for addressing the technical issues and were working towards a solution to the industries fire barrier problems.
From this meeting, it was my understanding that NUMARC had agreed to work with the staff and have a mutual understanding and agreement of the program details prior to it's implementation.
On June 28, 1993, we met to discuss the (NUMARC's) program for resolving the fire endurance and combustibility issues associated with Thermo-Lag 330-1 fire barrier systems.
During this meeting we stated several technical issues which required additional information and technical justification.
In my July 13, 1993 letter, we expressed these technical concerns in writing.
On July 26, 1993 NUMARC initiated construction of test specimens. On July 29, 1993, NUMARC responded to these technical concerns.
l The staff has reviewed the NUMARC response to our request for additional information.
Enclosed are the results of this review. This review indicates that the concerns which were previously identified have not been fully addressed by your response.
The staff has remaining concerns associated with thermocouple placement, cable fill used to improve fire barrier performance, lack of cable functionality testing, and based on our observations of the test specimen construction activities we have concerns regarding the placement of thermocouples on the cable tray side rails and the use of multiple fire barrier construction techniques on a single test specimen.
The staff is concerned that the Phase 1 testing program acceptance criteria does not follow the fire barrier acceptance criteria recommended by Generic Letter (GL) 86-10," Implementation of Fire Protection Requirements," or the t
testing methodology and acceptance criteria proposed by Supplement I to GL 86-10, " Fire Endurance Acceptance Criteria for Fire Barrier Systems Used to Separate Redundant Safe Shutdown Trains Within the Same Fire Area." As a result of these concerns, the current Phase 1 test plan introduces
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uncertainties which brings doubts as to its generic applicability and the fire t'
resistive functionality of the fire barrier system being tested.
l To enable the staff to review the industry Thermo-Lag program and assure that
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the results of these tests can be reasonably applied on a generic basis, we request that NUMARC take the necessary actions to resolve the staff's 5
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technical concerns. We are prepared to meet as soon as possible to resolve these issues.
l If you have any questions, please contact Mr. Steven West, at (301) SO4-1220.
i Sincerely,
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6 y. cz, onrad E. McCracken, Thief Plant Systems Branch Division of Systems Safety and Analysis l
Office of Nuclear Reactor Regulation i
Enclosure:
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i ENCLOSURE NUMARC THERMO-LAG 330-1 FIRE BARRIER TESTING PROGRAM STAFF'S EVALUATION OF THE JULY 29, 1993 SUBMITTAL On June 22, 1993, NUMARC submitted Phase 1 of its fire test program to the NRC and on June 28, NUMARC met with the NRC staff, in a meeting open to the public, to discuss its plans to resolve the technical issues associated with the fire resistance and combustibility of Thermo-Lag 330-1 fire barrier material. Upon reviewing the NUMARC Thermo-Lag Phase 1 test plan and the information presented during the meeting, the staff concluded that several areas needed additional clarification.
By letter dated July 13, 1993, the NRC requested this additional information.
NUMARC, in their letter of July 29, 1993, provided a partial response to these questions and concerns and indicated that the requested additional information on the combustibility i
issues and the Phase 2 testing program would be provided at a later date.
l The staff has reviewed this additional information provided by NUMARC and has i
found the following technical issues were not adequately addressed:
I.
THERMOCOUPLE PLACEMENT AND FIRE ENDURANCE TESTING The method of measuring internal temperature conditions and averaging the data from thermocouples identified in the NUMARC Phase 1 test plan is not consistent with the proposed supplement to Generic letter (GL) 86-10. " Fire Endurance Acceptance Criteria for Fire Barrier Systems Used to Separate Redundant Safe Shutdown Trains Within the Same Fire Area."
The bare copper conductor instrumented with thermocouples used to measure the temperatures of the unexposed surface of the fire barrier material on the bottom of the cable tray fire barrier assembly are routed in the tray with the cables on top of the tray rungs and not along the bottom of the rungs as specified in the proposed supplement to GL 86-10.
The fire barrier acceptance criteria guidance provided in GL l
86-10 specifies that fire barrier performance be judged on the j
temperature of the unexposed surface of the fire barrier material.
In 1
addition, the NUMARC proposed location for the instrumented bare copper t
conductor is insulated by air and the cable jacket material.
The inclusion of cables to improve the thermal performance of these fire barrier systems introduce uncertainties as to the generic applicability of these tests to the industry. This is not an accurate measure of the thermal performance of the fire barrier.
In addition during the week of July 26, 1993, NRC staff observed NUMARC's construction activities at Omega Point Laboratories in San Antonio, Texas, and noted that the cable tray construction was not consistent with the tray construction depicted in revision 4 of the NUMARC test plan.
The NRC rsted that the side rails of the tray were an l-beam in lieu of a C-channel.
In the test plan, the test specimen design details indicate that the trays are of a C-channel construction with the flat surface of the C-channel up against the fire barrier material.
This would give the impression that the cable tray side rail thermocouples are in direct contact with the fire barrier material's unexposed surface.
With the 1-beam tray construction that is being used by NUMARC, the cable tray side rail thermocouples are place on the web between the flanges.
This introduces a -inch insulating air gap
between the thermocouple and the fire barrier material. This placement is non-conservative with respect to determining actual fire barrier performance. This air gap insulates the thermocouples and causes them to indicate temperatures which are lower than the actual unexposed fire barrier surface temperature.
The staff considers this cable tray thermocouple placement proposed by NUMARC to also introduce uncertainties that may impact the generic applicability of these tests to the industry.
In their response, NUMARC indicated that the purpose of the fire test is to ensure cable functionality and that measurement of temperatures below the cable rungs has no relation to cable functionality.
NUMARC's Phase 1 test plan does not include any provisions to perform functionality testing of the proposed cables included in the cable tray test specimens.
NUMARC's approach is inconsistent with the~ proposed supplement to GL 86-10, which clearly states that the fire barrier functionality, as demonstrated by limited temperature rise, not cable functionality, is the principle objective of a fire endurance test.
NUMARC has asserted that the NRC approval of the TV Electric acceptance criteria is an adequate basis to approve their thermocouple placements.
The staff does not agree with this assertion.
It should be noted that the TU approach was focused on plant specific application of the Thermo-Lag fire barrier system.
In addition, the TV Electric test specimens used representative cable fill conditions and plant specific cables.
The cables were conservatively instrumented with thermocouples and cables were functionality monitored using an appropriate megger testing method which was consistent with the proposed supplement to GL 86-10.
The staff concluded that TU Electric took appropriate actions towards solving the Thermo-Lag fire barrier technical problems for Comanche peak Unit 2.
In addition, it should be noted that the raceway thermocouples installed on the TV Electric test specimens were in contact with the fire barrier material unexposed surface.
The staff, from their review of the NUMARC July 29, 1993, submittal concludes that NUMARC did not address the concerns identified by NRC question II.B.1 and 2 and does not find the NUMARC proposed placement of the copper conductor or the side rail thermocouples equivalent in performance to the placement as recommended by the proposed supplement to GL 86-10.
In addition, NUMARC, in their July 29, 1993 submittal, did not propose a criterion for applying thermocouples on the cables within the cable tray test specimens.
In addition, NUMARC did not address questions on how bare cooper conductors will be rcuted through the junction boxes (JBs) and how cables laying up against the JB inner surface will be simulated.
NUMARC indicated that they reserve the right to terminate a particular test if observations indicate imminent breach of the barrier.
The staff considers that this type of approach can lead to indeterminate results.
From a practical testing perspective, tests are terminated only after a l l
known failure has occurred.
From an analysis standpoint, due to the fact that NUMARC wants to include non-instrumented cables in the cable trays and not perform cable functionality testing, neglecting to include thermocouples on the cable tray side rails and the instrumented bare copper conductor which are in contact with the fire barrier material introduces additional uncertainties associated with the actual fire barrier performance which may lead to indeterminate results.
II.
CABLE FItt. AND FL'NCTIONALITY TESTS NUMARC, by their July 29, 1993 submittal, maintains that cables will be installed in cable trays because "this thermal mass is important to the performance of the fire barrier." The staff contends that this is not a true test of fire barrier performance.
The fire barrier acceptance criteria recommended by the proposed supplement to GL 86-10 clearly states that the fire barrier functionality, as demonstrated by limited temperature rise, not cable 'inctionality, is the principle objective.
The staff finds a true test f the barrier system and its raceway compontnts to be germane to determining fire resistive performance, and the inclusion of a cable fill to improv fire barrier thermal performance is non-conservative.
NUMARC, in their July 29, 1993 submittal, did not address our concern about the internal temperature profiles being indeterminate for cable types and fills other than those tested.
The staff finds the validity and the applicability of the temperature profiles derived by the NUMARC Phase 1 cable tray tests to be a significant technical issue. The indeterminate results derived by these tests could create additional regulatory concerns regarding those licensees which attempt to use the test results (temperature profiles) to evaluate in-plant barrier 3
configurations, which have a wide range of cable fills, cable types and sizes.
For example, if a fire barrier system had no cables installed, as in the case of the TVA tests, were tested, the temperature measured on the unexposed irface of the fire barrier were maintained at or below the 139'C [250 delta limit criterion, the data wou'd provide clear j
assurance that ik i' ire barrier pertormed its intended function and that' this. specific barcice configuration could be applied generically.
From the generic perspective, the TVA methodology for determining the internal raceway temperature profiles provided a sound basis for determining the thermal impact on cable functionality.
NUMARC's submittal asserted that cable functionality is a significant unresolved technical issue. The staff disagrees with this assertion.
The staff noted that while NUMARC wants to take credit for a thermocouple placement method which they assert is equivalent to the TU method, it has elected to ignore the cable functionality testing methodology used by TV Electric.
The staff finds that NUMARC's response to questions NRC questions II.D.1, 2 and 3 did not address the technical concerns.
r III. MULTIPLE ASSEMBLY / CONSTRUCTION TECHNIQUES FOR A SINGLE TEST SPECIMEN During the staff's July 26-30, 1993, observations, it was noted that NUMARC was constructing a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> Thermo-Lag fire barrier assembly on a 36" :. 4" galvanized steel ladder back cable tray (Scheme 1-3).
This
" baseline" test specimen utilized 1-inch nominal thickness "v-rib" panels with stress skin on both inner and outer surfaces. The panels were dry fitted and held in place by steel bands on the straight run portion of the tray, and the radial bends were enclosed with differing installation techniques. One radius was enclosed with scored panels, held in place by 2 steel bands on each scored section, and the other radius was enclosed with mitered pieces, held in place by 2 tie wires on each mitered section. After the dry fit enclosure was completed, NUMARC applied Thermo-Lag 330-0 trowel grade material to the seams and joints of the prefabricated panels such that seams and joints were completely covered.
In addition, the staff noted that a Thermo-Lag enclosure for Scheme 1-1, a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> " baseline" test utilizing a 36" x 4" aluminum cable tray, also included the two different installation techniques (scoring and mitering) at the radial bends.
Testing multiple assembly and construction techniques on a single test specimen instead of two or more test assemblies could result in indeterminate test results and inadequate qualification for certain fire barrier design features.
In order to demonstrate that these construction techniques (e.g., band spacing, seam and_ joint construction) are representative of installations which would be installed in plants, it becomes imperative to test configurations with horizontal and vertical runs. This would include testing radial tray bends and cable tray T-sections. The staff considers the NUMARC approach of testing multiple construction techniques on one test specimen to be a non-conservative fire testing qualification practice.
IV.
OTHER ISSUES NOT ADDRESSED On July 13, 1993, the NRC requested additional information concerning the NUMARC Thermo-Lag fire barrier test program. The staff has determined that the July 29, 1993, NUMARC submittal has not adequately eddressed the following technical questions from our July 13, 1993 request:
Question II.A.1 The NUMARC response did not provide clarification as to the range of raceway configurations the Phase 1 program is intended to bound and which test specimen will qualify the configuration.
Question II.A.2 In its response, NUMARC did not explain in detail the construction of Phase 1 baseline assemblies or demonstrate that the construction attributes for these baseline assemblies represent the fire barrier
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construction techniques used to construct the barriers currently 3
installed within the industry.
Question II.C.1 i
The NUMARC response did not quantify the thermal masses of the j
raceway components associated with the Phase 1 test program.
Question III.B i
The NUMARC response did not explain, in detail, the procurement and receipt inspection processes and the specific responsibilities of NUMARC, ABB Impell, Omega Point Laboratories, other contractors, TSI and other vendors, and individual licensees in these processes.
In addition, the NUMARC response did not address how these processes would be applied to all components to be used in the test program such as raceways, cables, and fire barrier materials.
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