ML17333A670
| ML17333A670 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 12/02/1996 |
| From: | John Hickman NRC (Affiliation Not Assigned) |
| To: | Fitzpatrick E INDIANA MICHIGAN POWER CO. |
| Shared Package | |
| ML17333A671 | List: |
| References | |
| GL-92-08, GL-92-8, TAC-M85538, TAC-M85539, NUDOCS 9612060344 | |
| Download: ML17333A670 (10) | |
Text
~ h II December 2,
1996 Hr. E.E. Fitzpatrick, Vice President Indiana Michigan Power Nuclear Generation Group 500 Circle Drive
- Buchanan, MI 49107
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING THERMO-LAG RELATED AMPACITY DERATING ISSUES FOR D.
C.
COOK NUCLEAR POWER PLANT (TAC NOS.
H85538 AND M85539)
Dear Hr. Fitzpatrick:
By letter dated May 12,
- 1995, you submitted a response to the NRC Request for Additional Information (RAI) related to Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers," for the Donald C.
Cook Nuclear Power Plant (DCNPP),
Units 1 and 2.
The staff in conjunction with its contractor, Sandia National Laboratories (SNL), has completed the preliminary review of your submittal, and has identified a number of open issues and concerns requiring'larification by the licensee.
Your response to the enclosed Request for Additional Information (RAI), is needed for resolving our concerns on the ampacity derating factor determinations for DCNPP.
Please respond to this RAI 90 days after receipt so that the outstanding issues can be resolved for the application of Thermo-Lag 330-1 Fire Barriers at the Donald C.
Cook Nuclear Power Plant.
If you have any questions on these
- items, please contact me at (301) 415-3017:
Sincerely, Original, signed by:
John B. Hickman, Project Manager Project Directorate III-3 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos.
50-315 and 50-316
Enclosure:
As stated cc w/encl:
See next page DISTRIBUTION:
Docket File PD3-3 Reading OGC PUBLIC EAdensam(E)
JRoe GHarcus JCaldwell, RIII RJenkins ACRS DOCUMENT NAME:
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'E'opy with ettechment/endoetee 'N'o copy OFFICE LA:PD33 c~
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~0 December 2,
1996 Hr. E.E. Fitzpatrick, Vice President Indiana Michigan Power Nuclear Generation Group 500 Circle Drive
- Buchanan, MI 49107
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING THERMO-LAG RELATED AMPACITY DERATING ISSUES FOR D. C.
COOK NUCLEAR POWER PLANT (TAC NOS.
M85538 AND H85539)
Dear Mr. Fitzpatrick:
By letter dated May 12,
- 1995, you submitted a response to the NRC Request for Additional Information (RAI) related to Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers," for the Donald C.
Cook Nuclear Power Plant (DCNPP),
Units 1 and 2.
The staff in conjunction with its contractor, Sandia National Laboratories (SNL), has completed the preliminary review of your submittal, and has identified a number of open issues and concerns requiring clarification by the licensee.
Your response to the enclosed Request for Additional Information (RAI), is needed for resolving our concerns on the ampacity derating factor determinations for DCNPP.
Please respond to this RAI 90 days after receipt so that the outstanding issues can be resolved for the application of Thermo-Lag 330-1 Fire Barriers at the Donald C.
Cook Nuclear Power Plant.
If you have any questions on these
- items, please contact me at (301) 415-3017.
Sincerely, Docket Nos.
50-315 and 50-316
Enclosure:
As stated cc w/encl:
See next page DISTRIBUTION:
Original signed by:
John B. Hickman, Project Manager Project Directorate III-3 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket File PD3-3 Reading OGC PUBLIC EAdensam(E)
JRoe GMarcus JCaldwell, RIII RJenkins ACRS DOCUMENT NAME:
G:iDCCOOKIi,C085538.RAI To teoetee ~ oopy of thte dootenent. Indoete In the bott: 'C Copy withoMt ettechment/endoetee
'E'opy with ettechment/endcevre
'N' No copy OFFICE LA:PD33 c~
PH:PD33 NAME JHickman M
DFoster-Curse DATE i 8/W /9
///
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON> D.C. 20555-0001 December 2, f 996 Hr. E.E. Fitzpatrick, Vice President Indiana Michigan Power Nuclear Generation Group 500 Circle Drive
- Buchanan, HI 49107
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING THERMO-LAG RELATED AMPACITY DERATING ISSUES FOR D. C.
COOK NUCLEAR POWER PLANT (TAC NOS.
M85538 AND H85539)
Dear Hr. Fitzpatrick:
By letter dated Hay 12,
- 1995, you submitted a response to the NRC Request for Additional Information (RAI) related to Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers," for the Donald C.
Cook Nuclear Power Plant (DCNPP),
Units 1 and 2.
The staff in conjunction with its contractor, Sandia National Laboratories (SNL), has completed the preliminary review of your submittal, and has identified a number of open issues and concerns requiring clarification by the licensee.
Your response to the enclosed Request for Additional Information (RAI), is needed for resolving our concerns on the ampacity derating factor determinations for DCNPP.
Please respond to this RAI 90 days after receipt so that the outstanding issues can be resolved for the application of Thermo-Lag 330-1 Fire Barriers at the Donald C.
Cook Nuclear Power Plant.
If you have any questions on these
- items, please contact me at (301) 415-3017.
Sincerely, Docket Nos. 50-315 and 50-316
Enclosure:
As stated cc w/encl:
See next page ohn B. Hickman, Project Manager Project Directorate III-3 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation
Mr. E.
E. Fitzpatrick Indiana Michigan Power Company CC:
Regional Administrator, Region III U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532-4351 Attorney General Department of Attorney General 525 West Ottawa Street Lansing, Michigan 48913 Township Supervisor Lake Township Hall P.O.
Box 818 Bridgman, Michigan 49106 Al Blind, Site Yice President, Donald C.
Cook Nuclear Plant 1 Cook Place Bridgman, Michigan 49106 U.S. Nuclear Regulatory Commission Resident Inspector's Office 7700 Red Arrow Highway Stevensville, Michigan 49127 Gerald Charnoff, Esquire
- Shaw, Pittman, Potts and Trowbridge 2300 N Street, N.
W.
Washington, DC 20037 Mayor, City of Bridgman Post Office Box 366 Bridgman, Michigan 49106 Special Assistant to the Governor Room 1 State Capitol
- Lansing, Michigan 48909 Drinking Water and Radiological Protection Division Michigan Department of Environmental guality 3423 N. Hartin Luther King Jr Blvd P. 0.
Box 30630 CPH Hailroom
- Lansing, Michigan 48909-8130 Donald C.
Cook Nuclear Plant Hr. Steve J.
Brewer Indiana Michigan Power Nuclear Generation Group 500 Circle Drive
- Buchanan, Michigan 49107
E VEST FOR ADDI IONAL INFORMATION DONALD C.
COOK NUCLEAR POWER PLANT FIRE BARRIER AMPACITY DERATING ISSUES TAC NOS.
M85538 AND M85539
1.0 BACKGROUND
By letter dated May 12,
- 1995, Indiana Michigan Power Company (the licensee) submitted a response to the NRC Request for Additional Information (RAI) related to Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers," for the Donald C.
Cook Nuclear Power Plant (DCNPP), Units 1 and 2.
This response included the following attachments:
Attachment 1:
Summary of Ampacity Derating Analyses : AIEE Transactions Papers57-660 8 50-52 : Cable tray Allowable Fill Design Standard : Analyses and Mathematical Models : Representative Ampacity Derating Calculation Results : Results from Test Report 8CL-542 The DCNNP ampacity derating methodology involves the application of two separate but related models.
In the first model (denoted Part 1 Analysis),
the licensee calculates the ampacity of individual cables by partitioning the estimated overall heat rejection capacity of the tray.
This partitioning is based on the available surface area of each cable in comparison to the total exposed cable surface area.
In the second model (denoted Part 2 Analysis),
the licensee estimates the actual heat rejection capacity of a given cable tray.
The second model is generally based on the Neher-McGrath mathematical methodology.
The staff, in conjunction with its contractor, Sandia National Laboratories (SNL), has completed the preliminary review of the licensee's submittal, and requires that the following questions be addressed by the licensee.
- 2. 0 QUESTIONS 2.1 General Modelin Concerns
~
Although the licensee submitted the results of its analysis for one cable tray and several
- conduits, there was no overall summary provided to assess the full range of fire barrier configurations installed at DCNPP.
The licensee is requested to provide a summary of all ampacity derating assessment results for all Thermo-Lag Enclosure
enclosed raceway configurations (e.g. tray, conduit, air drop) installed at DCNPP.
The level of documentation provided is not adequate to complete a
full evaluation of your ampacity assessments.
In general, there is no discussion of how the two parts of the licensee analysis methodology are made to work together, the example calculations do not provide enough information to verify the calculations, and the experiments purported to support validation of the thermal models are either not provided, or no direct one-to-one comparison of the experiments to modeling results is provided.
The licensee is requested to provide further documentation in the area stated above.
No discussion was provided as to how in-plant cable service loads were determined, which cables have been considered in the analysis, and the basis for the elimination of other cables from consideration.
The licensee is requested to clarify how the above information was treated in its analysis.
2.2 Part I Anal sis A
endix A of Attachment 4
4 The staff agrees with its contractor, SNL that the information provided to date does not provide an adequate basis for validation of its assumption that the overall heat rejection capacity of a sparsely loaded cable tray can be partitioned to individual cables in proportion to the cable diameter.
The limited information provided by the licensee (one plot with no supporting data and no indicated units) is unconvincing given the potential for minor errors in the calculation could lead to larger error in the final estimation of ampacity limits.
The licensee has cited a set of experiments as the basis for this plot, and hence, for the validation of this methodology (see reference to Appendix C in Licensee ).
However, this documentation of these experiments was not provided for staff review.
The licensee is requested to provide Appendix C as well as any other documentation to support the validation of the experiments cited in the licensee analysis.
2.3 Part 2 Anal sis A
endix B of Attachment 4
~
The assumption of equivalent annular regions appears to give inadequate treatment to the importance of surface area in heat transfer calculations.
The actual rates of heat transfer are directly proportional to surface area; hence, it is important that the thermal model use actual available surface areas in its formulation.
The licensee should provide examples which encompasses all raceway types installed (i.e., conduit, cable tray) to illustrate the effective heat transfer areas assumed for each of the layers in its modeling and compare those assumed areas to the actual heat transfer areas available in the physical system.
The analysis as provided in the submittal dated May 12,
- 1995, provided no meaningful validation of its analysis method for calculating cable ampacity limits and cable tray limiting heat rejection capacities.
The licensee should provide for the direct comparison of predicted cable ampacity limits to those measured in experiments on the corresponding system in order to validate its calculations.
The thermal model for the subject analysis is based on heat transfer correlations which were originally published in the 1929-1933 time frame.
These correlations are badly dated, and the impact of using more modern correlations in the model should be assessed by the licensee.
It is stated by the submittal dated Hay 12, 1995, in the development of correlation for heat transfer from the cables to the surrounding air gap, that "the thermal resistance per conductor will be the total number of conductors divided by the total thermal conductance" (see the first sentence in the paragraph immediately preceding Equation 20 of the licensee analysis).
The licensee should further explain and clarify the basis,
- intent, and impact of this statement.
Directly related to the comment regarding the heat transfer correlation from the cables to the surrounding air gap, the correlations for "the thermal resistance through relatively thin cylinders (i.e., cable jacket, tray, fire barrier)" (Equation 16 per the licensee Analysis) and for the "thermal resistance from the last surface to ambient" (Equation 21 per the licensee Analysis) each include a factor (n') described as "the number of conductors within the section."
This would appear to be, in effect, a thermal partitioning factor which is based on a simple conductor count, and as such, may be in direct conflict with the stated assumptions of the model described in "Appendix A" of Licensee Attachment 4 (where it is assumed that surface area will be the basis for thermal partitioning).
The licensee should clarify the basis,
- intent, and implementation of this factor (n')
as it is applied to each of these two equations and how this factor applies when cables of different physical dimensions are present in a common cable tray.
The subject analysis treats all cable tray systems using a model based on circular geometries.
This practice is said to have been validated based on the "excellent correlation between computer data and test data."
- However, no evidence of such validation has been provided in the subject submittal.
The licensee is requested to provide the technical justification which validate its assumptions in this regard.
~
The correlation cited for the thermal resistance between the outer surface of the barrier and the ambient environment (Licensee Equation
- 21) applies only to pipes.
These correlations should not
4 be applied to flat plate surfaces such as those which would be experienced around a cable tray.
The analysis model provides no treatment of the effects of spacing on the radiative heat transfer behavior of the cables.
Reduced view factors due to cable proximity might significantly reduce the predicted rates of radiant heat transfer.
The licensee is requested to address how the effects of spacing should be accounted for in the radiative heat transfer correlations.
The licensee is requested to provide information on the specific inputs used in any example case as well as any computer code which process the subject calculations.
The licensee has apparently applied one or both of its thermal models to the analysis of cables in conduits as well as those in trays.
The applicability of both licensee analysis models to conduits needs to be further clarified by the licensee.
Specifically, the thermal model for cable trays is based on the unique configuration of "maintained spacing" for its power cables in cable trays.
This same factor cannot generally be assumed to exist for cables in conduits.
The licensee should provide an explicit discussion of the applicability of its two thermal models (the "Appendix A" surface area based heat load partitioning model and the "Appendix B" direct thermal analysis model) to conduits, and should discuss how these models were implemented for conduit analyses.
2.4 ttachment 5
Re resentative Calculation Results A nominal comparison between the licensee ampacity predictions and those obtained using more conventional approaches to the ampacity assessment showed that the DCCNP estimated ampacity limits were nonconservative.
In the case of the conduits, the licensee estimated ampacity limits including derating for the fire barrier system which were in excess of the tabulated ampacity limits for cables in conduits without a fire barrier as set forth in the NEC
- tables, even given the most generous interpretation of the conduit loadings (only a single cable per conduit with no more than three conductors).
These results indicate that the subject thermal model may be generating unrealistic and nonconservative estimates of actual cable ampacity limits.
The licensee is requested to address these discrepancies.
As a par t of the validation process, the licensee should provide a
direct comparison of its own modeling results to the results obtained using more conventional ampacity derating approaches.
In any future submittal, the licensee should also provide a
sufficient base of information (i.e.,
more detailed descriptions of the physical characteristics of each
- system, and the characteristics of the installed fire barrier system) regarding specific applications.
The example results for conduits predicted the exact same ampacity limits down to four significant figures (25.85A) for a 3/C 812AWG cable in both a 1/2" conduit (cable 8026R) and a 1" conduit (cable 8505R for example).
While the ampacity tables would not distinguish between these two cases, given the differences in the physical configurations, the thermal model certainly should provide different results.
This licensee is requested to identify the source of, and resolve, this discrepancy.
The full load amperes (FLA) for the equipment as shown appears low.
Motor
~Volta e FLA Used FLA Per NEC Table 430-150 2
HP 3
460 V
460 V
460 V
2.6 3.8 16 20 3.4 4.8 21 27 Provide the basis for the full load current projections.
The nameplate FLA which is at rated voltage and rated load is acceptable provided the loads are not operating at an overload condition or at a service factor greater than one and the rated voltage is maintained at the load terminals.
Provide a discussion about the impact of overload conditions, the service factor of the load and the voltage availability at the load terminals given the stated ampacity derating margins.
The allowable ampacity as calculated for 812AWG in Appendix R trays is extremely high.
ICEA Standard P-54-440, "Ampacity of Cables in Open-Top Cable Trays" allows only 15 A (maximum) for 1.0" depth of fill and cable diameter of 0.49".
The cable used in this calculation has a diameter of 0.32".
For 0.32" diameter cable, the allowed ampacity per ICEA Standard P-54-440 will be (0.32/0.49) x 15 9.79 amps.
This amperes would be reduced further due to fire wrap material (Thermo-Lag).
Provide a comparison of the calculated allowable ampacity for Appendix R trays versus the allowed ampacity without the Thermo-Lag pdff Add 444444 d df-44444~
fd cable diameter and depth of fill adjustments.
The staff believes that the calculated ampacity for wrapped trays must be less than that obtained from ICEA Standard P-54-440.
The licensee should provide adequate justification for ampacity values exceeding ICEA Standard P-54-440.
Provide a comparison of calculated allowed ampacity in Appendix R
conduit versus allowed ampacity in conduit as published in ICEA Standard P-46-426 (including factors for the number of conductors, grouping factors for cables in exposed or enclosed conduit in air, etc.).
Provide sufficient details (cable type, cable diameter, number of conductors, conduit size, percent fill, temperature, etc.) to assess ampacity rating for the example cases.
The staff believes that the calculated ampacity for wrapped conduits must be less than that obtained from ICEA Standard P-46-426.
The licensee should provide adequate justification for ampacity values exceeding ICEA Standard P-46-426.
Attachment:
Letter report to U.S.
NRC, Revision 0, dated June 28,
- 1996, prepared by Steve Nowlen of Sandia National Laboratories