ML20211B349

Requests That Proprietary Version of Calculation Rev 0 to ESI150-1, Allowable Heat Intensity in Cable Trays Be Withheld from Public Disclosure

ML20211B349
Person / Time
Site:	Byron, Braidwood
Issue date:	09/19/1997
From:	Hosmer J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20046D808	List: ML20211B333 ML20211B349
References
NUDOCS 9709250170
Download: ML20211B349 (9)

Text

. - _. . . .- ~ . . . . . . _ . . . - . . . . - . . . . .... .

r ATTACHMENT 2 APPLICATION FOR WITHHOLDING PROPRIETARY INFORMATION FROM PUBLIC DISCLOSURE 9709250170 970919 ,

PDR ADOCK 05000454, P PDR p.

k:nta bybwd rei ex:;9 '

Onnmonwrahh Nimn Company

, 1400 Opp 11xe

. Downen Grow, il 60515 5'01 September 19,1997 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Document Control Desk APPLICATION FOR WITHHOLDING PROPRIETARY iNFORMATION FROM PUBLIC DISCLOSURE

Subject:

Calculation # ES1150-1, Rev. O.

The proprietary information for which withholding is being requested is further identified in Commonwealth Edison Company in the enclosed Affidavit signed t,y the owner of the proprietary information. The affidavit, which accompanies this letter, sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR Section 2.790 of the Commission's regulations.

Accordingly, this letter authorizes the utilization of the accompanying Affidavit by Commonwealth Edison Company.

Correspondence with respect to the proprietary aspects of the application for withholding and should be addressed to the undersigned.

Very truly yours, M,Mwm John Hosmer Engineering Vice President k:nla tgtmd raidoc:10 A Unioim Conyuny '

Commonwealth Edison Company AFFIDAVIT I, Kenneth Kostal, being duly sworn, depose and state as follows:

(1) I am Executive Vice President of Sargent and Lundy (S&L) and have been delegated the function of reviewing the confidential commercial information described in paragraph (3) which is sought to be withheld, and have been authorized to apply for its withholding.

(2) Department Heads, and Resource Leaders are responsible for classifying (or delegating the classification) of proprietary or confidential information. These

. persons are most likely to be acquainted with the value and sensitivity of the information in relation to industry knowledge.

(3) The information sought to be withheld was developed by S&L, pertaining directly to Analysis of Ampacity Derating for Thermo-Lag and Darmatt Fire Wraps performed by S&L. S&L is the owner of such confidential commercial information and the related reports. Specifically this information includes:

(a) Calculation # ES1150-1, Rev. 0 (4) In making this application for withholding of such confidential commercial information, S&L relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA),5 USC S 552(b)(4), and NRC Regulations 10 CFR 99 9.17(a)(4), and 2.790(a)(4) for " commercial or financial information obtained from a person and privileged or confidential"(Exemption 4). The confidential commercial information should be withheld from disclosure under 10 CFR 9 2.790 (b)(4) for the following reasons:

(a) The information marked Proprietary or Confidential and is of a sort customarily held in confidence by S&L. Access to such documents within S&L is limited on a "need to know" basis. Disclosures outside S&L are limited to regulatory bodies or licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or proprietary agreements; Ontahimd rai doc:II

4 (c) The information sought to be withheld is being submitted to the NRC in confidence; and (d) The information is not available in public sources.

(5) The calculation in paragraph (3) is a confidential compilation of information related to Analysis of Ampacity Derating for Thermo-Lag and Darmatt Fire Wraps. This calculation was developed in response to S&L '

internal reviews. The development of this calculation was undertaken by S&L at considerable cost and has considerable financial value to others, (6) Public disclusure of the information sought to be withheld is likely to cause substantial harm to S&L's competitive position and foreclose or reduce the availability of profit-making opportunities for such information. S&L's competitive advantage will be lost if its competitors are able to use the results of S&L experience to avoid fruitless avenues, or to normalize or verify their own process, or to claim an equivalent understanding by demonstrating that they can arrive at the same or similar conclusions.

State of Illinois )

) ss:

County of Cook )

Kenneth Kostal, being duly sworn, deposes and says:

That he has read the foregoing affidavit and the matters stated therein are true and correct to the best of his knowledge, information, and belief.

Executed at Chicago, Illinois, this /8 day of /MME1997. ,

$N L Kenneth K'ostal Executive Vice President Subscribed and sworn before me this /89sday of bC 1997.

= :::. - =- WrA<A+ $. bR i N6tary Public, State of Illinois

• OFFICIAL SEAL" Olsela F.Denton h Notary Public. State of1111 nots -

g Ny CcWa @S?"_f_$3_,

k:nla 19bv4 rai. doc t 2

ATTACHMEh /1 RESPONSE TO RAI k nla hbwd rai.&c4

Question 2.1: It appears that Comed's base case comparisons are not applied on a consistent basis. In particular, the licensee is comparing a calculated clad case ampacity limit to a base casa ampacity derived on a different basis. The estimates of fire barrier Ampacity Derating Factor (ADF) should be based on self-consistent treatment of the clad and base line cases. In Inis case, it is considered critical to assess both the clad and base line ampacity limits using a self-consl< tent thermalmodel. If the thermalmodelis used to predict the clad ampacity limits, then a

!bermalmodel ty!!y consistent with the clad case analysis should also be used to assess the base line ampacity limits as weII. The licensee is requested to implement a thermal model for the analysis of the base line case ampacity that is fully consistent witt, the its clad case analysis, and to then base its final ampacity derating assessments on a comparison of the clad and base line thermalcnalysis results.

Response: Consistent models have been applied to the base case open tray ampacity values and the base line ampacities for deriving the Ampacity Derating Factors (ADFs).

In Calculation BYR96-082 / BRW-96-194, Revision 0, ampacity factors were developed that were applied to the cable open tray ampacity values generated by the cable management program (SLICE) used at Byron and Braidwood, as discussed in reference 3. The resulting fire wrapped tray ampacities were compared to cable load currents to verify that cables are loaded within their ampacities. The SLICE program utilized the Stolpe/ICEA Model to generate the open tray ampacities for the cables at the routing points based on routing point depth of fill. The same Stolpe/ICEA Model was utilized in Calculation ESl150-1, Rev. O, which was used to provide the base line ampacities for deriving the ADFs. Therefore, consistency has been maintained between the thermal model used as a base line for developing the ADFs and the thermal model used to develop the open tray ampacities in the SLICE program, (to which the ADFs were applied to obtain the fire wrapped tray ampacity). Ensuring consistency between these two models is critical since it will ensure that the fire wrapped tray ampacity obtained by applyin0 the ADF to the Stolpe open tray ampacity is the same as the fire wrapped tray ampacity obtained by the fire wrappad tray thermal model. As discussed further in the response to Question 2.2, the methodology of Calculation ESl150-1, Revision 0 demonstrates that consistent approaches have been utilized.

The thermal model used to calculate fire wrapped tray ampacities was also based on and derived from the Stolpe model. The model used the same modeling assumptions for the cable mass in the tray, and the same general approach for radiation ar.d convection heat transfer. The model was expanded to contain the physical elements of the fire wrap material, and the heat transfer coefficients were refined to accommodate the new configurations described in reference 3. It is not necessary to implement an additional thermal model as requested, because the fire wrapped tmy model used is fundamentally consistent with the Stolpe model utilized for the base line and for the SLICE program.

Furthermore, the fire wrapped tray model was compared and verified against actual industry test results in Calculation BYR96-059 / G-70-96-092, enclosed with and discussed in reference 3. This verification provided assurance that the fire wrapped ampacities provided by the model are reliable as ampacity values, and not simply as relative values for deriving deratings. Therefore, the ADFs have been derived in a manner to ensure that when they are applied to the SLICE ampacities, the resulting ampacity is consistent with the validated fire wrapped tray thermal model.

L nl4 Mwd rai doe:S

Question 2 2: The licensee has presented a table of heat intensity versus depth of fill values (Item 13 of page 13 of BYR96-082 /BRW 96194). This table is in apparent conflict with the heat intensity values cited by Stolpe and in the ICEA standard P-54-440. The cited values appear to modestly over state allowable heat intensity limits, and hence might lead to optimistic estimates of the cable ampacitylimits.

2.2.1 The licensee is requested to establish the basis for how this heat intensity table was developed and how it is applied in practice, and to reassess the ampacity limit calculations in light of this apparent discrepancy.

2.2.2 The licensee is also requested to provide the supporting calculation cited in BYR96-062 / BRW-96-194 as the basis for this table (i.e., Calculation ESl150-1, Revision 0).

Response: As requested, a copy of Calculation ESl150-1, Revision 0 is attached.

Calculation ESl150-1, Pevision 0 calculated the allowable heat intensity of a cable mass in cable tray, as was done by Stolpe and ICEA P 54-440 (NEMA WC 51). The tray represanted in the model is a solid bottom tray, which is the type of tray installed at Byron and Braidwood. As stated in the NRC staff review, there are two altemative definitions of depth of fill and two alternate definitions of the cable area that can be multiplied by the heat intensity to give the allowable cable heat generation. Each pair of definitions differs by a multiplier of (Pi)/4. Calculation ESl150-1 used the " square cable" definition of depth of fill, as is used in ICEA P-54-440. However, it used the "round cable" definition of the cable area to determine the allowable cable heat generation.

Calculation ESl150-1 gives a heat intensity of 2.095 W ft4 in.2 at a depth of fill of 2.473 inches and a heat intensity of 1.962 W ftd1n'* at a depth of fi!! of 2.594 inches.

Interpolating to obtain the heat intensity (HI) at a depth of fill of 2.5 inches:

(2~473 9~' 5) d HI = 2.095 + (2.473 - 2.594) x (1.962 - 2.095) = 2.065W l

The usameter of the 3/C, #6 AWG,600 V c6e used at Byron and Braidwood is 0.953 inches, so the appropriate cable arca (A) is:

2 2 A = f x 0.953 = 0.713in The cable resistance (CR) for #6 AWG 600 V cable:

CR = 0.0513 x 10~2O The calculated cable ampacity (l) is determined by:

i Hl x A

/= (Where 3 represents the number of conductors) 3xCR k:nl4 bybmt rai doc:6 l

~

v 2.065 x 0.713 7 . = 30.93A 3 x (0.0513 x 10-2 )

The calculated value of 30.93 amperes is in agreement with the ampac ity va lue of 31.77 amperes calculated in the NRC staff review based on the ICEA standard, considering that the Comed ampacity is for a solid bottom cable tray and the ICEA ampacity is based on ladder type cable trays. It is expected that a solid bottom cable tray would result in a lower ampacity value. Therefore, the cited values do not over-state allowable heat intensity limits, and do not lead to optimistic estimates of the cable ampacity limits.

Question 2.3: The licensee cites in Item 2 on Page 12 of BYR96-082 /BRW-96-194 that the base line ampacity for a 3/C, #6 AWG, 600 V cable with a 2.S* depth of11llis 27.5 A. The basis for this value is not clear. SNL was unable to reproduce this limit using standard approaches to ampacity analysis given that the licensee has cited the ICEA definition as the basis for till depth calculations. The licensee is requested to describe, in detail, how this value was obtained, or attematively the subject caMulation should delete references to and reliance upon this value as the ' base line ampacity" for the cases examined.

Response: In addition to developing the Ampacity Derating Factors (ADFs),

Calculation BYR96-082 / BRW 96-194, Revision 0, determined a maximum cable tray depth of fill at which the ampacity of the cables in the fire wrapped tray would equal or exceed their maximum load current carrying capability. This approach was used as a screening process to identify cable tray routing points that require further ampacity evaluations. Evaluated cable tray routing points, with depths of fill that do not exceed this criterion, required no further analysis.

Included in the initial design of Byron and Braidwood was the development of a project ampacity table. The project ampacity table governed the selection of the cable sizes for the various power cables. The table was based on ICEA cable ampacity in an open l cable tray, deratad to account for cable tray covers. The significance of the project ampacity table amperage is that it represents the maximum load currents for the cables installed in the plant. The 27.5 A value for 3/C, #6 AWG,600 V cable is considered to be a representative value of cable ampacity for installations in the plant.

l The maximum depth of fill calculations determined a depth of fiP value of a wrapped tray where the ampacity of the cables would equal or exceed the amperage values

given in the project ampacity table, used to select the cables at the time of design. in .

! ' this approach, the conductor temperature at all routing points with a depth of fill that is less than or equal to the project ampacity table value will be less than the rated temperature of the cable conductor. Therefore, no further analysis of these routing points was required. In this regard, the 27.5 A value was not used as a base line ampacity; instead it was used as a limiting value of full load current.

l knla.bybwd tai.doed .

In the calculation sections that develop the ADFs, the 27.5 A current value was also used as the amperage level at which the fire wrapped tray model was evaluated. It was the appropriate value to use since it represents the maximum expected cable full load condition for a cable of this size in the plant. In the methodology uss.iin these calculations, the 27.5 A value has not been relied upon to represent any industry standard or base line ampacity.

Question 2.4: Several references are made in BYR 96-082/BRW 96-194 to a 'SilTemp Sheet" but the fire barrier descriptions do not include a discussion of any such sheet used in the installation process. The licensee is requested to clarify if such a material is used in its fire barrier constructions.

Response: In the Mathcad 0 !culation BYR96-059 / G-70-96-092, enclosed with and discussed in reference ?, the cable tray from the industry test, used to validate the model included a SilTemp@ sheet in its construction. This SilTemp@ sheet value was

- maintained in the Ma'ncad file, as a part of the validation performed. In Calculation BYR-96-082/BRW-94194, which is also a Mathcad calculation, based on Calculation BYR96-059 / G-70-06-092, the SilTemp@ sheet was not included because this material is not installed in the Byron and Braidwood fire barrier constructions. The calculation sheet equations were modified to reflect the absence of the SilTemp@ layer. However, the text commentary referring to the SilTemp@ sheet remained in the calculation. This reference is not relevant and has no impact on the results of Calculation BYR96-059 /

G-70-96-092.

A N