ML20197D075
| ML20197D075 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/20/1998 |
| From: | Nowlen S SANDIA NATIONAL LABORATORIES |
| To: | Ronaldo Jenkins NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20197D072 | List: |
| References | |
| CON-FIN-J-2503 NUDOCS 9809150269 | |
| Download: ML20197D075 (14) | |
Text
. . . - . . -. _. . . - - - .
A A Review of the 10/3/97 Entergy River Bend Ampacity Derating RAI R'esponse A Letter Report to the USNRC January 20,1998 i
Revision 1 Prepared by:
Steven P. Nowlen Accident and Consequence Analysis Dept.
Sandia National Laboratories Albuquerque, New Mexico 87185-0748 1
i l
Prepared for:
Ronaldo Jenkins l Electrical Engineering Branch Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission j Washington,DC 20555 i USNRC JCN J-2503 ENCLOSURE 2 9009150269 900903 {
_ _ _ . . _ _ _ _- _. . ~ _ _ __ _ _ - .
=
a TABLE OF CONTENTS:
Section Eage FORWARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii i
1.0 INTRODUCTION
i 1.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1
1.2 B ackground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 j 2.0 LICENSEE DIRECT RAIRESPONSES
, 2.1 RAI Item 1: Resolution of Overloaded Cables . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 RAI It em 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 j 2.2.1 Item 2a: Internal Convection Coef5cients . . . . . . . . . . . . . . . . . . . . . . . 4 3 2.2.2 Item 2b: Treatment ofExternal Convection . . . . . . . . . . . . . . . . . . . . . . 5 2.2.3 ltem 2c: Treatment of Conduits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 -
2.2.5 Item 2e: Consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.6 Item 2f: Conduit Conductor Count Facters . . . . . . . . . . . . . . . . . . . . . . 8
- 2.2.7 Item 2g
- Independent Treatment of Multiple Source Heat Transfer . . . . 8 2.2.8 Item 2h: Use of Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1 2.3 RAI Item 3: Reassessment of Supported Calculations . . . . . . . . . . . . . . . . . . . . 9 2.4 RAIItem 4: Conduit Fill Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 l 2.5 RAI Item 5: Conduit Fills in Excess of NEC Limits . . . . . . . . . . . . . . . . . . . . . 10 1
3.0
SUMMARY
OF FINDINGS AND RECOMMENDATIONS
! 3.1 General Findings and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1 4
3.2 One Unresolved Point of Concern Noted For the Record . . . . . . . . . . . . . . . . . I1
(
V l
l i
l l
i i
l
FORWARD The United States Nuclear R egulatory Commission (USNRC) has solicited the support of Sandia National IAoratories (SNL) in the review oflicensee submittals associated with fire protection and electrical engineering. This letter repon represents the third report in a series of review repons associated with ampacity derating submittals from Entergy Operations Inc. (EOI) for the River Bend Station Unit 1 (RBS-1). The submittal reviewed by SNL under the current effons doewnents the licensee's response to the USNRC RAI of May 2,1997. This work was performed as Task Order 2 of USNRC JCN J-2503.
l l
1 iii
[
i
1.0 INTRODUCTION
1.1 Objective The objective of this repon is to document fmdings and recommendatione resulting from a Sandia National laboratories (SNL) review of a licensee submittal for the River Bend Station Unit 1 (RBS-1) on the subject of 6re barrier cable ampacity derating. De subject submittal was forwarded to the USNRC Document Control Desk under an Entergy Operations Inc. fEOI) cover letter dated 10/3/97, and was provided by the licensee in response to an USNRC Request for
. Additional Information (RAI) of 5/12/97.
1.2 Background
This is the first revision of the third report in a series of SNL review repons associated with the River Bend Station. The history of this review effon is summarized as follows:
9/25/95: The USNRC issued a RAI requesting more information on ampacity load calculations for RBS-1 to funher clarify the licensee position regarding Generic I.4tter 92-08.
11/9/95: The fir::t licensee RAI response is forwarded to the USNRC Document Control Desk. This original submittal documented the licensee position regarding cable ampacity loads associated with its installed fire barrier systems.
6/7/96: SNL completes a technical review of the licensee 11/95 submittal under the
- terms of a general task ordering agreement, USNRC JCN J-2017.
10/16/96: A second RAI is submitted to the licensee by the USNRC.
12/19/96: The licensee responds to the 10/96 RAI. The response includes a new set of calculations for a range of non standard barrier configurations including multiple items in common enclosures.
3/21/97: SNL completes a review of the 12/96 licensee submittal under USNRC JCN J-2503. This review Snds that all of the previously identified items have been resolved, but also identi6es a number of new points of potential concern regarding the new calculations.
5/12/97: A third USNRC RAI is issued to the licensee.
10/3/97: The licensee submits its response to the 5/97 RAI. .
\
12/24/97: Revision 0 of the current repon is forwarded to the USNRC )
documenting initial review findings and recommendations. The licensee response !
to one RAl item (2d) is cited by SNL as non responsive.
1 l
l
l i
- 1/20/98: A conference call between the USNRC, SNL, and the licensee is .,
conducted to discuss the licensee response to RAI item 2d and this report is -
revised to reflect the information discussed during that conference call.
Note in pnticular that this revision to the current repon (revision 1) includes the consideration of information provided by the licens 4 during a conference call on 1/20/98 as cited immediately above. This, in particular, impacts the SNL evaluation of the licensee response to Item 2d.
i E
i o
m l
2
. 1 2 .
- 2.0 LICENSEE DIRECT RAIRESPONSES 2.1 RAI Item 1
- Resolution of Overloaded Cables SynonsLs of concern- The licensee was requested to describe the course of action to resolve nominally overloaded cables. It was also stated by the USNRC that the NEC overcurrent 4
protection ratings cannot be used as a basis for the resolution of overloaded cables. An assessment of remaining life for the overloaded cables was requested.
Svnensin of Resnonse The licensee response has included the followin3 major points: l The licensee stated that "the SNL comment related to th use of the NEC overcurrent
- protection provisions" has been incorporated.
The licensee also cites that the concept of" qualified life" is "not meaningful" for the
- impacted cables because they are not subject to severe accident environment and are hence
- not encompassed by the plant EQ program requirements.
An assessment is described in which the cables were physically inspected including testing with an EPRI device called the " Franklin Indenter" or the "EPRI Cable Indenter." It was i noted that the cables were " absent of any observable change" in comparison to un-used l stockpiles of the same cable.
- Field observations also are cited as indicating that the cables in question were operating at very little above ambient temperature in contrast to the estimated operating temperature from the thermal model of130*C.
The licensee cites that the fire barriers in question have been removed.
Some supplemental information regarding this response was provided by the licensee during a USNRC/SNiilicensee conference call on 1/20/98. This supplemental information is relevant primarily to the assessment of the licensee response to RAI item 2d. This supplemental information is discussed in detail in Section 2.2.4 below.
~
Assessment of Resnonse SNL's assessment of these points is as follows:
SNL takes the first point, incorporation of the NEC overcurrent comments, to imply that the licensee will not use this as a basis for resolving cable overloads. Given this ;
interpretation, the licensee response is acceptable.
SNL considers that the concept oflife expectancy as is often applied in EQ studies is a meaningful concept in the ampacity arena. The major difference is that cable life is considered in comparison to the nominal cable insulation temperature rating of 90*C as compared to the cable equipment qualification qualified life temperature that will typically be much lower (often on the order ofjust 50-60'C). Nonetheless, the same concepts of accelerated aging can be applied to non EQ based applications.
?
i
- A review Of the ampacity loads cited by the licensee did reveal that those cables that were '
! field evaluated are indeed the worst-case cables for the special configuration fire barders ;
(in terms of their relative ampacity load). Hence, a demonstration that these cables are l
)
acceptable should bound the other cables present in the envelope.
- The licensee assessment of the cables based on physical inspection and measurements with
! the EPRI indenter are considered adequate demonstration that premature degradation of
- the cables has not been realized. SNL has had considerable experience with the EPRI i indenter through a cooperative USNRC/EPRI/SNL cable research program (Reference l NUREG/CR-5772) as cited by the licensee. In these tests it was found that for cables
! with a Hypalon jacket, indenter measurements for the jackets did generally reflect the extent of aging degradation. Hence, use of this device for the cited Hypalonjacketed cables at River Bend would appear appropriate. (Note that this device did not work well
- as an agi ig indicator for certain other material types; hence, in this case the fact that the cable jackets are Hypalon is critical to this assessment.)
- The removal of the fire banier implies that future life performance will not be compromised. Hence, only the life to-date impact need be demonstrated for these j applications. For the cited cable types, the indenter results r.re sufficient to demonstrate that the life-to-date operation has not adversely impacted the cable life expectancy.
l Findings and Recommendations The licensee response is considered fully adequate to resolve the identified concems. In particular, the measurement of the in-service and stockpiled cables with the EPRIindenter, and the removal of the fire barder are especially telling points. SNL finds that for the cited cables, the field measurements are adequate to demonstrate that the cables have not been subjected to adverse accelerated thermal aging. SNL recommends that no further action on this RAIitem is required.
2.2 RAIItem 2 2.2.1 Item 2a: Internal Convection Coefficients Synopsis of Concern The licensee applied convection coefficients for an external surface to the confined spaces intedor to the fire barriers.
Synoosis of Reinonse The licensee response recognizes the point of the concern raised by SNL.
The response correctly points out that the complex geometry of the interior spaces means that no '
direct correlations for confined space convection are available. The licensee also provides a comparison of the values used in the study to those obtained using the available confined space conelations and shows that the chosen values are generally consemtive.
Assessment of Response Of the points raised by the licensee, the compadson of the convection values used in practice to the corresponding confined space coefficients was most telling. This comparison has demonstrated that the licensee chosen values are conservative. This is largely because of the small temperature differences that result in relatively small convection coefficients in Eeneral. In this case, the convection treatment is approaching, or has passed, the point where 4
L conduction through the air gap is actually more eEcient. Hence, use of the convection correlations actually results in a more conservative heat transfer prediction.
Findings and Recommendations: SNL finds that the licensee has adequately addressed the identified concern, and no further actions on this item are recommended.
2.2.2 Item 2b: Treatment ofExternal Convection Svnoosis of Concern The licensee had provided a very crude treatment of external convection that was not consistent with common practice in this regard.
Synoosis of Resnonst; The license response cites that while crude, the treatment gives was, in fact, conservative. This includes comparison of the chosen correlation parameters to those considered representative for the conditions under analysis.
Assessment of Reinonse: The licensee response has demonstrated that the treatment provided will i be conservative.
Findings and Recommendations: SNL finds that the lictnsee has adequately addressed the identi6ed concern, and no further actions on this item are recommended. i 2.2.3 Item 2c: Treatment ofConduits
)
Synoosis of Concern: It was not clear from the submittal how the licensee had handled the probiem of heat transfer between the cables and the conduit.
Synopsis of Resnonse The licensee response has clarified that the cable to conduit beat transfer has been based on an examination of the IEEE conduit ampacity tables. A composite heat transfer coemeient is developed on the basis of these tables. Hence, the treatment is in fa:t consistent with the Neher /McGrath approach.
Assessment of Resnonse: The licensee response was fully adequate to resolve the identiSed concern. The licensee practice of" backing out" the cable to conduit heat transfer coefficients, and then applying those same coemeients is technically valid. l Findings and Recommendations SNL finds that the licensee has adequately addressed the identified concern, and no further actions on this item are recommended.
1 2.2.4 Item 2d: Calculation of Radiation View Factors Svnensis of Concern The licensee had apparently not calculated radiation view factors properly l for cases involving multiple raceways in a common fire barrier t;nclosure. The concern cited by SNL was that blocking elements such as other cable trays or conduits were not factored into the l calculation as appropriate. Hence, the radiation view factors calculated are inappropriate and overly optimistic.
5
Synonsis of Resoonse The licensee response cites that the fire barriers in question have been ,
~
removed. However, the response also further discussed the process by which radiation view :
factors have been calculated and made two points of particular importance as follows:
- The licensee modified analyses are now crediting heat transfer to the concrete surfaces
. which form one or more sides for cenain of the analyzed enclosures. Hence, the radiation view factors should include communication with these surfaces.
- In the discussion ofheat transmission to the walls and to blocking raceways, the licensee makes the following statements: "Regardless, the assumption of no heat dissipation through the concrete walls does not imply that they can not receive and reradiate / convect the heat received from the raceways. This is also valid for the control / instrument raceways in the same enclosure. These raceways may block the view of the power raceways but still participate in radiative heat transfer. Accordingly, the calculation of the shape factors does not consider the concrete walls or the non-power raceways as rad:ation i blocking elements."
The licensee closes with a revised set of radiation view factors.
Supplemental information regarding this response was provided by the licensee on 1/20/98 in a conference call between the USNRC, SNL, and the licensee. In particular, the licensee cited that there was a direct link between the response to item 1 (discussed above) and to item 2d. In panicular, the findings discussed in response to item I apply to the exact same cables, conduits and trays as those impacted by the calculations discussed in item 2d. The licensee clarified that
! the response to item I was intended to demonstrate that the ca.lculation was indeed conservative ,
because the calculated cable temperature far exceeded the actual cable temperature based on 6 eld observations. The licensee cited this as a basis for concluding that the radiation view factors used in the calculation were actually conservative.
Assessment of Resnonte' With regard to crediting the concrete walls in the heat transfer process, SNL has no objections in principal to this practice. That is, SNL finds that crediting of the heat transfer role of the concrete in this procers is an appropriate approach to analysis. Clearly the
! concrete walls may absorb a significant amount of heat from the system depending on their own l temperature conditions.
~
With regard to the licensee statements related to blocking elements, SNL finds this argument to be without merit. While blocking elements are available to participate in the heat transfer process, L the efficiency of this process is much lower than is the assumed efficiency of the tray to enclosure surface heat transfer provided in the licensee model. Consider the case of a control tray that is
. blocking the radiative view between a power tray and the barrier wall. While it is true that the l blocking tray can participate in the heat transfer process, this participation will introduce a significant " penalty" in the form of a sharply reduced heat transfer rate. This is because the heat must first pass from the surface of the power tray, to the near surface of the control tray, through the control tray, and finally from the far surface of the control tray to the fire barrier wall surface.
Each of these interfaces / elements introduces its own unique temperature drop. For radiative heat transfer these temperature drops are especially important given the dependence of radiation on temperature to the fourth power. To propose that this has no impact and need not be considered 6
'. pn .
J in the formulation of t heat transport model is technically insupportable. The heat transfer through this blocking, element will be far less efficient than direct unobstructed communication between the power t ay and the barrier wall surface. The licensee practice ofignoring blocking elements in the form lation ofradiation view factors is not valid and is unrealistically optimistic.
As noted by the lice ;ee elsewhere in the submittal (see response to item 2a for example), for these analyses the rac ~ative heat transfer terms are dominant as compared to the convective heat transfer rates. Hence the licensee practice regarding the calculation of radiation view factors is inappropriate and overly optimistic.
These observations remain valid despite the supplemental infonnation gained from the conference call. A re-examination of the licensee response to item 1 does confirm that there was net conservatism in the thermal model. However, this conservatism most certainly does not derive I from the radiation view factors. Rather, other conservative elements in the thermal model have clearly overwhelmed the optimistic nature of the view factors. The most likely source of the net I conservatism is the licensee treatment of the cab!e tray itselfusing a Stolpe-like model in which i
there is assumed to be no load diversity. It would appear that the actuaJ cases include ;
considerable load diversity. This same conservatism may not be present in other applications; hence, SNL still recommends that the licensee practice regarding the calculation of radiation view factors not be accepted by the USNRC.
1 Findings and Recommendations SNL finds the licensee discussion of radiation view factors to be l
inadequate and inappropriate. The failure to consider thermal blocking elements in the I formulation ofraceway-to-enclosure wall radiation view factors introduces an obvious and l
inappropriate source of excessive optimism in the licensee thermal model.
However, offsetting this observatien are (1) the fact that the fire barriers in question have been removed and (2) the insights gained from the licensee response to RAI Item 1. Based in particular on the field evaluations of the those cables identified as the worst case cables, SNL finds that the licensee has, in fact, provided an adequate demonstration that the subject cables have not been subjected to significant accelerated thermal aging. In effect, these observations i render the special configuration calculation moot. !
In summary, SNL recommends that:
The licensee practice ofignoring thermal blocking elements in the calculation of radiation view factors not be accepted by the USNRC.
The licensee has demonstrated that life-to-date operation of the subject cables has not resulted in excessive thermal aging. Hence, it is recommended that the results of the thermal calculation are rendered moot by the removal of the fire barrier and the field measurements of cable condition.
Further interactions with the licensee to resolve the concerns related to the radiation view factors would not serve any useful purpose at this point; hence, no further licensee interactions on this RAI item are recommended. The unresolved concerns may simply be noted "for the record."
7
- . . . - = - . -.._.- -- - - . - . - . - . . .- - - - --..--
2.2.5 Item 2e: Consistency Svnopsis of Concern The licensee was asked to ensure that the baseline and clad case ampacity limits were derived on a consistent basis.
Synopsis of Responte The licensee has provided a funher clarification ofits modeling practice as regards the baseline ampacity limits. The cable trays model in a baseline configuration was compared to the ICEA ampacity limits and was found to yield conservative results. The conduit thermal model derives the conduit to cable heat transfer behavior from the IEEE tables using conservative assumptiora regarding the conduit thermal properties. Hence, consistency is maintained inherently by this practice.
Assessment of Response The licensee response has clari6ed that appropriate consideration was in fact given to intemal consistency between the clad and baseline models. The licensee has demonstrated adequately that use of the tabulated ampacity limits is equivalent to or more conservative than would be reliance on a full implementation of the baseline model.
Findings and Recommendations SNL finds that the licensee has adequately addressed the identified concern, and no funher actions on this item are recommended.
2.2.6 Item 2f: Conduit Conductor Count Factors Synopsis of Concern The licensee had committed to use of the more modern non-diversity based conduit conductor count ampacity correction factors but it appeared that the older diversity based values were still used in the submittal.
Svnoosis of:Resnonse The licensee has reiterated its commitment to use the non-diversity based correction factors where appropriate. The case from the submittal cited in SNL's review was noted as an application error, and has been corrected. -
Assessment ofResnonse: The licensee response has adequately addressed the concern raised by SNL.
Findings and Recommendations SNL finds that the licensee has adequately addressed the
- identified concern, and no funher actions on this item are recommended.
2.2.7 Item 2g: Independent Treatment ofMultiple Source Heat Transfer Synoosis of Concern: The licensee thermal model appeared to be treating heat transfer between the various raceways of a multiple raceway enclosure to and through the surface of the enclosure as independent processes, rather than as simultaneous processes.
Synoosis of Response The licensee response has clarified that the thermal model does indeed provide for the simultaneous treatment of the heat transpon.
8
, I Assessment of Resnonse: The licensee response has clarified the model practice in this regard.
. Given the new information provided, SNL has been able to verify that the licensee model is appropriate in this regard.
)
Findings and Recommendations SNL finds that the licensee has adequately addressed the l identified concern, and no further actions on this item are recommended.
2.2.8 Item 2h: Use oftest Data Synopsis of concem SNL had recommended that the licensee calculations for single conduits may be unnecessary. It was recommended that industry test data be reviewed for applicability at l
River Bend. I Svnopsis ofResponse The licensee has reviewed the available test results and will base single conduit ADF values on testing by Texas Utilities (TUE) including the uncertainty in those resuhs documented during the USNRC test review process. The licensee compares the TUE value of l
21% ADF to the model result of 20%. ;
Assessment of Response The licensee use ofindustry test data is consistent with SNL's ;
recommendations. Indeed, the licensee has chosen to apply the most conservative of the available l
ampacity derating test results when in fact more optimistic results might have been cited. '
Findings and Recommendations: SNL finds that the licensee has adequately addressed the identified concern, and no further actions on this item are recommended.
2.3 RAI Item 3: Reassessment of Supported Calculations Svnopsis of concem: The licensee was asked to review calculation E218 in light of the comments ;
raised in the previous RAIitems.
Synonsis of Resnonse The licensee has provided a revised version of the calculation.
Assessment of Response: The revised calculation hu included the updated results. Note that SNL found one RAI item unresolved,1 tem 2d, hence, the update does not reflect resolution of
- this item. _
Findings and Recommendations The licensee hu updated its supported calculations. However, resolution ofitem 2d may require that the licensee once again update Calculation E-218.
4 2.4 RAIItem 4: Conduit Fill Questions Synoosis of concem The licensee had cited conduit fills in excess of 100%. An explanation was requested.
Synopsis of Resnonse: The licensee has clarified that the cited conduit fills are relative to the recommended NEC fill limits. Actual conduit filllimits have been based on manufacturer specifications regarding conduit fill and pull tension limits for the installed cables.
9
1 l Assenment of Recnonse The licensee response has clarified this point cruncertainty.
Findings and Recommendations SNL finds that the licensee has adequately addressed the
, identi6ed concern, and no further actions on this item are recommended.
. 2.5 RAI Item 5: Conduit Fills in Excess of NEC Limits
- svnensis of concern: The licensee had cited conduit fills in excess of the NEC guidelines.
Synonsis of Reinonse: The licensee response refers the reader to its response for Item 4. In j particular, the response to item 4 cited that "the NEC conduit fill limits are based on 'commen i conditions ofproper cabling and alignment of conductors where the length of the pull and (ne i number of bends are within reasonable limits.'" They further cite that "the absolute restri:: tion is l~ de6ned by the cable manufacturer's allowable cable pulling tension. Utilities perform calculations and measure pulling tension during certain pulls to assure that pulling tension does not exceed
- . manufacturer's limits." The licensee also cites that cable ampacity limits are derated on the basis
- ofconductor count rather than fill.
1 i
Assessment of Resnonse SNL has reviewed the applicable sections of the NEC. It would appear that the licensee interpretation is corr 1 in that the primary intent of the NEC fill limits is to prevent damage to the cables during installation. Indeed, there is no direct tie made between conduit percentage fill and ampacity in any of the code provisions. While the licensee does appear to be taking a somewhat liberal interpretation of the applicability of the cited NEC fill limits, SNL finds that the nominal overfill conditions have no relevance to the assessment of cable ampacity limits.
Findings and Recommendations: SNL finds that the licensee has adequately addressed the identified concem in the context of the ampacity assessments, and no further actions on this item are recommended.
1 V
b k-10
.- 3.0'
SUMMARY
OF FINDINGS AND RECOMMENDATIONS 4
. 3.1 General Findings and RecommeaMons
'SNL finds that the licensee has provided sufficient information to conclude that the cables
! contained in the two multiple raceway, special con 6guration, fire barriers have not been subjected to adverse accelerated aging due to their life-to-date operation. This finding is based primarily on i the cited EPRI Indenter measurements for the worst-case cables as installed in the plant and the
! comparison of those measurement to uninstalled cables taken from the plant material stocks.
?
Critical to this assessment is the fact that the cables in question are Hypalon jacketed, and the EPRI indenter does reveal aging induced changes for this material (based on SNUUSNRC Equipment Qualification test results from NURERG/CR-5772). The fire barriers in question have
. been removed, and clearly continued operation in the absence of the Sre barriet s will also not be a concern.
Given these observations, SNL finds that the licensee has provided adequate information to resolve the ampacity-related points of concern raised in USNRC Generic Letter 92-08. No further licensee interactions are recommended.
3.2 One Unresolved Point of Concern Noted For the Record There was one point of technical concern raised in the RAI that was not adequately resolved by the licensee. RAI item 2d cited that the licensee practice in the calculation ofradiation view factors for the multiple raceway special configurations was inappropriate and overly optimistic. SNL finds that the licensee failed to adequately address this concern and implemented no corrective actions in the updated thermal model. Hence, SNL recommends that the licensee special configuration thermal model not be accepted as currently implemented for ampacity assessments.
However, in the larger picture of the issues and concerns raised in Generic Letter 92-08, this fmding has no impact. This is because the results of the thermal calculation were essentially rendered moot by removal of the subject fire barriers and by the licensee field observations of the condition of the formerly clad cables (documented in the licensee response to RAI item 1).
Because the lack of adverse aging impact has been independently verified, and the fire barrier ir, been removed, the thermal calculation serves no real purpose.
Hence, it is recommended that this unresolv'ed concern be noted "for the recor'd" but that no further licensee interactions to resolve the concern be undertaken.
v.
, 11
_