ML20115C111
| ML20115C111 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/03/1996 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML19311C080 | List: |
| References | |
| NUDOCS 9607110174 | |
| Download: ML20115C111 (18) | |
Text
Station Support Department y
PECO NUCLEAR eecan c-mv Nuclear Group Headquarters A UNtr or PECO EMucy 965 Cheste,. brook Boulevard Wayne. PA 19087-5691 July 3,1996 Docket Nos. 50-352 50-353 License Nos. NPF-39 NPF-85 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
SUBJECT:
Limerick Generating Station, Units 1 and 2 Reuse of Fuel Channels on Ex-Shoreham Fuel Bundles
)
Gentlemen:
This letter is being submitted to inform the NRC of PECO Energy Company's plan to reuse nuclear fuel channels from discharged initial core fuel assemblies from Limerick Generating Station (LGS) Units 1 and 2, on ex-Shoreham fuel j
l bundles. The " reused" channels will be utilized en unchanneled ex-Shoreham i
fuel bundles over the next several cycles at LGS Units 1 and 2. The first application of reused fuel channels will be for LGS Unit 2 Cycle 5, currently scheduled to begin in February 1997.
1
- to this letter describes the fuel channel reuse program at LGS Units 1 and 2 in more detail. PECO Energy will provide an information update to the NRC prior to each fuel channel reuse cycle. The information update will include the number of reused channels to be utilized, their core location, and validation that the original evaluation remains applicable., prepared by General Electric Company (GE), " Evaluation of Umerick initial Core Channels for Re-Use on ex-Shoreham Fuel Bundles," dated April 1996, provides the evaluation of the potential impact of reused fuel l
channels on channel-control blade interact lon, thermal 1:mits and the safety limit Minimum Critical Power Ratio (MCPR). contains information proprietary to GE. GE requests that the bgh@
document be withheld from public disclosure in accordance with 10 CFR 2.790(a)(4). An affidavit supporting this request in accordance with 10 CFR 2.790(b)(1) is provided with Attachment 2.
/
l!lk l,/j A safety evaluation has been performed for the tuei ciiannel reuse on ex-Shoreham fuel bundles at LGS Units 1 and 2 and concluded that this activity 4
does not involve an unreviewed safety question.
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if you have any questions please do not hesitate to contact us.
l Sincerely, f.4 George A. Hunger, Jr Director - Licensing i
Attachments i
cc:
T. T. Martin, Administrator, Region I, USNRC N. S. Perry, USNRC Senior Resident inspector, LGS R. R. Janati, Director, PA Bureau of Radiological Protection 9
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ATTACHMENT 2 LIMERICK GENERATING STATION
. Units 1 and 2 Docket Nos. 50-352 50-353 License Nos. NPF-39 NPF-85 General Electric Company Report, " Evaluation of Umerick initial Core Channels for Re-Use on
-i ex-Shoreham Fuel Bundles," dated April 1996 Affidavit supporting General Electric Company's request to withhold the report from public disclosure i
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General Electric Company AFFIDAVIT i
l 1, Ralph J. Reda, being duly sworn, depose and state as follows:
(1) I am Fuel and Facilities Licensing Manager, General Electric Company ("GE") and have been delegated the function of reviewing the information described in paragraph (2) which is sought to be withheld, and have been authorized to rpply for its withholdNg.
1 (2) TI. information sought to be withheld is contained in the attached GE propnetary document entitled Evaluation ofLimerick Initial Core Channelsfor Re-Use on ex-Shoreham FuelBund/es, prepared by G. N. M::rrotte/R. P. Higgins, April 1996, and i
I is indicated by bars in the right hand margin.
(3) In making this application for withholding of proprietary information of which it is the owner, GE relies upon the exemption from disclosure set forth in the Freedom of Information Act ("FOIA"), 5 USC Sec. 552(b)(4), and the Trade Secrets Act,18 USC Sec. 1905, and NRC regulations 10 CFR 9.17(a)(4), 2.790(a)(4), and 2.790(d)(1) for " trade secrets and commercial or financial information obtained from a person and privileged or confidential" (Exemption 4). The material for which exemption from disclosure is here sought is all " confidential commercial information",
)
and some portions also qualify under the narrower definition of " trade secret", vdthin the meanings assigned to those terms for purposes of FOIA Exemption 4 in, respectively, Critical Mass Enerev Proiect v. Nuclear Regulatory Commission.
975F2d871 (DC Cir.1992), and Public Citizen Health Research Group v. FDA.
704F2d1280 (DC Cir. I983).
(4) Some exanples of categories of information which fit into the definition of proprietary information are:
a.
Information that discloses a process, method, or apparatus, including supporting data and analyses, where prevention ofits use by General Electric's competitors without license from General Electric constitutes a competitive economic advantage over other companies; b.
Information which, if used by a. competitor, would reduce his expenditure of resources or improve his competitive pcsition in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product; 12/1393RTil Affidavit Page 1
- - - -. -.-~
Information which reveals cost or price information, production capacities, c.
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budget levels, or commercial strategies of General Electric, its customers, or its i
suppliers;
- d. 'Information which reveals aspects of past, present, or future General Electric customer-funded development plans and programs, of potential commercial value to General Electric; Information which discloses patentable subject matter for which it may be e.
desirable to obtain patent protection.
1 The information sought to be withheld is considered to be proprietary for the reasons set fonh in paragraph (4)a and (4)b above.
(5) The information sought to be withheld is being submitted to NRC in confidence. The information is of a sort customarily held in confidence by GE, and is in fact so held.
The information sought to be withheld has, to the best of my knowledge and belief, l
consistently been held in confidence by GE, no public disclosure has been made, and it is not available in public sources. All disclosures to third parties including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or proprietary agreements which provide for maintenance of the information in confidence. Its initial designation as proprietary information, and the subsequent steps taken to prevent its unauthorized disclosure, are as set forth in paragraphs (6) and (7) following.
(6) Initial approval of proprietary treatment of a document is made by the manager of the originating component, the person most likely to be acquainted with the value and l
sensitivity of the information in relation to industry knowledge. Access to such i
documents within GE is limited on a "need to know" basis.
(7) The procedure for approval of external release of such a document typically requires
'~
review by the staff manager, project managet, principal scientist or other equivalent authority, by the manager of the cognizant marketing function (or his delegate), and by the Legal Operation, for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside GE are limited to regulatory bodies, customers, and potential customers, and their agents, suppliers, and licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or proprietary agreements.
(8) The information identified in paragraph (2), above, is classified as proprietary because it would provide other panies, including competitors, with information related to General Electric fuel designs, analysis results and potential commercial ofTerings which were developed at a considerable expense to General Electric.
111393RTI<
AfTidavit Page 2 i
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(9) Public disclosure of the information sought to be withheld is likely to cause substantial harm to GE's competitive position and foreclose or reduce the availability of profit-making opportunities. The information is part of GE's comprehensive BWR technology base, and its commercial value extends beyond the original development cost. The value of the technology base goes beyond the extensive physical database j
and analytical methodology and includes development of the expertise to determine and apply the appropriate evaluation process.
j The research, development, engineering, and analytical costs comprise a substantial investment of time and money by GE.
The precise value of the expertise to devise an evaluation process and apply the correct analytical methodology is difficult to quantify, but it clearly is substantial.
GE's competitive advantage will be lost ifits competitors are able to use the results of the GE experience to normalize or verify their own process or if they are able to claim an equivalent understanding by demonstrating that they can arrive at the same or similar conclusions.
The value of this information to GE would be lost if the information were disclosed j
to the public. Making such information available to competitors without their having l
been required to undertake a similar expenditure of resources would unfairly provide l
competitors with a windfa'1, and deprive GE of the opportunity to exercise its competitive advantage to seek an adequate return on its large investment in developing these very valuable analytical tools.
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12/1333RTH Affidavit Page 3 1
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STATE OF NORTH CAROLINA
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ss:
COUNTY OF NEW HANOVER
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l Ralph J. Reda, being duly sworn, deposes and says:
That he has read the foregoing affidavit and the matters stated therein are tme and correct l
to the best of his knowledge, information, and belief.
Executed at Wilmington, Nonh Carolina, this /f dayof8 E / !
1996.
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IMalph J. Reda General Electric Company Subscribed and sworn before me this /fA day of do //
1996.
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%./2w Notarffublic, State of North Carolina i
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1 12/13S3RTH AHidavit Page 4
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ATTACHMENT 1 LIMERICK GENERATING STATION Units 1 and 2 1
Docket Nos. 50-352 1
50-353 1
License Nos. NPF-39 NPF-85
" NUCLEAR FUEL CHANNEL REUSE, LIMERICK GENERATING STKTION j
UNITS 1 AND 2" (9 pages) 1 l
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ATTACHMENT 1 j
NUCLEAR FUEL CHANNEL REUSE
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LIMERICK GENERATING STATION UNITS 1 AND 2 Introduction The attachn! core map (Figure 1) shows candidate locations for reused fuel channels at 1_imerick Generating Station (LGS) Units 1 and 2.
The candidate locations for reused channels are all peripheral cells. Figure 2 summarizes the number of reused fuel channels which are projected to reside in the LGS Unit 1 and Unit 2 cores over the next several cycles. A bounding approach, documented
)
ir; Reference 1, has been utilized to evaluate various scenarios of fuel channel reuse. Limerick Unit 2 Cycle 5 will be the first reuse application with a reactor startup projected in February 1997. The map in Figure 3 reflects the potential locations of reused channels in LGS Unit 2 Cycle 5.
l Fuel Bundle Descriotiga A total of 260 ex-Shoreham fuel bundles remain in the LGS fuel pool which require fuel charnels. Of these 260 ex-Shoreham fuel bundles,188 are 2.19 w/o U-235 bundle average enrichment and 72 are 1.76 w/o U-235 bundle average enrichment. Ex-Shoreham fuel bundles are of the GE6 (non-barrier) 8x8 fuel design with two water rods. They were initial core bundles from the Shoreham Nuclear Power Station on Long Island, NY. The ex-Shoreham fuel bundles are considered " fresh" fuel in that they have received less than two (2) effective full power days of exposure during startup testing. The ex-Shoreham fuelis of a much j
lower enrichment than the reload fuel being utilized at LGS. The typical average 1
enrichment of reload fuel at LGS is approximately 4.00% U-235 bundle average enrichment. The ex-Shoreham fuel will be placed in low power core locations -
i peripheral cells (Figure 1). Average values for the relative radial power per bundle 1
for peripheral cell bundles are 0.50 for peripherallocations and 0.73 for locations one-row-in from the periphery. A representative maximum relative radial bundle power for the core is 1.35. All ex-Shoreham fuel bundles with reused channels are projected to be utilized for two cycles of operation. The reused channel will remain j
with the same ex-Shoreham bundle for the two cycles of operation. All cycles in which reused channels will be utilized are conventional core loading patterns.
Reference 1 analyses were performed for both conventional and control cell core loadings.
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l Fuel Channel Reuse Candidates l
The 260 fuel channels which will be reused at Limerick Units' 1 and 2 were discharged after one cycle of operation (the initial cycle at each unit). The channels resided.on either peripheral bundles (natural uranium) or on certain control cell bundles (bundle average enrichment of 0.94% U-235). The thickness of the Limerick Unit 1 channels is 100 mils, while the thickness of the Limerick Unit -
2 channels is 80 mils. Both channel types are made of Zircaloy-4 material. The l
exposures on these channels range from 2.0 GWd/ST to approximately 8.0 GWd/ST. Figure 4 shows the exposure distribution of channel reuse candidates.
Channel Manaoement All fuel channels reused at Limerick will be subject to channel management as l
outlined in GE Service information Letter (SIL) No. 320, " Recommendations for Mitigation of the Effects of Fuel Channel Bowing", and its Supplements. GE has confirmed that SIL 320 recommendations are valid for this particular reuse j
application.
Records will be maintained that document reused fuel channel i
locations, orientations and exposures. Peripheral fuel channels will be positioned such that the flux gradient will be equalized for opposite' channel faces in successive cycles. Additionally, no more than two reused channels in their second reuse cycle will reside in an individual peripheral cell. Channels will be managed such that assignment with ex-Shoreham bundles will match low exposure channels with projected higher exposure bundles. This will be achieved by utilizing the lowest exposure channels on ex-Shoreham bundles that initially reside one-row-in from the periphery. The higher exposure channel reuse candidates will be placed f
on ex-Shoreham bundles that remain on the periphery where the lower exposures will be obtained. Conservative calculations by GE indicate that cumulative channel exposure will be less than 35 GWd/MT.
Best estimate calculations by PECO Energy indicate that the maximum end-of-life exposure will be approximately 28 GWd/MT. Due to the low projected cumulative exposure on the reused channels,
- the channels are considered to be in their "first bundle lifetime". Reference 2 states that single bundle / channel lifetime exposures are taken to be below approximately 40-50 GWd/MT (36-45 GWd/ST).
Channel Bow Calculations The channel bow evaluation method and results are provided in detail in Reference l
- 1. The methodology has been reviewed by the NRC and approved for use in determining cell average bow as per Reference 2.
The maximum expected channel exposure calculated by GE is 35 GWd/MT based on conservative channel l
reuse assumptions. GE evaluated several different scenarios of channel usage to determine the bounding cases for cell average bow and control blade interaction.
j With channel management in place, the worst cell bow is calculated to be 52 mils, while the average cell bow is 50 mils. With channel management, no instances of j
settle pressure reduction below 30 psi were calculated for either 80 or 100 mil j
channels (i.e., no channel-control blade interaction).
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1 Page 3 of 9 Thermal Margin Imoact j
The impact of reused channels on thermal margins for Limerick Units 1 and 2 were evaluated in Reference 1. In standard core designs, with single lifetime channels, j
the effects of bow on the limiting Maximum Fraction of Limiting Power Density (MFLPD)' are so small that GE bases nuclear library pin power peaking factors on zero bow calculations. Ex Shoreham fuel bundles will be utilized in such a manner that the MFLPD is far from limiting. Projections indicate a minimum of 25%
2 margin to leading bundle for Limerick Unit 1 Cycle 7. The MAPRAT margin is also projected to be over 30% throughout the cycle. This is because the ex-Shoreham bundles are loaded in low power core locations and are of relatively low enrichment.
However, peak LHGRs for some nodes of the non-barrier ex-Shoreham fuel residing in non-peripheral locations may approach the conservative PCIOMR threshold (which is considerably below the MLHGR limit) at certain times during the cycle. The kW/ft margin will be directly affected by any change in the maximum pin peaking factor caused by channel bow. Therefore, new nuclear libraries will be generated for the ex-Shoreham fuel with reused channels based on the bounding worst cell bow. The worst cell bow calculated at a maximum end-of-life exposure of 35 GWd/MT is 52 mits. PECO Energy will utilize nuclear libraries generated at 52 mils bow for ex-Shoreham fuel bundles with reused channels in the plant process computer and off-line core simulators. This is an extremely conservative approach for the first two applications of channel reuse (LGS 2 Cycle 5, LGS 1 Cycle 8) beceuse the channels will be well below their projected maximum exposures. Aside from ex-Shoreham fuel, all other fuel in peripheral cells is the 9x9 barrier type which is not subject to a conservative PCIOMR threshold.
Ex-Shoreham fuel bundles residing in peripheral locations operate far from the conservative PCIOMR threshold. Application of the peaking factor penalties calculated in Reference 1 do not place the bundles located on the periphery near the PCIOMR threshold.
The effect of bow on power peaking factor increases with void fraction. The prirnary nodes which may approach the conservative PCIOMR threshold are in the bottom half of the ex-Shoreham bundles residing in non-peripherallocations. For the majority of the cycle, the peak kW/ft value occurs near the bottom of the fuel bundle coincident with the axial power peak (" bottom-peaked"). Due to the low power core locations and low bundle enrichments, the void fraction in the lower nodes is also relatively low (< 0.40). Therefore, the effect of bow on power peaking will be small due to the low void fraction. The percent change in peaking j
2 Ratio of peak kW/ft in a node to the steady-state thermal-mechanical kW/tt limit.
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j Page 4 of 9 factor with the worst cell bow will be less than 5% based on a bow of 52 mils and void fractions less than 0.40.
The impact of channel bowing on the BWR thermal margin calculation is incorporated as a bundle adjustment applied directly to the R-factor used in the GEXL critical power ratio correlation. Bundle R-factor is dependent upon the local power distribution and details of the bundle mechanical design. Larger bow results in increased R-factors and reduced MCPR margin. Typically, a single core average bow is used for all fuel types in the core. This value is calculated per GE Technical Design Procedure "TDP-0027, Channel Bow Effects on Critical Power Calculation".
If reused channels were placed on the ex-Shoreham fuel, it would be an unnecessary conservatism to penalize the interior (limiting) fuel bundles by using a single core average bow which included the reused channels in low power peripheral cells. Use of a single core average bow based on only the interior (single lifetime channels) fuel can be justified by showing that the cells with reused channels are far from limiting at all points throughout the cycle.
l The effects of increased bow are small when compared to the available Minimum Critical Power Ratio (MCPR) margin for the ex-Shoreham fuel. Projected rod patterns for Limerick Unit 1 Cycle 7 show at least 37% MCPR margin for the ex-Shoreham fuel and at least 40% margin for the other fuel types in cells that contain ex-Shoreham fuel. These results are based on a core average bow of 25 mils.
Use of the worst cell bow (52 mils) would decrease the MCPR margin by less than 5%. The worst cell bow (52 mils) is based on a conservative, bounding scenario.
Limerick Unit 2 Cycle 6 is projected to have the largest inventory of reused channels (estimated 172). Therefore, the MCPR impact for all other cycles will be much smaller than for the bounding scenario. In order to confirm that adequate thermal margin exists on a cycle-by-cycle basis for ex-Shoreham bundles with reused channels, channel management procedures will be developed to include a validation of a minimum of 25% thermal margin throughout the cycle based on representative rod patterns.
Imoact on Safetv Limit Minimum Critical Power Ratio (SLMCPR)
Development of the fuel product line dependent generic SLMCPR utilizes a probabilistic approach whereby bundles fairly close to limiting for MCPR significantly influence the probability of boiling transition during a limiting event. For l
bundles located in peripheral cells, the bundle powers are sufficiently low for these locations not to be limiting (i.e., within 10% of the limiting bundle).
- Thus, application of reused channels in the peripheral cells will have no effect on the validity or results of the existing SLMCPR analysis because of the large amount of MFLCPR margin. The SLMCPR for the first reuse application (Limerick 2 Cycle 5) will be based on the limiting fuel product lines for that cycle.
8 Ratio of MCPR Umit to the MCPR for a fuel bundle.
r Page 5 of 9 REFERENCES 1.
General Electric Company Report, " Evaluation of Limerick initial Core Channels for Re-Use on ex-Shoreham Fuel Bundles", April 1996.
2.
Letter, A. C. Thadani (NRC) to J. S. Charnley (GE), " Acceptance for Referencing of Topical Report Titled 'GE-Nuclear Energy Report MFN086-089*, January 11, 1991.
3.
NRC Bulletin Number 90-02, " Loss of Thermal Margin Caused by Channel Box Bow", March 20,1990.
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Page 6 of 9 Figure 1 Candidate Locations for Placement of Reused Channels Limerick Generating Station Units 1 and 2 59 55---------
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Candidate Locations for Ex-Shoreham Fuel with Roused Channele l
Page 7 of 9 Figure 2 Projected Usage Scenario for Reused Channels at LGS l
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Number of Reused Estimated us Total Number of ha""' * "
l Plant / Unit / Cycle' Startup
. Channels in Reused ~
S c nd e se l
Date First Reuse Chnnels Cycle.
l Cycle -
l Umerick 2 Cycle 5 Feb.1997 88 0
88 Umerick 1 Cycle 8 April 1998 88 0
88 Umerick 2 Cycle 6 April 1999 84 88 172 Umerick 1 Cycle 9 April 2000 0
88 88 t
f Umerick 2 Cycle 7 April 2001 0
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l Page 8 of 9 Figure 3 Limerick 2 Cycle 5 Preliminary Loading Pattern Bundle Types 1
2 3
4 5 6 7 8 9 10 11 12 13 14 15 1
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15 19 15 18 15 18 15 18 15 18 15 18 11 18 15 11
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Note: Quarter Core Map (Upper Left-Hand Quadrant)
Fuel Type Description Initial Enrichment, %
Exposure 11 GE11 3.54 Twice Burned 15 GE11 3.99 Once Burned 16 Shoreham GE6 (new channels) 2.19 Once Burned 17 Shoreham GE6 (new channels) 1.76 Once Burned 18 GE13 4.15 Fresh 19 Shoreham (reused channels) 2.19 Fresh 20 Shoreham (reused channels) 1.76 Fresh i
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Evaluation of Limerick Initial Core Channels for Re-Use on ex-Shoreham Fuel Bundles P
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