ML20135D557

Responds to 961105 Telcon RAI Re TS Change Request 96-18-2 on Minimum Critical Power Ratio Safety Limit

ML20135D557
Person / Time
Site:	Limerick
Issue date:	12/04/1996
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9612100034
Download: ML20135D557 (13)

Text

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Ctition tupport Deptrtment

_Q 10 CFR 50.90

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PECO NUCLEAR recos c -

l A Unit of PECO Energy w7[p$*$.$***

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December 4,1996 L

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Docket No. 50053 1

License No. NPF-85 I

U.S. Nuciear Regulatory Commission j

Attn: Document Control Desk Washington, DC 20555

Subject:

Umerick Generating Station, Unit 2 l

Technical Specifications Change Request No. 96-18-2 Response to Request for Additional Information l

Gentlemen:

l Attached is our response to your Request for Additional Information (RAl), discussed in our telephone conversation on November 5,1996 regarding the change in the Minimum Critical 4

Power Ratio (MCPR) Safety Umit due to t_he plant specific evaluation performed by General Electric Co. (GE), for Umerick Generating Station (LGS) Unit 2, Cycle 4. The revised MCPR Safety Umit is the subject of Technical Specifications Change Request (TSCR), No. 96-18-2 which was forwarded to you by letter dated June 25,1996. At that time, we anticipated that the new MCPR Safety Umit for LGS Unit 2. Cycle 4 would bound the MCPR Safety Umit for LGS Unit 2, Cycle 5. However, the GE plant specific analysis for LGS Unit 2, Cycle 5 provided recently by GE Indicates a different value for the MCPR Safety Umit. Therefore, we are processing another TSCR for LGS Unit 2, Cycle 5, which will be forwarded to you in the near.

future.

This additional information is being submitted under affirmation and the required affidavit is enclosed.

If you have any questions, please do not hesitate to contact us.

Very truly yours, b.a. M b.

G. A. Hunger, Jrf Director - Licensing Attachments Enclosure k

l cc:

H. J. Miller, Administrator, Region I, USNRC (w/ enclosure, attachments) g()i N. S. Perry, USNRC Senior Resident inspector, LGS (w/ enclosure, attachments) q R. R. Janati, PA Bureau of Radiation Protection (w/ enclosure, attachments) i 9612100034 961204 PDR ADOCK 05000353 p

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COMMONWEALTH OF PENNSYLVANIA ss.

I COUNTY OF CHESTER D. B. Fetters, being first duly sworn, deposes and says: That he is Vice President of PECO Energy Company, the Applicant herein; that he has read the enclosed response to the NRC Request for Additional Information involving the change in the Minimum Critical Power Ratio (MCPR) Safety Limit at Limerick Generating Station, Unit 2 Cycle 4, concerning Technical Specifications Change Request No. 96-18-2 for Facility Operating Ucense No. NPF-85, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.

Wa Vice President Subscribed and sworn to before me this [ day of 1996.

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ATTACHMENT 1 LIMERICK GENERATING STATION UNIT 2 l

Docket No. 50-353 l

Ucense No. NPF-85 i~

TECHNICAL SPECIFICATIONS CHANGE REQUEST i

No. 96-18-2 Additional Information (2 pages) d 4

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I Docket No. 50-353 License No. NPF-85 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION LIMERICK GENERATING STATION, UNIT 2 (Per Telecon dated November 5,1996)

TECHNICAL SPECIFICATIONS CHANGE REQUEST NO. 96-18-2 Question 1:

What types of fuel are in Umerick Unit 27 a)

Cycie 47 b)

Cycle 5?

Resoonse 1:

Fuel Bundle Inventorv - Limerick Unit 2 Cycle 4 Descriotion 112 GE9B - 3.25 w/o 4

GE11 - 3.04 w/o 4

ABB - SVEA96 (modeled as GE98 - 3.25 w/o) 4 SPC - 9x9-9x+ (modeled as GE9B - 3.25 w/o) 284 GE11 - 3.54 w/o 276 GE11 - 3.99 w/o 40 GE6 - 2.19 w/o

_4Q GE6 - 1.76 w/o 764 I

Fuel Bundle Inventorv - Limerick Unit 2 Cycle 5 Descriotion 4

GE11 - 3.31 w/o (LGS 1 Reinserts) 44 GE11 - 3.54 w/o 276 GE11 - 3.99 w/o 284 GE13 - 4.16 w/o 96 GE6 - 2.19 w/o

_JQ GE6 - 1.76 w/o 764

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Docket No. 50-353 License No. NPF-85

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Question 2:

What inputs and assumptions were used in calculating the Safety Limit Minimum Critical Power Ratio (SLMCPR), for Limerick Generating Station (LGS), Unit 2?

a)

Cycle 47 b)

Cycle 57 Resoonse 2:

a)

Please see Attachment 2 for Cycle 4 information in response to this question.

3 b)

Please see Attachment 3 for Cycle 5 information in response to this question.

1 Ouestion 3:

What is the basis for the Single Loop Operation SLMCPR at LGS Unit 2?

l Resoonse 3 l

4 Please see Attachments 2 and 3 for Cycle 4 and Cycle 5, respectively, information in response to this question.

Question 4:

What is the value of SLMCPR for LGS Unit 2 Cycle 57 Resoonse 4:

Please see Attachment 3 for LGS Unit 2, Cycle 5 SLMCPR value.

l i

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ATTACHMENT 2 LIMERICK GENERATING STATION UNIT 2 Docket No. 50-353 License No. NPF-85 TECHNICAL SPECIFICATIONS CHANGE REQUEST NO. 96-18-2 Additional Information Letter, R. M. Butrovich (GE) to H. J. Diamond (PECO Energy)

"Umerick Unit 2 Cycle 4 Safety Umit MCPR,"

dated November 11,1996 I

GE Nuclear Energy

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Rochard M Butrovoch November 11,1996

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RMB:96-239 Mr. H. J. Diamond, Director Fuel & Services Division PECO NUCLEAR 965 Chesterbrook Boulevard Wayne, PA 19087-5691

SUBJECT:

Limerick Unit 2 Cycle 4 Safety Limit MCPR

REFERENCE:

1. Letter, R. M. Butrovich to H. J. Diamond, " Generic gel 1 Safety Limit MCPR Calculation", April 2,1996

2. Letter, R. M. Butrovich to H. J. Diamond, " Limerick Unit 2 Safety Limit MCPR", May 21,1996

3. NEDC-32505P, R-Factor Calculation Methodfor gel 1, GE12 and GE13 Fuel, November 1995.

4.

Licensing Topical Report, GeneralElectric BWR Thermal Analysis Basis (GETAB): Data, Correlation andDesign Application, NEDO-10958-A, January 1977.

5. Letter, R. M. Butrovich to H. J. Diamond, " Limerick Unit 2 Safety Limit MCPR Revision", July 7,1996

Dear Hugh:

Reference I advised PECO Nuclear of discoveries related to the methodology used by GE to calculate SLMCPR that indicated the generic SLMCPR may not always yield the most conservative resuh. GE performed a plant unique evaluation for Limerick Unit 2 Cycle 4 (Reference 2). A separate cycle specific calculation was performed for Single Loop Operation.

The value obtained for SLMCPR was 1.11. These calculations were based upon USNRC approved methods (" General Electric Standard Application for Reactor Fuel," NEDE-24011-

Mr. H.1 Diamond 2

t t/t t/%

4 P-A-11, and U.S. Supplement, NEDE-24011-P-A Il-US, November 17,1995) and interim implementing procedures. Revision 11 of the aforementioned document, "GESTAR II",

requires that the SLMCPR be reconfirmed each cycle. His reconfumation was performed using the intedm implementing procedures which the NRC staff discussed with GENE during their meetings on April 17,1996 and May 6,1996 through May 10,1996. Rese interim i

procedures include cycle-specific parameters which include: 1) the actual core loading, 2) conservative variations ofprojected control blade patterns, 3) the actual bundle parameters (e.g., local peaking), and 4) the full cycle exposure range.

i ne following is clarification of " conservative variations ofprojected control blade patterns" l

used to calculate the SLMCPR for Limerick Unit 2 Cycle 4.

y s

Projected control blade patterns for the rodded burn through the cycle are tised to deplete the core to the cycle exposures to be analyzed. For Limerick Unit 2 Cycle 4, control blade patterns were projected from an actual exposure accounting case near middle of cycle. Actual begmning of cycle conditions were checked and found to be non-limiting for SLMCPR. At the desired cycle exposures, the bundle exposure distributions and their associated R-factors, determmed in accordance with Reference 3, are then utilized for the SLMCPR cases to be analyzed. Using different rod patterns, to achieve the desired cycle exposure, has been shown i

to have a negligible impact on the actual SLMCPR calculated. An estimated SLMCPR is obtained for an exposure point near beginning ofcycle (BOC) and end ofcycle (EOC), as well i

as the calculated cycle exposure for peak hot excess reactivity (PHE), in order to establish

]

which exposure point (s) will produce the highest (most conservative) calculated SLMCPR. At these exposure points, the goal of page IV-7 ofReference 4 is applied:

l

"%e objective in e t bli his ng the initial condition power distribution is to sa satisfy total power and local limits and to maximim the calculated number of j

rods expected to experience boiling transition."

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nis is achieved by following the mie on page IV-6 in Reference 4.

"For a given reactor, at a particular exposure, there is a variety of rod patterns which produce ka = 1.0 [within the established tolerances] and satisfy local i

power and MCPR constraints. For conservatism, the statistical analyses of the i

core are performed for only those operating states yielding MCPR equal to the limit, unless this involves an unreasonable power distribution or gross violation 4

of kW/fI limits."

i To maximize the calculated SLMCPR value at the exposure point ofinterest, different control j

rod patterns are evaluated to fmd the patterns that yield the most bundles on or near the operating limit MCPR at this cycle exposure point. His is what is meant by " conservative 1

variations ofprojected control blade patterns" ne variations are conservative since they are selected to maximize the number of rods susceptible to boiling transition by maximizing the i

number ofcontributing bundles. He highest SLMCPR from these pattems that meet the criteria above, was chosen as the cycle-specific SLMCPR value. His occurred at an exposure j

point near end ofcycle.

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Mr. H. J. Diamond 3

11/11/ %

Limerick Unit 2 Cycle 4 SLMCPR is 1.10 versus the generic GElI value of 1.07. GESTAR II requires that the SLMCPR analysis for a new fuel design shall be performed for a bounding equilibrium core. This is how the 1.07 value was obtained for the gel 1 product line. However, Limerick Unit 2 Cycle 4 is not an equilibriem core. It is a mixed core of gel 1/GE9/GE6 fuel.

Over the last several cyc!es, the average enrichment for the fresh fuel has progressively increased.

j Higher enrichment in the fresh fuel (compared to the rest of the core) produces Fgher power in the fresh bundles which causes more rods to be susceptible to boiling transition in the statistical analysis than for an equilibrium core. 'Ihe fresh Cycle 4 Gell bundles have a flatter RFACTR distribution than the GElI bundles analyzed in the generic case. In cores that operate for two 1

years it is typical that almost all of the bundles close to the limiting MCPR of the core are fresh fuel. Also, Limerick Unit 2 Cycle 4 is loaded aggressively with a high batch fraction to achieve a two year cycle. With this loading it is easier to put more bundles in this core on MCPR limits than is generally possible for assumed equilibrium core designs. For the above reasons the j

Limerick Unit 2 Cycle 4 SLMCPR is higher than the generic 1.07 value.

If you have any questions, please give me a call.

i Very truly yours,

/

k. Butrovah j

t el Project Manager I

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ATTACHMENT 3 LIMERICK GENERATING STATION UNIT 2 Docket No. 50-353 License No. NPF-85 TECHNICAL SPECIFICATIONS CHANGE REQUEST NO. 96-18-2 Additional Information Letter, R. M. Butrovich (GE) to H. J. Diamond (PECO Energy)

" Limerick Unit 2 Cycle 5 Safety Limit MCPR,"

dated November 11,1996 1

GENuclearEnergy Rochore M Burreveen

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November 11,1996

• ~ E-lu RMB:96-243 Mr. R J. Diamond, Director Fuel & Services Division PECO NUCLEAR

%5 Chesterbrook Boulevard Wayne, PA 19087-5691

SUBJECT:

Ilmerick Unit 2 Cycle 5 Safety Limit MCPR

REFERENCE:

1. Later, R. M. Butrovich to R J. Diamond. " Generic gel 1 Safety Limit MCPR Calculation", April 2,1996

{

2. NEDC-32505P, R-Factor Calculation Methodfor GEli, GE12 and GE13 Fuel. November 1995.

i

3. Licensag Topical Report, GeneralElect-ic BWR Thermal Analysis Basis (GETAB): Data. Correlation andDesign Application, NEDO-10958 A, j

January 1977.

}

4. GeneralElectric Standard Applicationfor Reactor Fuel, NEDE-24011-j P-A-13, and US Supplement, NEDE-24011-P-A-13-US, August 1996.

5. Letter, A. M. Olson to R. M. Butrovich, " LGS Unit 2 Reload 4 SLMCPR Determination", October 30,1996

Dear Hugh:

Reference 1 advised PECO Nuclear of discoveries related to the methodology used by GE to calculate SLMCPR that indicated the generic SLMCPR may not always yield the most conservative resuh. GE has performed a plant unique evaluation for Limericir Unit 2 Cycle 5.

A separate cycle specific calculation was performed for Single Loop Operation. He SLMCPR value obtained was 1.12. Dese calculations were based upon (" General Electric Standard Application for Reactor Fuel," NEDE-240ll-P-A-13, and US Supplement, NEDE-G

Mr. H.1 Diamond 2

11/11/95 l

24011-P-A-13-US, August 1996) and the Technical Design Procedure ("GETAB Safety Lindt", TDP-0049, Revision 0, July 1996). Revision 13 of the aforementioned document, i.

"GESTAR 11", requires that the SLMCPR be reconfirmed each cycle. His reconfirmation 1

was performed using technical design procedure which replaced the interim implementing procedures which the NRC staffdiscussed with GENE during their meetings on April 17,1996 and May 6,1996 through May 10,1996. He technical design procedure includes cycle-l specific parameters which include: 1) the actual core loading, 2) conservative variations of j

pro,iected control blade patterns, 3) the actual bundle parameters (e.g., local peaking), and 4) l the full cycle exposure range.

l.

he foRowing is clarification of " conservative variations ofprojected control blade patterns" used to calculate the SLMCPR for Limerick Unit 2 Cycle 5.

Projected control blade patterns for the rodded burn through the cycle are used to deplete the core to the cycle exposures to be analyzed. At the desired cycle exposures, the bundle exposure distributions and their associated R-factors, determined in accordance with Reference 2, are then utilized for the SLMCPR cases to be analyzed. Using different rod pattems, to achieve the desired cycle exposure, has been shown to have a neghgible impact on the actual SLMCPR calculated. An estimated SLMCPR is obtained for an exposure point near beginning of cycle (BOC) and near end of cycle (EOC), as well as the calculated cycle exposure for peak hot excess reactivity (PHE), in order to establish which exposure point (s) will produce the highest (most conservative) calculated SLMCPR. At these exposure points, the goal of page IV-7 of Reference 3 is applied:

The objective in establishing the initial condition power distribution is to satisfy total power and local limits and to madmire the calculated number of rods expected to experience boiling transition."

This is achieved by following the rule on page IV-6 in Reference 3.

"For a given reactor, at a particular exposure, there is a variety of rod patterns which produce k, = 1.0 [wnhin the established tolerances] and satisfy local power and MCPR constraints. For conservatism, the statistical analyses of the core are performed for only those operating states yielding MCPR equal to the limit, unless this involves an unreasonable power distribution or gross siolation ofkW/ft limits."

To madmire the calculated SLMCPR value at the exposure point ofinterest, different control rod patterns are evaluated to find the patterns that yield the most bundles on or near the operating limit MCPR at this cycle exposure point. His is what is meant by " conservative variations ofprojectedcontrol blade patterns". ne variations are conservative since they are selected to maximize the number ofrods susceptible to boiling transition by madmiring the number of contributing bundles. He highest SLMCPR, from these patterns that met the 4

criteria above, was chosen as the cycle-specific SLMCPR value. His occurred at an exposure point near end ofcycle.

~.

Mr. H. J. Diamond 3

11/11/96 Limerick Unit 2 Cycle 5 SLMCPR is 1.11 versus the generic GE13 value of 1.09. The Single 3

Loop Operation SLMCPR is 1.12 as determined by a separate cycle specific calculation.

GESTAR 11 requires that the SLMCPR analysis for a new fuel design shall be performed for a bounding equilibrium core. His is how the 1.09 value was obtained for the GE13 product line. However, Limerick Unit 2 Cycle 5 is not an equilibrium core. It is a mixed core of i

GE13/ Gell /GE6 fuel. Over the last several cycles, the average enrichment for the fresh fuel has progressively increased. Higher enrichment in the fresh fuel (compared to tha rest of the core) produces higher power in the fresh bundles which causes more rods to be susceptible to boiling transition in the statistical analyns than for an equihirium core. He fresh Cycle 5 GE13 bundles have a flatter RFACTR distribution than the GE13 bundles analyzed in the j

generic case. In cores that operate for two years it is typical that almost all of the bundles close to the limiting MCPR of the core are fresh fuel Also, Limerick Unit 2 Cycle 5 is loaded i

aggressively with a high batch fraction to achieve a two year cycle. With this loading it is easier to put more bundles in this core on MCPR limits than is generally possible for assumed equilibrium core designs. As requested by PECO Nuclear (Reference 5), the SLMCPR calculations for Limerick Unit 2 Cycle 5 used a feedwater flow uncertainty of 2.24% rather than the generic value of 1.76% (Reference 4). For the above reasons the Limerick Unit 2 Cycle 5 SLMCPR is higher than the generic GE13 1.09 value.

1 1

Ifyou have any questions, please give me a call.

i Very truly yours, p 44 R.

. Butrovich F el Project Manager 4

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