ML20107B329

Application for Amend to License NPF-3,changing Tech Specs to Revise Min RCS Flow Requirement to Take Credit for Decrease in Core Bypass Flow

ML20107B329
Person / Time
Site:	Davis Besse
Issue date:	02/13/1985
From:	Crouse R TOLEDO EDISON CO.
To:
Shared Package
ML20107B324	List: ML20107B329 ML20107B332
References
TAC-57219, NUDOCS 8502200347
Download: ML20107B329 (10)

Text

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APPLICATION FOR AMENDMENT TO FACILITY OPERATING LICENSE NO. NPF-3 FOR DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 Enclosed are forty-three (43) copies of the requested changes to the Davis-Besse Nuclear Power Station Unit No. 1 Facility Operating License No. NPF-3, together with the Safety Evaluation for the requested change.

The proposed changes include Figure 2.1-2, 2.2-1, Table 3.2-1 and Bases.

By /s/ R. P. Crouse Vice President, Nuclear Sworn and subscribed before me this 13th day of February, 1985.

/s/ Laurie A. Hinkle, nee (Brudzinski)

Notary Public, State of Ohio SEAL My Comission Expires May 16, 1986 p PDR

p h .

.6 Docket No. 50-346 I

License No. NPF-3 Serial No. 1125 Februa ry 13, 1985 i

Attachment I. Changes to Davis-Besse Nuclear Power Station Unit 1, Appendix A Technical Specifications Figures 2.1-2, 2.2-1, Table 3.2-1 and Bases.

A. ' Time required to implement. This change is to be effective upon NRC approval.

B. Reason for Change (Facility Change Request 85-0021). Revision to the minimum RCS flow requirement to take credit for decrease in the core bypass flow as a result of using Lump Burnable Poison rods in Cycle 5 design.

C. . Safety Evaluation (See Attached)

D. Significant Hazard Consideration

. (See Attached)

SAFETY EVALUATION This FCR proposes a change to the DB-1 Tech. Spec. minimum RCS flow requirement to take credit for the use of the Lumped Burnable Poison (LBP) rods and the corresponding decrease in core by pass flow in the Cycle 5 reload core design.

The safety function of the Tech. Spec. minimum reactor coolant system (RCS) flow requirement is to ensure adequate cooling of the reactor core such that the minimum required DNBR is maintained. To justify the proposed change it is necessary to demonstrate that this decrease in system flow does not result in a decreased core cooling capability. The coolant flow available for core cooling represents the difference between the total RCS flow and the core by pass flow. Core by-pass comprises the RCS flow within the reactor vessel that does not flow around fuel rods. Major

'by pass paths that exist in the reactor vessel include:

1. Empty guide tubes in fuel assemblies.

2. Baffle plates.

3. Gaps around the hot leg nozzle in upper core internals.

A change in the total cross-sectional area of all by-pass paths will directly affect the system flow and the split between core flow and by-pass flow. Assuming all other variables remain constant, a decrease in by-pass area results in a slight decrease in system flow, a decrease in by-pass flow, and an increase in core flow.

Cycle 5 utilizes Lumped Burnable Poisons (LBP's) in the 64 new fuel assemblies to accommodate the IN-0UT-IN fuel shuffle scheme. Since the presence of the LBP rod assemblies reduces the core by pass flow path, the by pass flow for Cycle 5 is therefore less than that for earlier cycles (except cycle IA where LPB and orifice rods were used). B&W stated in their letter BWT-85-2316 (Attachment A) that the Cycle 5 Reload thermal L hydraulic analysis assumed no LBP insertion when determining by pass flow.

They also stated that insertion of 64 LBP's would decrease by pass flow from the 10.7% used in the Cycle 5 Reload Report to 8.1%. This decrease in by-pass flow would result in a larger core coolant flow than was assumed in the Cycle 5 Reload analysis. Therefore, a reduction in the Tech. Spec. minimum RCS flow requirement can be justified.

The new minimum RCS flow must ensure that the core coolant flow associated with it and an 8.1% by-pass flow is greater than or equal to the core L coolant flow associated with the present minimum flow and 10.7% by pass flow. The minimum DNBR requirement remains unchanged. B&W in letter BWT-85-2317 (Attachment B) has specified these new flow rates for 4 RC pump and 3 RC pump operation. These reduced minimum RCS flow rates can be used without invalidating the results of the Cycle 5 Reload Report.

The proposed change affects Table 3.2-1 of Tech. Spec. Section 3.2.5. The flow requirement for 4 pumps operation (396,880 gpm) represents 110% of design flow plus 2.5% uncertainty. The revised flow will be 389,664 gpm which corresponds to 108% of' design flow and includes 2.55% uncertainty.

The 3 pump case is also changed from 297,340 gpm to 291,080 gpm. To t

2-maintain consistency, other Tech. Spec. Sheets (2-3, 2-7, B2-1, B2-8) are also changed since they have quoted flow rates that correspond to 110% of the design flow. The flow changes on these pages do not include the 2.5%

uncertainty used in Table 3.2-1.

On Tech. Spec. Sheet 2-7, an editorial change is made to clarify that the 3 pump operation represents an "approximately" 25% flow reduction. On Tech. Spec. Sheet B2-8, there is a typo error. The 89.3% for 3 pump operation should have been 89.1% (to be consistent with Tech. Spec. Sheet 2-3).

'The proposed Tech. Spec, changes to not degrade the safety function of the Technical Specifications for Davis-Besse nor do they represent an unreviewed safety question.

ER0MJPD.LYNCHEURG VA 01/23/85 11:49 P. 2 Babcock & Wilcox w e- m

.u:om e mm m pysgygama Lyxhtwg VA 2450809E (604) 305 2000 January 23, 1985 bht-85-2317 Dr. Frank Y. Chen - Phil Stop 710 Ttie Toledo Edison Company Edison Plaza 300 Madison Avenue Toledo, OH 43652

Subject:

Davis-Besse Nuclear Power Station Unit 1 Syster. Design Flow - Revised

Dear Dr. Chen:

As a follow-up to rny letter of January 22 (bht-85-2316), attached is a comparison between current and proposed technical specification syste'.

design flow values for 4-pump and 3-pump operation. l The following technical specification pages will require change:

Page 2-3 (RequiredSystemFlow) i Page 2-7 (Required System Flow, 3-Pump)

Page B 2-1 (Required System Flow, 4-Pump; Percent of Design Flow)

PageB2-8(RequiredSystemFlow) l f Page 3/4 2-14 (Required Systen Flow plus heasurenent Error) y ry ulyyoq-9 ) q _- =

D.M. Rainey Project Manager Nuclear Fuel Services l

Dm/ds Attachment l

FROMilPDLYNCHBURGVA 01/23/85 11:52 P. 3 Attachment Minfrman Acceptable Reactor Coolant Flow (GPM) 4-Punp Operation _

3-Pu.Tp Operation Current TS Proposed TS Current TS Proposed TS Requimd System Flow 387,200 300,160 290,100 283,980 Required System Flow Plus 396,880 389.664 297,340 291,080 2.5% Measurement Error Percent of Design 110% 108% 110% 108%

Flow Rate

FR0tiliPD LYlKHBURG VA 01/22/85 13:54 P. 2

=~ em, o,.wo.,

sabcock & Wilcox a McDermott compaar [3y5gic fg Roed Lynchbars.VA?4506 0935 (834) sBb 2000 January 22, 1985 BWT-85-2316 Dr. Frank Y. Chen - Mail Stop 710 The Toledo Edison Company Edison Plaza 300 hidison Avenue Toledo, OH 43552

Subject:

Davis-Besse Nuclear Power Station Unit No. 1 Revised System Design Flow

Dear Dr. Chen:

Forwarded herewith is the following document:

Trans 85-1155464-03

• Revised System Design Flow." one (1) page, dated January 17, 1985. ,

D. M. Rainey Project Manager Naclear Fuel Services DMR/drs O

'FR0r.gPBLYNCHBlJRGVR 01/22/85 13:58 P. 3 _

me.mm- 2 u-su

~, m ar mi/r*- a use-660-095E 081-CY5 W U" -

~'

C.C. 385 taass. a6 .

1155464 _00 REF.PG(s) 1 m ai p u.-- - - == a . == _.,== =. so. .

2Less Tul.g Revised System Design Flow _

yggrango y E. R. Miller Jr3P1UM am n R. L. Name g TITt2 Te h (n.e_111 MTN ///743 TITLE Engineer 11I can [-f74[

FURP065 To document lower systen design flow calculated for Davis Bessa 1. Cycle 5.

References:

1) 32-1155463-00, " Revised System Design Flow," 660-095E, E. R. Ptiller. January 15, 1985.

2) 32-1146814-01, " Fuel Thermal Analysis - Cycle $ Revised,"

660-095E, E. R. Miller, April 30, 1984.

l l

5420tARY OF RESULTS (INCLUDE DOC. ID'S OF FREVIOU$mAlamT Lt 's. aouaCE 'Chu:ULanOt1AL j FACKAGES FOR TRt3 TRANSMITIAL) . .

The Reference 1 calculation package supports lowering the !bvis Besse 1 minimum systen design flow from 1101 to 108% of 88000 gpr/ pump. The accident and technical specification analysis results doceented in Ref-erence 2 as applicable for c.ycle 5 operation used a conservative leakage of 10.7% based on no LSP insertion. Reference I showed that the use of the reduced leakage allowed by the insertion of 64 LBps for cycle 5 (8.11) with the 108% system design flow will result in a higher predicted core flow than was considered in Reference 2. Thus, the reduction of system design flow to 108% can be r.ede without invalidating the results previously docu-

mented for Davis Besse 1. Cycle 5.

. The minimum flow rate now equals 380160 gpm (1081 of 88000 qpai/ pump). The i maximar flow renains unchanged (417120 gpn).

A change in flow measurement ernsr was not considered in the Reference 1 calculations, l

l DISTRIBUTICW 5ee DRtt. .

I'

1 SIGNIFICANT HAZARD CONSIDERATION

~

This amendment request is to revise the minimum Reactor Coolant System (RCS) Flow requirements to take credit for decrease in the core bypass flow resulting from the use of Lump Burnable Poison (LBP) rods in Cycle 5 design. This amendment request does not represent a Significant Hazard.

The Cycle 5 core utilizes Lumped Burnable Poison in the 64 new fuel assemblies to accommodate the IN-0UT-IN fuel shuffle scheme. Since the presence of the LBP rod assemblies reduces the core by pass flow path, the by-pass flow for Cycle 5 is therefore less than that for earlier cycles (except cycle IA where LPB and orifice rods were used). The Cycle 5 Reload thermal hydraulic analysis assumed no LBP insertion when determining by pass flow. The analysis stated that insertion of 64 LBP's would

decrease by pass flow from the 10.7% used in the Cycle 5 Reload Report to 8.1%. This decrease in by pass flow would result in a larger core coolant

' flow than was assumed in the Cycle 5 Reload analysis. Therefore, a reduction in the Technical Specification minimum RCS flow requirement can be justified.

The RCS flow requirement is to ensure adequate cooling of the reactor core

'such that the minimum required DNBR is maintained. To justify the proposed change it is necessary to demonstrate that this decrease in system flow does not result in a decreased core cooling capability. The coolant flow available for core cooling represents the difference between the total RCS flow and the core by pass flow. Core by pass comprises the RCS flow within the reactor vessel that does not flow around fuel rods. Major by pass paths that exist in the reactor. vessel include:

1. Empty guide tubes in-fuel assemblies.

2. Baffle plates.

3. Gaps.around the hot. leg nozzle in upper core. internals.

A change in the fuel cross-sectional area of all by pass paths will

.directly affect the system flow and the split between core flow and by pass flow.- Assuming all other variables remain constant, a decrease in by pass. area results in a slight decrease in' system flow, a decrease in by pass flow, and an increase in core flow.

The new minimum RCS flow must ensure that the core coolant flow associated with it and an 8.1% by pass flow is greater than or equal to the core coolant flow associated with the present minimum flow and 10.7% by-pass flow. The minimum DNBR requirement remains unchanged. These reduced minimum RCS flow rates can be used without invalidating the results of the

. Cycle 5 Reload Report.

The' flow requirement for 4 pumps operation (396,880 gpm) represents 100%

of design flow plus 2.5% uncertainty. The revised flow will be 389,664 gpa which corresponds to 108% of design flow and includen 2.55% uncertainty.

The 3 pump case is also changed from 297,340 gpm to 291,080 spm.

l

The granting of this request would not:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated (10CFR50.92.(C)(1).

All accidents previously evaluated within the reload report or other evaluations remain unchanged. The minimum flow requirement will ensure adequate DNBR is maintained as assumed in Davis-Besse accident analysis. Therefore, the change.does not involve a significant increase in the probability of an accident previously evaluated.

2) Create the possibility of a new or different kind of an accident previously evaluated (10CFR50.92(C)(2).

The flow change will not affect minimum required DNBR for all previously evaluated accidents. Therefore, this amendment would not create the possibility of new or different kind of accident.

3) Involve a significant reduction in a margin of safety,10CFR50.92(C)(3).

The amendment request changes the minimum flow requirement but maintains the DNBR limit and all other accident evaluations assumptions and limits. Therefore, with all evaluation assumptions and limits unchanged, there is no reduction in the margin of safety.

Based on the attached safety evaluation and the above Significant Hazard Consideration, this amendment request does not contain a Significant Hazard.

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