ML19344D914

to BAW-1598, Davis-Besse Nuclear Power Station, Unit 1,Cycle 2 Reload Rept. Includes Discussion of Revisions for Max Stuck Rod Worth & Rod Insertion Limits

ML19344D914
Person / Time
Site:	Davis Besse
Issue date:	08/22/1980
From:	TOLEDO EDISON CO.
To:
Shared Package
ML19344D906	List: ML19344D905 ML19344D910 ML19344D914
References
645, BAW-1598, BAW-1598-R2, NUDOCS 8008260330
Download: ML19344D914 (9)

Text

• Docket No. 50-346 Lican2c No. NPF-3 Serial No. 645 August 22, 1980 Discussion of Revisions for Maximum Stuck Rod Worth (For Revision 2 of BAW-1598)

The maximum stuck rod worths for Davis-Besse 1 Cycle 2 were reported in the Reference as 1.099L4aat Beginning-of-Cycle (B0C) and 1.20tdy at End-of-Cycle (EOC).

These worths were calculated for core location N12. Subsequently, double stuck rod worth calculations for the Physics Operating Manual indicated location H14 might have a higher stuck rod worth than location N12. The worth of a stuck rod in location H14 was then calculated at BOC, Hot Zero Power (HZP) conditions and a 1.14%4p worth was obtained, which is indeed higher than that for location N12.

The BOC scoping calculations which had been used to determine the location of the maximum stuck rod had indicated a 1.09 tap worth for location N12 and a 0.89 worth for location H14. The difference between the stuck rod worths generated with the design model and those generated with the scoping model was traced to a power distribution difference in the allrods inserted cases. The relative power density (RPD) in location N12 was 1.2% higher in the scoping calculations than in the design calculations while the RPD in location H14 was 5.7% lower in the scoping calculations. The lower power in location H14 in the scoping calculations resulted in a substantially lower stuck rod worth in that location. Since the RPD's in location N12 in both calculations were in good agreement the stuck rod worths were the same. End of cycle calculations showed similar trends and the maximum stuck rod worth at EOC has also been revised. Changes were made in Tables 5-1 and 5-2, as shown on attached pages.

Calculations for other plants and cycles were checked and the accuracy of the maximum stuck rod worth prediction was verified in all cases. B&W's other 177FA plants contain 61 full length control rods and there is usually one rod location much higher in worth '.an the others such that the scoping calculations easily predict the maximum stuck rod location. In the case of Davis-Besse where there are only 53 full length control rods, the gap in the control rod pattern in locations symmetric to K11 results in a significantly lower maximum stuck rod worths and results in several locations having worths near the maximum. To ensure that the location of the most worthy stuck rod is accurately predicted in the future, addi-tional calculations will be made with the design model to confirm the selection of the maximum stuck rod location.

Reference:

Davis-Besse Nuclear Power Station Unit 1, Cycle-2 Reload Report, Toledo Edison Company revision dated May 19, 1980 to BAW-1598.

800826 0 3N

Dockst No. 50-346

- Lic;nra N2..NPF-3 Ssrisl No. 645

- August 22, 1980 Discussion of Revisions for Rod Insertion Limits (For Revision 2 of BAW-1598)

An error was found in the shutdown rod insertion limits for_ Cycle-2 of Davis-Besse Unit 1. Incorrect power deficits were used in a hand calculation of Required Rod Worths for the icwer power limits only; the full power limits remain unchanged. The power deficits have been corrected and checked against 2D PDQ calculations to verify power deficit versus power behavior.

Revised figures illustrating regulating group position limits are attached; the LOCA linear heat rate rod insertion limits for the "after 150+10 EFPD" cycle length span have been modified due to intersection of the cArrected shutdown margin limits and the LOCA rod insertion limits.

The attached Technical Specification Figures 3.1-2a, 3.1-2b, 3.1-3a, and 3.1.-3b supersede those reported in BAW-1598, January, 1980, revised by Toledo Edison Company February 6,1980, Davis-Besse Nuclear Power Station Unit 1 Cycle-2 Reload Report.

e I

Dockst Ns. 50-346 Licents No. NPF -3 Serial No. 645 BAW-1598

^E*

• DAVIS-BESSE NUCLEAR POWER SIAT10N UNIT 1 -

CYCLE 2 - RELOAD REPORT List of Effective Pages Page Revision 11 -- iv Original Submitted; 1-1 2-1 3-1 -- 3-4 B&W Rev. 1 (5/13/80)*

4-1 -- 4-3 Original Submitted 4-4 -- 4-5 B&W Rev. 1 (5/13/80)*

5-1 -- 5-2 5-3 B&W Rev. 2 (8/21/80)**

5-4 B&W Rev. 1 (5/13/80)*

5-5 B&W Rev. 2 (8/21/80)**

5-6 B&W Rev. 1 (5/13/80)*

6-1 6-2 Original Submitted 7-1 -- 7-2 7-3 B&W Rev. 1 (5/13/80)*

8-1 Revised by TECo (5/19/80)*

8-2 -- 8-10 Original Submitted 8-10a B&W Rev. 1 (5/13/80)*

8-11 -- 8-13 ,

Original Submitted 8-13a B&W Rev.1 (5/13/80)

Revised by TECo (5/19/80)*

8-13b B&W Rev. 1 (5/13/80)*

8-14 -- 8-23 Original Submitted 8-24 -- 8-27 B&W Rev. 2 (8/21/80)**

8-28 -- 8-35 Original Submitted 8-36 B&W Rev. 1 (5/13/80)*

9-1 -- 9-9 Original Submitted

• Submitted to NRC May 21, 1980 (Serial No. 618)

• • Submitted to NRC August 22, 1980 (Serial No. 645)

LL N Lic;nsa No. NPF-3

. Sarici No. 645 Augu2t 22, 1980 B&W Revision 1 (5/13/80), BAW-1598 B&W Revision 2 (8/21/80), BAW-1598 Table 5-1. Davis Besse 1 Cycle 2 Physics Parameters (*)

Cycle 1 Cycle 2 Cycle length, EFPD 433 248 Cycle burnup, mwd /mtU 14,360 8,240 Average core burnup - EOC, mwd /mtU 14,360 17,069 Initial core loading, mtU 83.6 83.4 Critical boron - BOC, ppm (no Xe)

HZP(b), group 8 (37.5% wd) 1,520 1,379 HFP, group 8 inserted 1,408 1,197 Critical boron - EOC, ppm (eq Xe)

HZP 456 422 HFP gr UP 8 (37.5% wd, eq Xe) 129 149 Control rod worths - HFP, BOC, % ak/k Group 6 2.00 0.98 Group 7 1.50 1.47 Group 8 (37.5% wd) 0.46 0.34 Control rod worths - HFP, EOC, % Ak/k Group 7 1.12 1.56 Group 8 (37.5% wd) 0.30 0.41 Max ejected rod worth - HZP, % Ak/k(#

BOC 0.85 0.77 EOC 0.63 0.82 1 Max stuck rod worth - HZP, % Ak/k BOC 2.98 1.14 2

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EOC 1.25 1.25 Power deficit, HZP to HFP, % ok/k BOC -1.00 -1.51 EOC -2.24 -2.24 Doppler coeff - BOC 10-5 (ak/k/*F) 100% power (no Xe) BOC -1.25 -1.44 100% power (eq Xe) EOC -1.45 -1.53 Moderator coeff - HFP, 10-4 (ak/k/*F) -

BOC (no Xe, 1064 ppm, group 8 in) -0.06 -0.56 EOC (eq Xe,17 ppm, group 8 in) -2.60 -2.73 Boron worth - HFP, ppm /% Ak/k BOC (1150 ppm) 99 171 EOC (17 ppm) 102 98 Xenon worth - HFP, % ok/k BOC (4 EFPD) 2.73 2.67 EOC (equilibrium) 2.71 2.78

7 . . DocL4t No. 5@2346 g- Licznra No. NPF-3

. Strici No. 645 B&W Revision 1 (5/13/80), BAW-1598 '

Augu::t 22,1980 B&W Revision 2 (8/21/80), BAW-1598 Table 5-2. Shutdown Margin Calculation for Davis Besse.1 Cycle 2 BOC, EOC,

% Ak/k  % Ak/k Available Rod Worth Total rod worth, HZP(*) 7.09 7.47 Worth reduction due to burnup of poison material -0.05 -0.10 Maximum stuck rod, HZP -1.14 11.25  :

Net worth 5.90 6.12 2 Less 10% uncertainty -0.59 -0.62 Total available worth 5.31 5.50 Required Rod Worth y

Power deficit, HFP to HZP 1.51 2.24 Max allowable inserted rod worth 0.25 0.40 Flux redistribution 0.60 1.10 Total required worth 2.36 3.74 Shutdown Margin Total available minus total required 2.95 1.76 2 Note: Required shutdown margin is 1.00% Ak/k

(* HZP denotes hot zero power (532F T""E); HFP denotes hot full power (584F core T ).

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