ML20043F579

Requests That Meeting W/Nrc & Westinghouse Be Held During Wk of 900624 to Further Discuss Intended Cycle 2 Fuel Design Features & Fuel Mgt Strategies

ML20043F579
Person / Time
Site:	Seabrook
Issue date:	06/08/1990
From:	Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NYN-90122, NUDOCS 9006150122
Download: ML20043F579 (5)

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New Hampshire Ted C. Feigerhoum Yh Senior Vice President and Chief C4eroting C6cer NYN- 90122 June 8, 1990 United States Nuclear Regulatory Commission Washington, DC 20555 Attention: Document Control Desk

References:

Facility Operating License No. NPP-86 Docket No. 50-445

Subject:

Cycle 2 Fuel Design Features Gentlemen:

New Hampshire Yankee (NHY) is currently finaliaing fuel design features and fuel management strategies for Cycle 2 operation of Seabrook Station

. Unit 1. This letter briefly describes these Cycle 2 fuel design features and fuel management strategies.

The Cycle 2 fuel design will assume a 12-month operational period (Fall 1991 to Fall 1992) and will incorporate various enhancements to the Vesting-house 17 x 17 Standard Fuel Assembly as described in the enclosure to this letter. These fuel design features are intended to improve operating perfor-mance and fuel cycle economics. Each of these fuel design features has been consnercially proven by numerous other customers of Vestinghouse. The Cycle 2 fuel design is not expected to necessitate an amendment to the operating license.

New Hampshire Yankee requests that a meeting of NHY, Yankee Atomic Electric Company (YAEC). NRC, and Westinghouse representatives be held during the week of June 24, 1990, to further discuss the intended Cycle 2 fuel design features and fuel management strategies.

Should you have any questions regarding this letter, please contact Mr. Terry L. Harpster. Director of Licensing Services, at (605. 474-9521, extension 2765.

Very truly yours.

2?CA Y

Ted C. Feige'yt{

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}&h TCF/ALLijt/ hW il Enclosure i 9006150122 900o08 -)M 4 DR ADOCK0500(g3 New Hampshire Yonkee Division of Public Sewice Company of New Hampshire P.O. b 300

• Seabrook, NH 03874 e Telephone (603) 474 9521

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.y O_- i United States Nuclear Regulatory Comunission June 8. 1990

' Attention: Document Control Desk Page 2 i i

i cca Mr. Thomas 7.' Martin I Regional Administrator  !

United States .Muclear Regulatory Connission Region I' .:

475 Al'.adaA Road i King <t Prus' , PA 19406 i t, -

Mr. Not J1ey NRC Sen., Resident Inspector .i P.O. Box'1149 8eabrook, NH 03874

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.e New Hampshire Yankee June 8, 1990 ENCLOSURE 1 TO NYN- 90122 CYCLE 2 FUEL DESIGN FEATURES l

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4 SEABROOK STATION UNIT 1 CYCLE 2 FUEL FEATURES AND FUEL MANAGEMENT STRATEGIES The following fuel design features and fuel management strategies will be incorporated in Cycle 2. These design features are enhancements to the Westinghouse 17 x 17 Standard Fuel Assembly.

CYC1.E 2 FUEL FEATURES: 4

• Debris Filter Bottom Nozzle (DFBN)

The DFBN improves upon the existing 17 x 17 bottom nozzle design by using ,

smaller flow holes to reduce the passage of debris into the fuel assembly, t The redesign maintains the structural integrity of the nozzle and matches the hydraulic performance of the original design.

DFBNs have been accepted for use in 38 Westinghouse plants. By the end of 1989, there were 1,645 assemblies in operation in 23 plants.

• Removable Too Nozzle (RTN)

Unlike the current standard fuel top nozzle design, the RTN is designed to allow top nozzle removal and reattachment throughout the fuel assembly lifetime. The RTH design should permit easier inspection and replacement  !

of individual fuel rods compared to the current top nozzle design.

RTNs were first put into service in 1986 and have been accepted for use in 46 Westinghouse plants. By the end of 1989, there were 1,402 assemblies in operation.

• Hich Burnuo (HB)

Higher discharge burnup levels are achieved through the dimensional changes of the RTH and DFBN designs in conjunction with a longer fuel rod length.

The longer fuel rods have a larger plenum to accommodate the additional fission gas release associated with higher burnups. In addition, the RTN and DFBN have a reduced height to provide space for fuel rod growth which l 1s also associated with higher burnup levels. The active fuel length remains the same.

l The increase in discharge burnups reduces the number of fuel assemblies required for a given reload. Consequently, the number of fuel assemblies discharged to the spent fuel pool over the life of the reactor will be less.

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. Intental Fuel Burnable Absorber (IFBA)

IFBA fuel consists of a thin (i.e., less than 0.001 inch) coating of zirconium diboride (ZrB 2) on the exterior surface of the fuel pellet.

IFBAs have a lower reactivity penalty compared with WABAs because they burn completely and involve no additional parasitic structural material. Since IFBA rods combine fuel and burnable absorber they eliminate the separate handling of absorber rods during refueling and eliminate absorber storage /

disposal costs.

IFBAs were first put into service in 1986 and have been accepted for use by 25 Westinghouse customers. By the end of 1989, there were 77,200 IFBA rods provided to 14 plants.

IFBA may be used alone or in combination with WABA (see description below).

. Wet Annular Burnable Absorber (WABA)

Wet annular burnable absorbers consist of annular pellets of aluminum oxide-boron carbide contained within two concentric Zircaloy tubes. Reactor coolant flows inside the inner tube and outside the outer tube of the annular rod and therefore provides better neutron thermalization allowing for a more complete absorber depletion. Like the Pyrex absorber rods used at Seabrook, these rods are placed in the thimble tubes of fuel assemblies that do not contain control rods. After their first cycle of irradiation, WABAs (as well as Pyrex absorbers) are removed from the fuel assembly. Because WABA rods are Zircaloy cladded, they have less parasitic neutron absorption compared with stainless steel clad absorbers. Therefore, the residual reactivity penalty at end-of-cycle is less with WABAs than with Pyrex absorbers.

WABAs have been accepted for use in 32 Westinghouse plants. By the end of 1989, there were 46,021 WABA rods provided to Westinghouse customers.

CYCLE 2 FUEL MANAGEMENT:

. Low Leakane Loadinn Pattern (LLLP) 1he placement of fresh fuel in the interior core region and burned fuel along the core periphery is known as a low leakage loading pattern. This fuel management technique reduces neutron leakage and, therefore, increases net core reactivity. Compared to the conventional out-in-in fuel management practice, a LLLP results in a longer cycle length for the same feed enrich-ments or reduced feed enrichments for the same cycle length. A LLLP has the additional advantage over the out-in-in patt.ern of reducing the neutron fluence on the reactor pressure vessel.

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