ML20154L967

Forwards Summary of Fuel Assembly Changes Included in Plant Cycle 11 Core,Per Util 871120 License Change Application 161 Re Nuclear Fuel Upgrade.Startup Rept for Cycle 11 Not Required Since Fuel Design Considered Essentially Same

ML20154L967
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	05/27/1988
From:	Cockfield D PORTLAND GENERAL ELECTRIC CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
NUDOCS 8806010120
Download: ML20154L967 (4)

Text

_ _ _ _ _ _

=

4 t

m smuse mes

~

Portland General Elect.ic Cortyxiny David W. Cockfield Vice President. Nuclear May 27, 1988 Trojan Nucioar Plant Dockot 50-344 Licenso NPF-1 Nuclear Regulatory Commission ATTN; Document Control Desk Washington, DC 20555

Dear Sir:

Addendum to Licenso Change Application 161

Reference:

Lotter to NRC Document Control Desk from D. W. Cockfield, PCE "License Chan*o ; Application 161, Nuclear Fuel Upgrado" dated November 20, 1987 Attached for your information is a summary of the fuel assembly changes, described in t.be referenced licenso change application, that are included in the Trojan Cycle 11 coro. The fuel changes have beet' determined not to constituto a significantly different fuel design nor a significant altera-tion to the nucicar, thermal, and hydraulic performanco of the Plant.

Because the fuel design is considered to be essentially the same as that used in the previous cycle, and in accordanco with Technical Specifica-tion 6.9.1.1, submittal of a startup report for Cycle 11 is not required.

Sincerely.

Attachment c: Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. Bill Dixon Stato cf Oregon Department of Energy Mr. R. C. Barr \

NRC Resident Inspector Trojan Nuclear plant s\

8806010120 880527 PDR ADOCK 05000344 P DCD e S v Ea non ? 4 Pcom. c~pn 9w m

. c; Attachment page 1 of 3 ADDENDUM TO LICENSE CHANGE APPLICATION (LCA) 161 Differences Between Current (Cycle 10) and Upgraded (Cycle 11) Fuel Assemblies As described in LCA 161, Design Feature section, the Trojan upgraded fuel design for Cycle 11 is very similar to the previous fuel. Both designs are a 17 x 17 array of standard diameter (0.374-inch outer diameter)

Zircaloy 4 clad fuel rods supported by inconel grids. The fuel assembly structure remains the same - 24 Zircaloy thimble tubes (and one contral Zircoloy instrument tube) swaged to the grids and fastened to the top and bottom nozzles. A comparicon of Cycle 10 and Cycle 11 fuel assembly dimensions is provided in Table 1.

The top and bottom nozzles now feature a remove:lile design in order to facilitate in-pool fuel repairs. The bottom nozzle retains the same means of locking the thimble tubes to the nozzle, but the nozzle is changad to be somewhat thinner and shorter than che previous version.

The top nozzle is shorter and has the reconstitutable features described in LCA 161. These changes to the nozzles did not significantly change the function, strength, flow resistance, or other features of the nozzles related to the fuel assembly design.

The fuel rod design for Cycle 11 is slightly longer than was previously used. The fuel rod to nozzle gap dimension is increased slightly because of the shorter nozzles. The position of the grids is shifted slightly, but the grids remain at elevations that are compatible with previous assemblies. In addition, the end plugs have been changed to include a more tapered chape to facilitate fuel repairs.

The external changes to the fuel as=emblies have a minute effect on the assembly thermal-hydraulic performance. Because these changes are very small, there is no change expreted in core flow or average coolant temperature. Likewise, the response to transient events, such as coast-down of reac*.Fe coolant pumps, remains tha same. Externally, the new and old assemblies are the same in the active fuel region.

Internal changes to the fuel rods are small and evolutionary in naturo.

The fuel rod is now somewhat longer to allow more internal voluine for fission ges accumulation. The internal shape of the top and bottom fuel red end plugs also allows more space for fiscion gas. Axial blankets of natural UO2 are provided in the top and bottom 6 inches of the fuel pellet stack. The fuel pellets used for the axial blankets are of a slightly longer design to preclude mixing them with other fuel pellets.

While the regular fuel pellets are now shorter, with slight chamfer and dish changes; these changes do not adversely affect the function of the fuel. Indeed, all changes have boon made with the intent of imoroving fuel performance and attaining higher burnup.

L .

a.

. .o Attachment i Page 2 of 3 The internal changes to the fuel will slightly affect the axial power.

profile due to the axial blankets, however, the power peaking factors are still met. The changes to the pellet length and plenum space have been evaluated by 'Jestinghouse and existing limits for fuel temperature, clad-ding creep, and other pertinent parameters continue to be met for the new fuel.

Portland General Electric (PCE) concludes that changes to the design of the Trojan fuel are small and of a nature that do not require reunalysis.

The changes to operating limits are described and analyzed in LGA 161.

Furthermore, PGE has reviewed these changes and compared them to Technical Specification 6.9.1.1 and concludes that a startup report is not needed, since the new fuel assemblies are not significantly different from those previously used.

GRA/2587P

.u

. 1.ttcchment

• P go 3 cf 3 TABLE 1 COM.PARISON OF CHANCES TO CYCLE 11 TROJAN FUEL DESIGN COMPONENT CYCLE 10 CYCLE 11 DESCRIPTION

. Top Nozzle Height, inches 3.670 3.475 Nozzle height reduction to accommodate longer fuel rods.

Fastening Method See Trojan Sco WCAP- Allows nondestructive removal of top FSAR 10444-P nozzlc. Mechanical design critoria met.

Fig. 4.2-10 Fig. 2-4

. Fuel Rod Top End Plug - -

Shcrter plus permita larger plenum volume Plenum length. C.3 7.32 to allow higher burnup, inches Blanket Pellets Axial fuel blankets improve acutron Enrichment, wt% - 0.74 oconomy.

Length, in. -

0.530

. Fusi Pellets Enrichment, wt% 3.40 3.45 Shorter pellets with new chamfor provides Length, in. 0.530 0.387 for retaining original nonchamfered fuel Shapc chamfered chamfered loading (sm/cm). Also, inadvertent mixing with blanket pellets is readily identifiable.

Bottom Plus Shapo tapered more taper Facilitates reinsertion of fuel rods.

P,od Length, inches 151.63 152.16 Additional length to provido for fission gas release.

Bottom Nozzle Height, inchos 2.738 2.383 Decreased nozzle height to allow longer fuel rod and increased fuel rod to nozzle gap.

Fuel Ascombly Height, inches 159.785 159.915 0.13 in. greater length accommodated by springs Rod: nozzle Cap, 1./27 1.897 Slightly larger to allow more fuel rod inches growth.

Grid Positions -

0.35-in. Crid-to-grid contact retained, lower L.