ML20101F578

Nonproprietary Safety Evaluation for Vantage 5 Demonstration Fuel Assemblies in VC Summer Nuclear Station

ML20101F578
Person / Time
Site:	Summer
Issue date:	12/14/1984
From:	WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
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ML20101F524	List: ML20101F521 ML20101F547 ML20101F564 ML20101F578
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NUDOCS 8412270228
Download: ML20101F578 (5)

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, WESTINGHOUSE PROPRIETARY: CLASS 3

~ ATTACHMENT 2 SAFETY EVALUATION FOR ~THE VANTAGE 5 DEMONSTRATION FUEL ASSEMBLIES IM THE l VIRGIL C. SUMMER NUCLEAR STATION Introduction

A demonstration program to confirm the performance of the

- improved Westinghouse fuel assembly design known as VANTAGE 5

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and described in WCAP-10444, " VANTAGE 5- Fuel Assembly, Reference Core' Report," (submitted for NRC Staff review in

' December.1983). has been undertaken in the Virgil C.' Summer plant. ' The demonstration assemblies contain all the VANTAGE 5 -

features described in WCAP-10444 which are axial blankets, an integral fuel burnable absorber (IFBA), intermediate flow mixer grids (IFM) , increased burnup and a reconstitutable top nozzle.

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'For Cycle 2 operation, the location of the four VANTAGE 5

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demonstration assemblies is given on Figure 1. The-following

~ isla synopsis of the safety review performed on the VANTAGE 5

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demonstration assemblies:

~ Mechanical Design 4

The1 VANTAGE 5 demonstration assembly design is mechanically compatible with the existing standard design and the fuel and >

' core component' handling systems. The demonstration assemblies

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cancoccupy any core-location subject to peaking factor limits.

The design basis for the demonstration fue'l assemblies including the VANTAGE 5 features was satisfied. .The details of-t' the mechanical design and evaluation are contained in

. WCAP-10444.

I' Thermal-Hydraulic Design The IFM ' grid alters the hydraulic characteristics of the fuel assemblies ' because of the additional pressure drop induced by the IFM grids. The VANTAGE 5 demonstration assembly has about a[ ]+ higher resistance to flow than the standard fuel a,c assembly design. Because only four VANTAGE.5 demonstration assemblies are in the reactor, this will have a negligible effect on the core pressure drop ~and flow rate.

, Since the IFM grids are not present in the standard fuel assemblysdesign, a hydraulic

• resistance mismatch'at the IFM grid elevations . exists. The-fuel assemblies represent semi-open channels and result in crossflow out of~the

- demonstration assemblies near an. IFM grid elevation and back

-into the-demonstration' assemblies.further down stream. To

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f atudy ' this' effect, tests were perfonned ' with side-by-side standard 7and VANTAGE 5 assemblies. Fuel rod vibrations were

-found to be_ acceptable and clad wear was negligible after

-extensive testing.

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- Attachment 2 Page 2 WESTINGHOUSE PROPRIETARY CLASS 3 DNB-. tests were performed on a full scale 5x5 array. of heated-rods modeling the interior of'a VANTAGE 5 fuel assembly.. The '

Eresults showed the WRB 1 correlation to.be-conservative in its-

- DNB prediction for this geometry.

Analyses were performed and indicated that the demonstration assemblies met all DNB design criteria and did not affect the minimum DNBR for the standard core.

Fuel average:and centerline temperatures were calculated for

+ _ the VANTAGE 5 demonstration assembly fuel rods and the standard

. fuel rod design'. The.results showed that both' designs have o almost identical maximum centerline and' average : fuel P temperatures.

Nuclear Design The' VANTAGE 5 demonstration assemblies have two 'different types of fuel rods in a 17x17 OFA lattice. One type contains three

- axializones: [ ]+ inch natural uranium. blankets at the tcp a,c and bottom and a1[ ]+ inch uniformly enriched central _

a,c region.- The other: type of fuel rod contains a part length section of boride coated fuel pellets. - The coated fuel section

' is [ - ]+ inches long and is positioned symmetrically about a,c-

the fuel stack midplane. These fuel rods have five axial zones;-[ ]+ inches of natural uranium at the top ' and bottom

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a,c followed by [ ]+ inches of enriched, uncoated fuel, and the a,c

[- ]+ inch central section of enriched, coated fuel. Each a,c L

. - demonstration assembly contains ' [ ]+ fuel rods which have a,c the boride coated pellets. The enriched section of'every VANTAGE 5 fuel rod is the same as the enrichment of the STD i- fuel rods, 3.45 w/o. The effect of demonstration assemblies on corewise reactivity behavior is accounted for in- the calculations.used to perform the core design.

The Virgil:C. Summer Cycle 2 loading pattern, using four demonstration assemblies, is designed such that they do not lead the core and do not become limiting during transient conditions. Two of the demonstration assemblies are placed in I' instrumented locations.

The core power distributions containing the four VANTAGE 5 demonstration assemblies meet all pertinent safety criteria, p -There are .no restrictions on F-delta-H for the demonstration l assemblies beyond those applicable for the rest of the core.

L -Due to LOCA considerations, the demonstration assemblies are l'

required to operate to Fg values at least [ ]+ less than a,c the limiting value for the STD~ fuel assemblies. This operation is assured by the proper placement of the VANTAGE 5 demonstration assemblies in the core and will not require any l additional ' plant monitoring.

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Attachment 2 Page 3

' WESTINGHOUSE PROPRIETARY CLASS 3 Non-LOCA

, The location of . the VANTAGE 5 demonstration assemblies has been selected to ensure.that they do not lead the core during normal operation or transient conditions. Given this criteria-and the results of the nuclear'and thermal-hydraulic analyses for the demonstration assemblies in the Virgil C. Summer core, an evaluation concluded _that all~ existing non-LOCA safety criteria were still met, and all corresponding safety limits were still valid.

.IDCA.

The 'large bre .' LOCA analysis for record of Virgil C. Summer iss the FSAR analysis modeling 17x17 standard fuel. The Westinghouse ECCS Evaluation Model analysis, demonstrates that

. a peaking factor (Fg) of.[ ]+ is acceptable at 100% a,c power.- .To support the introduction of VANTAGE 5 demonstration assemblies,. thermal-hydraulic parameters consistent with _the Virgil C. Summer FSAR-analysis have'been applied in a rod

- heatup calculation of a VANTAGE 5 fuel assembly. Pertinent fuel _ design parameters for the VANTAGE 5. demonstration assemblies were employed in.this. calculation. The result-for the' VANTAGE 5 fuel in the Virgil C._ Summer-plant is'a calculated peak < clad temperature (PCT) which~ meets the

- 10CFR50.46 limit of 2200*F.

- The introduction of VANTAGE 5 assemblies as part of- a STD fuel reload produces a transition core configuration at Virgil'C. ~

In assessing the impact of transition cores on large

?. Summer.

break Loch analysis, the transition core can have a greater-calculated PCT than either a complete core of the reference p"

' design or a complete core of the new fuel design. For a given-peaking factor, the only mechanism available to cause a transition. core to have a greater calculated PCT than a full E

core of.either fuel is the possibility of flow redistribution .

_ due to~a fuel assembly hydraulic. resistance mismatch. This hydraulic resistance mismatch for transition cores -involving

!-- the VANTAGE 5 fuel design could result in PCT increase at the core axial elevations where PCTs can possible occur.-

- Using established relationships, operation of the VANTAGE 5 demonstration assemblies at a total peaking factor (Fg) cat-least [ ]+ lower than the limiting value allowed for the a,c ,

.STD fuel assures a LPCT for= the. VANTAGE. 5 assemblies which. meets

< the. established 10CFR50.46 regulatory limit of,2200*F.

hn ,

Large break ECCS performance-requirements continue to be met for-Virgil C. Summer provided the VANTAGE 5 demonstration i assemblies are positioned in the core such that they operate at 1-

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Attachment 2 Page 4 WESTINGHOUSE PROPRIETARY CLASS 3

]+ less than the limiting value a,c an Fg value'at least [

allowed for the_STD fuel assemblies. The small break ECCS analysis presented in the Virgil C. Summer FSAR is not significantly affected by introduction of VANTAGE 5 demonstration assemblies.

Conclusions Based upon the evaluation cummarized above, it can be concluded that the introduction of VANTAGE 5 demonstration fuel assemblies will not reouire NRC review under the provisions of 10CFR50.59 in that no technical specification changes are involved and no unroviewed safety questions result.

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,' VIRGIL C. SUMMER NUCLEAR STATION a CYCLE 2 CORE LOADING PATTERN WESTINGHOUSE PROPRIETARY-CLASS 3 RPNMLKJHG EDCBA

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l X Region Number .

I location of VANTAGE 5 Demonstration Assemblies e