ML20150E411

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Criticality Analysis of Maine Yankee Spent Fuel Pool & New Fuel Vault
ML20150E411
Person / Time
Site: Maine Yankee
Issue date: 02/29/1988
From: Adli D, Cacciapouti R, Napolitano D
YANKEE ATOMIC ELECTRIC CO.
To:
Shared Package
ML20150E410 List:
References
YAEC-1637, NUDOCS 8803310254
Download: ML20150E411 (61)
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YANKEE ATOMIC ELECTRIC COMPANY

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Criticality Analysis of Maine Yankee's spent ruel Pool and New Fuel Vault By D. G. Napolitano D. G. Adli February 1988

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Prepared by: .i n g . day.I _

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D. G. Napolitanp/ Nudlear Engineer / D6te Reactor PhysictVGroup Nuclear Engineering Department Prepared by: [. [ .3/Date II/W D. G. Adli, Nuclear ~ Engineer Reactor Physics Group l Nuclear Engineering Department l Approved by: M d!//!Pg

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'R/[J . Cacci ics R(actor Ph Group Nuclear Engineering Department Approved by: / 3!//88 Date B. C. Sli(er, Director

[ Nuclear Ugineering Department Yankee Atomic Electric Company Nuclear Services Division 1671 Worcester Road Framingham, Massachusetts 01701

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DISCLAIMER OF RESPONSIBILITY This document was prepared by Yankee Atomic Electric Company

("Yankee"). The use of information contained in this document by l

anyone other than Yankee, or the Organization for which this I document was prepared under contract, is not authorized and, with

[ respect to any unauthorized use, neither Yankee or its officers, directors, agents, or employees assume any obligation, r responsibility, or liability or make atiy warranty or l representation as to the accuracy or completeness of the material contained in this document.

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ABSTRACT This report presents the criticality analysis for the Maine Yankee spent fuel pool and the new fuel vault. The analysis This is performed with the YAEC criticality stifety mechodology.

includes: NITANL-5/ KENO-Va Monte Carlo analysis and CASMO-3

( integral transport analysis. The Maine Yankee spent fuel pool is described, and a model of the spent fuel racks is developed with both KENO-Va and CASMO-3. KENO-Va is used to model the reference

( configuration, and CASMO-3 is used to perform sensitivity analysis.

Calculations of K vs. enrichment are perform, and a determinationof$$kimumfreshfuelenrichmentismadeforthe spent fuel racks. The Maine Yankee new fuel vault is described, Calculations of and a 3-D KENO-Va model of the vault is developed.

K vs. moderator density are performed and maximum fresh fuel e8f(chmentatoptimummoderationisdetermined.

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ACKNOWLEDGMENTS The authors would like to express their apprecittion to Fred

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Csrperito for reviewing the spent fuel storage rack criticality calculations presented in this report.

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TABLE OF CONTENTS f

Page 11 DISCLAIMER .......................>...................

iii ABSTRACT .............................................

iv ACKNOWLEDGMENTS ......................................

V TABLE OF CONTENTS ....................................

( Vi LIST Or FIGURES ......................................

viii LIST OF TABLES .......................................

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1.0 INTRODUCTION

1.1 Regulations and Design Basis ................ 1 1.1 The YAEC Criticality Safety Methodology ..... 2 1.3 The Maine Yankee Atomic Power Station 4 ruel Building Arrangement ...................

1.4 The Maine Yankee Fuel Assembly .............. 6 14

( 2.0 SPENT FUEL POOL CRITICALITY ANALYSIS..............

14 2.1 Spent Tuel Rack Mechanical Design ........... 16 l

2.2 NITAWL-S/ KENO-Va Modelling ..................

{ 2.3 CASMO-3 Modelling ........................... 17 18 2.4 K vs. Enrichment .........................

2.5R$bkSensitivityAnalysis................... 18

[ 2.6 Determination of Maximum rresh ruel 19 Enrichment with Uncertainties ............... 20 2.7 Accident situations .........................

.............. 40 3.0 NEW FUEL VAULT CRITICALITY ANALYSIS 3.1 New Tuel Rack Mechanical Design ............. 40 41

[ 3.2 NITAWL-S/ KENO-Va Modelling ..................

42 3.3 K,gg vs. Moderator Density .................. 43 3.4 K,gg vs. Enrichment at Optimum Moderation ...

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4.0 CONCLUSION

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54 REFERENCES ....................................... i

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I LIST Or TIGURES

?itle Page Number YAEC Criticality Safety Methodology 8 1.1 1.2 Maine Yankee ruel Building Arrangement, P16ne A-A 9 Maine Yankee ruel Building Arrangement, Plane B-B 10 1.3 Maine Yankee ruel Building Arrangement, Plane C-C 11 1.4 Maine Yankee Spent ruel Pool Arrangement 12 1.5 A 7 X 9 Spent ruel Rack Module 22 2.1 2.2 Maine Yankee Spent ruel Rack Canister Design 23 Axial Profile

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2.3 Maine Yankee Spent ruel Rack Canister Design 24 Radial Profile

{ 25 2.4 Canister Type 1 j 2.5 26

( Canister Type 2 l l

27 l 2.6 Canister Type 3 l 2.7 KENO-Va Model of Canister Type 1 28 l 2.8 KENO-Va Model of Canister Type 3 29 2.9 CASMO *2 Model of Canister Type 1 30 2.10 CASMO-3 Model of Canister Type 3 31 2.11 K vs. Assembly Enrichment 32 eff 95/95 Maine Yankee New Tuel Vault Axial Profile 44 3.1 3.2 Maine Yankee New ruel Vault Radial Profile 45 3.3 KENO-Va Basic Unit of Analysis for the Maine Yankee New ruel Vault 46 3.4 KENO-va ruel Array for the Maine Yankee New ruel Vault 47 I 3.5 KENO-Va Vault Array for the Maine Yankee New ruel vault 48

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Title Page Number 3.6 K vs. % void for the Maine Yankee NIh'F8hI'haultwithFuelat3.5w/oU235 49

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3.7 K vs. Enrichment for the Maine Yankee NIbr$hI9haultwithModeratorat95% void 50

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LIST OF TABLES Page Number Title 13 1.1 Maine Yankee Fuel Assembly Designs 33 2.1 The Phase I canister Dimensions and Tolerances

{ 34 2.2 The Phase II Canister Dimensions and Tolerances 35 2.3 Canister Type 1 K,gg vs. Enrichment 36 2.4 Canister Type 3 K,gg vs. Enrichment 37 2.5 Canister Type 1 Sensitivities 38 2.6 Canister Type 3 Sensitivities f with Uncertainties vs. Assembly Enrichment 39 2.7 K,gg 3.1 New Fuel Vault K vs. % Void with Assembly Enrichment at 3.$gd/oU235 51

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3.2 New Fuel Vault K vs. Enrichment with Moderator 52

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l.0 .tNTRODUCTION

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1.1 Regulations and Design Basis The applicable codes, standards and regulations of criticality safety for spent fuel and new fuel storage include the followings o General Design Criterion 62 - Prevention of Criticality in ruel Storage and Handling o NUREG-0800, USNRC Standard Review Plan, Section 9.1.2,

( Spent ruel Storage and section 9.1.1, New ruel Storage.

o ANSI /ANS-57.2-1983, Design Requirements for Spent ruel

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l Storage racilities At Nuclear Power Plants, Section 6.4.2.

o ANSI /ANS-57.3-1983, Design Requirements for New ruel

[ Storage racilities at LWR Plants, Section 6.2.4.

These regulations and auides require that for spent fuel

( racks the maximum calculated K,gg including margin for uncertainty less than or

[ in calculational method and mechanical tolerances be i equal to .95 with a 95% probability at a 95% confidence level. 1 ror new fuel vaults, a dual criteria applies in which the maximum l I

calculated K,gg including uncertainties is less than or : qual to

.95 when flooded and less than or equal to .98 under conditions of

( "optimum moderation".

In order to assure the true reactivity will always be less than the calculated reactivity, the following conservative assumptions are made for spent fuel racks:

o Pure, unborated water at 68'r is used in all calculations, o an infinite array with no radial or axial leakage is modelled, and i.e.,

o neutron absorption from spacer grids is neglected, replaced by water.

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secause the new fuel vault is normally dry and low density moderation or "optimum moderation" produces strong coupling between assemblies, the following assumptions are made:

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o the vault is water tight,

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o unborated water is introduced uniformly throughout the vault and in the space between fuel pins, o water density is varied uniformly from flooded to dry, o neutron absorption from spacer grids is neglected, i.e.,

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o a 3-D semi-infinite array is modelled with reflection

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from the floor, wall and ceiling.

In new fuel vault criticality analysis, leakage is explicitly

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low density moderation. Leakage suppresses criticality at low moderator density. Without 3-D modelling of the array, erroneously high Valves of K,gg are calculated. Thus, the l assumption on array leakage is relaxed, but reflection from the walls, floor and ceiling is included.

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1.2 The YAEC Criticality Safety Methodology The YAEC criticality safety methodology is shown in rigure 1.1. Input to the methodology begins with fuel assembly and storage rack data. This data is transformed into material compositions and geometry input for the methods that follow. The methodology has three calculational paths: NITAWL-S/ KENO-Va,

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CASMO-3 and CASMO-3/ CHART-2/PDQ-7.

( The reference calculational method is NITAWL-s/ KENO-Va(1,2) ,

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The NITAWL-S code prepares a working nuclide library and performs resonance self-shielding for U238 In this analysis, the 123 group data is used in all KENO-Va calculations. The working

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nuclide library along with case specific compositions and rack KENO-Va performs multi-group,

( geometry data are input to KENO-Va.

Monte Carlo criticality analysis. The results from KENO-Va analysis are K,gg vs. generation, fluxes and reaction rates.

Since Monte Carlo is stochastic in nature, results will always have some uncertainty (1 e). .

The auxiliary calculational method is CASMO-3 and/or CASMo-3/

CHART-2/PDQ-7(3,4,5) .

CASMo-3 is an integral transport lattice

( code with a hierarchy of energy condensation and spatial detail leading to a seven-group, transmission probability model of the unit cell, CoxY. The 40 micro-group nuclear data is used in all CASMo-3 calculations. CASMo-3 is flexible enough to handle up to a 19x19 fuel assembly array with storage canister regions, poison sheets and water gaps. In this analysis, CASMO-3 is used to study unit cell sensitivity to mechanical perturbations. Since, the result of CASMO-3 calculation is a deterministic K., a resultant AK from a mechanical perturbation are not overwhelmed by stochastic uncertainty like a 4K from Monte Carlo would be. )

( CASMo-3 can produce few group cross sections which preserve unit cell reactivity. These cross sections can be processed by the CHART-2 coGe for use in PDQ diffusion theory analysis. Using PDQ, a refined unit cell analysis or large array studies can be performed. Also, axial and radial leakage effects can be

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Additionally, CASMO-3 can perform burnup credit analysis. Hot f

full power lattice depletions can be executed, and cold rero pover restarts in rack geometry can be performed. The effects of incore depletion and long term out-of-core nuclide decay can be studied.

However, burnup credit is not included in the present report.

The calculational paths of the YAEC criticality safety methodology has been validated by comparison to 2'. B&W fuel storage critical experimentsI6'7I. The methodology bias a::d uncertainty determined f rom this validation will be ta 'd on the l calculation of K,gg at a 95/95 probability / confidence level. l

[ f 1.3 The Maine Yankee Atomic Power Station ruel Building Arrangement Maine Yankee Atomic Power Station is a 2630 MWth, C-E, pressurized water reactor located in Wiseasset, Maine. The fuel

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building arrangement is shown in rigures 1.2, 1.3 and 1.4. This building, adjacent to the containment, comprises the spent fuel

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pool, new fuel vault and associated equipment.

The Maine Yankee spent fuel pool arrangement is shown in rigure 1.5. In early 1985, the spent fuel pool was teracked with 10.25" center-to-center, high density, BORAL poisoned spent fuel racks manufactured by GCA/ PAR. The reracking was done in two phases. Modules from the two phases occupy roughly half of the spent fuel pool apiece. There are a total of 26 high density finel storage rack modules with a total of 1476 storage locations.

Criticality analysis in support of the licensing of these racks allowed the placement of fresh fuel with enrichments up to 3.5 w/o

( 235 ir, the spent fuel racksIEI. However, at the time of U

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b fuel racks (flooding of installation, a design change in the spent the BORAL plenum region) was instituted which increased the criticality safety margin of the racks. The present report incorporates this design change and other as-built feat.ures in the criticality analysis. This new analysis will justify the 235 in placement of fresh fuel with enrichments up to 4.13 w/o U the Phase I racks and the placement of fresh fuel with enrichments 235 in the Phase II racks.

up to 3.72 w/o U The new fuel vault is a temporary storage area for fresh

'. . diated fuel. The vault is adjt : int to the spent fuel pool i l

\ .. on one side and has l' thick conctete walls on three sides.

The vault dimensions are 28' by 47' by 14' in height. Tresh assemblies can be arranced in an 8 by 20 array with a minimum spacing of 20" center-n cinter. Aluminum grids at the top and

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bottom of the vault hold the assemblies in the proper spacing.

The total capacity of the vault is 160 locations; but, normally, j 72 assemblies are placed in tt.e new fuel vault for refueling the Maine Yankee core e.ach cycle. Criticality control in the new fuel vault is accomplished by the dry, wide spacing between arrays of fuel assemblies. However, since the intrusion of water by flooding or fire fighting sprays cannot be totally precluded, the criticality of the vault is studied as a function of moderator density with particular emphasis on conditions of low density (.40 to .05 g/cc of water). The present analysis will justify the 235 in the placament of fresh fuel with enrichments up to 5.5 w/o U new fuel vault even under conditions of "optimum moderation".

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l.4 The Maine Yankee Fuel Assembly The Maine Yankee fuel assembly is a 14 X 14 array of fuel This pins with 5 large (2 X 2 fuel pin) guide tube positions.

fuel assembly design has been manufactured by both C-E and Exxon l 1

Nuclear. The fuel assembly design is summarized is Table 1.1.

Due to its higher stack height density, the Exxon design is slightly more reactive than the C-E design; therefore, the Exxon design will be used in all criticality calculations.

Enrichments for Maine Yankee fuel assemblies have varied in 235 to the 3.5 w/o U 235 in Cycle 10, the past from about 2.0 w/o U 235 in order

.the present cycle. Cycle 11 will contain 3.70 w/o U to achieve an 18 month cycle length, and even higher enrichments may be needed for fine tuning cycle lengths or a 24 month cycle.

Normally, some burnable poison (BP) pins are present in the l assemblies of a fresh batch of fuel. BP pins are solid Al O23-B C4 pellets clad with zircaloy. Thes' pins displace fuel pin positions and are an integral part of the fuel assembly. Credit is allowed for such bps in spent fuel rack criticality analysis.

However, Maine Yankee loading pattern optimization has reduced BP requirements to the point where credit for bps is not viable.

Thus, the criticality analysis will assume all unshimned assemblies are placed in the spent fuel racks.

The two major assembly tolerances impacting spent fuel rack criticality are the fuel (UO2) density deviation and the enrichment (w/o) deviation. The tolerance on fuel density is 1 0.07 g/cc based on the C-E spec on pellet theoretical density and 1 0.08 g/cc based on the Exxon spec on theoretical density. The L

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more conservative 1 0.08 g/cc will be used in the criticality L

analysis. The maximum (100%) variation on enrichment is by DOE contractual agreement 1 0.013 w/o U235 However, the variation in I

fuel assembly enrichment for a fresh batch of fuel can be as high t

as 1 0.05 w/o U235 This deviation will be used in the c

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Figure 1.1 YAEC Criticality Safety Methodology FUEL ASSEMBLY DESIGN STORAGE RACK DESIGN MATERIAL COMPOSITIONS AND GEOMETRY REFERENCE AUXILARY CALCULATIONAL METHOD CALCULATIONAL METHOD NITAWL-S CASMO-3 INTEGRAL TRANSPORT WORKING UNIT CELL NUCLIDE SENSITIVITIES LIBRARY CHART-2 FEW GROUP X-S KENO-Va MONTE CARLO PDQ-7 DIFFUSION THEORY REFERENCE K-EFF LARGE ARRAY STUDIES t

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Maine Yankee Fuel Building Arrangement L Plane A-A F

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  • oo 160 LOCAT10'45 AREA l on om oc so 35'1oa on on on et oo SPENT FUEL POOL oo oe oe oo 0.,'_ 8" -I,

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Maine Yankee Fuel Building Arrangement Plane B-B l

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SPENT FUEL l i CRANE i a L -

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.. , P ?$ AND PURIFICATION

$ PENT FUEL RACKS e'. EQUIPMENT -j o, . ,,, _.

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Figure 1.4 Maine Yankee Fuel Building Arrangement Plane C-C B

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rigure 1.5 Maine Yankee Spent Fuel Pool Arrangement Inspection l Sta; ion l l

  1. m p g c o pr 6x9j 6x8- 6x9 A p AREA  ;
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p 6x9j 6x8 6 x 9 .+-- Array f Y f H I J K L M i

36 Ft. - 10.625 8x9 8x9 7 x 8. 6x8 7x8 8x9 i REF. j j g j t'  ? y N O P R S T 8x9 8x9 7x8 6x8 7x8 6x9 J ,

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+- a er outlet U 'V W X Y 6x6 Pipo 7x9 8x9 7x8 6x8 7x9 z

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6x6 NEW FUEL FUEL TRANSFER + - F. LEVATOR MECHANISM 41 Ft. - 4.75 -

REF.

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. A PHASE I RACK PHASE II RACK

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Table 1.1 ,

Maine Yankee Fuel Assembly Designs Type E Types L & M Types N & P Fuel Vendor -

C-E ENC C-E

  • Fuel Assembly overall Length 156.718 156.718 156.718 Spacer Grid size 8.115 8.115 8.115 No. Zirc Grids 8 0 8 No. Inconel Grids 1 0 1 No. B1 metallic Grids 0 9 0 Spacer itaterial 18.2164 14.2239 18.2164 (g/cc axial)

Fuel Rod Active Length 136.7 136.7 136.7 Clad OD 0.440 0.440 0.440 Clad ID 0.384 0.378 0.384 I Clad Material Zr-4 Zr-4 Zr-4 l Pellet OD 0.3765 0.370 0.3765 Pin Pitch 0.580 0.580 0.580 Stack Height Density 10.0458 10.1994 10.0458 (g/cc)

J Guide Tube i Tube OD 1.115 1.115 1.115 '

Tube ID 1.035 1.035 1.035 Tube Material Zr-4 Zr-4 Zr-4

  • All dimensions are inches unless otherwise specified

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2.0 SPENT FUEL POOL CRITICALITY ANALYSIS 2.1 Spent ruel Rack Mechanical Design The spent fuel racks comprise canisters which are welded l together at the top to each other and at the bottom to a frame forming rectangular arrays or modules. A 7 x 9 module is shown in Figure 2.1 and a canister axial profile is shown in rigure 2.2.

The criticality analysis will concentrate on unit analysis of the l

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canister at the active fuel length, see rigure 2.3. {

A spent fuel canister comprises a thick (.105") inner )

. canister of steel for assembly storage and structural support, four boral poison sheets on each side, a thin (.036") outer wrapper of steel creating the boral plenum region and water gaps on each side of the outer wrapper. Criticality control for the Maine Yankee spent fuel racks is achieved by the boral poison and a flux trap principle. Fast neutrons leaking from the fuel assemblies are thermalized in the water gap between storage canisters. These thermal neutrons are then captured by the boral poison as they leak back into the fuel assemblies. Also, 1720 ppm E of soluble boron poison is typically present in the water of the L

spent fuel pool but credit is not allowed for its presence except in accident situations, The Phase I canister dimensions and tolerances are given in p

Table 2.1. Two major changes from the original analysis were r incorporated in the Phase I canister design: the use of 0.08" thick boral plate with 50 w/o B C4 boral core and a flooded boral plenum. The flooding of the boral plenum was done after W

installation in the spent fuel pool. The reason for this design change is explained in the next paragraph. The original analysis assumed .177" boral plate thickness with a 35 w/o B 4C core and a voided plenum. This boral was to be reclaimed from the previous spent fuel racks. Early calculations, which assumed a voided plenum, indicated these two boral poisons were neutronically equivalent in terms of K eff. All modules produced in the Phase I rerack maintained the specs on the outer wrapper dimension of

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9.56" and on the flux trap thickness of 0.69".

The Phase II canister dimensions and tolerances are given in Table 2.2. The canisters produced in Phase II were complicated by the fact that some of the new .080" thick boral and some of the old .177" thick boral was used in thi,s Phase of teracking. Also, the reclaimed boral thickness was greater, in some cases, than l expected, ~0.2". This lead to a design increase in outer wrapper dimension of 9.747" and a design decrease in the flux trap gap of 0.503". Since the flux trap is very important in maintaining criticality control for this high density design, a' decision was made to flood all boral plenums. This design change increases the effectiveness of the flux trap gap in criticality control for both Phase I and Phase II canisters. Note, that of the 721 canisters produced in Phase II, 120 contain only the 0.08" thick boral plate, 242 contain both the 0.08" and 0.177" thick boral plate in a rectangular configuration and 359 contain only 0.177" thick boral plate in a square configuration. Thus, there are three types of fuel storage canister configurations. These are summarized in Figures 2.4, 2.5 and 2.6. The most limiting L

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This canister design canister in the Phase II modules is type 3.

will be used in the criticality analysis for the Phase II modules.

2.2 NITAWL-S/ KENO-Va Modelling is used to process the raw 123 group data into a f NITAWL-S working library and perform resonance calculations for U 238 ,, , f function of enrichment. The working library along with KENO-Va input data are used to create a model of the rack canister with a fresh fuel assembly. In this analysis, the model is used to study function of the criticality of the storage rack canisters as a fresh fuel enrichment.

KENO-Va is used to perform a Monte Carlo neutron transport, In eigenvalue calculation. The output gives average K,gg +

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this analysis, a flat starting source distribution is used as an initial guess. Calculations of 600 neutrons per generation for 303 generations are executed. After skipping the first three value is selected. In addition, plots of generations, aK eff average K,gg vs. generations run and average K,gg vs. generations skipped are assessed for convergence.

The KENO-Va model of the fuel storage canister includes one  !

quarter of a fuel assembly and canister with half the flux trap gap on two sides. Reflecting boundary conditions are imposed on the side, top and bottom, simulating an infinite array with no axial or radial leakage, rigures 2.7 and 2.8 show the KENO-Va modvis for canister types 1 and 3, respectively. Each pin cell with pellet, gap, cladding and moderator region is explicitly modelled as a UNIT. The only geometric approximations in the

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model are the squaring of the canister walls and the squaring of the guide tubes. KENO-Va geometry does not allow quarter cylinders. The guide tubes are squared, preserving inside water area and guide tube metal area. Four UNITS are used to model the guide tubes in this way. The pin cell and guide tube UNITS are arranged in a CORE array simulating a quarter Maine Yankee fuel assembly. Canister steel walls, internal and external water gaps are explicitly modelled with array REFLECTOR regions surrounding l the CORE array. The BORAL sheets are explicitly modelled as l

separate KENO-Va UNITS with aluminum clad and BORAL core. The j l

sheets are placed in the plenum region using the KENO-Va HOLE l geometry technique.

1 2.3 CASMO-3 Modelling The CASMO-3 code with the 40 microgroup library data is used

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as a consistency check of the KENO-Va results vs. enrichment and as a deterministic tool for calculating unit cell sensitivities to mechanical perturbations. CASMO-3 has an internal calculational sequence which begins at the pin cell level using 40 group data. l The 40 group library is read and resonance self shielding is

{

performed for each pin cell type in the lattice. A 40 "micro-( group" pin cell calculation for each cell type is performed. The "microgroup" calculations produce collapsed 23 group data for a cylindrical geometry model of the unit cell called the "macro-group" calculation. This "macrogroup" calculation includes an homogenized fuel region, water gaps, steel walls and poi sn. This calculation, in turn, produces collapsed 7 group data for the unit cell in "2-D" x-y geometry, called COXY. In the COXY model, the pin cells are homogenized into squares, but the water gaps, the steel canister walls and BORAL core are explicitly modelled. This final model is a half unit cell, 7 group, transport theory calculation with no axial or radial leakage. The CASMO-3 models for canister types 1 and 3 are shown in Figures 2.9 and 2.10, respectively.

2.4 K,gg vs. Enrichment Calculations of canister ):,gg vs. enrichment are performed for both canister types 1 and 3 using both KENO-Va and CASMO-3. j 235 in increments of Enrichment was varied from 3.00 to 4.25 w/o U 0.25 w/o U235 The results, without uncertainties added, are given in Tables 2.3 and 2.4, for canister types 1 and 3 respectively. KENO-Va calculations for canister type 2 fall between types 1 and 3, but these are not included. Agreement between KENO-Va and CASMO-3 is within a standard deviation with KENO-Va slightly more conservative.

2.5 Rack Sensitivity Analysis

{

Perturbations of the mechanical and compositional tolerances are performed using CASMO-3. A nominal configuration of the spent 235 was perturbed + one fuel rack canister with fuel of 3.5 w/o U tolerance at a time. Perturbations considered are: center-to-center spacing, inner canister dimension, outer wrapper dimension, BORAL plate width, BORAL plate thickness, BORAL core thickness, BORAL core B 4 C loading, assembly UO 2 density and assembly UO2 le -

enrichment. Sensitivity analysis was done separately for both canister type 1 and type 3, and the results are shown in Tables 2.5 and 2.6, respectively. The final root sum of squares is also shown, and this is defined to be the 95/95 mechanical uncertainty.

2.6 Determination of Maximum Fresh Fuel Enrichment With Uncertainties A determination of maximum fresh fuel enrichment allowable in each canister type is made by adding all uncertainties to the KENO-Va nominal K,gg vs. enrichment and then solving for the enrichment at which K eff with uncertainty equals .95. The KENO-Va validation quantified the calculational bias and methodology

{

uncertainty to be used in this determination I

I.

f K eff is calculated at 95/95 probability / confidence level by the following equation:

K,gf = Knom + 0 h* (O c + 0 (

m i

( where:

"K for Nominal Configuration, l K

nom eif AK = Calculational Bias, b

AK = 95/95 Calculational Uncertainty, c

and AK, = 95/95 Mechanical Uncertainty.

For KENO-Va with the 123 group library, the bias, as given in Reference 7, was found to ba:

6K = 0.00395.

b For KENO-Va Monte Carlo, the 95/95 calculational uncertainty is the root sum of squares of two terms: the 95/95 methodology uncertainty, e m95/95, and the 95/95 KENO-Va uncertainty for the f

L I L

I nominal case, i. e.

AK = + * (2) c (em95/95) I"95/95 ' nom) where:

0.01245 for 123 group calculations, from em95/95 = Reference 7, a95/95 = 95/95 One Sided for number Toleranceexecuted of generations Factor in nominal case, from Reference 9, and e" " = KENO-Va Standard Deviation of nominal cace.

The 95/95 mechanical uncertainty is root sum of squares combination of oK(s) due to mechanical tolerances set at a 95/95 confidence level, i. e.

AK, =

(e,) +(ab) + (#c} ~ *** ( '

where e,, eb' #c, etc. are are quantified in sensitivity analysis of the rack configuration. From Tables 2.5 and 2.6, this was I found to be.

0.00615 for canister type 1, ,

= or 6K" 0.00636 for canister type 3.

Tables 2.7 shows the final K,fg(s) with uncertainties added and Figure 2.11 shows the results plotted. Linear interpolation

[

235 as the maximum to .95 for canister type 1 gives 4.13 w/o U allowable fresh fuel enrichment for the Phase I racks, and linear 235 as the interpolation for canister type 3 gives 3.72 w/o U maximum allowable fresh fuel enrichment for the Phase II racks.

2.7 Accident Situations Situations involving fresh assemblies next to and on top r

L I t

of the spent fuel racks have been analyzed (8) . In these

{

situations, credit for soluble boron in the spent fuel pool water

[ can be taken. The refueling concentration of soluble boron for the Maine Yankee spent fuel pool is 1720 ppm. This refueling concentration of soluble boron provides a 30% reduction in rack K

eff.

Criticality calculations of fresh assemblies next to the sides and directly on top of the racks indicate less than 1%

increase in K,ff. This increase is more than adequately suppressed by the refueling concentration of soluble boron.

Therefore, the results of the accident conditions provided in Reference 8 are still valid and the calculations have not been repeated here.

1 I  !

(

[

(

(

t r

I - - - - _ _

Figure 2.1

[ A 7 X 9 Spent rael Rack Module 71.75" l

l

+ +- + +

h.{ . +

t + + + + +

+' x I 10.25" .

[ + + + + + + +

~~-- _ ,n 92.25" LIFTING EYE

[

T T'~+T T +

+ + + + t + +/

+ + +

-+-]+ + -[+

10.25" O

I' P' Fl! l ( l l l l

) 6 <. 6 m 6 < w < .g<. 8 - i

== ==. == == ==. == == ,

M W

'O 175.75"  ! 142.00" l

I

[ , , . . .

I 1 hhEh5 M4MMM NR5h I

p '* T / w a

-ap -.

22 -

b

[

rigure 2.2 Maine Yankee Spent Fuel Re.ck Canister Design

( Axial Profile

[

- 10.25" - F10. 25 MC, ELEVATION (IN) C ' 1.5"

~

[

175.75 3, i .

( v if g i

)

t I

\ \\"

o" \ '

{ 164.09 m MA f i '

ASSEMBLY c *-; j:4y y a ,e :. .

( 14.0411 r-----

1 I , s>

252.5e  : 1 ,1

{ BOAAL i

t

' s l l

i l '

_.,,o

_.v -

,- _- A 7 i

{ r '

1E ! U E .

,~ ~ t l  :

[

ymt n ,

  • T.,.,. . c q. '
el

{t

" ' i

[

2.325  : i :g:  ; -

FUEL SUPPORT SURFACE l l

el. f.'Igl l I,

(

p/

h m' N

'} /D 0.0 FLOOR 23 -

f i ..

rigure 2.3 Maine Yankee Spent ruel Rack Canister Design Radial Profile

(

SE CTION B -3

{

9.56 r I

Flux Trap Gaps outer Wrapper (0.690) l

}lli/

(

f

b. h .

Boral Boral h 8.75

' i 1 i

[

j l l*

8.00 l

8 i .'

Inner l i

{  ! Canister i Boral i I Plenum )

[ -  : i x

=== _

f ,,_ .- -

(

Flux Trap Gaps (0.690)

( '

~10.25 7 Canister Center-to-Center l Spacing (

(

r L I

(

Figure 2.4 Canister Type 1

(

[

(  : 9.56 -

Flux Trap Gaps Outer Wrapper (0.690) l

^ -

. y4 1 00 0 000 0

!O100 0 000 000 0 00 0 lx[G50000000 0 0 0.0 0 0 1' n OO O O O O O All / '00 0000 000 n 00 l 3 QQpOO O DDtJOO O OOO tJDD J OOO f

l Thin BORAL -e '

)

l OO m (0.08) l 0 0 0 0 000 000 0 0 0 0 4 o0 00 000 D OO O O OOCD'O O OOd i 00 0 0 0 0 0

[ ) l I O 0 0 0 00(pO00 0 00 .

OO O O O Og i  ! OO O O OOVO O O O OO i i OO O O OO u 0  ; O0 0 0 00 0 0 0 0 0 0 00 l O0 00000

[ [ O.0 0 0 00 0 0 0 0 00 00 I i 0 0 0 0000 i i O'O f30,0 0 00 0f) OO I ( QQOOOO I dDUO!OO OOOUDD '

i l0 0 V OO;O 0 0 0:0 0 00.

[  ! j 'j 00 0 0 00 0 0 0 0 0 0 00  : y I

jj 0 0 0 0 0 0 0000000 0 0 0lO 00 0 s C3

=. A kl O l

[ / ci riux Trap Gaps 3 i l

l

[ (0.690) i

.: 10.25  :

Canister Center-to-center Spacing f All Phase I Canisters and 120 Phase II Canisters 0.69" Flux Trap Gap on Each side i

i

[

r

Figure 2.5 Canister Type 2

9.56 r Outer Wrappet Thick l BORAL ( 0.17 7 ) ll m

W t uk  :. .

OOC 0 000 000 0 00 0 0 0C- 0 00 0 000 0 0 0 0 6 j'(f,0000000 00 0 0 0 0 0 Thin BORAL (0.08) 0000 00 000 Q 00 QQf3O OO  ?

D'JOO O O O O (JDO , i 00(J OlO O 1 0 0 0'0 000 0 000 0 0 0 1 00 0 0 0 0 0 i 1 UUb0 000 00 0 0 0 00 i OO O O OQO O OO O OOOO OO O O 9.747 -

j i OO'O CDUO O OOGOO O O O OO e i O O OO dOQ O OL s 0iO0.0 00 00 0 0 0 0 00 O O O O O OiO O!O O O O;O 00DD

) 'iOjOOO OIO O O OOT1 00 ) l QQO O OlO i ll i O O O 00010 i

OnOf 3 I DO (J O 0.0 OO OVDD l' l O O V OO'O j 0 0 0 0 00'0 0 0 00 0 00  ; 0 0 00 000 l 000 0 000 0 000 0 00 0 010.0 0 C-y e

~,

I N T h( 0 -

Jumamammes \

Flux Trap Gap

[! '

ll

/ Flux Trap Gap (0.690) l (0.503) l

10.25 =

Canister Center-to-Center Spacing 242 Phase II canisters 0.69" and 0.503" Flux Trap Gaps on

{ Adjacent Sides E

L I

{

I Figure 2.6 Canister Type 3

9.747 r Outer Wrapper 1 m. ,, _ I OO O OOO O

'O000 000 0010 0 00 0 i All 0 000 00 0 00'0 00 0 0  ; , 00 0 0 0 0 0 Thick BORAL 000000 000 n 0 Q '[i QQOOOO (0.177) DD(JOO O OOO(JDO0 .

r OOkJ O'OO QQDO O OO

'O 00 0 000 0000 0 0

( j 0 00 0 0 0000 0 0 0 00 ,:

i. 00 0 0 0 0.0 9.747 00 0 0 00QO0 0 0 00 L i OO O OO O'Q 00 0 0 00(JO 0 0 0 00 i O O OO OOt.

00 00 00 00 0 0 0 0 00. i 00 0 0 0 00 0.00 0 00 0 0 0 0 00 00 0 0 0000 O!O f30i0 0 00 0Tl OiO i-li QO I OOO QDLJO!OO OO OLJDG ' , ' ,. OLJ OCO

.00 0 0000 0.0 0 0 0 00 j', 0 0 O!OlO'O O 100 0 000 0 010 0 0 0 0:0

~

y L m p j p O O;O!O OjO_

I Flux Trap Gaps ' l (0.503)

10.25  :-

Canister Center-to-Center Spacing 359 Phase II Canisters 0.503" Flux Trap Gaps on Each Side r

r k -

Figure 2.7 KENO-Va Model of Canister Type 1 Pin Pitch Fuel Pin Guide Tube

- 1.4732 cm Cell Cells l [  ! y

@ 0000

~

~--

~

Inner water

[

OOOO 0 00

,  : ,n ,, eel

-- 0 0 0 0 00 0 -

~ " " "

iii ssis O O O - / OO '

c

;;;; O O O '

OO - .

.:r -""""-

PPe

[

~~

000000 0 '

-: Intr

/ /

/ // / / /// / / / /'/ ,

'\

,,,,,,,1 1 - s. , , ,7-10.1600 en X

n

[

r L

r*

Figure 2.8 KENO-Va Model of Canister Type 3 Pin Pitch fuel Pin Guide Tube 1.4732 cm Cell Cells

-. l / / ,.

9 QO ,

E OOOO O GO ': M:"'

= ::; O 0 0 0 00 0 $

O O O / O O  :

22:a ' ' 8 0 0 0 O O - Jr 0000 000 ; '

":J:"'

O00000_0 , J - muir m - ~;

c , , ,A;

. 1o .1oo ..

l x ,

[

l

[

[

[

29 -

r l

Figure 2.9 CASMO-3 Model of Canitter Type 1 Cb FWR Parameters:

NFST-14, s= 1.4632 es, CHw=22.2250 cm,

[

N Half Flux exw=.2908 cm, GAW=GAN=.3899 cm CRD Farameterst CRT=.15748 cm, CRs=1.6332, ABL 20.32 cm ggy %

FST Farameters:

\ a=.3480 cm, b=.8763 cs 7

'/ Inner Water

/ Gap CHW

/

~

7' /

-  ; - \ 8 l1, \h Fuel Pin Cell

/ j. / s

\

/ $ / \, Guide Tube g

/

\ >C ells

- e -- x /

^S'

- 9 <\  ;

?

' \ I

- N

- N

\  !

N i

1

[ -

s b / \

/

h

~ '

' _ / Steel' + Al ' Clad + H 2 0 /

[

CRS 2

0 ^"

] CR a / '/ Steel + Al C',ad + H O 2_ / A }

b

[

b i CRS

. ,; ABL L

a

Figure 2.10 CASMo-3 Model of Canister Type 3 Cg FwR Parameters:

{ MPsr=24, s. 1.4632 cm, Cww 22.2250 cm, N /

Half Flux Trap Gap sxw . n 45 es , caw cAN . 4632 cm CRD Farameters:

car. 23393 es, CR$=1.1902, ABL 20.32 cm G AW 4*--

FST Farameterat

~

a. 4285 cm, b=.6388 cm

/

  1. Inner Water

/ Gap CHW

/

k ' h s

/  !. e .._ h Fuel Pin

\ Cell

' hf [j / .\

' o Guide Tube

/ ^C ells e , g f ABL n

  • l

/ $

,7

\

/ N I  ! s \

j N

( o - -

x g ,

\ j

/ 'N CRS

/ Steel + Al Clad + H 2 0 /

GAN

' HO2 ' BORAL Cor e :T --] ! CRT

'  !/

~

Steel + Al Clad + H 2O if }

b l --

+b

- CRS .-* : ABL

\

L

- 31 -

Figure 2.11 K vs. Assembly Enrichment eff95/95 I# o - CANISTER TYPE 1 o - CANISTER TYPE 3 l

0.970 f-

/

/

a l

, /

J

/

0.950-

.95 LIMIT

/ e/ ~

tn

( $

m

/ /

, / '

}(

i w

J

/ /*

k /

W /

../

0.925- ,

7

/

l ,

f

/ ,/

/ ,/

0.900 - ..# '

{

/

l

./

n l 0.B75 4.25 3.00 3.2s 3.50 3.75 4.00 l ASSEMBLY ENRICHMENT (W/0 U235)

[ - 32 -

F

{

[

Table 2.1 The Phase I Canister Dimensions and Tolerances I

3 Item Dimension (In.)

Canister '. enter-to-Center 10.25 + 0.10 Spacing Iriner Canister Dimension 8.75 1 0.10 Inter Canister Thickness 0.105 Outer Wrapper Dimension 9.56 1 0.10 Outer Wrapper Thickness 0.036 Flux Trap Thickness 0.694 Boral Plate Width 8.00 1 0.125 Boral Thickness 0.081 1 0.004 Boral Core Thickness 0.062 1 0.003 Boral Core w/o B ac 50 1 1.00 t

[

N

~

l

[

l

( The Phase II Canister Dimensions and Tolerances Table 2.2 Item T>imension(In.) l

[ Canister Center-to-Center 10.25 +-

0.10  !

Spacing Inner Canister Dimension 8.75 1 0.10 Inner Canister Thickness 0.105 Outer Wrapper Dimension 9.56 1 0.10 9.7471 0.10*

Outer Wrapper Thickness 0.036 Flux Trap Thickness 0.690 0.503*

(

Boral Plate Width 8.00 2 0.125 Boral Thickness 0.081 + 0.004 0.177 5 0.012*

( Boral Core Thickness 0.062 6 .003

~

0.0921 1 0027*

" Boral Core w/o B 4C 50 1 1.00 35 1 1.62*

r *Using thicker (.177") BORAL L

r k

r t

N L

L L

L -

[

I Table 2.3 Canister Type 1 K,gg vs. Enrichment Enrichment XENO-Va CASMO-3

[

(w/o 'J ) K,gg i a K,gg 3.00 .870861.00284 .86999 3.25 .886661.00294 .88458 3.50 .900171 00297 .90145 3.75 .91572+.00313 .91479 4.00 .926391 00333 .92703

(

4.25 .936031 00191 .93805 l

c

( .

[

[

[

(

4 L -

[

Table 2.4

{ Canister Type 3 K,gg vs. Enrichment Enrichment KENO-Va CASMO-3 h

(w/o U 35) g,gg , g gg

)

3.00 .887111 00303 .88542 3.25 .905721.00303 .90239 3.50 .919441 00180 .91759 3.75 .933421 00183 .93127 4.00 .941651 00299 .94375 4.25 .956431 00191 .95507

[

[

l P

[

1 F

L 1

L Table 2.5 Canister Type 1 Sensitivities

(

6K Center-to-center Spacing 70.00420 Inner Canister Dimension +0.00254 Outer Wrapper Dimension 70.00006 BORAL Plate width 70.00147 e BORAL Plate Thickness 1 0 00025 L

~

BORAL Core Thickness 70.00144 .

BORAL B4 C Loading 70.00053

(

Assembly UO2 Density 1 0 00084 L Assembly UO 2 Enrichment 1 0 00290 Root Sum of Squares 0.00615 r

F

]

b 9

37 -

[

Table 2.6

[ Canister Type 3 sensitivities 4K l

Center-to-center spacing T0.00420 Inner Canister Dimension 10.00273 Cater Wrapper Dimension 70.00006 BCML Plate Width 70.00143 BORAL Plate Thickness 10.00120 BORAL Core Thickness 70.00094 BORAL B4 C Loading 70.00137 Assembly U0 2 Density 10.00084 Assembly U0 2 Enrichment 1 0 00290 Root Sum of Squares 0.00636

{

(

[

[

r L _ 3g _

[

Table 2.7 f

% K,gg with Uncertainties vs. Assembly Enrichment Enrichment Canister Canister (w/o U 35) Type 1 Type 3 3.00 .88961 .90607 3.25 .90547 .92468 3.50 .91900 .93771 3.75 .93465 .95170 4.00 .94546 .96058 4.25 .95428 .97475

[

[

[

[

[

[

[

(

L -

[ l 3.0 NEW FUEL VAULT CRITICALITY ANALYSIS

~

3.1 New ruel Rack Mechanical Design ,

' I The new fuel racks comprise type 6061, aluminum grids embedded in the ceiling and bolted to the floor of the new fuel vault. The ceiling is 13' from the floor and comprises a carbon steel walkway structure bolted to the aluminum grid structure which in turn is bolted to the concrete wall, see rigure 3.1. The I floor is 15" thick concrete. Both top and bottom grids are made from 2" by 1/4" flanges connected square aluminum funnels with a minimum opening of 8.5" by 8.5".

ruel assemblies are placed in the vault from the top by crane. Assemblies are maintained in an 8 by 20 array with a major spacing of 52" center-to-center and a minor spacing of 20" center-to-center, see rigure 3.2. Normally, 72 assemblies are

(

placed temporarily in the vault in an 8 by 9 array close to the new fuel elevator of the spent fuel pool.

Normally, the vault is dry but does contain water piping to the spent fuel pool with 1720 ppm of soluble boron and a steam heating pipe. The vault cannot be considered water tight since there are two floor drains. Fuel assemblies are placed in the vault free from the plastic covers they come in, but they do have small plastic dust covers on the upper end fitting assembly. The vault grids are covered with fire-retardant plywood at the walkway level. Sprinklers are not present, but portable fire-fighting

{

foam is available elsewhere in the plant.

I

-o-

r 3.2 NITAWL-S/ KENO-Va Modelling 1

NITAWL-S is used to create two working libraries. One

[ library is used to study the criticality of the vault as a function of void or water density with fuel assembly enrichment held at 3.5 w/o U235 The other library is used to study criticality as a function of enrichment at the "optimum" void or

{

water density determine from the first study.

The KENO-Va model of the new fuel vault includes four fuel assemblies, the metal ceiling, the concrete floor and the concrete wall, see rigure 3.3. This 3-D semi-infinite model allows axial leakage from the top and bottom and radial leakage to one side.

Reflecting boundary conditions are imposed on three sides simulating half the vault with an infinite number of rows. The

(

model utilizes the KENO-Va ARRAY of ARRAYS geometry technique with

[ the first level ARRAY being the fuel assembly pins and the second level ARRAY being the fuel vault array.

The fuel assembly array explicitly models each pin cell as a UNIT with a pellet stack, alumina spacer, plenum region, cladding,

[

end plugs, moderator region, upper and lower shoulder regions.

The guide tubes, as in the spent fuel rack model, are squared and made into four UNITS. Since one of the model boundary lines cuts E the fuel assemblies in half, the first level ARRAY is half a fuel assembly, i.e. a 7 by 14 by 1 ARRAY, see rigure 3.4. Surrounding this ARRAY are top and bottom REFLECTOR regions of homogenized metal and moderator, simulating the upper flow plate, the upper

(

end fitting assembly, the lower end plate and the lower end plate L legs. Thus, a full length assembly UNIT is modelled including top I

and bottom structure. However, grid structure in the active fuel length is neglected.  !

The fuel vault ARRAY models four half assembly UNITS along ]

[  !

with two small inter-assembly gap UNITS and one large inter-Surrounding this assembly gap UNIT, i.e. a 1 by 7 by 1 ARRAY.

ARRAY are REFLECTOR regions of inter-assembly gap, concrete floor and walls, and metal ceiling, see rigure 3.5. This final ARRAY with REFLECTOR regions is the Maine Yankee new fuel vault model.

3.3 K,gg vs. Moderator Density criticality of the new fuel vault fully loaded with 235 is studied as a function of moderator dssemblies of 3.5 w,'o U density or equivalently i void. The flooded condition or 0% void correcponds to water at 68'r or .9982 g/ce. The dry condition or 100% void is modelled by KENO-Va composition 0, vacuum. Moderator

(

is introduced uniformly throughout all pin cells, guide tube cells, assembly upper and lower regions, and inter-assembly gap space. Increments of 10% void is taken from 0 to 90% and increments of 2.5% void is taken from 90 to 100%. The K,gg of the veult vs. void is shown in Table 3.1, and the K,gg with uncertainties is plotted in rigure 3.6. ,

The behavior of K,gg vs. moderator density can be understood if one considers that there are two types of moderation occurring in the vaults moderation between assembly pin cells and moderation in the space between assemblies. The former type of moderation

{

dominates the criticality of the array in high density situations, and the latter dominates in low density situations. This second

type of moderation can produce large increases in reactivity. The moderator density at which the peak occurs is called "optimum

( moderation". In the Maine Yankee new fuel vault, "optimum moderation" occurs at 95% void or about .05 g/cc of water. For 235 3.5 w/o U fuel assemblies K,gg is still considerably below the limit of .98. Also, in a fully flooded condition, the K,gg is considerably below .95. The optimum moderator density of .05 g/cc of water appears to be the most limiting condition, see Table 3.1.

3.4 K,gg vs. Enrichment at optimum Moderation The K,gg of the vault vs. enrichment at optimum moderator density is studied next to see how high enrichment can be in order f to meet the .98 limit. KENO-Va cases are run with moderator density set at .05 g/cc or 95% void and with enrichment increasing in increments vf .25 w/o U2 3 5 ,' rom 3. 5 w/o U235 to 5.50 w/o U235.

The results are shown in Table 3.2, and K,gg with uncertainties is I plotted in Figure 3.7. Results indicate that even with 5.50 w/o U

235 fuel assemblies there is still -0.3% AK margin to .98. The highest conceivable enrichment to achieve 24 month cycles in 3-batch fuel management for Maine Yankee is approximately 5.00 w/o U 235, so, criticality in the new fuel vault even at optimum moderation should not be a concern.

[

[

[ )

b

[

l rigure 3.1 Maine Yankee New ruel Vault Axial Profile Carbon Steel Top Grids Walkway A .. ,.=  :

/ .

=w n

Il ,l -

7 w;ph n[

- - - J  ;

l'l - -

3 d =' E, M,E, ,

. n "ri 6 i

o #f- i i

I, y, _ J'. a ' W. d'. 4'. ,2r' _l d' d' ' 2', -

I .

ruel Assembly .

  1. Profile ,

- 1 l ,

l l l .

- s l i

1 5 4 4 # l 4

' ' 1 l

l

,.,,,,g..---

i- > r7 r-p i P 1~..t F-P 1

ic j . 8 6i i II .

6.a s lI t i De l'"t1Li_

- M

  • i ]

i

  • . a .,d p.

ji; ,

    • ) l Bottom Grids

(

(

(

[ ,

i

[

u-

[

Figure 3.2 Maine Yankee New Fuel Vault Radial Profile

d. s' W ,,,u '__

_,I _ y', y t. a' w d./ 2

! T ' . . h* .

, l .I

[ , T , :-

e.- > > . , ... 1 .s ., . i .,

I l s

v

's I i N  !. '. i 4). .. ,. .

t-

\

.,h j l .... ', .

i~ '

) ..

, P .

g j . .T. ,. ..l

'8 g gtfq ;, ,'; " ,' B

[ u- .g -

" ;/.1, 3,, . =

, , . ~

c. .-ru - f, ,

j g

m-e .' . .

c p- r, s

a a

. .'ey. .

s.

a g < Ar.-Lg - '

gl N s

. i u- y,

,. . 3 --

u D

. iv ,,.

,/ -

a m-. ,i.g y- .

[  % *4.*

t- <

s

-6 -

p

,. e t, n,'a 7.

(

>- y , , -

}>

m I i n

l f

q ~

m.,y,,/ / ,

[

x

, -j. b,.f r* , ._ ,, .:'*

M '.',a:: . . s- . ..

~ t;-- .

    • tr*'.- -

,.i .  % .e..  :,

z. n ,,o - .

[ -

i

- f ,

/ .

i. , .'-

.t /

5-O.. G$ i r i- ,

[ s

[

/

] J ,

/

I

' ' l. / j

(

i h ' ~s

, .. i. s t- s

[ .

s ,i

  • I d

l

{ , i , /  !* .,

L l i ..

t o i <*

s e

\ s i s

. I i .

[

Figute 3.3

( KENO-Va Basic Unit of Analysis

( for the Maine Yankee New Fuel Vault 20- 26 12- 50- 20- 52=

y- , L i

- t

[

J1 2 l

( .

p- g$

M== % 4 < Axial Profile l

Concrete Wall  :-

, ruel Assemblies l

i f' ' I 160.5-

[ I' t.

[

. _ , . ,_ _ 3 r a r=

Y,

, :I., _ -L c$ I N -

l_. - - ' , a+- - Concrete Floor 15- -

A_._ -

Basic Unit of Analysis cL

s' . /

i 6 f lo- l~ m r- h m T. Radial Profile YW Y t'

[

TZ JI i_:

[i] _J

( -_m rt _ rh m e

t f

l __ _ _________

k

( 1 Figure 3,4 KENO-Va Fuel Array

[ for the Maine Yankee New Fuel Vault I

-10.3124 cm +10.3124 cm D O OOOOL" l O!O'O O O O 000 0 000- 010100 0 0 0

'"$15'"-00 0 00000~O:0 0 0 QQ OOO OOO m O O Radia Profit'

_OO F  !

QGC=) OO O OOO L.=i O O Guide Tube <O00 000 00000 0 0 0 c' '

00 0 000 0 0000000

+10.3124 cm

< X

( '

z

[ + 2 01. 416 9 cm -

( Homogenized i

Upper End Fitting Assembly

+HO2

  • ~

( Homogenized Up er Flow Plate

+187.7060 cm Axial Profile

( +162.3060 cm - - - - - - ~ -

\-

Y 4 # i i i i i#

A,ctive, Core ,

Ex311 cit Fuel Pins

(

-184.9120 cm. - - ---- - - - ---- - - -------

f ~187.7060 cr.-

Homogenized Lower End Plate + H 2 O

-189.2935 cm Homogenized Lower End Plate LeQs

( 2 0

-194.6008 cm

(

Figure 3.5 KENO-Va Vault Array

(- for the Maina Yankee New Fuel Vault 0 0 8 0 86 68 o

o 8

  • e *e e w '$  % $

N r- N r- r- a n m e N

  • 0$ $" N$
  • 4  ; n' a aa aa
  • n y "

y7i T7 7 7 7 I I I l '

3 mus+ w _ s e 'l o

N/ +25.4000 cm N/

Inter-Assembly Gap Assembly UNITS o X Inter-Assembly Gap REFLECTOR Region '

UNITS 2 C L

+209.3562 cm ~ ~

+208.7212 cm ' -

+201.4169 cm

( -/ 11. / _ \

(

i- f ,l J

{ f_' '

)

n/ s n

ml m

i

h. :,{

l

{ -

.s .

I .

i h

o i

, n

,. , h ,

"I

[ Wall Q  ; l  ; '

. d e t [

P i

'  !- Yl llI ,

l J .

J

[4) ,,

. 4; 'l -

i

[ a  ! i ir + <

- b,[ j'l- f [ h} ,

( ,. Il I

I s ,,

i e  ; e 4  ! h L h f d i ,j l n

. d l

It d ' I 1 l -

,e

c. .

d -

s.4 .

( -194'.6808 cm i i i i i i

-198.3058 cm .. ' ,- gConcrete.. ' .,

,), , , , ,

i.

, , , Floor r .- .

  • i

( - -it REFLECTOR Region',cf s . .

,,- e., . .

-236.4058 cm ' -

I

_ 48 -

[

(

Figt 3.6

[

K eff95/95 vs. 4 with void for tin Maine Yankee New ruel vault ruel at 4.5 w/o U235

( 1.0

.98 LIMIT O.9 -

(

0.8-

\x )

m

)

{ _

O., : \ .

(

i; 0..

Ns

(

l 0.5 -'

( 0.4-1 0.3 0 10 20 30 to 50 60 70 80 90 100 l f  % VOID

{

49 -

( -

i

(

Figure 3.7

(

R vs. Enrichment for the Maine Yankee New Fuel Vault L

eff95/95 with noderator at 95 % void

[

( i .w

( 0.99 -

I

.98 LIMIT

{

0.27 p

I O.95 =

i

/

( $ -

a 5

0.9s= ,-

[ ... .

2i 0.94-

. /

0.93-

/

( ,

0.92 --

l 0.91 1r

/

oa 3.,, 4.m 4.s 4.2 4.7s s.w s.= s.w 3.2 ENRICHMENT (W/01

[

(

f -

L

( '

f Table 3.1 l New Fuel Vault K vs. % Void withAssemblyEnrichmIklat3.5w/oU235

% Void K,gg i e

( (Flooded) 0 .847941 00492 10 .810171 00385 20 .771101 00393

{ 30 .724051 00464 40 .690991 00441 50 .641181 00419 60 .609551 00428 70 .619221 00407 80 .682571 00428 90 .814671 00406

{

92.5 .861151 00376 (optimum) 95.0 .890241 00431 97.5 .812131.00413 (Dry) 100 .356741 00244

{

{

{

l l

l

(

{  !

[

Table 3.1 r

New Fuel Vault K vs. Assembly Enrichment

( withModeraI$fDensityatOptimum w/o U235 K,gg i e 3.50 .890243.00341

{ 3.75 .897361 00401 4.00 .904761 00362 b 4.25 .914381 00390 4.50 .928101.00361

[ 4.75 .940241 00392 5.00 .945121 00492 5.25 .950511 00437

{ 5.50 .958261.00442

(

{

{

l

{

(

{

( <

l l

[

4.0 CONCLUSION

S

(

The criticality analysis of the Maine Yankee spent fuel racks rhows that the maximum fresh fuel enrichment to meet the .95 NRC 235 and 3.72 w/o U 235 for limit with uncertainties is 4.13 w/o U f- the Phase I and Phase II racks respectively. Based on this, the following is validt

[

Fuel assemblies with enrichments no higher than 4.13 w/o r

l U235 can be placed in rack modules: A, 15 , E, H, I, J , N, 0, P , U , V , and W.

and f

ruel assemblies with enrichments no higher than 3.72 w/o

[

U235 can be placed in rack modules: C,D, r,G, K, L, M, t Q,R, S, T, X, Y, and 2.

Criticality of analysis the Maine Yankee new fuel vault shows l

[ 235 g, that fresh fuel with enrichment as high as than 5.5 w/o U allowable in the vault even under condition of "optimum moderation".

(

l l

{

l  !

(

l

(

REFERENCES

1. ORNL/NUREG/CSD-2/V2, "NITAWL-S, SCALE System Module for Performing Resonance Shielding and Working LibraryL.Production", Lucius, R. M. Westfall, L. M. Petrie, N. M. Greene and J.

)

f October 1981. i

2. ORNL/NUREG/CSD-2/V1/R2, "KENO-Va, An Improved Monte Carlo i j criticality Program with Supergrouping", L. M. Petrie and l N. F. Landers, December 1984.

( 3. STUDSVIK/NTA-86/7, "CASMo-3, A ruel Assembly Burnup Program",

User' Manual, M. Edenius, A. Ahlin and B. Forssen, November 1986.

f 4. YAEC-1453P, "C-H-A-R-T-2 CASMO To HARMONY Tableset Conversion Processor User's and Programmer's Manuals", D. Napolitano and P. J. Rashid, September 1984.

5. EPRI/ARMP Documrntation ,"PDQ-7/ HARMONY User's Manual", B. M.

Rothleder, Maren 31, 193:.

6. ash-1484-7, "Critical Experiments Supporting Close Proximity Water Storage of Power Reactor ruel", N. M. Baldwin, G. S.

Hoovler, R. L. Eng and T. G. Welfare, July 1979.

7. YAEC-1621, "Validation of the YAEC Criticality Safety Methodology", D. G. Napolitano and T. L. .rponi to , Janua ry .

f 1988.

8. YAEC-1285, "Maine Yankee Spent ruel Rack Modifications -

Criticality Analysis", D. G. Napolitano, March 1983.

[

9. SCR-607, "ractors for one-sided Tolerance Limits and for variables and Sampling Plans", Table 2.4, page 46, D. B. Owen, March 1963.

f l

I

' -. _ _ _ _ _

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