BSEP 07-0102, ANP-2661 (Np), Revision 0, Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM-10 Fuel

ANP-2661 (Np), Revision 0, Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM-10 Fuel

ML072840221
Person / Time
Site:	Brunswick
Issue date:	09/30/2007
From:	AREVA NP
To:	Office of Nuclear Reactor Regulation
References
BSEP 07-0102, TAC MD4061, TAC MD4062, TSC-2006-05 ANP-2661 (NP), Rev 0
Download: ML072840221 (25)

Text

BSEP 07-0102 AREVA Report ANP-2661 (NP), Revision 0, Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-10 Fuel, dated September 2007

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AREVA NP AREVA NP Inc.

ANP-2661(NP)

Revision 0 Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM -10 Fuel sip

AREVA NP AREVA NP Inc.

ANP-2661(NP)

Revision 0 Copyright © 2007 AREVA NP Inc.

All Rights Reserved

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-10 Fuel ANP-2661(NP)

Revision 0 Paaei Nature of Changes Item Page Description and Justification

1.

All This is the initial release.

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AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-10 Fuel ANP-2661(NP)

Revision 0 Page ii Contents 1.0 In tro d u ctio n....................................................................

................................................... 1 -1 2.0 S u m m a ry......................................................................................

2 -1 3.0 Criticality Safety Design Criteria.......................................................................................

3-1 4.0 Fuel and Storage Array Description................................................................................

4-1 4.1 F ue l D e s ig n............................................................................................................

4 -1 4.2 Fuel Storage Array.............................................................................................

4-1 5.0 Calculation Methodology................................................................................................

5-1 6.0 Storage Array Reactivity (k-eff)......................................................................................

6-1 6.1 Geometry Model.................................................................................................

6-1 6.2 KENO.Va Results...............................................................................................

6-1 6.3 Maximum Credible Accident Condition Results..................................................

6-1 6.4 Maximum New Fuel Storage Vault k-eff.............................................................

6-2 7.0 Conclusions.....................................................................................................................

7-1 8.0 References......................................................................................................................

8-1 AREVA NP Inc..

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Paqe iii Tables 2.1 Criticality Safety Limits for Fuel Assemblies Stored in the Brunswick Nuclear Power Plant New Fuel Storage Vault..................................................................

2-2 4.1 ATRIUM-10 Fuel Assembly Parameters..........................................................................

4-2 6.1 New Fuel Storage Vault Reactivity Results.....................................................................

6-4 Figures 4.1 4.2 4.3 ATRIUM-10 Fuel Assembly............................................................................................

4-3 Brunswick New Fuel Storage Rack................................................................................

4-4 Brunswick New Fuel Storage Vault KENO Model Dimensions......................................

4-5 This document contains a total of 24 pages.

AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Page iv Nomenclature effective neutron multiplication factor infinite neutron multiplication factor k-eff k-AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Paqe 1-1 1.0 Introduction This report presents the results of a criticality safety evaluation performed for the storage of AREVA NP Inc.* ATRIUMTM-101 fuel assemblies in the new fuel storage vault of the Brunswick Nuclear Power Plant.

AREVA NP Inc. is an AREVA and Siemens company.

t ATRIUM is a trademark of AREVA NP.

AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-10 Fuel ANP-2661(NP)

Revision 0 Page 2-1 2.0 Summary The ATRIUM-10 fuel design can be safely stored in the Brunswick new fuel storage vault as described in Section 4.2 of this report per the criticality safety limits defined in Table 2.1. The new fuel storage vault is a moderation controlled area subject to the proper administrative controls..

The evaluation summarized in this report shows that under worst credible conditions and including uncertainties the highest k-eff of the new fuel vault with ATRIUM-10 fuel at 4.70 wt% U-235 and containing eight 2 wt% gadolinia rods is 0.928 at the 95% confidence level (CL). This meets the acceptance criterion of k-eff *0.95 for fully flooded conditions, (Reference 1). (Under dry conditions the k-eff is much less than the 0.90 limit specified in Reference 1). The conditions assumed for these cases are described in Sections 6.1 and 6.2.

This evaluation is conservative because:

I Table 6.1 shows that for the limiting condition (fully flooded), the storage of assemblies with fuel channels produces the largest k-eff. The maximum k-eff includes the worst condition relative to fuel channel, i.e., with channels. Hence, fuel assemblies may be stored with or without fuel channels.

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AREVA NP Brunswick Nuclear Plant ANP-2661 (NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 2-2 Table 2.1 Criticality Safety Limits for Fuel Assemblies Stored in the Brunswick Nuclear Power Plant New Fuel Storage Vault

1.

ATRIUM-10 Fuel Configuration Parameter Nominal ATRIUM-10 Values Clad OD, in.

.3957 Clad ID, in.

.3480 Pellet Diameter, in.

.3413 Rod Pitch, in.

.510 Fuel Density, % Theoretical 96.26 Water Rods Internal Channel

2.

Fuel Design Limitations Maximum Lattice Average Enrichment, wt% U-235 4.70 Minimum Number Gd* Rods 8

Minimum wt% Gd 203 in each Gd Rod 2

3.

New fuel storage rack design and dimensions are as defined in Reference 2.

4.

Any protective wrapping material around the fuel assemblies must be open at the bottom to allow for water drainage.

Gd means gadolinia-bearing (Gd20 3) fuel rods.

AREVA NP Inc..

AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 3-1 3.0 Criticality Safety Design Criteria The criticality safety design criteria defined in Section 9.1.1.3 of Reference 1 was used for the new fuel storage vault evaluation. In general, the main criticality safety acceptance criteria applicable to this evaluation are as follows:

The k-eff of the array under dry conditions will be *_0.90.

The k-eff of the array under flooded conditions will be <0.95.

In addition, the new fuel storage vault needs to be designated as a "moderation controlled area."

This means keeping extraneous hydrogenous material out of the array through both administrative means, e.g., posting the area as indicated above, and engineered means, e.g.,

shielding any overhead water lines so that if there is a pipe burst water will not spray directly into the array.

AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 4-1 4.0 Fuel and Storage Array Description 4.1 Fuel Design The base fuel design assumed for the analysis is the ATRIUM-1 0, which is a 1Ox10 fuel assembly with an internal square water channel near the center of the assembly (taking the place of nine fuel rod locations). Table 4.1 summarizes the mechanical design parameters which define the assembly and Figure 4.1 depicts the assembly graphically. This analysis supports enriched ATRIUM-10 lattices with 4.70 wt% U-235 (maximum) and eight 2.0 wt%

gadolinia rods. This is the highest reactivity design considered for the new fuel storage array.

4.2 Fuel Storage Array The new fuel storage vault dimensions defined in Reference 2 are represented in Figures 4.2 and 4.3. The new fuel vault consists of 21 fuel storage racks (Figure 4.2) arranged side by side to create an array of storage cells on 11.5" x 6.6" centers (Figure 4.3). There are 5" or 5.25" gaps between the racks and the surrounding 11" thick concrete walls. The floor is modeled as 12" of concrete with a 3.38" gap and the ceiling is modeled as 24" of concrete with a 17.6" gap.

The storage vault includes a floor drain that is plugged when fuel is stored in the vault to preclude the possibility of steam backing up through the drain system. The racks are designed to prevent accidental insertion of a fuel assembly in non-rack locations. The aluminum structural material in the racks has little impact on array reactivity and has been neglected in this analysis.

AREVA NP Inc

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Page 4-2 Table 4.1 ATRIUM-10 Fuel Assembly Parameters Fuel Assembly Fuel Rod Array 1 0x10 Fuel Rod Pitch, in.

0.510 Number of Fuel Rods Per Assembly 91 Water Channel 1

Fuel Rods Fuel Material U0 2 Fuel Enrichment, wt% U-235 4.70 Pellet Density, % of Theoretical non-96.26 liner fuel Pellet Diameter, in.

0.3413 Pellet Void Volume, %

Enriched U0 2 1.2 Cladding Material Zircaloy-2 Cladding OD, in.

0.3957 Cladding ID, in.

0.3480 Internal Water Channel Outside Dimension, in.

Inside Dimension, in.

Channel Material Fuel Channel (100-mil standard)*

Outside Dimension Inside Dimension Channel Material 1.378 1.321 Zircaloy-2 or Zircaloy-4 5.478 5.278 Zircaloy-2 or Zircaloy-4 The conclusions in this report are equally valid for fuel channels that may differ. Presence or absence of fuel channels has no significant impact on the results of this report. Hence, conclusions remain valid for other fuel channel types, e.g., AREVA Advanced fuel channels or similar design.

AREVA NP Inc..

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Page 4-3 Tie Plate tod bly Channel JLTRAFLOW Spacer

-Partial Length Fuel Rod Assembly

-Lower Tie Plate Assembly (Assembly length and number of spacers are reduced for pictorial clarity)

Figure 4.1 ATRIUM-10 Fuel Assembly AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Paqe 4-4 Figure 4.2 Brunswick New Fuel Storage Rack AREVA NP Inc..

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Page 4-5 7-"I x

x x

x_

I x

I I x Figure 4.3 Brunswick New Fuel Storage Vault KENO Model Dimensions AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 5-1 5..0 Calculation Methodology The base case storage array k-eff calculations were performed with the KENO.Va Monte Carlo code, which is part of the SCALE 4.2 Modular Code System (Reference 3}. Cross-section data input to KENO.Va were taken from the ENDF/B-IV, 27 energy group data library (Reference 3).

The CASMO-4 bundle depletion code (Reference 4) was used to calculate isotopic number densities for the fuel. CASMO-4 is a multigroup, two-dimensional transport theory code.

Both the KENO.Va and the CASMO-4 computer codes are widely used throughout the nuclear industry. They are used primarily for criticality safety and core physics calculations, respectively.

AREVA hap broad experience using both of these codes.

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AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUMTM-10 Fuel Page 6-1 6.0 Storage Array Reactivity (k-eff)

The limiting conditions include the worst credible conditions addressed in Sections 6.3 and 6-4, and the ATRIUM-1 0 fuel assembly as defined in Section 4.1. The base k-eff is calculated with the KENO.Va code and the uncertainties due to manufacturing tolerances are primarily evaluated with CASMO-4.

6.1 Geometry Model The storage vault is modeled in KENO.Va as defined in Section 4.2 and Figure 4.3. The center-to-center spacing of assemblies within the storage cells is 6.6" in the X direction (nominal spacing) and 11.5 inches in the Y direction (minimum spacing). Each cell is 150.0 inches in the Z direction.

The array is reflected by concrete in all directions; 11 inches on the sides, 24 inches on the top of the array and 12 inches on the bottom.

6.2 KENO.Va Results KENO.Va calculations were performed for dry and fully flooded conditions within the array. The base fuel assembly assumed for these calculations is defined in Section 4.1. Cases were run with and without a fuel channel. The results of the calculations are summarized in Table 6.1.

6.3 Maximum Credible Accident Condition Results The design of the new fuel storage vault precludes the accidental insertion of a fuel assembly in any position not intended for fuel storage. In addition the new fuel storage vault is maintained as a moderation controlled area. This implies that the storage vault will be maintained at dry conditions and in an accident scenario it could be (partially or completely) flooded with water. The fully flooded condition bounds the partially flooded condition and has been directly modeled in this evaluation.

The case of a fuel assembly lying on the floor above the storage array is not considered significant because the 24 inches of concrete in the ceiling cap will effectively isolate the horizontal assembly from the assemblies in the storage array.

]

The orientation of the bundles within the racks is not restricted and since the ATRIUM-10 water channel and U235 enrichment distributions are not % lattice symmetric, the effect of different AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-10 Fuel ANP-2661(NP)

Revision 0 Paqe 6-2 assembly orientations must be considered. [

I 6.4 Maximum New Fuel Storage Vault k-eff The maximum k-eff for the new fuel storage racks includes: the highest KENO-Va calculated k-eff for the array at fully flooded conditions, the calculational bias, an adder for the limiting accident condition defined in Section 6-3, and uncertainties associated with the KENO.Va calculation and fuel manufacturing, i.e., fuel enrichment, gadolinia weight percents, uranium density, pellet diameter, cladding thickness, and storage cell pitch. The maximum k-eff is therefore defined as:

kmax = kc + bb + A + U (aC2 + O+b2

+ at2)%

where:

k, and a, equal the keff and standard deviation values from the worst case KENO.Va output I

The highest k-eff was obtained for the fully moderated condition with fuel channels. For this case (KENO.Va):

k,= 0..9012 oc= 0.0006 The maximum keff then, using the above parameters is:

I

= 0.928 This is below the acceptance criterion of 0.95 for the fully flooded condition.

AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUM TM-10 Fuel ANP-2661(NP)

Revision 0 Page 6-3 By inspection of the results listed in Table 6.1, the k-eff of the storage vault is significantly less than the 0.90 acceptance criterion for the dry condition.

AREVA NP Inc-

AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 6-4 Table 6.1 New Fuel Storage Vault Reactivity Results Fuel Assembly Physical

Description:

See Section 4.1 Enrichment:

4.70 wt% U-235 in all rods Gadolinia:

8 rods at 2.0 wt% Gd 203 in each Fuel Channel 100-mil Storage Cell Cell Center-to-Center Spacing:

6.6 x1l1.5-inch centers Array modeled explicitly with concrete walls, floor and ceiling. The storage rack was not modeled.

Moderator Temperature:

1000C KENO.Va Results Without fuel channel With fuel channels

% of full density water k-eff a

k-eff a

0 0.6484 0.6350 100 0.8976 0.9012 0.0006 AREVA NP Inc-

AREVA NP Brunswick Nuclear Plant ANP-2661 (NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 7-1 7.0 Conclusions This evaluation demonstrates that ATRIUM-10 fuel can be safely stored in the Brunswick Nuclear Plant new fuel storage vault given the assumptions defined in this report and assuming that the fuel to be stored meets the criticality safety limits and requirements defined in Table 2.1.

Under dry storage array conditions, the k-eff of the new fuel storage vault will not exceed 0.90 at the 95% confidence level. Also under fully flooded conditions, the k-eff of the new fuel storage vault will not exceed 0.95 at the 95% confidence level.

AREVA NP Inc.

AREVA NP Brunswick Nuclear Plant ANP-2661(NP)

New Fuel Storage Vault Criticality Revision 0 Safety Analysis for ATRIUM TM-10 Fuel Page 8-1 8.0 References

1.

Updated FSAR Brunswick Steam Electric Plant, Units 1 and 2, Revision 20, 2006.

2.

ANP-2547(P) Revision 1, Brunswick Unit 1 Cycle 17 Plant Parameters Document, April 2007. (103-2547P-000)

3.

A Modular Code System for Performing Standardized Computer Analyses for Licensing Evaluation, SCALE 4.2, Oak Ridge National Laboratory, revised December 1993.

4.

EMF-2158(P)(A) Revision 0, Siemens Power Corporation Methodology for Boiling Water Reactors: Evaluation and Validation of CASMO-4/MICROBURN-B2, Siemens Power Corporation, October 1999.

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AREVA NP Brunswick Nuclear Plant New Fuel Storage Vault Criticality Safety Analysis for ATRIUMTM-1 0 Fuel ANP-2661(NP)

Revision 0 Distribution Controlled Distribution Richland

0. C. Brown R. E. Fowles K. D. Hartley C. D. Manning T. E. Millsaps J. L. Parker P. D. Wimpy AREVA NP Inc.