ML18057B433

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Forwards EMF-91-174(NP), Criticality Safety Analysis for Palisades Spent Fuel Storage Pool NUS Racks & EMF-91-1421(NP), Criticality Safety Analysis For... in Support of 911028 Request to Increase Fuel Enrichment
ML18057B433
Person / Time
Site: Palisades Entergy icon.png
Issue date: 12/18/1991
From: Slade G
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML18057B434 List:
References
NUDOCS 9112270222
Download: ML18057B433 (49)
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Text

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PDWERINli

  • MICHlliAN'S PROliRESS Palisades Nuclear Plant:

27780 Blue Star Memorial Highway, Covert, Ml 49043 December 18, 1991 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 GB Slade General Manager DOCKET 50-255 - LICENSE DPR PALISADES PLANT - TECHNICAL SPECIFICATIONS CHANGE REQUEST - FUEL ASSEMBLY ENRICHMENT ALLOWED IN NEW FUEL AND SPENT FUEL RACKS - ADDITIONAL INFORMATION Consumers Power Company letter dated October 28, 1991 requested an increase in

  • \\~

the fuel assembly enrichment allowed in the new fuel and spent fuel storage racks and included Siemens Nuclear Power Corporation's proprietary reports, "Criticality Safety Analysis for the Palisades Spent Fuel Storage Pool NUS Racks," (EMF-91-174(P)) and "Criticality Safety Analysis for the Palisades New Fuel Storage Array," (EMF-91-142l(P)).

Subsequent discussion between the NRC, Palisades and Siemens staff's regarding the proprietary material in those reports has resulted in Siemens issuing non-proprietary versions having the same titles but different report numbers.

The report numbers of the non-proprietary reports are EMF-91-174(NP) and EM-91-142l(NP).

This letter places those non-proprietary reports on the docket.

They are included as Attachments 1 and 2.

The differences between the proprietary (P) and non-proprietary (NP) versions are in Table 1 of EMF-91-1421, and in Table 3.1 and page 9 of EMF-91-174.

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Gerald B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment

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J A CllliS ENERGY COMPANY I

ATTACHMENT 1 Consumers Power Company Palisades Plant Docket 50-255 EMF-91-174(NP)

CRITICALITY SAFETY ANALYSIS FOR PALISADES SPENT FUEL POOL NUS RACKS

',~1... :*

Siemens Nuclear Power Corporation CRmCAUTY SAFETY ANALYSIS FOR THE PALISADES SPENT FUEL STORAGE POOL NUS RACKS December 1991 EMF-91-174(NP)

Issue Date:

12/09/91

CUSTOMER OISCt.AIMER IMPORTANT NOTICE REGARDING CONTENTS ANO USE OF ililS DOCUMENT PLEASE READ CAREFULLY Siemens Nudem' Pcwer Corporation's wananlies and representalicns ccnceming the subject matlar ct this dccument are ltlcse set fcntl in ttle Agreement between Siemens Nuc:!ear Power CoCl)Cralicn and the Custcmer pursuant ta which this

  • dccument is issued. Accardingly, except as otherwise expressly p~vided in such Agraement. neither Slemens Nudear Power CoCl)Cration _ncr any perscn ac1ing on its behalf makes any warranty er representalicn, expressed er implied. wilh respect ta th* accurac'f, ccmpleteness, or usetulness cf the infcrmalicn ccntained in this dccument. or that 1tle use of any infcrmalicn, apparatus, method or precess diac:lcsad in this dccument will net infringe privately owned rights; or as~mes any liai:lililiea wi1h respecl tc the use of any infcrmaticn, apparatus, methcd or process disclosed in this document.

The infcmtalicn ccntained herein is fer the sole use cf !tie Customer.

In order tCI avoid impairment of rights of Siemens Nuclear Pcwer Corporation in p8llK1tS ot inventions which may be induded in the infcrmalicn contained in this dccurnent, the recipient, by its acceptance of !tlis document, agrees net tc publish or

  • rnaice public use (in the patent use cf !tie tarm) cf ~ch infcrmalicn until sc authorized in wriling by Siemens Nudear Power Corpcralicn or until attar six (6) mcnths following 19tmination er expiralicn cf the aforesaid Agreement and any extension thereof, unless e~resaly ~vided in the Agreement. No rights er licenses in or tc any paranta are implied by !tie furnishing ct this document

TABLE OF CONTENTS

. EMF-91-174(NP)

Page i Section

  • Page 1.0

SUMMARY

........................................................ 1 2.0 MAJOR CONSERVATISM USED IN ANALYSIS............................. 3 3.0 DESIGN BASES.................................................... 4 4.0 CALCULATIONAL METHODS AND MAJOR ASSUMPTIONS................... 8 5.0 UNCERTAINTIES............................................,... *.... 9 6.0 NORMAL' ABNORMAL CONDITIONS AND RESULT......................... 1 O 7.0 VALIDATION OF CALCULATION METHODS.............................. 14

8.0 REFERENCES

........................................ :........... 1 6

UST OF TABLES EMF-91-174(NP)

Page ii Table Page 3.1 Palisades Cycle N Fuel Bundle Design Parameters.......................... 5 6.1 K-Effective for Normal Conditions...................................... 11 7.1 Benchmark Calculation Results Keno-Va with 16 Group Cross Sections......... 15

LIST OF FIGURES EMF-91-174(NP)

Page iii Figure Page 1.1 Palisades Spent Fuel Pool Map........................................ 2 3.1 Palisades Main Pool Storage Cell Nominal Arrangement...................... 7

EMF-9_1-174(NP)

Page 1 1.0

SUMMARY

Since 1987, the Palisades Nuclear Generating Station spent fuel storage pool has undergone various modifications. These modifications include the installation of high density spent fuel storage racks, designed by Westinghouse, at the north end of the fuel storage pool and on both sides of the NUS storage racks located in the north tilt pit.

This criticality safety reanalysis of the NUS spent fuel storage pool, shown in Figure 1,

demonstrates the maximum k-eff of the NUS racks loaded with the 15x1 5 fuel assemblies at worst credible conditions to be.9131 at the 95/95 confidence level. Storage of 15x15 fuel assemblies meets the requirements of NUREG-0800 and ANSI/ANS 57.2-1983 subject to the conditions given

  • below:

Fuel Design-As listed *in Table 1 with a maximum bundle average enrichment of 4.4 wt.% U-235. Any significant deviation from this design may require additional analysis.

When stored, the fuel bundles must be fully inserted into the fuel storage boxes.

The 84C plates must contain no significant gaps or missing plates and the B4C content must remain constant over time.

This analysis does not include spent fuel storage in the Westinghouse spent fuel storage racks. Misplacement of a 4.4 wt.% U-235 bundle in the Westinghouse spent fuel storage rack was not addressed.

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2.0 MAJOR CONSERVATISM USED IN ANALYSIS The conservatisms in the model include the following:

EMF-91-174(NP)

Page 3 The fuel enrichment is modeled as the bundle average in all rod locations.

The poison plates are all modeled as having the minimum allowed width and thickness.

  • The modeled temperature is 2C°C. The higher temperatures in the actual system will result in k-eff values lower than those reported here.

The system was modeled as flooded with pure water (zero soluble poisons).

The NUS storage array reactivity (k-eff) was determined assuming a full array with a fuel bundle average enrichment of 4.4 Wt.% U-235 and no burnable poisons.

3.0 3.1 DESIGN BASES Fuel Assembly Description and Design Parameters EMF-91-174(NP)

Page 4 The mechanical design for this assembly is consistent with the mechanical designs of the recent past and foreseeable Mure. This fuel assembly is a 15x15 arrangement and includes a single instrument tube and eight guide bars (Reference 1 ). The parameters from the cycle N design are listed on Table 3.1.

EMF-91-174(NP)

Page 5 TABLE 3.1 PALISADES CYCLE N FUEL BUNDLE DESIGN PARAMETERS Fuel Rod Array 15 x 15 Number of Rods/Assembly 216 Number of Nonfueled Positions/ Assembly 9; 8 guide bars, 1 instrument tube Assembly Maximum Envelope Dimensions 8.3245 inch square Fuel Rod Pitch 0.550 inch Cladding OD 0.417 inch Cladding ID 0.3580 inch Cladding Thickness 0.0295 inch Fuel Rod Active Length 131.8 inches Fuel Rod Pellet-to-Clad Diametrical Gap 0.0070 inches Fuel Pelret Design Parameters*

Pellet OD 0.3510 inch Density 94.5% TD Dish Volume

3.2 Storage Racks Description and Cl EMF-91-174(NP)

Page 6 The Palisades spent fuel storage acks comprising the main pool and tilt pit pool.

The pool layout is shown ie main pool consists of NUS and Westinghouse storage racks. The NUS30Uth end of the main pool in a 24x16 array. The* NUS racks have a 2-inch w~1g them from the Westinghouse racks (Reference 2). The NUS racks in the m11ave 8.56 inch square ID storage cells and a 10.25 inch center to center spacinit pool consists of a north-to-south row of three storage racks. The center rackJrage rack. The NUS rack is designed to store control rods as well as fuel as.iCk has a 9.0 inch storage cell ID and

  • cells are located on 10.69 x 11.25 inch out is also shown in Figure 1.

The storage cells each consi~ outer stainless steel can. The gap between the inner and outer can is.25 a two cans is a neutron absorber plate.

The plate is composed of B4C bonded t The plate is 0.21 inch thick and 8.26 inches wide with a B-1 o loading of o.osr. Between each storage cell is a water gap with nominal thickness of 0.69 incl arrangement of the Main Pool Storage Cell is shown in Figure 3.1.

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EMF-91-174(NP)

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Can 00-9.SG" Inside llatl.!r C:ap-0.155" Outside Water Gap-0.69" With the poison plate in place a qap of 0.04" (total) is allow~d in the ~oison plate slot.

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FIGURE 3.1 PALISADES MAIN POOL STORAGE CELl. NOMINAL ARRANGEMENT

4.0 CALCULATIONAL METHODS AND MAJOR ASSUMPTIONS 4.1 Calculational Methods EMF-91-174(NP)

Page 8 The methodology used included CASM0-3G (Reference 3) and KENO-Va (Reference 4).

Both codes share wide acceptance for fuel analysis throughout the nuclear industry.

CASM0-3G was used to determine the small changes in reactivity due to uncertainties in the design tolerances of the fuel assembly and spent fuel storage racks.

KENO-Va was used to model the fuel storage pool.

Hansen-Roach 16 group cross sections prepared by BONAMl/NITAWL are used with the KENO-Va models. KENO-Va, BONAM!,

NITAWL and the cross section library used are all part of the SCALE 3 system and have been extensively benchmarked against data from critical experiments. Supplemental benchmarking using data from critical experiments with bundle arrays containing boron-containing plates is included in section 7.0.

4.2 Major Assumptions The majo~ assumptions made in this analysis are as follows:

Fuel enrichment is the. bundle average in all rod locations.

Fuel bundleS' contain no burnable poisons.

No soluble poisons are present in the water.

Spent fuel pool bulk water temperature is 2C°C.

B4C content in the neutron absorber plates is constant over time and tie plates contain no significant gaps or missing plates.

The first four assumptions make the analysis conservative. The last is a limiting condition.

As part of Facility Change Package FC-375 each storage cell was weighed after absorber plate loadi~g and compared to a reference weight. Random sampling of cells with a neutron source. was also done before final approval of FC-375. Had significant gaps been present, they would have been found by these two checks (Reference 5).

EMF-91-174(NP)

Page 9 5.0 UNCERTAINTIES The effect of dimensional and material tolerances on the system k-eff was determined using CASM0-3G.

CASM0-3G is a 2-D transport code used extensively for fuel depletion calculations. CASMO delta-k values are preferred over those from KENO-Va with a Monte Carlo uncertainty. The fuel was modeled without burnable poison and with all rods at a bundle average U-235 enrichment of 4.0 wt.%.

The effect of various tolerances is detailed below.

Enrichment - When the nominal enrichment was increased by 0.05 wt.% U-235, the k-infinity increased by.00215.

Pellet Density - The nominal smear density is TD based on a volume

% dish and a m pellet density. K-inf increased by.00182 with a TO pellet density and a volume % dish:

Pellet Diameter - Increasing all pellet diameters by inch produced a.00028 rise in k-inf.

Cladding 0. D. - Decreasing cladding 0. D. by inch produced a.00186 rise in k-inf.

Temperature - Temperature of the fuel and moderator was decreased to 4°C which resulted in an.00206 increase in k-inf.

Inner Can Wall Thickness - The inner can wall thickness was decreased by with a resulting decrease in k-inf of.00101. The inner wall thickness was increased by

. with an increase in k-inf of.00085.

Outer Can Wall Thickness - The value of used again for the outer can thickness.

from the inner can thickness is Cell Pitch -

The storage rack cell pitch was decreased by.04 inch to 10.21 inches. The resulting increase in k-inf is.00476.

The RMS sum of the nine uncertainties due to tolerances is.00631. The tolerance uncertainty is used with the bias uncertainty and the KENO standard deviation to prepare the 95/95 upper limit of k-eff. Section 7.0 reports the bias to be 0.0035 +.00368. The 95/95 upper limit for k-eff is calculated using the methodology presented in Reference 9.

6.0 NORMAUABNORMAL CONDITTONS AND RESULT EMF-91 -174(NP)

Page 1 o All conditions were modeled using KENO-Va and were found to have an acceptable reactivity (k-eff) of~.95 after accounting for all uncertainties and bias. The maximum k-effective at the 95/95 confidence level for any credible abnormal condition is.9131. The assumption that the entire NUS spent fuel storage rack contains 15x15 *fuel with 4.4 wt.% U-235 conservatively accounts for the presence and potential intermixing of older and lower enriched fuel bundles.

6.1 Normal conditions The main spent fuel storage pool was shown to be more reactive than the north tilt pit pool in Reference 6. The 24x16 NUS spent fuel storage rack was modeled as both a finite and an infinite system. The resulting k-eff and a description of each model used is listed in Table 2.

Case ID 4.4bndlR 4.4infR1 4.4inf-zA 4.4fin2R2 EMF-91-174(NP)

Page 11 TABLE 6.1 K-EFFECTJVE FOR NORMAL CONDITIONS.

Description k-eff.95.UL A 15x15 fuel assembly modeled as infinitely long

.8985 and reflected on four sides with 30 cm of water.

Model is used for comparisons and to show a single dropped bundle has acceptable reactivity.

An inf. x inf. array of infinitely long fuel

.9006 I

assemblies in infinitely long NUS fuel storage racks.

An inf. x inf. array of 335 cm long fuel assemblies

.9053 in fuel storage racks. The neutron absorber plate length is 339 cm. The top and bottom of the array is reflected with 30 cm of water.

A 24x16 array of 335 *cm long fuel assemblies in

.9091 fuel storage boxes. The neutron absorber plate length is 339 cm. All sides of the array are reflected by 30 cm of water.

6.2 Interaction EMF-91-174(NP)

Page 12 The NUS fuel storage racks and the Westinghouse fuel storage racks are separated by a 2.00 inch water gap. Therefore, potential neutron interaction between the two racks was analyzed. This analysis included modeling the entire spent fuel storage pool. The NUS racks were modeled as described in case 4.4fin2R2. The Westinghouse racks were modeled at nominal conditions containing 15x15 fuel bundles. All positions in the 15x15 fuel bundles were assumed to contain fuel with 1.5 wt.% U-235. The entire fuel pool with a 2.0 inch water gap between the two racks was shown to have k-eff =.9053 +.0037. This same model with a 6.0 inch water gap which essentially isolates the two racks has k-eff =.9046 +/-.0036. The difference between the two is 0.0007 and demonstrates that interaction between the two racks is negligible.

6.3 Abnormal Conditions 6.3.1 Spacing Given the arrangement of the spent fuel storage rack and the size of the fuel bundles it is not possible for fuel bundles to be accidently placed in the water channels between the fuel storage racks or between the racks and the concrete pool walls.

The only abnormal spacing condition results from eccentric positioning of the fuel assemblies in the fuel storage boxes. In order to eccentrically space the fuel assemblies in the fuel boxes, the four aligning pins on the bottom of the lower tie plate must be placed on the steel floor of the fuel storage box. Normally, these aligning pins fit into four 0.88 inch diameter holes in the bottom of the fuel storage boxes. This type of misplacement of the fuel assembly causes the assembly to be elevated 1.47 inches. Although the length of the poison plates only exceeds the length of the active rod length by 2.2 inches, elevating the fuel assembly by 1.47 inches does not give the active portion of the fuel assemblies a line of sight path to other fuel assemblies without passing through a neutron absorber plate.

The worst case model for eccentric spacing was an Infinite x Infinite array of eccentrically spaced fuel assemblies. The fuel assembly in this model was placed at the lower left corner of the fuel storage box with specular reflection placed around the fuel assembly. K-eff for this arrangement is.9131 at the 95/95 Upper Limit.

6.3.2 Shifted Poison Plates

~---------~-----

EMF-91-174(NP)

Page 13 The poison plates in the NUS rack could 'be shifted to one side instead of being centered in the poison plate channel. This condition was modeled by creating an inifinite array of fuel storage boxes. The poison plates for each storage box were shifted to provide the maximum possible gap between the plates at two diagonal corners. For this arrangement, the 95/95 upper limit of k-eff is.9080.

6.3.3 Dropped Fuel Bundle A dropped fuel bundle during fuel handling operations is also considered a credible abnormal event. If a fuel bundle were dropped into the spent fuel rack and lay horizontally across the top of the. fuel storage rack, this bundle would be approximately seven inches above the active portion of the fuel assemblies in storage. Seven inches of water separation will decouple the fuel in storage and the fuel in the dropped bundle. A single fuel bundle reflected on all sides by 30 cm of water has a 95/95 upper limit k-eff =.8985. Rack design prevents a vertical fuel bundle from being placed outside of the fuel storage racks.

7.0 VALIDATION OF CALCULATIONAL METHODS EMF-91-174(NP)

Page 14 Supplemental benchmarking of the methods employed in the analysis was performed using experimental data with boron poison sheets in arrays of bundles. The experiments are 0

described in References 7 and 8. The benchmark data are in Table 3.

Using the methods in Reference 9, the weighted average k-eff and the standard deviation of the bias were calculated:

Weighted average k-eff: 1.0035 Bias Standard Deviation: 0.00368 The weight of each k-eff value is proportional to the reciprocal of its variance.

I I

TABLE 7.1 BENCHMARK CALCULATION RESULTS KENO-Va WITH 16 GROUP CROSS SECTIONS CASE NO.

CALCULATED K-EFF

REFERENCE:

T EXPERIMENTS 2378 1.00395 +/- 0.00376 2384 1.00037 +/- 0.00306 2388 0.99886 +/- 0.00341 2420 1.00038 +/- 0.00367 2396 0.99443 +/- 0.00360 2402 1.00694 + 0.00283 2411 1.01223 + 0.00286 2407 1.00647 +/- 0.00332 2414 1.00967 +/- 0.00327 REFERENCE a* EXPERIMENTS 9

1.00092 +/- 0.00487 10 1.00181 +/- 0.00412 11 0.99786 +/- 0.00413 12 0.99885 + 0.00487 31 1.00442 +/- 0.00421 EMF-91-174(NP)

Page 15 I

I

8.0.

REFERENCES EMF-91-174(NP)

Page 16

1.

Principal Reload Fuel Design Parameters Palisades Reload M. ANF-89-063(P).

2.

Palisades Facility Change Package #FC-860.

3.

"CASM0-3:

A Fuel Assembly Bumup Program (Methodology),"

  • Studsvik/NFA-86/8, Studsvik Energiteknik AB, Nykoping, Sweden, November 1986.
4.

"SCALE: A Modular Code System for Performing Standardized Computer Analyses for Ucensing Evaluation," NUREG/CR-0200.

5.

Palisades Facility Change Package #FC-375.

6.

"Palisades Nuclear Generating Station Spent Fuel Storage Pool Criticality Safety REANALYSIS." XN-NF-542, May 1980.

7.

Baldwin, M. N., etal., "Critical Experiments Supporting Close Proximity Water Storage of Power Reactor Fuel, "BAW-1484-7, July 1979.

8.

Bierman, S. R., Durst, 8. M., and Clayton, E. D., "Critical Separation between Subcritical Clusters of 4.31 % Enriched uo2 Rods in Water with Fixed Neutron Poisons.," NUREG/CR-0073, May 1978.

9.

W. Marshall, P. D. Clemson, G. Walker, "Criticality Safety Criteria," ANS Trans, 35, 278 (1980).

CRmCAUlY SAFETY ANALYSIS FOR THE PALISADES SPENT FUEL STORAGE POOL' NUS RACKS DISTI118UT10N Consumers Power (5)

J. W. Hulsman C. D. Manning T. C. Probasco Document Control (5)

EMF-91-174(NP)

Issue Date:

12/09/91

ATTACHMENT 2 Consumers Power Company Palisades Plant Docket 50-255 EMF-91-142l(NP)

CRITICALITY SAFETY ANALYSIS FOR PALISADES NEW FUEL STORAGE ARRAY

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PDR ADOCK 05000255 P

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I Siemens Nuclear Power Corporation CRITICALITY SAFETY ANALYSIS EMF-91-1421 (NP)

Issue Date:

12/09/91 FOR THE PALISADES NEW FUEL STORAGE ARRAY December 1991

e e

CUSTOMER OISCtAIMER IMPORTANT NOTICE REGARDING CONTENTS ANO USE OF THIS DOCUMENT PL.EASE READ CAREFULLY Siemens Nudear Power Corporation's warranties and representations cx:inc:am1ng the subject matter of this document are those sat font! in the Agreement bei:ween Siemens Nudest Power Corporation and the Custcmer pursuant to whic:h this document is isSYe<i. Accordingly, except as otherwise expressly provided in such Agreement neither Siemens Nudear Power Corporation nor any person ac!lng on its behalf makes any warranty or representation. expressed or implied. with resoect to the acaJracy, cx:impleteness. or usefulness of !he information contained in tl'l1s dcc:wnent or that the use of any informaaon, appararus. method or process disdosed in !his document will not infringe pnvatejy owned rights; or assumes any liabilities wid'I respect to the use of any inlormat1on, apparatus. method or process disdosed in this doc;ument.

The intcrmalion cx:intarned herein is for the sole use of !he Customer In order to awid impairment of nghts of Siemens Nuclear Power Corporation 1n patents or inventions wnic:h may be induded in !he informaaon contained in tl'l1s document the recipient. by its acceptance of this doct.1ment. agrees not to publish or maK8 public use (in the patent use of the term) of suc:h informaaon untli so autriortzed in wri1ing by Siemens Nudear Power Corporation or unol after six (6) months following termination or expiration of the aforesaid Agreement and any extension thereof, unless expressly provided in the Agreement. No rights or licenses 1n or to any pai.nts are implied by the furnishing of this document

CRITTCAUTY SAFETY ANALYSIS EMF-91 -1421 (NP)

Issue Date:

FOR THE PALISADES NEW FUEL STORAGE ARRAY Prepared by:

R. A. Jensen~ Senior Research Engineer Approved by:

G)(V ~

e:tn.

S. W. Heaberlin, Manager Reactor Systems Analysis Section Aw.g"Jf/ :i1 1Cf"1(

Date

TABLE OF CONTENTS EMF-91 -1421 (NP)

Page 1 Section Page No.

1.0 INTRODUCTlON

.................................................... 1 2.Gl

SUMMARY

........................................................ 2 3.0 FUEL ASSEMBLY DESCRIPTlON........................................ 2 4.0 STORAGE ARRAY DESCRIPTION

....................................... :)

5.0 CALCULATlONAL METHODOLOGY...................................... 3 6.0 METHODS VALJDATlON 3

7.0 MAJOR CONSERVATlSMS........................................... 10 8.0 RESULTS..,....................................................

1 ~

9.0 ABNORMAL COND!TlONS............................................ 1 4

10.0 CONCLUSION

S.................................................... 1 5

11.0 REFERENCES

LIST OF TABLES EMF-91-1421 (NP)

Page ii Table Page No.

Design Base Palisades Batch N Fuel Assembly Parameters.................... 4 2

Critical Experiment Benchmark Results

................................... 9 3

Palisades New Fuel Storage Arrat Reactivity (K8ff)

Calculation Results for 4.25 w/o 35u Fuel................................ 1 3

Figure 2

3 LIST OF FIGURES Reload N1 Assembly Palisades New Fuel Storage (Measurements of EMF-91-1421 (NP)

Page iii Page No.

3 Installed Rack)............ '................................

7 Palisades New Fuel Storage Array (Worst Case Geometry)

1.0 INTRODUCTION EMF-91-1421 (NP)

Page 1 In July 1975 a criticality safety analysis(1l was performed for the Palisades New Fuel Storage Array to allow storage (checkerboard arrangement) of fuel assemblies enriched to 3.2 wt.% 235u. This analysis included a parametric search to define the maximum array reactivity (keff} as a function of unifo[m interspersed moderation within the array. The maximum ketf was shown to occur when the array is fully flooded with water. s*ubsequent to this evaluation, an~ther criticality safety analysis(2l was performed in 1979, which demonstrated the storage array to be adequately subcritical at a maximum average fuel assembly enrichment cf 3.317 wt.% 235u.

It is the intent of this report to demonstrate that Palisades fuel (using Batch N fuel assembly parameters) enriched to 4.20 wt.% 235u can be stored in the new fuel storage array and continue to meet the reactivity limit criterion tketf s 0.95) stipulated for the storage cf new fuel by the Technical Specifications for the Palisades Nuclear Power Station.

This criticality analysis was performed in accordance with NUREG-0800 and ANSl/ANS-57.3-1983 (including Section 6.2.4 and all applicable subsections).

2.0

SUMMARY

EMF-91-1421 (NP)

Page 2 The following criticality safety analysis of the new fuel storage array, containing steel box beams in alternate storage locations of the 3 x 24 array, demonstrates the array to be adequately subcritical for Batch N type fuel having a maximum average fuel assembly enrichment of 4.2 weight % 235u. The analysis demonstrates the storage array to have an effective multiplication factor of <0.95 for assumed worst credible array conditions of fuel assembly spacing and uniformly interspersed moderation.

The subject storage array meets the applicable criticality safety criteria (NUREG-CSCO and ANSl-57.3-1983) subject to the following limitations:

1.

Fuel Design: As specified in Section 3.0. Any significant deviation from this may require additional analysis.

2.

Array Design: As described in Section 4.0.

3.

If fuel assemblies are stored with plastic wrapping, the bottom of wrapping shall be open to assure drainage.

3.0 FUEL ASSEMBLY DESCRIPTION The fuel assembly design (Batch N) assumed for the analysis is depicted in Figure 1.1 As indicated, the 15 x 15 lattice arrangement includes a Figure 1 actually depicts a Palisades Batch N1 assembly which is the most reactive fuel assembly design of batch N". All other assembly designs of this batch have lower average planar enrichments than the N1 design and include various loadings of godolinia bearing fuel pins.

---~--- ------------

~'NG I.

EMF-91-1421 (NP)

Page 3

~NG

. I

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1.

I LL! L L LI GI L I L L I L LIG!LIL!L1LL L L M M!MIMiMIMIMJMIM/MIM!L ! L LjM MIHIHIHIH HI H HJH/HIMIM!L LjMjH JHIHJHjHJHIHJH!H!HIH!M!L GJM!H IH!HIHJHJHIHJHjH!HIHiM;G L M H HIHIHIHjHJHJHIHIHIHiM L L M HIHiH/HJHIH H I H I H I H I H ! M L L M H HI H ! HI H I I H HI Hi HJ HIM L L M H H H I H ! H I H H H!HIHJH/M L L Mi HI H HI HI HI HI HJ HI Hi HI HIM [ LI G/M H I H HI H ! HI HI HI HI* Hi HI H : M j G LIM I H I H H ! H I H H HjH!HJHjH~M:L L MI M I H Hi H ! H jH HJHIHiHIM!M 1 L L IL M IM MiM IM MJM M!MiM\\MiL :L LLj L I L I L G i L I L L L L JGiL IL jL /LL LL* 2.40 L

  • 3.1 o w10 *u-2:35 Fuel H

Guide Sar I

Instrument Tube C

Identifiers: 'NG

  • Wide lnterassemoly Gao NG. Narrow lnterassemt:lty Water Gae FIGURE 1.

Reload Nl Assernbly( 3l

~.. 108067.1

EMF-91-1421 (NP)

Page 4 single zirconium instrument guide tube located in the center of the assembly and eight zirconium guide bars positioned on the exterior of the assembly. The remain!ng positions within the assembly are occupied by 216 U02 fuel rods.

The fuel assembly specifications and lattice cell parameters assumed in this evaluaticn are given in Table 1. The parameters such as pellet size, pellet density, clad thickness. etc..

have been set to conservative values within the expected manufacturing tolerances.

TABLE 1. Design Base Palisades Batch N Fuel Assembly Parameters(5l Parameter Nominal Model Lattice Pitch, in.

0.550 Clad OD, in..

0.417 Clad Material Zircaloy-4 Clad Thickness, in.

0.0295 Pellet OD, in.

0;3510 Pellet Density, % TD 94.5 Dish Volume, %

Active Fuel Length, in.

131.800 Fuel Rod Array 15 x 15 Fuel Rods 216 Guide Bars 8

Instrument Tubes.

. EMF-91-1421 (NP)

Page 5 Note that since the manufacturing enrichment uncertainty/tolerance is 0.05 wt% 235u the analysis was performed using 4.25 w/o 235u fuel so that the rack could be qualified to store *4.20 w/o 235u fuel. (4)

. 4.0 STORAGE ARRAY DESCRIPTION The Palisades new fuel storage rack has been measured to determine actual "as built" dimensions. Figure 2 is an arrangement drawing giving those measured dimensions. This information was supplied by Consume.rs Power Company.(6) Subsequent information(?)

established that the dimensions indicated are actually measured center-to-center distances between adjacent top bands. Such dimensions, therefore, represent nominal center-to-center spacings between adjacent storage locations. It should be noted that the nominal center-to-center separation between assemblies was designed to be 9.5 inches. Measurements of the installed rack, however, show that a maximum negative tolerance of 1 /8 inches exists on the design value. (Therefore, minimum nominal center-to-center separation of 9-3/8 inches was assumed for this analysis.)

Concrete walls are adjacent to three sides of the storage array and are separated from the fuel by 0.5 to 1.5 inches. For the purpose of this analysis, a 16 inch thick concrete reflector was assumed to be touching three sides and bottom of the storage rack. The fourth side and top of the array was assumed to be reflected by 6 inches of water, which is effectively an infinitely thick water reflector.

EMF-91-1421 (NP)

Page 6

. The 3 x 24 array contains 36 fuel assemblies with alternate positions occupied by 8 x 8 inch structural steel box beams having a nominal wall thickness of 5/16 inch. (2) A minimum wall thickness of 0.25 inches was established for this analysis. (B)

6 0..

I I

v

= -:.ST' :c.J:;c*.::.:; :u.:..3 ;u1Li; I'".. 9.!.::."' cult.:" i:J s**;:~u

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  • n.;:;- * !vJ s:*:.;Lu FIGURE 2.

Palisades N2*,*1 Fuel Storage Measurements of Installed Rack EMF-91-1421 (NPJ Pag.:i I

5.0 CALCULATlONAL METHODOLOGY EMF-91-1421 (NP)

Page 8 The KENO-Va Monte carte computer code(10) was used to mockup the Palisades New Fuel Storage Array. The pin cell composed of fuel rod, gap, clad and moderator regions was explicitly modelled. The Palisades N1 assembly with 8 guide bars and a single instrument tube was also explicitly modelled with the exception of using a constant average planar enrichment for the 216 fuel pins within the assembly {this is a conservative assumption, see below).

In conjunction with KENO-Va, the SCALE 27 Group Ubrary(11l was used. Both the 235U and 238u cross sections were corrected for the effects.of resonance self-shielding using the NITAWL code. (12) NITAWL uses the Nordheim 1.ntegral Treatment to compute a neutron spectrum which is used to obtain "effective" resonance cross sections. Oancoff correction factors are used to account for shielding effects due to the close proximity of lattice pins.

To demonstrate that assigning fuel pins an average planar enrichment through out the assembly, rather than using zoned enrichments, is conservative the 2-0 transport code, CASM0-2e<13l was used. CASMO calculat,ions indicate that the actual "zoned" N1 assembly design is approximately 9 mK less reactive than the corresponding constant enrichment assembly.

6.0 METHODS VALIDATION The calculational methodology used in this analysis was benchmarked against six critical experiments. (14* 15) This set of criticals simulated conditions associated with light

EMF-91-1421 (NP)

Page 9 water fuel storage pools and were conducted at both the Battelle Critical Mass Laboratory and the Babcock and Wilcox CX-1 O critical facility.

The benchmark results are given in Table 2. The corresponding bias (mean difference) and benchmark'uncertainty (difference standard deviation) of these benchmarks are 0.00755 and 0.00414, respectively.

TABLE 2. Critical Experiment Benchmark Results Calculated Measured Bench No.

K-Effective. C K-Effective. M 4

0.99552 +/- 0.00308 1.00000 7

0.99109 +/- 0.00306 1.00000 29 0.99870 +/- 0.00379 1.00000

. 2245 0.98983 +/- 0.00255 1.00000 2266 0.99244 +/- 0.00267 1.00000 2321 0.98710 +/- 0.00300 1.00000 Mean Difference = 0.00755 (Bias)

Standard Deviation = 0.00414 (Benchmark Uncertainty)

A Kolmogorov-Smirnov test was conducted and indicated that the above difference distribution agrees well with a theoretical normal distribution.

Difference M-C 0.00448 0.00891 0.00130 0.01017 0.00756 0.01290

7.0 MAJOR CONSERVATISMS The major conservatisms of this analysis were:

EMF-91 -1421 (NP)

Page 1 o An average planar enrichment was used for all pin locations, rather than using "zoned" enrichments.

The most reactive Batch N fuel assembly design (i.e., highest enrichment sub batch with no burnable poisons) was used in determining storage array reactivity (k-eff).

Fuel design parameters such as pellet size, pellet density, clad thickness, etc., were collectively set to conservative values within the expected manufacturing tolerances.

The system was modeled as flooded with pure water (zero soluble poisons).

8.0 RESULTS EMF-91-1421 (NP)

Page 11 I~ determining the maximum array reactivity (K9ff) for 4.25 w/o 235u fuel this analysis evaluated the effects of varying moderator density and fuel assembly spacing within the rack.

All rack conditions were found to have an acceptable reactivity of K8ff <0.95 after accounting for all uncertainties and bias. The maximum K-effective at the 95% confidence level was 0.945.2 The highest calculated reactivity occurs when the array is fully flooded with water and the fuel assemblies are located in the rack as depicted in Figure 3. A summary of the results is given in Table 3.

2 95 upper limit K9ff = Cale. K8ff + Bias + Kg5 {Benchmark Variance + KENO Variance

= 0.92682 + 0.00755 + 2.015..f0.004142 + 0.003482

= 0.945 Where Kg5 = 2.015 is based on a one-sided normal Students t Distribution at the 0.05 significance level for 5 degrees of freedom.

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e EMF-91-1421 (NP)

Page 13 TABLE 3. Palisades New Fuel Storage Array Reactivity (K9ff} Calculation Results for 4.25 w/o 235u Fuel}

Array Rack Moderator Calculated Geometr:£ Void Fraction K-effective Nominal 0.0 0.91399 +/- 0.00343 Adverse 0.0 0.92682 +/- 0.00348 Adverse 0.05 0.91123 +/- 0.00310 Adverse 0.10 0.89581 +/- 0.00309 Adverse 0.30 0.85648 +/- 0.00288 Adverse 0.50 0.81299 +/- 0.00329 Adverse 0.70 0.80100 +/- 0.00323 Adverse 0.75 0.79879 +/- 0.00305 Adverse 0.80 0.79041 +/- 0.00303 Adverse 0.90 0.71333 +/- 0.00283 Adverse 0.95 0.63454 +/- 0.00275

  • Adverse Rack Geometry is depicted in Figure 3. Three sides and bottom reflected by 16 in. of concrete; open side and top reflected by 6 in. of water at full density.
  • Fuel/moderator temperature was 20°c.
  • Other than the steel box beams no rack structual components were modelled.

9.0 ABNORMAL CONDITlONS EMF-91-1421 (NP)

Page 14 In accordance with ANSl/ANS-57.3-1983 (6.2.4.1) this analysis evaluated the potential adverse effects of fuel handling accidents. Due to the fact that the Palisades New Fuel Array is a dry storage rack fuel handling accidents do not adversely impact nuC!ear safety. The infinite multiplication factor (K..) for dry 5 w/o 235u uranium oxide systems is less than 0.8. (iSJ Specific design features(9) of the rack which preclude flooding include:

1)

All cells and spaces between cells have openings at the bottom to facilitate draining.

2)

The rack is situated 3 ft above a course steel grading floor.- The floor below the grading is approximately another 12 ft.

10.0 CONCLUSION

S EMF-91-1 421 (NP)

Page 15 This analysis conservatively demonstrates the reactivity of the Palisades new fuel storage array as described for a Batch N fuel assembly with an enrichment ot 4.20 w/o 235u to be less than 0.95 under the worst credible storage array conditions.3

  • 3 Although this analysis was performed using an average planar enrichment of 4.25 wt%

235u it is necessary to lower the allowable enrichment by the manufacturing enrichment uncertainty/tolerance which is 0.05 wt% 235u. (4)

I.

11.0 REFERENCES

EMF-91-1421 (NP)

Page 16 (1)

L E. Hansen, "Palisades New Fuel Storage Array Criticality Safety Analysis", XN-NF-309, Exxon Nuclear Co., (July 1975).

(2)

C. 0. Brown, Palisades New Fuel Storage Array Criticality Safety Reanalysis, XN-NF-508, Exxon Nuclear Co., (February 1979).

(3)

Advanced Nuclear Fuels Drawing, "Fuel Assembly Load Map Type N1," ANF-307, 309, Revision O.

(4) "Palisades Characteristics of *Reload.N," ANF-CS-386, Revision 1.

\\

(5)

"Principal Reload Fuel Design Parameters Palisades Reload M," ANF-89-063(P).

(6).

Letter, W. J. Beckil;JS (CPCO) to W. E. Niemuth (E.NC), May 13, 1975.

(7)

W. J. Beckius, Personal Communication, Consumers Power Company, June 1 O, 1975.

(8).

  • B. Webb, Personal. Communication, Consumers Power Company, June 1 O, 1975.

(9)

T. Hollowell, Personal Communication, Consumers Power Company, August 26, 1991.

(10)

L M. Petrie and N. F. Landers, "KENO V.A An Improved Monte Carlo Criticality Program with Supergrouping." NUREG/CR-0200, December 1984.

(11)

"SCALE: A Modular Code System for Performing Standardized Computer Analyses for Ucensing Evaluation," NUREG/CR-0200.

(12)

R. M. Westfall, "NITAWL-S," ORNL/NUREG/CR-0200, October 1981.

(13)

"CASM0-2E: A Fuel Assembly Burnup Program (Methodology)," Studsvik/NFA-86/8, Studsvik Energitekmik AB, Nykoping, Sweden.

it:..., '*

~

~

Q e

EMF-91-1421 (NP)

Page 17 (14)

M. N. Baldwin, et al., "Critical Experiments Supporting Close Proximity Water Storage of Power Reactor Fuel, "BAW-1484-7, July 1979.

(15)

S. R. Bierman, 8. M. Durst, and E. D. Clayton, "Critical Separation between Subcritical Clusters of 4.29% Enriched U02 Rods in Water with Fixed Neutron Poisons," PNL-2615.

March 1978.

(16)

S. R. Bierman and E. D. Clayton, "Gmelin Handbook of Inorganic Chemistry,

Supplement Volume A6, 8th Edition, 1983.

CRITICALJrf SAFE1Y ANALYSIS FOR THE PALISADES NEW FUEL STORAGE ARRAY OISTRIBUT10N Consumers Power (5)

J. W. Hulsman C. 0. Manning T. C. Probasco Document Control (5)

EMF-91-1421 (NP)

Issue Date:

12/09/91

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