ML20058N382

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Rev 1 to Criticality Safety Analysis:BU-7 Shipping Container for UO2 Pellets/Powder W/Enrichments at or Below 4.10%
ML20058N382
Person / Time
Site: 07109019
Issue date: 11/29/1993
From:
GENERAL ELECTRIC CO.
To:
Shared Package
ML20058N366 List:
References
NUDOCS 9312210364
Download: ML20058N382 (26)
v • d • e


Text

( )

%s APPENDIX E

" CRITICALITY SAFETY ANALYSIS:

BU-7 SHIPPING CONTAINER FOR 00 PELLETS / POWDER WITH ENRICHMENTS 2

AT OR BELOW 4.10%"

SEPTEMBER 9, 1993 REVISION 1, DATED NOVEMBER 29, 1993 i

I I

LICENSE SNM-1097 DATE 12/03/93 PAGE DOCKET 71-9019 REVISION O

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9312210364 931203 PDR ADOCK 07109019 C

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Criticality Safety Analysis:

j BU-7 Shipping Container for UO Pellets / Powder with j

2 Enrichments at or Below 4.10%

f September 9,1993

-j Revision 1, dated November 29,1993 t

O Revisions marked by revision bars in left margin

-l

.l O

September 9,1993 i Rev.1, dated 11/29193 ]

Page 1 of23 b

Criticality Safety Analysis: BU-7 Shipping Container for UO 2 t

Pellets / Powder with Enrichments at or Below 4.10%

I.

INTRODUCTION Model BU-7 shipping containers are used by the General Electric Company for the transportation of low-enriched unirradiated uranium dioxide powder, pellets and scrap. The BU-7 235U enrichment of container is a Fissile Class I package which is currently licensed for a maximum 5.0% for powder and 4.0% for pellets and scrap. In the previous case for enrichments below 4.0%, the

_{

containers were restricted to two 5 gallon pails or three 3 gallon pails which are limited in contents to no l

more than 70 kg of UO2 Powder or two safe batches of UO2 Pellets (or powder) per package. Each package was also limited in the amount of hydrogenous moderation that may be present in the fuel.

(

In a prior analysis for UO2 Powder enriched in the range of 4.0% to 5.0%, the BU-7 container l

was demonstrated to comply with Fissile Class I requirements even with optimum moderation and

[

maximum geometry for the accident conditions specified in 10CFR71.57. Each container was restricted i

to UO mass limits as follows: 35.0 kg UO for enrichments greater than 4.0% but no more than 4.2.5%,

2 2

32.5 kg UO for enrichments greater than 4.25% but no more than 4.50%,30.0 kg UO enrichments 2

2 greater than 4.50% but no more than 4.75%, and 27.5 kg UO for enrichments greater than 4.75% but no j

2 more than 5.0%. The normal case restriction for the fuel contents to a H/U atomic ratio of 0.45 was applied, but the contents were limited so that the total mass of hydrogenous moderator in the inner j

containment vessel was no greater than 1000 grams or 3.6% of the weight of the uranium dioxide, Q

whichever was smaller.

In the present analysis for UO2 Pellets (and powder) enrichments below 4.10%, the BU-7 l

l container is demonstrated to comply with Fissile Class I requirements for the same conditions. Each -

container is restricted to UO mass limits as follows: 30.0 kg UO for enrichments greater than 3.06%

i 2

2 but no more than 4.10%, and 50.0 kg UO for enrichments at or below 3.06%. The normal case i

2 restriction of the fuel contents to a H/U atomic ratio of 1.6 applies and the contents must belimited so that the total mass of hydrogenous moderator in the inner containment vessel is no greater than 5.3% of the weight of the uranium dioxide.

Specifications for the geometry and materials of construction of the BU-7 container,5 and 3 gallon pails are the same as those for the existing Certificate [1] with one exception. Alinercontaining a strong neutron absorbing material has been added to the inside drum, surrounding the pails of UO2 powder. The liner is made from "Boral," which is essentially a B C and Aluminum compound. The 4

liner is composed of 0.080 inches (minimum,0.085 nominal) of Boral, sandwiched between two sheets of 0.026 inch (minimum,0.030 nominal) stainless steel. The Boral liner has a minimum height of 26.0 inches and is designed to fit against the inner drum of the BU-7. - The Boral material has a minimum density of Bm atoms per unit surface area of 0.011 g/cm,

2 II.

ANALYSIS A.

BU-7 Container The BU-7 shipping container consists of a 55 gallon DOT Specification 17H outer drum constructed of 18-gauge steel. The outer drum contains 7 - 9 lbs/ft3 fire-retardant phenolic resin

September 9, I993 l Rev.1, dated 11/29193 J Page 2 of 23 insulation sandwiched between it and a 13.75 to 14.05 inch diameter by nominal 27 inch long ste drum. The inner drum (also described as the " inner containment vessel"), has a gasket and is sealed with a bolted metal lid to insure water tightness, and normally holds two 5 gallon pails or three 3 gallon pails. A liner of Boral is included inside the inner containment vessel. Figure 1 depicts the container with a cutaway section showing the internal container and the phenolic resin.

B.

General Requirements for Fissile Class I Shipping Containers As specified in Parts 71.55 and 71.57 of Reference 2, the criticality safety requirements for a Fissile Class I shipping container are that suberiticality be maintained for the following:

1.

Single Containers - with the most reactive credible configuration of the package and contents, including moderation by water, and assuming clos: reflection by water on all sides.

2.

Infinite Arrays of Containers - undamaged, in any arranpment with optimum interspersed hydrogenous moderation.

3.

Arrays of Damaged Containen - two hundred and fifty " damaged" containers stacked together in any arrangement, closely reflected on all sides by water and with optimum interspersed hydrogenous moderation. " Damaged" means in the condition resulting from being subjected to the " Hypothetical Accident Conditions" specified in Part 71.73 of the Rules and Regidadons.

The " Hypothetical Accident Conditions" tests were conducted for the BU-7 cocainer in g The results of the tests showed that while deformation of the 1979-80 and are reported in Reference 3.

outer 55 gallon drum occurred at the points of contact, there was no evidence of punctures, fractures or separation of the container sides from the bottoms. No damage was found to the sealing features or the integrity of the inner container or the UO2 Pellet / powder pails inside it. After the fire and water immersion tests, the inner container remained dry, the silicone rubber gasket sealing it was undamaged, and no significant increase in the moisture content in the powder was found. The report concluded that in the tests, the outer container did not suffer any significant damage that would affect criticality safety considerations.

Notwithstanding the results of these tests, the current analysis will tak.e into consideration accident conditions in which water is assumed to enter the inner containment vessel and the UO2 powder, the three or five gallon pails spill out into the larger inner containment vessel and UO2 Powder j

mixes with the water. For simplicity in modelling, the three and/or five gallon pails will conservatively j

be omitted from the analysis and the water and UO pellets will be modelled solely in the inner 2

containment vessel. The phenolic resin will also be considered to absorb water and the same amount of water analyzed outside of the container will be assumed to be present in the resin. This includes full density water for water reflection of the single container.

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September 9,1993 [ Rev.1, dated 11/29/93 ]

Page 4 of 23 C.

UO Pellets and Water 2

Previous criticality safety analyses of the BU-7 container are documented in References 4,5,6 and 7.

For the present analysis, the contents of the container are taken to be within the inner containment vessel (including liner) with uranium dioxide powder enriched up to 4.10% in U235, which is restricted in moderation to a H/U atomic ratio of 1.6.

The fuel is modelled as UO and water and 2

therefore applies to all uranium dioxide powders having theoretical densities no greater than 10.96 3

g/cm.

Atom densities for theoretical density UO2 used in this analysis are listed in Table Homogeneous mixtures of UO and water are less reactive than the heterogeneous case and so are 1.

2 bounded by this analysis where all the UO is in solid form.

2 Table L Atom Densities for Maximum Density UO Pellets 2

Enrich-NU235 NU238 No ment (%)

(atoms / barn-cm)

(atoms / barn-cm)

(atoms / barn-cm) 3.06 7.5740E-04 2.3691E-02 4.8897E--02 4.10 1.0148E-03 2.3437E-02 4.8903E-02 3

For full density water (OH2O = 1.00 g/cm ) Na = 6.6743E-02 atoms / barn-cm and No =

3.3372E-02 atoms / barn-cm. The water-to-fuel ratio may be varied through the geometry of the system (i.e., pellet array pitch, pellet diameter and/or total height of fuel in the container).

O The water-to-fuel volume ratio (W/F) may be determined from the volume of water surrounding the pellet (a function of the pitch) and the volume of the pellet itself. The water-to-fuel ratio can be written W/I, = (Pitch)2_ gp2 4 (Pitch)2 -I D2 392 (1)

An average density of the materials may be calculated (although this is not explicitly used) for each of the water-to-fuel volume ratios. The total volume of fuel and water, as well as the height of the fuel and water in the container, can be determined from the average density value. The average density can be found from a mass balance (TH2O + Tuo2) Gave = TH2O OH2O + I o2 0U02 (2)

U In terms of the water-to-fuel ratio, equation (2) can be rearranged to give 0 8vc -_ (W/F) OH2O + Ovo2 w/F + 1 (3)

Since the mass and average density of the system is known, the volume and corresponding dimensions of the problem can be determined.

D.

Materials of Construction The major constituents of the BU-7 comainer are the carbon steel drums and phenolic g 3

resin. Carbon steel has a density of 7.82 g/cm and its component atom densities are 3.921E-03

September 9,1993 ( Rev. I, dated 11/29/93 ]

i Page 5 of 23 i

O atoms / barn-cm for carbon and 8.3491E-02 for iron. Stainless steel,if used for construction,is a better neutron absorber than is carbon steel. Thus, the analysis applies to BU-7 containers constructed of stainless steel as well as those constructed of carbon steel.

3 The density of phenolic resin compound with the minimum specification (i.e.,7 lbs/ft ) is given below (Table 2). One-hundred percent of the minimum specified phenolic resin density is used in this analysis, although no credit has been taken for boron which is present.

Table 2.

Phenolic Resin Atom Densities in the BU-7 Container Element Atom Density (Atom / barn-cm)

Hydrogen 3.0140E-03 Boron 10 0.0000E+00 Boron 11 0.0000E+00 Carbon 2.3050E-03 Oxygen 2.0510E-03 Silicon 5.2890E-05 Table 3 gives the constituent elements and associated atom densities for the Boralliner. As an O

added conservatism in the treatment of the liner, only 75% of the minimum specified density is used in IO the analysis (e.g., only 75% of the B atoms are included in the liner for the analysis).

Table 3.

Boral Liner Atom Densities l

Element Atom Density (Atom / barn-cm)

Carbon 3.0675E-03 Boron 10 2.4418E-03 Boron 11 9.8285E-03 Aluminum 4.5406E-02 E.

Analytical Method Neutron multiplication factor calculations in this criticality analysis have been performed with the GEMER Monte Carlo code [8]. GEMER. is a modified version of the Battelle Northwest Laboratory's BMC Monte Carlo code which has been combined with the geometry handling subroutines i

in KENO IV. Cross section sets in GEMER are pmcessed from the ENDF/B-IV library in 190 broadgroup and resonance parameter formats except for thermal scattering in water which is represented j

by the Haywood Kernelin the ENDF/B library. In GEMER, the resonance parameters describe the cross sections in the resonance energy range and Monte Carlo sampling in this range is done from the resonance kernels rather than from the broad group cross sections. Thus,there is a single, unique cross section set associated with each available isotope and dependence is not placed on Dancoff (flux j

shadowing) correction factors or effective scattering cross sections. The cross section libraryincludes I

September 9,1993 [ Rev.1, dated 11/29/93 J Page 6 of 23 fission, capture, elastic, inelastic, and (n,2n) reactions. Absorption is implicitly treated by applying the non-absorption probability to neutron weights at each collision point.

GEMER's bias has been determined (from an extensive validation against critical experiments) to vary fmm +0.006 to -4.021 over the range of moderation in the fuel mixtures considered in this analysis. For under-moderated mixtures with H/U atomic ratios less than about 5, the bias is positive denoting that neutron multiplication factors are over-predicted. The bias then decreases almost linearly to-0.015 at an H/U ratio of about 25. These values span the range considered for the BU-7 container since the highest degree of moderation (that for the UO and H O mixture with a WFH2O of 2

2 0.40) con esponds to an H/U ratio of about 28. Since the bias is positive for H/U ratios less than 5,it can be ignored for the array calculations involving undamaged containers. For the calculations involving the single container and a damaged array of containers, a value of-0.021 is conservative.

F.

Modelling of Geometry The geometry model used in this analysis of the BU-7 containeris illustrated in Figure 2 and the GEMER geometry input is tabulated in Tables 4 through 6.

The BU-7 was modelled with the 35.40 cm diameter,70.2 cm high inner containment vossel filled with UO pellets and water to the appropriate 2

height. The pellet height in the inner conta ner was determined by calculating the volume necessary to accommodate a given mass of pellets with a cpecified pitch and diameter. Since theinner containerand liner radii are fixed, this volume corresponds to some pellet array height. Note that due to a difference between the minimumliner height (26 inches or 66.04 cm) and the height of the innercontainment vessel (27.6 inches or 70.2 cm), a 4.16 cm gap exists. This gap in height is conservatively modelled by aligning the liner against the top of the inner drum, so that the UO and water mixture is not surrounded 2

by boron in the bottom of the vessel.

The UO2 pellets are modelled as columns (or rods of UO ) laying within the inner containment 2

vessel, oriented with their axes perpendicular to the axis of the BU-7. The orientation of the pellets makes no significant difference in multiplication; the pellets were modelled in this fashion to take full advantage of the geometry features available in the GEMER code. Note that the pellets are explicitly modelled. This is the key difference between the models of UO2 Powder / water mixtures and pellets. The heterogeneous case modelled here will be shown to be more reactive. Due to heterogeneous effects, the most reactive pellet size (diameter) must be considered.

The height is the total height of the water / fuel array of pellets in the inner containment vessel.

This height is related to the average density of material and the total amount of UO in the containment 2

vessel. The height may be calculated as:

h,,,,, - h ;,,, gave (1 - wrfrl/20) a rj,,,

Mass (UO ) -

2 i

f venct Height =

  • +

h,, - h,,,

i ii Gave (1 - wtfrgf2a) n q,,

vessel

~

~

The heights were determined by dividing the applicable UO mass (eg.,30.0 kg UO at 4.1%

2 2

enrichment less the amount of mixture in the region which mcy not surrounded by the liner) by the g product of the average UO component density for the mixture and the inne'r containment vessel's base 2

b September 9,1993 [ Rev.1, dated 11/29/93 ]

Page 7of23

- /"'

2 2

^

area (equal to a x 17.70 cm ) as shown above. These heights are shown in Tables 4A-C and 5A-C as referenced from the base of the inner containment vessel, whereas the model has as its reference the 1,

center of the BU-7 inner containment vessel (a constant difference of 35.1 cm).

l

. The Boral liner is modelled as having a minimum thickness and maximum outer radius (i.e., the r

liner is treated as if it were flush against the wall of the inner containment vessel). This treatment maximizes the outerradiusof the UO2 Pellet array. While this modelling results in the maximum mass of liner material in the BU-7, the effect of the maximizing the Boral mass is relativ'ely small in i

comparison with the impact of the geometric buckling. Maximizing the radius of the liner is a j

conservative treatment in the calculations.

For the case of Infinite Arrays of Normal Containers, the model in Figure 2 is placed into a triangular array and the array is spatially reflected on all six sides with varying amounts ofinterspersed l

water in the phenolie resin (Regions 2,11,13,23 and 27 in Table 4) and in the regions outside of the outer -

l container.

For the accident case of the Arrays of Damaged Containers, the array was modelled as an 9 x 7 x 4 j

triangular pitch array of BU-7 containers tightly reflected on all six sides by at least 30 cm of 1

water. The 9 x 7 x 4 triangular array is the one having a minimum of at least 250 units (it has 252 units) whose dimension is closest to a cube and therefore which has the minimum geometrical buckling-l (maximum neutron multiplication). Each BU-7 was modelled as in Figure 2 and the interspersed water was again added to the phenolic resin insulation (Regions 2,11,13,23 and 27 in Table 5).

(

For the Single Container case, the BU-7's outer 55 gallon drum is tightly reflected on all 6 sides by at least 30 cm of full density water and water was assumed to leak into the innercontainment vessel to

-l the extent of optimum moderation within the container. Full density water is also added to the phenolic

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resin (Regions 2,11,13,23 and 27 in Table 6) and in the regions outside of the outer container.

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September 9,1993 l Rev.1, dated 1]I29/93 J Page 8 of 23 G

17.70 28.57 z

5 45.3692 - - - - - -

c---------------------

- - - - - Interspersed Water 44.4167 - - - - - -

Carbon Steel 44.308 - - - - - -

PhenolicResin l 36.688 - - - - - -

Interspersed Water C

35.5763 - - - - - -

a 35.10 - - - - - -

r b

o n

Boral Liner S

t e

O

's a s s..vsa a s.. sea,

JJJJJJJJJJJJJJJJ, J J J. J. J. J. J. J,J. J J J,J. J. J. J.

jj j,

JJ Heterogeneous J,

1 J J * * * * *2 + H2O region J.

JJ UO ********J-

-30.94- - - - - - - JJJJJJJJJJJJJJJJth, 1

JJJJJJJJJJJJJJJJ*b,

-35.10 - - - - - -

carbon steel

-35.2087 - - - - - -

Phenolic Resin

-42.8287 - - - - - -

l

-42.9374 - - - - - -

Carbon Steci Interspersed Water

-44.8424 O

17.808 23.495 28.684 17.363 Dimensions in cm.

Ol Figure 2 GEMER Geometry Model for BU-7 Contamer i

September 9,1993 ( Rev.1, dated 11/29/93 ]

i Page 9 af 23 Table 4 GEMER Geometry Model for Infinite Arrays of Containers ~

I

-1.0

-1.0

-1.0

-1.0

-1.0

-1.0 BOX TYPE 1

/* LOWER PORTION OF BU-7 1

CYLINDER 3

17.808

-35.10 -35.2087 16*0.5 i

2 CYLINDER 5

28,575

-35.10 -42.8287 16*0.5 3

CYLINDER 3

28.5755

-35.10 -42.9374 16*0.5 4

CYLINDER 2

28 576

-35.10 -44 8424 16*0.5 5

CYLINDER 3

28.684

-35.10 -44.8424 16*0.5.

BOX TYPE 2

/* SINGLE BU-7

[

6 CUBOID 4

59.2

-59.2 59.2

-59.2 75.85

-75.33 16*0.5

-)

BOX TYPE 3 /* UPPER PORTION OF BU-7 7

CYLINDER 4

17.364 35.10 height 16*0.5 8

CYLINDER 3

17.429 35.10 height 16*0.5 9

CYLINDER 6

17.632 35.10 height 16*0.5 10 CYLINDER 3

17.808 35.10 height 16*0.5 11 CYLINDER 5

23.495 35.5763 height 16*0.5 12 CYLINDER 2

23.4955 36.688 height 16*0.5 13 CYLINDER 5

28.575 44.308 height 16*0.5 14 CYLINDER 3

28.5755 44.4167 height 16*0.5 15 CYLINDER 2

28.576 45.3692 height 16*0.5 16 CYLINDER 3

28.684 45.3692 height 16*0.5 BOX TYPE 4 /* FUEL CYLINDER CELL-WATER-TO-FUEL = 12.00 i

17 YCYLINCER 1

0.0952 17.70 -17.70 16*0.5 18 CUBOID 4

0.3040 -0.3040 17.70

-17.70 0.3040 -0.3040 16*0.5

'l 80X TYPE 5 /* INTERMEDIATE DISK OF FUEL CYLINDERS

(

O 19 CYLINDER 4

17.364 pitch 0.0 16*0.5 20 CYLINDER 3

17.429 pitch 0.0 16*0.5 21 CYLINDER 6

17.632 pitch 0.0 16*0.5 I

22 CYLINDER 3

17.808 pitch 0 0 16*0.5 23 CYLINDER 5

28.575 pitch 0.0 16*0.5 24 CYLINDER 3

28.684 pitch 0.0 16*0.5 l

BOX TYPE 6 /* INTERMEDIATE DISK OF FUEL CYLINDERS-BOTTOM, NO BORAL j

25 CYLINDER 4

17.700 pitch 0.0 16*0.5

{

26 CYLINDER 3

17.808 pitch 0.0 16*0.5 27 CYLINDER 5

28.575 pitch 0.0 16*0.5 j

28 CYLINDER 3

28.684 pitch 0.0 16*0.5 BOX TYPE 7 /* PROBLEM BOX FOR TRIANGULAR ARRAY - ONE LAYER DEEP 29 CUBOID 2.215.15

-215.15 227.7 -227.7 45.3692 -44.8424 16*0.5 30 CORE O 215.15

-215.15 227.7 -227.7 45.3692 -44.8424 16*0.5 7

'l 1 1 11 1 1 11 1

{

BEGIN COMPLEX

/* PLACE PINS INTO FLAT DISK COMPLEX 5 4

-17.70 0.0 0.3040 59 1 1 0.6080 0.0 00 /* WITH LINER' COMPLEX 6 4

-17.70 0.0 0.3040 59 1 1 0.6080 0.0 0.0 /* NO LINER

/* PLACE BOTTOM, DISKS AND TOP PORTIONS INTO BU-7 COMPLEX 2 1 0.0 0.0 0.0 1 1 1 0.0 0.0 0.0 COMPLEX 2 6 0.0 0.0 -35.10 117 0.0 0.0 0.6081

/* NO LINER 4

COMPLEX 2 5 0.0 0.0 -30.8433 11 34 0.0 0.0 0.6081

/* WITH LINER COMPLEX 2 3 0.0 0.0 0.0 11 1 0.0 0.0 0.0 0

September 9,1993 [ Rev.1, dated 11/29193 ]

Page 10 of 23 Table 4 (cont'd)

GEMER Geometry Model for Infinite Arrays of Containers

/* PLACE BU-7S INTO PRCBLEM BOX ONE HALF AT A TIME COMPLEX 7 2

-186.465 -199.015 0.0 7 51 57.37 99.50 0.0 COMPLEX 7 2

-157.78

-149.266 0.0 7 4 1 57.37 99.50

0.0 Materials

1 UO; + H O 2

2 Interspersed Water 3

Carbon Steci 4

Water Reflector (Full Density Water) 5 Phenolic Resin (Minimum Density) and Interspersed Water 6

Boral(75% Baron density)

Note: Region Numbers I through 30 noted on the left are for information only and are not part of geometry input.

Nx, Nzl, Nz2 arc integers such that: Nx 2 2x17.70/ pitch; Nzi=(hmner-htmer)/ pitch: Nz2 = (remaining height)/ pitch

  • Determined from height of fuel mixture. Sec Tabics 7A-C and 8A-C.

O O\\

i September 9,1993 [ Rev. I, dated 11/29/93 J Page 11 of 23 Table 5.

GEMER Geometry Model for 9

  • 7 a 4 Triangular Accident Array of Containers i

l BOX TYPE 1 /* LOWER PORTION OF BU-7 1

CYLINDER 3

17.808

-35.10 -35.2087 16*0.5 2

CYLINDER 5

28.575

-35.10 -42.8287 16*0.5 3

CYLINDER 3

28.5755

-35.10 -42.9374 16*0.5 4

CYLINDER 2

28.576

-35.10 -44.8424 16*0.5 5

CYLINDER 3

28.684

-35.10 -44.8424 16*0.5 l

BOX TYPE 2

/* SINGLE BU-7 6

CUBOID 4

59.2

-59.2 59.2

-59.2 75.85

-75.33 16*0.5 BOX TYPE 3 /* UPPER PORTION OF BU-7 7

CYLINDER 4

17.364 35.10 height 16*0.5 8

CYLINDER 3

17.429 35.10 height 16*0.5 9

CYLI*1 DER 6

17.632 35.10 height 16*0.5 10 CYLI4TDER 3

17.808 35.10 height 16*0.5 11 CYLItDER 5

23.495 35.5763 height 16*0.5 12 CYL.NDER 2

23.4955 36.688 height 16*0.5 13 CYLINDER 5

28.575 44.308 height 16*0.5 14 CYLINDER 3

28.5755 44.4167 height 16*0.5 15 CYLINDER 2

28.576 45.3602 height 16*0.5 16 CYLINDER 3

28.684 45.3692 height 16*0.5 l

BOX TYPE 4 /* FUEL CYLINDER CELL-WATER-TO-FUEL = 12.00

(

17 YCYLINDER 1

0.0952 17.70 -17.70 16*0.5 18 CUBOID 4

0.3040 -0.3040 17.70

-17.70 0.3040 -0.3040 16*0.5 l

BOX TYPE 5 /* INTERMEDIATE DISK OF FUEL CYLINDERS 19 CYLINDER 4

17.364 pitch 0.0 16*0 5 20 CYLINDER 3

17.429 pitch 0.0 16*0.5 21 CYLINDER 6

17.632 pitch 0.0 16*0.5 22 CYLINDER 3

17.808 pitch 0.0 16*0.5 23 CYLINDER 5

28.575 pitch O'.0 16*0.5 24 CYLINDER 3

28.684 pitch 0.0 16*0.5 BOX TYPE 6 /* INTERMEDIATE DISK OF FUEL CYLINDERS-BOTTOM, NO BORAL 25 CYLINDER 4

17.700 pitch 0.0 16*0 5 26 CYLINDER 3

17.808 pitch 0.0 16*0.5 27 CYLINDER 5

28.575 pitch 0.0 16*0.5 l

28 CYLINDER 3

28.684 pitch 0.0 16*0.5 l

BOX TYPE 7 /* PROBLEM BOX FOR TRIANGULAR ARRAY - ONE LAYER DEEP 29 CUBOID 2 215.15

-215.15 227.7 -227.7 45.3692 -44.8424 16*0.5 30 CORE 0 215.15

-215.15 227.7 -227.7 181.4768 -179.3696 16*0.5 31 CUBOID 4 246.15

-246.15 258.7 -258.7 212.4768 -210.3696 16*0.5 7

1 11 111 1 11 1 BEGIN COMPLEX

/* PLACE PINS INTO FLAT DISK COMPLEX 5 4

-17.70 0.0 0.3040 59 1 1 0.6080 0.0 0.0

/* WITH LINER COMPLEX 6 4

-17.70 0.0 0.3040 59 1 1 0.6080 0.0 0.0 /* NO LINER'

/* PLACE BOTTOM, DISKS AND TOP PORTIONS INTO BU-7 COMPLEX 2 1

0.0 0.0 0.0 1 1 1 0.0 0.0 0.0 COMPLEX 2 6

0.0 0.0 -35.10 117 0.0 0.0 0.6081

/* NO LINER i

COMPLEX 2 5 0.0 0.0 -30.8433 11 34 0.0 0.0 0.6081

/* WITH LINER

()

COMPLEX 2 3 0.0 0.0 0.0 11 1 0.0 0.0 0.0 l

m

~

September 9,1993 [ Rev.1, dated 1ll29/93 ]

Page 12 of 23 Table 5 (cont'd)

GEMER Geometry Model for 9

  • 7
  • 4 Triangular Accident Arrays of Containers

/* PLACE SU-7S INTO PROBLEM BOX ONE HALF AT A TIME COMPLEX 7 2

-186.465 -199.015 0.0 7 51 57.37 99.50 0.0 COMPLEX 7 2

-157.78

-149.266 0.0 74 1 57.37 99.50 0.0 UO + H O Materials:

1 2

2 2

Interspersed Water 3

Carbon Steel 4

Water Reflector (Full Density Water) 5 Phenolic Resin (Minimum Density) and Interspersed Water 6

Boral(75% Boron density)

Note: Region Numbers I through 31 noted on the left are for infonnation only and are not part of geometry input.

Nx, Nzl, Nz2 are integers such that: Nx 2 2x17.70/ pitch; Nzi=(h nner-h ner)/ pitch; Nz2 = (remaining height)/ pitch i

ii

  • Determined from height of fuel mixture. See Tables 7A-C and 8A-C.

O O

' September 9,1993 l Rev.1, dated 11/29/93 ]

Page 13 of 23 0:

1 Buie 6 cemen ceomei,7 mooei rO,siegie co iBi.e, BOX TYPE 1

/* LOWER PORTION OF BU-7 1

CYLINDER 3

17.808

-35.10 -35.2087 16*U.5 2

CYLINDER 5

28.575

-35.10 -42.8287 16*0.5 3

CYLINDER 3

28.5755

-35.10 -42.9374 16*0.5 4

CYLINDER 2

28.576

-35.10 -44.8424 16*0.5

-i 5

CYLINDER 3

28.684

-35.10 -44.8424 16*0.5 BOX TYPE 2

/* SINGLE BU-7 6

CUBOID 4

59.2

-59.2 59.2

-59.2 75.85

-75.33 16*0.5 BOX TYPE 3 /* UPPER PORTION OF BU-7 7

CYLINDER 4

17.364 35.10 height 16*0.5 8

CYLINDER 3

17.429 35.10 height 16*0.5 9

CYLINDER 6

17.632 35.10 height 16*0.5 10 CYLINDER 3

17.808 35.10 height 16*0.5 11 CYLINDER 5

23.495 35.5763 height 16*0.5 12 CYLINDER 2

23.4955 36.688 height 16*0.5 13 CYLINDER 5

28.575 44.308 height 16*0.5 14 CYLINDER 3

28.5755 44.4167 height-16*0.5 15 CYLINDER 2

28.576 45.3692 height 16*0.5 16 CYLINDER 3

28.684 45.3692 height 16*0.5 BOX TYPE 4 /* FUEL CYLINDER CELL-WATER-TO-FUEL = 12.00 17 YCYLINDER 1

0.0952 17.70 -17.70 16*0.5 18 CUBOID 4

0.3040 -0.3040 17.70

-17.70 0.3040 -0.3040 16*0.5 BOX TYPE 5 /* INTERMEDIATE DISK OF FUEL CYLINDERS 19 CYLINDER 4

17.364 pitch 0.0 16*0.5 20 CYLINDER 3

17.429 pitch 0.0 16*0.5 21 CYLINDER 6

17.632 pitch 0.0 1G*0.5

}

22 CYLINDER 3

17.808 pitch 0.0 16*0.5 23 CYLINDER 5

28.575 pitch 0.0 16*0.5 24 CYLINDER 3

28.684 pitch 0.0 16*0.5 BOX TYPE 6 /* INTERMEDIATE DISK OF FUEL CYLINDERS-BOTTOM, NO BORAL 25 CYLINDER 4

17.700 pitch 0.0 16*0.5 26 CYLINDER 3

17.808 pitch 0.0 16*0.5 27 CYLINDER 5

28.575 pitch 0.0 16*0.5 28 CYLINDER 3

28.684 pitch 0.0 16*0.5 2 1 1 1 1 11 111 1

BEGIN COMPLEX

/* PLACE PINS INTO FLAT DISK COMPLEX 5 4

-17.70 0.0 0.3040 NX 1 1 pitch 0.0 0.0

/* WITH LINER COMPLEX 6 4

-17.70 0.0 0.3040 NX 1 1 pitch 0.0 0.0 /* NO LINER

/* PLACE BOTTOM, DISKS AND TOP PORTIONS INTO BU-7 COMPLEX 2 1 0.0 0.0 0.0 1 11 0.0 0.0 0.0 COMPLEX 2 6 0.0 0.0 -35.10 1 1 NZ1 0.0 0.0 pitch /* NO LINER COMPLEX 2 5 0.0 0.0 -30.8433 1 1 NZ2 0.0 0.0 pitch /* WITH LINER COMPLEX 2 3

0.0 0.0 0.0 111 0.0 0.0

0.0 Materials

1 UO + H 0 2

2 Interspersed Water 3

Cartxm Steel 4

' Vater Reflector (Full Density Water) 5

?henolic Resin (Minimum Density) and Full Density Water 6

Doral(75% Boron density)

Note: Region Numbers I through 28 noted on the left are for information only and are not part of geometry input.

r Nx. Nz1, Nz2 are integers such that Nx a 2x17.70/ pitch: Nzl=(hmner-h mer)/ pitch; Nz2 = (remaining height)/piteh i

  • Determined from height of fuel mixture. See Tabics 7A-C and 8A-C.

l l

September 9,1993 [ Rev.1, dated 11/29!93 J Page l4 of 23 Table 7A.

Fuel / Water Heights and Pitches for 30.0 kg Theoretical Density UO2 Particles Surrounded by WTOF II 0 2

Mass:

30 kg Pellet Radius:

0.0635 cm WTOF WTFR pitch height 1

0.08 0.1590 5.612 2

0.15 0.1940 8.503 3

0.21 0.2250 11.393 4

0.27 0.2510 14.283 5

0.31 0.2750 17.168 6

0.35 0.2970 20.056 7

0.39 0.3180 22.946 8

0.42 0.3370 25.839 9

0.45 0.3550 28.734 10 0.48 0.3730 31.616 11 0.50 0.3890 34.513 12 0.52 0.4050 37.397 13 0.54 0.4210 40.296 14 0.56 0.4350 43.181 O

Table 711.

Fuel / Water 11 eights and Pitches for 30.0 kg Theoretical Density UO2 Particles Surrounded by WI'OF II 0 2

Mass:

30 kg Pellet Radius:

0.09525 cm WTOF WTFR pitch height 1

0.08 0.2380 5.612 2

0.15 0.2920 8.499 3

0.21 0.3370 11.389 4

0.27 0.3770 14.273 5

0.31 0.4130 17.162 6

0.35 0.4460 20.056 7

0.39 0.4770 22.952 8

0.42 0.5060 25.832 9

0.45 0.5330 28.734 10 0.48 0.5590 31.616 11 0.50 0.5840 34.498 12 0.52 0.6080 37.404 13 0.54 0.6310 40.288 g

14 0.56 0.6530 43.172

September 9,1993 [ Rev.1, dated 11/29/93 J Page l5 af23 1

l Table 7C.

Fuel / Water IIcights and Pitches for 30.0 kg Theoretical Density UO2 Particles Surrounded by WTOF 1I 0 i

2 l

i Mass:

30 kg Pellet Radius:

0.127 cm WTOF WTFR pitch height 1

0.08 0.3180 5.606 2

0.15 0.3890 8.503 3

0.21 0.4500 11.384 4

0.27 0.5030 14.273 5

0.31 0.5510 17.168 6

0.35 0.5950 20.067 7

0.39 0.6360 22.946

)

8 0.42 0.6750 25.826 9

0.45 0.7110' 28.734 10 0.48 0.7460 31.616 11 0.50 0.7790 34.498 12 0.52 0.8110 37.380 13 0.54 0.8420 40.296 I

14 0.56 0.8710 43.181

($)

Table 8A.

Fuel / Water IIeights and Pitches for 50.0 kg Theoretical Density UO2 Particles Surrounded by WTOF 110 2

Mass:

50 kg Pellet Radius:

0.09525 cm 1

WTOF WTFR pitch height (cm)

(cm)

]

1 0.08 0.2380 9.466 2

0.15 0.2920 14.279 3

0.21 0.3370 19.096 4

0.27 0.3770 23.907 5

0.31 0.4130 28.723 i

6 0.35 0.4460 33.543 7

0.39 0.4770 38.366 8

0.42 0.5060 43.173 9

0.45 0.5330 48.001 10 0.48 0.5590 52.810 11 0.50 0.5840 57.619 12 0.52 0.6080 62.452 13 0.54 0.6310 67.262 14 0.56 0.6530 72.073

September 9,1993 [ Rev.1, dated 11/29/93 J Page 16 of 23 Table 8B.

FuelAVater lleights and Pitches for 50.0 kg Theoretical Density UO2 Particles Surrounded by WTOF II 0 2

Mass:

50 kg Pellet Radius:

0.127 cm WTOF WTFR pitch height (cm)

(cm)

I 1

0.08 0.3180 9.459 i

2 0.15 0.3890 14.283 3

0.21 0.4500 19.091 4

0.27 0.5030 23.907 5

0.31 0.5510 28.728 6

0.35 0.5950 33.554 7

0.39 0.6360 38.360 8

0.42 0.6750 43.166 9

0.45 0.7110 48.001 10 0.48 0.7460 52.810 11 0.50 0.7790 57.619 12 0.52 0.8110 62.428 13 0.54 0.8420 67.270 g

14 0.56 0.8710 72.082 Table 8C.

FuelAVater IIeights and Pitches for 50.0 kg Theoretical Density UO2 Particles Surrounded by WTOF 110 2

Mass:

50 kg Pellet Radius:

0.15875 cm WTOF WTFR pitch height (cm)

(cm) 1 0.08 0.3970 9.462 2

0.15 0.4870 14.279 3

0.21 0.5620 19.091 4

0.27 0.6290 23.912 5

0.31 0.6890 28.712 6

0.35 0.7440 33.543 7

0.39 0.7950 38.348 8

0.42 0.8440 43.166 9

0.45 0.8890 47.994 10 0.48 0.9330 52.802 11 0.50 0.9740 57.611 12 0.52 1.0140 62.420 g

13 0.34 1.0520 6'i.270 14 0.56 1.0890 72.062

1 September 9,1993 l Rev.1, dated 11/29193 J Page 17 of 23 III.

CRITICALITY SAFETY ANALYSIS RESULTS The following sections summarize the results of the GEMER calculations performed for the fuel mixtures and geometry models described in Section II. The results are all suberitical with the most limi ing case being the accident condition array with zero interspersed water.

t A.

Triangular Array of Damaged Containers As noted previously, the most reactive condition for the Fissile Class 1 BU-7 container assuming failure of containment by the product pails (either 3 or 5 gallon cans) and loss of moderation control, is the 9 x 7 x 4 triangular pitch array of damaged containers. This is shown by the calculations summarized in the following tables. Note that in Tables 9A and 10A the results are complete in that the values are given as a function of water-to-fuel ratio and pellet diameter. The maximum kerr + 20 for each case is highlighted in boldface. This format verifies that the case for optimum moderation is shown and indicates consistency with other results within the analysis and with prior analyses.

Earlier analyses have demonstrated that the optimum amount of interspersed water for the accident case is 0.0, just as it is for the array of undamaged containers. This is an indication that components in the Boralliner, phenolic resin and steel are more etTective as absorbers when the neutrons are slowed down outside of the container as long as some moderator exists in the vicinity of the liner. Tables 9B and 10B support this assenion; here the weight fraction ofinterspersed moderator has been varied.

Since the maximum kerr + 20 value is less than 0.9290 (the limit of suberiticality including the l calculational bias), the BU-7 with the specified masses and enrichments U(E)O per container meets the 2

applicable requirements for a Fissile Class 1 package.

&ptember 9,1993 [ Rev. I, dated 11/29/93 }

Page 18 of 23 Table 9A. GENIER Results for an 9x7x4 Triangular Array of Damaged ITU-7s h

i 50 kg U(3.06)O Pellets 2

W/F Pellet Dia. (in) kerr a

kett + 20 0.075 0.8766 0.0026 0.8818 I

5 O.100 0.8748 0.0028 0.8804 O.125 0.8716 0.0030 0.8776 0.075 0.8900 0.0027 0.8954 1

7 0.100 0.8923 0.0024 0.8971 I

0.125 0.8901 0.0026 0.8954 0.075 0.8825 0.0028 0.8881 9

0.100 0.8781 0.0024 0.8829 l

0.125 0.8781 0.0025 0.8831 t

Table 911. GEMER Results for a Triangular Array of Damaged IlU-7s 50.0 kg U(3.06)O Pellets (100 mit Diameter) W/F = 7 2

WFInterspersed H O kerr io kerr + 20 g

2 0.00 0.8923 0.0024 0.8971 0.05 0.8794 0.0025 0.8844 0.10 0.8682 0.0025 0.8732 0.25 0.8580 0.0024 0.8628 0.50 0.8440 0.0025 0.8490 0.75 0.8470 0.0029 0.8528 1.00 0.8491 0.0029 0.8549 i Neutron multiplication factors based on the fission particle flux method.

O

September 9,1993 l Rev.1, dated 11/29/93 ]

Page 19 of 23 O

t GEMER Results for an 9x7x4 Triangular Array of Damaged BU-7s Table 10A.

30 kg U(4.10)O Pellets 2

W/F Pellet Dia. (in) kerr io kerr + 2a 0.050 0.8697 0.0029 0.8755 8

0.075 0.8722 0.0028 0.8778 0.100 0.8720 0.0029 0.8779 0.050 0.8762 0.0027 0.8816 10 0.075 0.8763 0.0027 0.8817 O.100 0.8696 0.0025 0.8747 0.050 0.8765 0.0026 0.8817 12 0.075 0.8696 0.0023 0.87412 0.100 0.8657 0.0028 0.8713 i

GEMER Results for a Triangular Array of Damaged BU-7s Table 10B.

30.0 kg U(4.10)O Pellets (75 mil Diameter) W/F = 10 2

WFInterspersed H O kerr a

kerr + 2a 2

0.00 0.8763 0.0027 0.8817 0.05 0.8693 0.0028 0.8749 t

0.10 0.8584 0.0028 0.8640 O.25 0.8481 0.0026 0.8533 0.50 0.8484 0.0025 0.8534 0.75 0.8488 0.0027 0.8542 i

1.00 0.8481 0.0028 0.8537 i Neutron multiplication factors based on the fission particle flux method.

B.

Single Containers Tables 11 A and B show k-effective values for the single container cases at various water-to-fuel ratios. The most reactive pellet diameter from the accident array (found in Section III. A)is used for the single container analysis. The sets of tables correspond to the limiting mass / enrichment pairs determined also from the accident array analysis. Allof the results are subcritical. Theresults forthe largest k-effective value (corresponding to optimum moderation) again appear in boldface. Optimum moderation occurs at a slightly lower water-to-fuel ratio for each respective case than in the accident array. This is consistent, since the single container is practically a subset of the accident condition array with the exception that the single container is tightly reflected, therefore owering the amount of intemal Q

moderator required for optimum moderation. As expected, the magnitudes of k-effective for the single container cases are correspondingly lower than in the accident array.

September 9,1993 [ Rev.1, dated 11/29193 J Page 20 of 23 i

GEMER Results for Single BU-7 Containers Table ll A.

50.0 kg U(3.06)O Pellets (100 mil Diameter) 2 W/F kerr io kerf + 20 5

0.8470 0.0026 0.8522 6

0.8546 0.0028 0.8602 7

0.8441 0.0025 0.8491 9

0.8226 0.0026 0.8278 t

Table 11B. GEMER Results for Single BU-7 Containers 30.0 kg U(4.10)O Pellets (75 mil Diameter) 2 W/F kerr to kerr + 2a 7

0.8491 0.0029 0.8519 8

0.8514 0.0031 0.8576 9

0.8464 0.0028 0.8520 10 0.8458 0.0029 0.8516

~

l1 0.8415 0.0025 0.8465 12 0.8353 0.0025 0.8403 i Neutron multiplication factors based on the fission panicle flux method.

C.

Infinite Triangular Array of Undamaged Containers i

The analysis of the infinite array of undamaged containers uses the optimum pellet diameter results obtained in Section III.A. For the 3.06% enriched case, the most reactive pellet diameter in the BU-7 configuration is 0.100". For the 4.1% enriched case, the most reactive pellet diameter in the BU-7 configuration is 0.075". The results are shown in Table 12A and B for both enrichments as a function of i

interspersed water density when the internal moderation is given by a water-to-fuel ratio of 1.0. As stated above, a water-to-fuel ratio of 1 is the equivalent of 8.6 wt% water for theoretical density UO.

2 The results in Table 12 show a maximum k. ofless than 0.65 for the infinite uiangular array of(normal)

BU-7 containers in both enrichment cases. This value is much lower than the single container case because the UO pellet configuration with only 8.4% water (WTOF=1)is significantly undermoderated.

2 l Again, this is for the highly conservative and bounding case of 30 kg U(4.1%)O and a water-to-fuel 2

ratio of 1.0 rather than the amount of moderator to which the containeris limited. Since the contents is g normally less than an H/U ratio of 1.6, which corresponds to a water content of 5.0 wt%, there is ample margin in the current analysis to allow additional moderators in the container, at least up to the extent i

that they do not exceed the amount which has been analyzed here. This allows for the stated values in the Introduction that "the contents must be limited so that the total mass of hydrogenous moderator in the l inner containment vessel is no greater than 5.3% of the weight of the uranium oxide, whichever is g smaller".

i

September 9,1993 l Rev.1, dated 11/29/93 i Page 21 of 23 i

GEN 1ER Results for an Infinite Triangular Array of BU-7 Containers Table 12A.

50.0 kg U(3.06)O Pellets (100 mil Diameter) 2 WFInterspersed H O kerr io keI;+ 20 2

0.00 0.6108 0.0028 0.6154 0.05 0.6241 0.0031 0.63i)3 l

0.10 0.6319 0.0027 0.074 0.25 0.6223 0.0028 0.6279 0.50 0.6037 0.0028 0.6093 0.75 0.6022 0.0026 0.6074 1.00 0.6044 0.0030 0.6104 i

Table 12B.

GEh1ER Results for an Infinite Triangular Array of BU-7 Containers 30.0 kg U(4.10)O Pellets (75 mil Diameter) 2 WFInterspersed H O kerr a

kerr + 20 2

0.00 0.5217 0.0027 0.5271 0.05 0.5445 0.0027 0.5499 0.10 0.5652 0.0031 0.5714 0.50 0.5556 0.0031 0.5619 1(X) 0.5531 0.0032 0.5595 t Neutron multiplication factors based on the fission particle flux method.

September 9,1993 l Rev.1, dated 11/29/93 J Page 22 of 23 D.

Presence of Plastic Bags or Other Moderating Materials Around the UO (or UO2 2

Containers)

It is sometimes desirable to ship UO enclosed in plastic bags in the BU-7 container. The bags may be 2

around the fuel either inside or outside of the three or five gallon pails. For the BU-7 container with the contents and assumptions described in the previous sections of this report and the safety analysis of Reference 6, the presence of these bags is acceptable. The demonstration of this is given in Reference 6 for the case of 5.0% enriched material. Since the 5.0% enrichment case is still the limiting (most reactive) of the accident arrays, thejustiGcation given in that report is unaltered by the present analysis.

Also, since the contents of the BU-7 container with UO2 pellets has explicitly modeled heterogeneous fuel regions, the geometry regions bordering the inner containment vessel are water regions. Since the water content is optimum for accident cases and highly conservative for undamaged arrays, any additional moderators such as the plastic bag, are already accounted for by the model as it has been constructed and analyzed.

IV.

SUMMARY

AND CONCLUSION This analysis has demonstrated that the BU-7 shipping container meets the requirements of 10CFR71.55 and 57 for a Fissile Class I package with contents specified as follows:

Iype and Form Uranium oxide pellets / powder enriched to not more than 4.1 w/o in the U-235 isotope. The maximum I m/U atomic ratio shall not exceed 1.6. The content H

oderator in the inner containment vessel is no greater than 5.3% of the weight of the uranium oxide.

Maximum Quantity per Package The bounds for the three sigma enrichment limits are presented below along with the corresponding nominal enrichments. The maximum contents per package shall be as specified below (Table 19).

l UO Pellet / Powder Mass Limits Versus Enrichment Table 11.

2 Maximum UO Mass Loading Nominal Enrichment Maximum Possible 2

(%)

Emichment (%)

(kg) 3.00 3.06 50.0 4.00 4.10 30.0 O

September 9,1993 ( Rev.1, dated 11/29/93 J Page 23 of23 V.

REFERENCES l

1.

U S. Nuclear Regulatory Commission " Certificate of Compliance for Radioactive Materials Packages," Certificate Number 9019, Revision 18.

2. " Packaging and Transportation of Radioactive Material," United States Nuclear Regulatory Commission Rules and Regulations, Title 10, Chapter 1, Part 71, Code of Federal Regulations, 11/30/88.
3. " Test Report for Model BU-7 Bulk Uranium Shipping Container," 4/25/80.

4.

" Criticality Analysis of BU-7 Container for Theoretical Density Pellets," 1/24/86.

5. " Criticality Safety Analysis of BU-7 Shipping Container for UO Powder," 3/6/80.

2

6. " Criticality Safety Analysis for BU-7 Shipping Container for 4.0% to 5.0% Enriched UO Powder with Failure of Containment and Moderation Control," 6/1/92.

2 7.

"The General Electric Model BU-7 Uranium Shipping Container - Criticality Safety Analysis," 2/74.

8.

GEMER/ MONTE CARLO, User's Manual,9/15/81.

9. " Criticality Safety Analysis for BU-7 Shipping Container For Enrichments Below 5.0%

UO Powder with Failure of Containment and Moderation Contml",8/31/93.

2 O

t t

O

-

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