ML20003A055

Safety Evaluation Supporting Proposed Change 27 to Tech Specs

ML20003A055
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	12/29/1971
From:	James Shea US ATOMIC ENERGY COMMISSION (AEC)
To:
References
NUDOCS 8101290351
Download: ML20003A055 (5)

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UNITED STATES

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D..L. Ziemann, Chief, ORB #2, DRL BIG ROCK POINT - TYPE "J-2" UO -Pu0 FUEL 2

2 Introduction I.

Consumers Power Company, by letter dated December 9,1971, proposed to insert two Type "J-2" UO -Pu02 fuel assemblies into the Big Rock 2

Point reactor core to replace two fuel assemblies to be removed during the scheduled February-March 1972 plant outage.

The. Type "J-2" UO -Pu02 2

f uel assembly contains 1.5 kilograms of plutonium distributed in 24 plutonium-bearing mixed oxide fuel rods arranged about the center of p

the fuel assembly in a 5 x 5 array (center rod does not contain plutonium Q

enriched fuel) and employs 50 mil cladding on the peripheral and other telected internal high power rods and a modified upper fuel rod tie plate design ~ to facilitate the remote disassembly of fuel rods.

In all other respects, except for the use of 35 grams of cobalt per foot E

of rod in the four cobalt rods per bundle instead of 70 grams of cobalt per f oot, the "J-2" fuel assembly is identical to the "J-1" fuel assembly.

(These loadings are used interchangeably in other Big

-Rock Point fuel bundles depending on cobalt demani.)

Description The "J-1" and "J-2" bundles accommodate four cobalt target rods and f our gado11nia-bearing fuel rods in the same relative positions (ref.

Dwg " Fuel Bundle Details Big Rock Point" Figure 5.7 Proposed Technical Specification change).

Eight tie rods and a central spacer capture rod also are used. With the exceptions noted, i.e., clad thickness and upper tie plate, all mechanical components are identical in the two designs, including spacers, lower tic plates, fuel rod assembly, i

fuel column length, the use of cold-pressed and sintered pellets and the basic 9 x 9 rod array with short dif f user at the inlet to improve flow distribution at the bundle entrance.

The 48 plutonium rods within the two fuel assemblies are enriched to 3.6 w/o plutonium thereby increasing the initial enriched plutonium in the Big Rock Point in accordance with two previously approved Technical Specification changes *,

by 3 kg to a total of 21.5 kg.

• Amendment No. 3 dated April 18, 1969 Change No. 19 dated February 20, 1970 j.

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Files DEC 2 S 197) 4 Evaluation

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Amendment No. 3 (dated April 118,1969) authorized Consumers Pouer Company.to possess 50 kg of plutocium in cixed oxide fuel rods for irradiation in the Big Rock Point core, and approved insertion of up to 32 fuel rods containing 1.3 to 1.5% plutonium enrichment, depending on pellet coring 'or' dishing, into two diagonal positions in. Iype E-G fuel assemblies to. replace 2.5% uranium enriched rods. We noted in our evaluation of the' proposal to insert 32 plutonium fuel rods con-taining a total of 1 kg of plutonium (Proposed Change No. 17 DRL Eval-uation dated April 18, 1969) that the total plutonium inventory of the i-Big Rock Point core was increased less than 4% at the beginning of.

that fuel cycle, ym Proposed Change No. 19 authorized irradiation of three fuel assemblies F ij d ~

containing plutonium fuel rods (designated as "EEI-UOandFebruary2b,Pu0" fuel).19h0, b~_.?

Memos to file dated February 18, 1970, that the three "EEI-UO -pug " fuel assemblies contained 17.5 kg total 2

2 of plutonium. When added to yhe plutonium in the 32 fuel rods inserted' 3..=

into the core,in May 1969, the total initial plutonium enrichment is 1~

18.5 kg.

The current proposal would increase the weight of plutonius '

in plutonium enriched fuel rods in the Big Rock Point reactor to 21.5 kg,

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43% 'of the amount that CPC is authorized to receive, possess and use in PuO -UO2 fuel rods in connection with operation of the Big Rock Point 2

g Nuclear Plant. We have determined that the 3.0 kg increase in the F

core plutonium inventory is modest when compared with the increase that

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acccmpanies extension of UO2 fuel life to 20,000 UND/HT where the

' initial fuel lifetime was 10,003 HWD/MI* and is therefore relatively unimportant with respect to potential increased plutonium inhalation hazard associated with fuel rod f ailure. We note that the "J-2" f uel is expected to remain in the core for 4 fuel cycles and is claimed to be mechanically capable of 25,900 ERD /HT average burnup co= pared with the expected 4 cycle operation for the "EEI-Puo -UO " fuel 2

2 with an average burnup of 20,000 MWD /MT.

6 The three approved type " eel-Puo2-UO " fuel assemblies each contain h

2 68 plutonium fuel rods with five different enrichments varying from p

1.6 to 9.0 w/o plutonium.

The CPC saf ety evaluation for these plutonium j

enriched fuel assemblies (dated December 22, 1969) revealed that the plutonium f uel density, reduced by about 10% compared with the standard UO fuel density, resulted in less heat storage capacity.

In combination 2

with the assumption that the prempt threshold of failure for non-homogeneous plutonium enriched fuel is 265 cals/gm (425 cals/gm for homo-fuel), the DBA reactivity excursion caused by a control geneous UO2 I"

• Ref. Conference 660308 - Commercial Fuels Conference, March 1-2, 1966, Figure 11 L'

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DEC 2 e 1971 rod drop of 0.021 delta k/k reactivity results in approximate 1'y 12 kg of fuel with enthalpies in excess of 265 cals/gm and a prompt energy

~ deposition in the coolant of 14 IMsec.

CPC has noted that information prs. Aously provided by them to support

! the proposal.for irradiation of three Type "EEI-Pu0 -UO " fuel assemblies 2

2 (Change No.19 and two supplements) can be applied to evaluate Type "J-2"

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fuel behavior during and following a DBA reactivity excursion.

Since

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t e total fissile content is 3.52 w/o for the "J-2" fuel assemblics in l.

contras t to 4.84 w/o for the "EEI-UO -Pu0 " fuel bundles as reported 2

2 by CPC on page 8 of the "J-2" proposal and theref ore is less reactive,-

we agree that a simple reactivity excursion analysis for the "J-2" fuel bundles based on the information previously submitted is con-o servative.

Thus, 3 kg of "J-1" plutonium, when related to 17.5 kg x_

of "EEI-Pu0 -UO " P utonium, omitting the corrections for non-fissile g{~

2 2

l plutonium isotopes, yields an. energy burst of 2.5 MWsec. Neglecting hj;.y plutonium depletion in the three " eel-Pu02-UO2" fuel assemblies currently Es

'being irradiated results in.a cumulative rele.se, if centermelt fuel

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bundles are inserted into the core. of 64 MWsec, a value previously E.

determined to be acceptable.

The margin f or rapid energy burst resulting

[L; from prompt energy deposition in water for fuel enthalpies in excess of 265 cals/gm is recognized to be appreciable if centermelt fuel is not simultaneously irradiated in the core, since the prompt release 4g=

for centermelt-fuel was calculated to be 47.5 FMsec, nearly 2.5 tLmes

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• greater than the prompt release from all of the 6nriched plutonium L

initially in the core, including that to be inserted in February-March F

1972. We have concluded, on this basis, that the consequences of the DEA reactivity excursion are acceptable, and considering depletion of the fissile plutonium enrichment in the three Type "EEI-Puo2-UO " fuel 2

assemblies currently being irradiated and the 32 low enrichment plutonium -

rods inserted near.ly two years ago, the total energy deposition due to a control rod drop accident may be less than the value calculated for the three unirradiated Type " eel-pug -UO " fuel assemblies when 2

2 initially placed in the,cora-l I

The use of increased cladding thickness on peripheral and selected internal high power fuel rods, i.e., 50 mils instead of 40 mils, improves E

the fuel rod integrity but increases the thermal flux slightly as a result of the small increase in water to fuel ratio in the vicinity of the thick clad rods.

The increase in control rod reactivity worth is, however, negligible according to the CPC evaluation. We have concluded that the increased clad thickness improves fuel integrity witnout changing significantly the consequences of the DBAs.

Howes ar, we note that the bundle uses fuel rods with 5 different fuel compositions and a variety of fuel pellet density (dished ends, cored centers, fuel i

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Files DEC 2 91971 compaction).

Tne possibilities for fuel rod loading mixups during fabrication are increased further by the necessity to employ pellets

- with 2 different outside diameters. We believe that with proper.

quality controls. and frequent inspection tne tuo fuel assemblies can be fabricated in' accordance with the design requirements, but such a

. variety of fuel pellet combinations might be unacceptable for the fabrication of.large numbers of product line fuel as'amblies because of the high probability of fuel' loading errors.

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Twelve 4.2 w/o enriched UO2 rods in each of the two "J-2" fuel assemblies have been _ designated experimental rode because of small but carefully controlled variacions in the fuel rod fabrication.

The objectives of this ' program are to develop a fabrication process that results in the g,

lowest f abrication costs and a fuel product of superior performance without increasing the probability of accidents or changing the con-sequences of such accidents. We were informed during a telecon with CPC personnel on December 22, 1971, that the test pellets will be

=d approximately one half of the normal length, i.e., about 0.36' ins tead Rs of 0.72", to reduce the hour glass effect due to irradiation. The fuel rods normally are designed for 40,000 MWD /T without excessive clad strain due to clad fuel' interaction.

Providing a fuel-clad gap of 94 0.011 + 0.003 inch in the experimental rods in contrast to the nurmal "J-2" fuel rod gap of 0.011 1 0.002 inch causes negligible change since the planned. irradiation lifetime is 20,000 MWD /T and there is ample margin before fuel clad strain limits are reached.

The minimum rg clearance of 0.008 inch compared with the normal minimum of 0.009 inch,

f-is of no consequence for the planned irradiation period.

The possibility b

of eliminating autoclaving to reduce the possibilities of water entrap-ment will he explored by irradiation of 3 experimental rods in each bundle whi. have not been processed in the autoclave.

Two other rods vill be autoclaved at reduced steam pressure.

Normally the fuel pellets pass through a grinding and polishing operation I7 using a water slurry.

Elimination of this operation results in a small increase in the pellet diameter, but a potential source of water and resultant zircaloy hydriding is eliminated.

Some of the experimental fuel rods will employ fuel pellets that have not received the grinding-polishing operation. The effect on fuel reliability by the omission of this process will not be significant unless fuel irradiation is extended beyond the planned 20,000 HRD/T m'erage fuel depletion. We have con-bi; cluded that 12 "experinental" r Js within the limits described may be inserted in each of the "J-2" fuel assemblies with reasonable assurance that the hazards to the public will not be increased beyond those pre-viously evaluated and accepted.

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' Conclusion We have concluded that insertion of two Type "J-2" fuel assettblies into the Big-Roch Point core Giarch 1972) increases the enriched plutonium 7

within the core by 3 k',lograms to a total of 21.5 kilograms.

The total pg core plutonium inventory is not changed significantly, and prompt energy

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deposition in water following the DBA. reactivity excursion is less than

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2.5 MWsec, an insignificant amount 1 contrast to the 65 MWsec prompt energy deposition that can be tolerated without damage to the backup core spray system. -Fuel temperatures in the "J-2" fuel' assembly following f~

the loss of coolant flow accident are no greater than the values cal-il culated and found acceptable fcr the Type "EEI-Puo2-UO " fuel.

The 2

increased clad thickness for some of the Type "J-2" fuel rods, modifi-

-cations-to the upper tie plate to facilitate remote disassembly of the p(-

fuel rods, and twelve 4.2 w/o enriched UO2 experimental rods per assembly introduce no new safety considerations. The 3.65 w/o plutonium enrieb- '

1.

- ment is within-the range of fuel red enricLeents currently being irraduted 7=3 in the Big Rock Point core and from the materials behavior standpoint is 1.g...,

acceptable. The fuel temperature, following loss-of-coolant acci(ents,-

";g is comparable to that for the enriched plutonium fuel rods previously approved by DRL and currently being irradiated in the Big Rock Poim

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core.

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We have concluded that the insertion of two Type "J-2" fuel assemblies into the Big Rock Point core does not increase the probability of the DBAs or significantly change the consequences of such improbable accidents.

f Accordingly, the Technical Specifications may be changed as indicated p

in Attachment A to permit' insertion of two Type "J-2" fuel assemblies into the Big Rock Point core la March 1972.

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DJSkovholt, DRL j

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DLZiemann, DRL JJShea, DRL RMDiggs, DRL IDinks, DR (2) 4

UNITED GTATES

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^5 ATOMIC ENERGY COMMISSION

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f Eleggs Q December 29, 1971 Doekst No. 50-155 Consumers Power Co=pany ATTN:

Mr. Ralph B. Sewell

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Nuclear Licensing Administrator 212 West Michigan Avenue Jackson, Michigan 49201 Change No. 27 License No. DPR-6 Gentlemen a.:=

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Your Proposed Change No. 27 dated December 9,1971, requested changes to the Technical Specifications of Facility License No. DPR-6 to permit operation of the Big Rock Point Nuclear Reactor with two " Type J-2-UO -Pu0 "

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fuel assemblies in the core.

im-The "J-2" fuel assemblies are nearly identical in mechanical design to O. -

L2 the two Type "J-1" fuel bundles which were inserted in the Big Rock Point reactor in March 1970 as approved by Change No. 21 dated February 9,1971.

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Each "J-2" fuel assembly contains 12 plutonium ear.ned al rods, 12 fuel rods, and thicker cladding on the 44 fuel rods

" experimental" UO2 with the highest power peaks. We have concluded that the resultant enriched fuel plutonium inventory within the Big Rock Point core with the proposed "J-2" fuel bundles inserted is within previously authorized limits, and that the consequences of design basis accidents are not increased significantly by insertion of two "J-2" fuel asse=i. lies into the Big Rock Point core.

Based on our evaluation of the changes that have been described by Consumers Power Company, we have concluded that use of 'the two proposed "J-2" fuel assemblies in the Big Rock Point core does not psesent signifi-cant hazards considerations not described or implicit in the Big Rock Point Safety Analysis ! aport or previous evaluations of Technical Specification changes for the use of plutonium fuel in the Big Rock Point core.

rbere is reasonable assurance that the health and safety of the public will r.ot be endangered by the operation of the Big Rock Point Nuclear Reactor with two Type "J-2" fuel bundles in the core.

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' Consumers Power. Company December 29, 1971 Accordingly, pursuant.to Section 50.59 of 10 CFR Part 50, the Technical Spec 1fications_of Facility License No. DPR-6 are hereby changed as

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indicated in Attachment A'to this letter.

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Sincerely, l

,1 nald Skovholt Assistant Director for Reactor Operations-Division of Reactor Licensing

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Enclosure:

Attachment A~

Changes ~ to -

l-Technical Specifications cc..

cc w/ enclosure:

' ff George F. Trowbridge, Esquire Shaw, Pittman, Potts, Trowbridge & Madden

,910 - 17th Street, N. W.

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Washington, D. C.

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ATT;#2'OT A CHANGE NO. 27 n; THE TECHNICAL SPECIFICATIONS FACILITY LICENSE NO. DPR-6 CONSUMERS POWER COMPANY

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DOCKET No. 50-155 i =i.-

1.

Change Section 5.1.5.(c) to read:

'4

"(c) Fuel Bundles _

The general design and configuration of the seven types 4.cgg of fuel bundles shall be as shown in Figures 5.2 through 5.7 (inclusively) of these specifications. Principal.

145 design features shall be as' indicated in Table 5.1."

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' Add Figure 5.7, Big Rock Point Type "J-2 (UO -Pu02)" Fuel, to ET.5 2

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Section 5.

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Add the attached column and footnotes to Table 5.1 of Section

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'5.1.5.

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Change Colunn 2 heading of Table 5.2 in Section 5.2 to read:

" Reload

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'J-l' and

'J-2'."

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k m-2 Section 5.1 5 - Table 5.1 - Add the following column and footnotes:

General J-2 (UO2-Puo2)

Geccetry, Fuel Rod Array 9x9 Rod Pitch, Inch 707 Standa'rd Fuel Rods per Bundle 49 Special Fuel Rads per Bundle 32

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3 Spacers per Bundle Fuel Rod Cladding Material Zr-2 Standard Rod Tube Wall, Inches (9)

Special Rod Tube Wall, Inches (9)

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Fuel Rods ~

!C. :.,. :.2 Standard Rod Diameter, Inch,

5625 y'

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Special Rod Diameter, Inch 5625 s:::-:

Fuel Stacked Density,. Percent Theoretical 907(7)

s.

Active Fuel Length, Inches Standard Rod 68 Special Rod 62.2 in Center Rod E

Fill Gas Helium 3 95%

i-(0)This includes: 24 mixed oxide (Pu02-UO2) rods, 4 cobalt bearing corner rods and 4 gadolinia bearing rods.

- (9)This includes:

44 fuel rods,.050"; 33 fuel rods,.040"; and 4 cobalt rods,.035".

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