ML20002C549
| ML20002C549 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 11/23/1976 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8101100458 | |
| Download: ML20002C549 (7) | |
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t Docket ko. 50-155 NOV 2 31976 Constners Power Company ATTN: Mr. Ralph B. Sewell Nuclear Licensing Administrator 212 West Michigan Avenue Jackson, Michigan 49201 Gentlemen:
RE: BIG ROCK UNIT N3.1 The NRC staf f has recently obtained information which indicates that fission gas releases from fuel pellets with high burnup may be under-predicted by the current industry models for fission gas release.
As a result, actual end-of-life fuel rod pressure stay be higher than that wtiich was considered in the safety analysis for your facility.
Although this situation does not lead us to suspect that fuel design limits have been or are currently being exceeded at your facility, the potential r:ay exist for such an occurrence in the f0ture as higher fuel burnups are reached. Consequently, you are requested to evaluate the effects of increased fission gas releases on the safety analysis for your facility in accordan e with the schedule specified below.
If tne estimated date on which any fuel. rod in your facility will reach a local exposure (burnup) of 20,000 Megawatt-days per metric ton of Uranium (MW3/tU) is sooner than June 1,1977, provide the following infomation within 30 days of receipt of this letter.
(If this estimated date is later than June 1,1977, your response may be submitted within 90 days of receipt of this letter).
a.
The estinated date on which any fuel rod in your facility will reach a local exposure (burnup) of 20,000 Megawatt-days per metric ton of Uraniun (MWD /tu).
b.
Using the correction technique described in the attached I
enclosure, modify the fission gas release model in the j
ther.ual perfonnance code for the fuel in your facility and calculate the fission gas release, fuel rod pressure, fuel te'aperature, etc. for burnups up to and including the G
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NOV 2 31976 Consumers Power Conpany j target peak-rod burnup. Provide a conparison of the results of your calculations with those obtained using the uncorrected fission gas release model.
c.
Describe the impact (if any) of larger fission pas releases on the LOCA analysis and other safety analyses for your facility.
d.
If internal fuel rod pressures, as calculated using the above-mentioned fission gas release correction, are predicted te i
exceed the nominal systen pressure for your facility, provide the date that this is anticipated to occur and discuss the implications of operating under bnth nomal and accident l
conditions with fuel cladding tensile stresses.
l We have advised all U. S. fuel manufacturers by separate correspondence that this infomation request is being sent to licensees of operating l
power reactors.
In our letter to the fuel manufacturers, we have indicated that boundino calculatinns for appropriate plant groupinos i
would be acceptable.
8 This request for generic infomation was approved by MO under a blanket clearance nonber B-180225 (R0072); this clearance expires July 31,1977. Three stoned originals and 40 cnpies of your response will be required.
I Sincerely, Waal a1 ned b I
8 Dennh L zg,m,,y, Dennis L. Zienann, Chief I
Operatina Reactors Branch #2 j
Division of Operating Reactors l
Enclosure:
DISTRIBUTION l
Burnup-Dependent Correction Docket RPSnaider for Fission Gas Release NRC PDR OELD Models Local PDR OI&E(3)
ORB #2 Reading DEisenhut cc w/ enclosure:
VStello TBAbernathy See next page TJCarter JRBuchanan DLZiemann ACRS (16)
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e Consumers Power Company.
NOV i'31976
- cc W/ enclosures:
Mr. Paul A. Perry, Secretary Consumers Power Company 212 West liichigan Avenue Jackson, flichigan 49201 Charles F. Bayless of Counsel Consumers Power Company 212 West 111chigan Avenue Jackson, flichigan 49201 George C. Freeman, Jr., Esquire Hunton, Williams, Gay and Gibson 700 East itain Street Richnend, Virginia 23212 Peter W. Steketee, Esquire Frethofer, Cook, Hecht, Oosterhouse and De Boer Union Bank Building, Suite 950 Grand Rapids, Michigan 49502
' Charlevoix Public Library 107 Clinton Street Charlevoix, Ilichigan 49720 i
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- Recent AN'S standards activities (1-3) lead us to believe that high; burnup gas' releases are underpredicted by current-LWR-industry models. We have previously _'(,1) looked for-a burnup' dependence and -found ' none for -LWRs -
in the burnup' range from-400.to 18,300 mwd /tu. Thus, we incorrectly pre,
'sumed that 'the strong burnup dependence exhibited by' LMFBR data (1) was not
~
. representative.of-LWR fuels durin6 their shorter burnup lifetimes.
-New high burnup UO2 data mentioned by Westinghouse to-the ANS group (2) ~
r and di1 cussed with the NRC (6) show,'however, that the sharp release increase
-seenLin LMFBR data occurs also in LWR fuels.
Therefore, in the absence of a complete analysis of high burnup LWR U02 data, we will assume that the burnup a
dependence is the same in LWR and LMFBR oxide fuels. This assumption, however, a-will be applied only in the high burnup region above 20,000 mwd /tU sinceithe
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current industry models have been checked with the data base (,1) ranging.to e
18'300 M'/d/tU.
r
'The following correction has been derived to give an increased release fraction F'(Bu,T) as a function of burnup and the uncorrected release i
prediction F(T). Burnup Bu is the local burnup in megawatt-days per metric l_
ton of uranium (mwd /tU), and T, which is not an explicit variable in the correction,'is temperature.
(1 - exp[-0.436 x 10 "(Bu-20000)])
.F*(Bu,T) = F(T) + [1-F(T)]
(1) f i
_ -, _.., _.,,.. ~.. _ _,
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t-Figure'1.shows schematically how this correction would be applied to the GAPCON gas-release model,lwhich is independent-of burnup...In the event an existing model contains a burnup dependence,-F(T) would be the' predicted release fraction under the' temperature conditions of interest, but with the b'urnup variable set equal to 20,000 mwd /tU.
Equation 1 is a replication of the Dutt and Baker- (J.) LMFBR correla-tion', which is an updated version of the correlation' in Ref. 5.
Equation.1 was derived by assuming a convenient functional form depending on~F(T) and-
~ Bu andifitting it to the Dutt and Baker curves using a non-linear regression procedure.: No conservatism has been intentionally added. Figure 2 shows how' closely Eq. 1 reproduces the Dutt and Baker curves.
i i
Seferences
]
1.
R. O. Meyer (NRC), memorandum to P. S. Check, " Summary of Meeting of ANS-5.4 Working Group on Fuel Plenum Gas Activity," February 25, 1976.
1 l
2.
R. O. Meyer (NRC), memorandum to P. S. Check, " Summary of ANS-5.1 (Decay Heat) and ANS-5.4 (Fission Gas Release) Activities," June 22, 1976.
J 3
R. O. Meyer (NRC), memorandum to. P. S. Check, " Summary of ANS-5.4 Meeting on Fission Gas Release," October 6, 1976.
4.
C. E. Beyer and C. R. Hann, " Prediction of Fission Gas Release from UO Fuel," Battelle report, BNWL-1875, November 1974.
i 5
D. S. Dutt, D. C. Bullington, R. B. Baker, and L. A. Pember, "A Correlated Fission Gas Release Model for Fast Reactor Fuels," Trans.
Am. Nucl. Soc..11, 198 (1972).
f 6.
R. O. Meyer (NRC), memorandum to P. S. Check, " Summary of Meeting with Westinghouse on Fuel Rod Pressures," September 22, 1976.
7 D. S. Dutt and R. B. Baker, "Siex:
A Correlated Code for the Prediction of Liquid Metal Fast Breeder Reactor (LMFBR) Fuel Thermal Performance,"
Westinghouse Hanford report, HEDL-TME 74-55, June 1975. f 1
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