ML19340B426
| ML19340B426 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 11/23/1976 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Bolger R COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8010270586 | |
| Download: ML19340B426 (7) | |
Text
_
l Docket M 50-237, Di 23 1970 50-249, 50-254, 50-265 Co'nonwealth Edison Company ATTH:
P. R. L. Bolger
<sistant Vice Presioent Post Office Box 767 Chicago, Illinois 60690 Gentl enen:
RE:
ORESDEN !;UCLEAR POWER STATION UdIT NOS.1, ? AND 3 03AD CITIES UUCLEAR P0wER STATION UNIT N05. 1 AND 2 Tne #RC staff has recently obtained infor=ation which inaicates that fission gas releases from fuel pellets with high burnup ray be uncer-predictec by the current industry raccels for fission gas release.
As a result, actual end-of-life fuel roa pressure nay be hicher than that unich was considered in the safety analysis for your f acilities.
Although this situation does not lead us to suspect that fuel desian linits have been or are currently being exceeded at your facilities, the potential may exist for such an occurrence in the future as I
bigber fuel burnups are reached. Consenuently, you are reonested to evaluate the effects of increased fission gas releases en the safety analysis for your facilities in accordance with tne cchedule specified below.
If the estimated date on which any fuel rod in your facilities will reach a local exposure (burnup) of 20,000 Megawatt-days per 'aetric ton of Uranium (FND/tU) is sooner than June 1, l'177, provide the follesin7 inforaation wite:in 30 days of receipt of ti.is letter.
(If this esticated date is later than June 1,1977, your res:cns?
av ee suc-itted tnthin 90 days of receipt at t!,i s l etter).
a.
T!-e esti"ated date on which any fuel rod in your facilities *:ill reach a local ex >osure (Darnuc) of E3,Ga':.eesatt-devs r.c r mtric ton of Urenitt, ( RJO/tU i.
b-5.
Using the correction tecnnicue described in tne attachad enclosure, modify the fission gas release odel in the trer,el ncrfer acce code for tre fuel in your facilities an<
c a calate te tiesier :es release, f uel -nd *+rsserc., fuci H-,
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Ccmonwealth Edison Conpany NOV 2 3 W6 target peak-rod burnup.
Provide a conparison of the results of your calculations with those obtained using
.E the uncorrected fission gas release model.
Describe the inpact (if any) of larger fission pas releases c.
on the LOCA analysis and other safety analyses for yuur f acil ities.
c.
If internal 'uel rod pressures, as calculatec using the above-rentioned tission gas release correction, are predicted to exceed the nominal system pressure for your facilities, provide the date that this is anticipated to occur and discuss the implications of operating under both nornal and accident conditions with fuel claddinc tensile stresses.
ele have advised ell U. S. fuel manufacturers by separate correspondence that thi, information request is being sent to licensees of operating poser rea: tors.
In our letter to the fuel manufacturers, we have indicated that bounding calculations-for appropriate plant groupings would be acceptable.
This request for generic information was approved by GAO under a blanket clearance number B-180225 (R0072); this clearance expires July 31, 1977. Three signed originals and 40 copies of your resconse will be required.
Sincerely 5
069 11*
9 Dennis L. Zisaann, Chief Operating Reac ? ors Branch #2 Division of Operatin: "esctors
Enclosure:
DISTRIBUTION Lurnup-Oependent Correction # 4=ts (5)
P0'Connor fo r vission Gas Release NRC PDRs (S)
JGuibert e cels Local PDRs (2)
OELD c
ORB #2 Reading 01&E (3) cc w/ enclosure:
VStello DEisenhut See next paqe TJCarter TBAbernthy DLZiemann JRBuchanan RM8iggs.
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3-Commonwealth Edison Company DV 2 3 ISIO cc w/ enclosures:
Mr. Charles Whitmore President and Chairman Iowa-Illinois Gas and Electric Company
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206 East Second Avenue Davenport, Iowa 52801 Mr. John W. Rowe Tsham, Lincoln & Beale Counselors at Law One First National Plaza, 42'nd Floor Chicago, Illinois 60603
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Anthony Z. Roisman, E. squire Roisman, Kessler and Cashdan 102515th Street, N. W., 5th Floor Washington, D. C.
2000E Moline Public Library 504 - 17th Street Moline, Illinois 61265 i
Morris Public Library 604 Liberty Street z..m.-
Morris, Illinois 60451 e
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t Recent ANS standard 3 activities (1-3) lead us to believe that high burnup gas releases art 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 j
representative of LWR fuels during their shorter burnup lifetimes.
New high burnup UQ2 data mentioned by Westinghouse to the ANS group (2) and discussed with the NRC (1) show, however, that the sharp release increase seen in LMFBR data occurs also in LWR fuels.
Therefore, in the absence of a complete analysis of high burnup LWT, UO2 data, we will assume that the burnup dependence is the same in LWR and LMFBR oxide fuels.
This assumption, however, will be applied only in the high burnup region above 20,000 mwd /tU sinc; the industry models have been checked with the data base (1) ranging to current 18,300 mwd /tU.
The following correction has been derived to give an increased release
-l 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 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)
. Figure 1 shows schematically how this correction would be applied to the GAPCON gas release model, which 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 burnup variable set equal to 20,000 mwd /tU.
Equation 1 is a replication of the Dutt and Baker (1) 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 and fitting it to the Dutt and Baker curves using a non-linear regression procedure.
No conservatism has been intentionally added.
Fi ure 2 shows S
how closely Eq. 1 reproduces the Dutt snd Baker curves.
References 1.
F. O. Meyer (NRC), memorandue to P. S. Check, " Summary of Meeting of ANS-5.4 Working Group on Fuel Plenu: Gas Activity," February 25, 1976.
2.
R. O. Meyer (MRC), memorandum to P. S. Check, "Su= mary of ANS-5.1 (Decay Heat) and ANS-5.4 (Fission Gas Release) Activities," June 22, 1976.
3 R. O. Meyer (NRC), memorandum to'P. S. Check, " Sum =ary 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 UU Fuel," Battelle rersrt, ENWL-1875, November 1074 5.
D. S. Dutt, D. C. Bullington, R. E. Baker, and L. A. Penber, "A Correlated Fission Gas Release Model for Fast Reactor Fuels," Trans.
Am. Nucl. Soc. 25, 196 (1972).
6.
R. O. Meyer (NRC), memorandum to P. S. Check, " Summary of Meeting witn Westinghouse on Fuel Rod Pressures," September 22, 1976.
7.
D. S. Dutt and R. E. Baker, "Siex:
A Correlated Coce for the Prediction cf Liquid "etal Fast Ereeder Reacter (L!:FERT Fuel Tnernsl Ferformance,"
Wertirrneuse Harferd report, REEL-T':E 7a-55. June
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