ML20003A191
| ML20003A191 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/20/1977 |
| From: | Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8101300843 | |
| Download: ML20003A191 (5) | |
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CORSumCTS F power
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C0mpany General Offices: 212 West Michigan Avenue, Jackson. Michigan 49 Area Code 517 788-OSSO January 20, 1977 c3
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Operating Reactor Branch No 2 x/g US Huclear Regulatory Commission
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(,O DOCKET 50-155, LICENSE DPR BIG ROCK POINT PLAUT -
FISSION GAS RELEASE INFORMATION Ref:
Letter from R B Sewell to D L Ziemann dated December 29, 1976.
This letter is in response to your letter of November 23, 1976 in which ycu request'ed information concerning fission gas releases frcm fuel pellets with high burnups at the Big Rock Point Nuclear Plant.
A number of fuel rods in the Big Rock Point core have already exceeded an exposure of 20,000 !Gd/ICU and no adverse effects, such as clad ballooning, attributable to high ex-posures have been observed. However, as requested, fission gas release cal-culations using the NRC burnup dependent correction formula have been performed for the Exxcn Nuclecr 11 x 11 reload fuel at the Big Rock Point Plant. The calculations were made for a maximum power all-uranium fuel rod and for a maximum power mixed oxide fuel rod.
In both cases, a power history was deter-mined from MAPLHGR limits and local peaking factors whimh envelopes the ma ci-mum of the individual peak power rod histories of the mixed oxide G assembly design and the all-uranium G-lU and G-3 assembly designs. The analysis there-fore, envelopes all 11 x 11 fuel assemblies at Big Rock Point.
The fission gas release and fuel performance parameters with and without the NRC correction vere calculated with Exxon Nuclear Corporations approved boil-ing water reactor fuel densification nodel(l). The MAPLHGR limits used to determine the bounding rod pcwer histories are the new limits contained in the proposed Technical Specifications change as transmitted by R B Sewell to the Director of Nuclear Reactor Regulation on December 17, 1976. The new
' limits yield greater fission gas release fractions than the prior limits.
The analysis for the mixed oxide fuel rod included the thermal conductivity penalty used in prior ECCS analyses for mixed oxide assemblies.
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A detailed comparison of the effect of the NRC gas release correction versus burnup is provided in Table 1.
The correction can be seen to be more sig-nificant as burnup increases with the biggest effect at end of life.
At
,756 V/0 M W
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end of. life, the NRC correction increases the amount of gas in the fuel pin '
by a: factor of 2; and hence, increases the pin pressure-by a like amount.
However, because of the relatively low power levels at Big Rock -Point, gas-release and pin pressures are never very substantial even when doubled by the NRC-release fraction correction. The peak pressure of 62.0.~ psi is only
.a.smallLfraction of the system operation pressure (1350 psia).
"The increased gas release'does~ lead to a-slight increase in fuel average te=per-atures.of ~ h2*F and 23F, respectively, for the peak UO2 rod and the peak mixed oxide rod at end of life. Because of this, increased fission gas release vill lead to an increas.e in predicted peak, clad temperature (PCT) during a LOCA.
The results of heatup sensitivity studies to quantify the PCT increase are
~given in Table 2.
The heatup analysis' calculations are bounding calculations since peak-power-rod fiscion gas release rates were assumed for all fuel. pins in the ll x 11 fuel assembly. The PCT increases for the G-lU (all uranium) design envelope the G.-3 (all uranium)-design since the former has' higher fuel rod linear. heat generation limits.
Calculations, with E20s BULGEXt2) computer code, confirmed that ballooning and failure do not occur during a LOCA even with the' increased fission gas amounts.
The increased fission gas release does not impact any other steady state or transient analyses since the internal pressure predicted remains well below the external system pressure and the fuel rod stored energy is only slightly increased.
The results presented in Table 2 show that the effect that the corrected fissien-gas release model has on the peak clad terperature prediction is extremely small (ie, less than a 17, reduction in MAPLEGR at end of life) for the predominant fuel assembly type (11 x 11) at Big Rock Point.
In addition, although the 9 x 9 fuel has not been analysed, we have concluded that the results would not be signifi-cantly different for the 9 x 9 fuel.
Coupling this with our belief that the fission gas release model proposed in your November 23, 1975 letter is very con-servative in the manner in which UEBR fuel data is applied to LWR fuel, we have concluded that the impact on the Big Rock Point LOCA analysis is insignificant and of no safety concern.
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David A Bixel Assistant Nuclear Licensing Administrator CC: JGKeppler, USHRC GASEX: A computer progra= for predicting pellet-to-cladding heat transfer coefficients, XH-73-25, August 13, 1973.
BULGEX: A computer code to determine the deformation and the onset of bulging of zircaloy fuel rod cladding, XN-74-27, Revision 2, December 21, 1974
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I e-s TABLE 1 Fuel Parameters Versus Burnup
-Enc 11 x 11 Fuel Parameter-Rod Parameter Values Peak Pellet LD Rod 13422 20000 27184 36098 h'3685 '
2 Burnup
,s.
(t&d/rfrM)
M0 Rod 12601 20000 25255 33341 40899
. 0008h5)*
.00101h (.000853)
.00156h
(.000860)
Released Gases UO Rod.000819
.000838.000868
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2 (Gram-Moles per Rod)
MO Rod.000769
.000785
.00080h
(.000791)
.000879 (.000798)..001163 (.000804)
Pin UO Rod 32 5 33.2 34.4 (33.5) 40.2 (33.8) 62.0 (34.1) 2 Pressure (psia)
M0 Rod 30 5 31.1 31 9 (31.h) 34.9 (31.6) h6.1 (31 9)
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Maximum LHGR UO Rd 8.05 8.13 8.17 8.09 7.79 2
Previously Allowable (kW/ft) Mo Rod 7 54 7.62 7.67 7.67 7 58 Puel UO Rd 1378 1246 1175 (1173) 1158 (1147) 1162 (1120).
2 Average Temperature ( F)
MO Rod 1374 1238 1180 (1178) 1160 (1155) 1167'(11hk)
-" Uncorrected results after 20,000 IWd/MTM shown.in parenthesis.
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TABLE 2 Heatup Results for Fission. Gas Study Peak Rod:
Assembly Nodal PCT ( F)
PCT-(*F) ggd/
Without;
.With
- APCT MAPLHGR Burnup
-(kW/ft) mwd /MTM 2
Correction Correction
( F)-
^r-"
G (Mixed Oxide) 6.843 30620
~33341/36098 2185~
2191
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G (Mixed oxide) 6.703 37h92 40899/h3685 2190 2211
+21 Uo2 G-lu (All Uranium) 7 161 32059
-36098 2180 2189-
+9 G-1U ( All Uranium) 6.958 38935
'h366, 2182 2214.
+32.
G-3 (All Uranium)
Results. Enveloped by G-lU (All Uranium) 0 4
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NRC DISTRi JTION roR PART 50 DOCKET MATERI AL TO: Mr Ziemann FROM: Consumers Power Company DATE oF DOCUME T_yy Jackson, Michigan D A Bixel DATE RECEIVED CLErtER ONOTORIZED PROP SNPUT FORM NUMBER oF COPtES RECEIVED GomoiNAL srUNetassiFiEo Ocony one signed DESCIIPTION E N CLOSU R E Ltr re our 11-23-78 Itr....trans the Information concerning Fission Cas Release....
following:
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