ML19329A864
| ML19329A864 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/21/1977 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Roe L TOLEDO EDISON CO. |
| Shared Package | |
| ML19329A865 | List: |
| References | |
| NUDOCS 8001150758 | |
| Download: ML19329A864 (2) | |
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1 DISTRIBUTION NRC PDR
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--- N Docket File Local PDR JAN 21 g LWR-1 File DVassallo 4
Docket No. 50-346 FJWilliams p
JStolz CThomas Toledo Edison Company EHylton B D ATTN: Mr. Lowell E. Roe TNovak (f
Vice President, Facilities GMazetis J
Develooraent LEngle Edison Plaza ACRS (16) 3C0 Madison Avenue ELD IE (3)
Centlemen:
HSmith bcc: JRBuchanan, NSIC, TBAbernathy, TIC EFFECTS OF FI EL RCD BOUING ON CEPARTURE FROM NCCLEATE 2 OILING On August D,1976, Westinghouse Electric Corcoration presented data to the NRC staff which showed that previously developed methods for accounting for the effect of fuel rod Fowing on decarture fren nucleate toiling nay not contain adecuate thermal margin when unheated rods (such as thimble tubes) are present. He have evaluated the ircact of the Uestinghouse data on all ocerating pressurized water reactors (P'.1R 's ). Models for treating the effects of fuel rod bowing on thernal-hydraulic perforrance have been derived for all PW's.
The redels are based on the procensity of the ind. *idual fuel desians to tow and on the themal analysis methods used to credict the coolant conditions for both normal operaticn and anticipated transients.
The staff has reviewed the extent of rei towinq which occurs :ith Gabccck
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' Nilcox (USW) fuel. Based on this review, an equation was derived 'cc tre clearance reduction between fuel rods due to fuel rod to4ing as a function of bur :up:
AC = a + b /DT
~Co
'here AC is the fractional amount of closure G
Bu is the bun !1e average tu..:un, and a, b are on,irical canstants fitted to Gfbi rod boy data.
The reduction in decature fron nucleate boiling ratio (SC') dtm te f'Jel rod bowing is assumed to vary linearly with the re ' action in clearance between the fuel rods (or fuel rod and thimble rod) but can
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II Toledo Edison Comoany 2-never be lover than that due to the pitch reduction factor used by the manufacturers of reactor cores to account for the reduction in DiiBR due to pitch reduction from fabrication tolerances and initial rod bow. -
You are requested to consider a rod bow penatly for the Davis-Basse Nuclear Power Station Unit t'n.1 as described in Section 3.2 of our
" Interim Saf2ty Evaluation v'eport on Effects of euel Red Bowing en Thermal "argin Calculations for Light Water Reactors", a ooy of which is enclosed. As discussed in Section 3.2 of that recort,
.a should use the rod bow versus burnup curve appropriate to your fuel in conjunction with the Westinghouse curve of 2NBP. reduction versus rod bow to deternine the reduction in OilCR as a function of burnup.
In detemining a rod bow penalty, you nay procose approcriate ther:::al margins as discussed in Section 2.5 of that recort to belo offset the "!$R reduction. You are also recuested to provide us with your plans for accomodating any resulting rod bow penalty in your proposed tecnnical scacification onerating limits.
Please provide the infomation requested aFeva for our revieu Sy Fecruary 1, 1977.
Sincerely, Origirm: Signed by John F. Siciz
'ohn C.
5tol::, Chief Light Uater bacters dranch i;c. 1 Division of Project N nanerent Ecclosure:
es stated cc:
"r. Donald H. Mauser, Esc.
The Cleveland Electric Illuminating Comoany Leslie Henry, Esc.
P.O. Box 5000 r ller, Sersey. ":nry and u
Cleveland, Ohio 44101 Hodge 300 Madisen 3 venue rcrald Charnoff, Ecri.
Toledo, nhio 43504 Sha'e, Pittran, Potts and n
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