ML19351F250
| ML19351F250 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/17/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19351F248 | List: |
| References | |
| NUDOCS 8101120059 | |
| Download: ML19351F250 (5) | |
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q[g UNITED STATES NUCLEAR REGULATORY COMMISSION c(
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO AMENDMENT NO. 44 TO FACILITY OPERATING LICENSE NO. OPR-42 AMENDMENT NO. 38 TO FACILITY OPERATING LICENSE NO. DPR-60 NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT UNIT NOS.1 AND 2 DOCKET NOS. 50-282 AND 50-306 Introduction By letter dated May 6, 1980 as sucolemented by letters dated September 19 and December 2,1980 Northern States Power Company (the licensee) reauested amend-ments to Facility Operating License Nos. DPR-42 and DPR-60 for the Prairie Island Nuclear Generating Plant Unit Nos. 1 and 2 (PINGP). The proposed amend-ments would change the Technical Specifications to include editorial changes to reflect the moditication to the logic for actuation of safety injection and to include changes in the control rod and power distribution limits.
Discussion The Commission's evaluation of the changes to the logic for actuation of safety injection is set forth in the Safety Evaluation accompanying Amendment Nos. 36 and 30 to Facility Operating License Nos. OPR-42 and DPR-60, issued on May 1,1979. The physical modifications authorized by those amendments were completed by the licensee en May 2,1980 for Unit 1 and on May 8,1980 for Unit 2.
Accordingly the edito-ial changes to the technical specifications to reflect the presently existing actuation logic may no.: be made.
The proposed amendments would change the power distribution control requirements involving rod bow penalities, exposure dependence of the peaking factor F$ and an updating of the power distribution control phase 2 methodology.
Editorial changes would be made to incorporate consistent terminology, to eliminate reference to part length control rods which were removed from the reactor at an earlier time, to regroup the limiting conditions for operation and the bases and inclusion of more detailed information that is useful to the operator.
Evaluation SAFETY INJECTION ACTUATION LOGIC The existing pages TS 3.5-2 and Tables 3.5-1 and 3.5-? refer to the original safety injection (SI) actuation logic which required coincident low E10
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pressurizer pressure and low pressurizer level. This logic has since been modified to a 2-out-of 3 low pressurizer pressure only logic consistent with the previously issued License Amendments Nos. 36 and 30 to License Nos. DPR-42 and DPR-60. Consistent with a previous connitment by the licensee, upon completing the physical modifications to the logic, the licensee's proposed amendment would eliminate editorial references to the previous coinci('nt pressure and level logic. We find these changes to be acceptable.
PART LENGTH RODS i
Throughout Section 3.10 of the TS references to the part length rods would be deleted by the proposed amendment. The staff set forth its evaluation and approved the removal of the part length rods from the reactor in Amendment Nos. 32 and 36 to License Nos. DPR-42 and DPR-60. Therefore, deletion of the remaining references to the part length rods is acceptable.
F Penalty Associated with Rod Bow g
The proposed TS revision would delete the multiplier (1-RBP (BU)) for the Westinghouse fuel. The deletion of this multiplier is proposed to be based on a combination of staff positions set forth in two documents, references 1 and 10.
Re"erence 1 is the staff's evaluation of information presented by Westinghouse as the basis for calculating critical heat flux on bowed rods..The staff's position as a result of that review stated the following:
"The letter report on CHF with partial and bow provides an acceptable data base for CHF on rods bowed to 85% of the bow necessary for contact.
Further, the relation for bow penalty as a function of gap closure, given in Figure 4 is an accep-table bow penalty for use on Westinghouse fuel des'gn."
Figure 4 of reference 1 descricas the rod bow on DNBR as a function of '
fractional gap closure between bowed rods. The staff's position, as presented in reference 16, describes the fractional gap closure as a function of burnup.
Reference 16, in conjunction with reference 1, defines the staff's present position on rod bow DNBR penalty as a function of burnup.
Reference 10 dated February 16, 1973 reports the staff's evaluation of the penalty required to be imposed on DNBR to account for the effects of rod-bow. Reference 10 relates the amount of penalty to burnup since the amount of rod bow is a function of burnup. Reference 10 also discusses the off-setting of the total penalty required on DNBR by the application of certain l
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well-known generic thermal margin credits. After these factors are taken into account, Reference 10 stipulates that reductions in F are found aH necessary to account for any remaining penalty on DNBR The present TS penalty on F is a function of the amount of burnup experienced by the fuel. TheremovalofHthe penalty on F must therefore be based upon the showing that sufficient margins exist to 3$ffset the effects of rod bow for all burnup of significant concern.
Certain well kncun DNBR design margin credits, as calculated by Westinghouse and verified by the licensee, to be applicable to Prairie Island, are as follows:
Credit Mj_ g 1.24 DNBR vs 1.30 DNBR 4.8%
Pitch reduction 3.3%
TDC (.019 vs.038) 3.0%
Axial heat flux densification spike effect on DNB 7.0%
TOTAL 18.1%
The staff has determined that these design thermal margin credits will offset the effects of rod bow on DNBR up until a region average burnup of 35,000 MWD /Mtu. We conclude that the depletion of fissile nuclides combined witn the buildup of fission products in fuel experiencing more than 35,000 MWD /Mtu will result in a sufficiently low peaking factor F, that F will not be limiting for this fuel even with the application oh the spe$fied rod bow penalty factor. Accordingly, we find that deletion of the rod bow penalty factor term (1-RBP(BU)) from the equation for F is acceptable.
AH F Limit penalty Associated with Rod Bow 3
The licensee proposes to delete the multi lier (1 - 2.35 x 10-6 (BU - 2.8 x 10 ))
on F. This multiplier is a penalty on F for fuel rod bowing and was applied 0
only to Exxon fuel. Our review of the Exkon bowing models is not complete.
These models would impose no penalty on F$ for fuel rod bowing. There is no penalty on F@ for Westinghouse fuel. Since we expect less bowing of the Exxon fuel, primarily because it has thicker cladding, we have reasonable assurance that a bowing penalty on Fg need not be applied to the Exxon fuel.
We therefore find it acceptable to remove this penalty.
Exoosure Dependence of FN The licensee proposes to add an exposure dependent function which limits Fh toward the top of the core at high exposures. This was done to conform with the NRC high fission gas release model. We reviewed the licensee's application of this model and agree that he has performed a conservative l
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. analysis. We therefore find the proposed exposure dependent function limiting F$ acceptable. This function should not affect operation of the Praitte Island units since the Fg limit decrease is not expected
.tti late in the second cycle or early in the third cycle when Fh values will be lower.
Power Distribution Control, phase II The licensee proposed several changes which reflect developments in PDC-II.I4 We earlier approved PDC-II for use in the Prairie Island reactors.15 The current changes reflect developments 3 in our review of PDC-II since this N and FN limits are specified In particular, the form of the F approval.
in a format designed to show that a measureh value Ys being compared to an A
analytically determined limit. This change does not alter the values of the parameters affected, and clarifies the specification.
It is therefore accepta bl e.
Another change involves removal of stringent requirements on reactor operation to ensure that the FN measurement is performed at equilibrium o
conditions. Our review of the PDC-II Yndicates this requirement is no longer necessary because the target flux difference incorporates the effect N
scecification to handle t9e case in which FAlso included gn the requested changes is a of slight variations in F.
increases (unexpectedly between Fj measurements ). This is part of the standhd PDC-II specifications.3 Ine licensee had commited to these procedures earlier, however they had not been placed into the Technical Specifications. This change is acceptacle because it provides conservative assessment of possible increasing Fy between measurements.
Editerial Changes The remaining changes requested by the licensee are all editorial. They clarify the specification by word changes or regrouping, remove references to part length rods which have been removed from the reactor, or change wording to conform with the Standard Technical Specifications. These changes have no significant safety impact and are acceptable -
The requested changes to the Technical Specification bases are all technically correct and therefore acceptable.
Environmental Consideration We have determined that the amendments do not authorize a change in effluent types or total amounts nor an ir.:rease in power level and will not result in any significant envirorimental hcpact. Having made this determination, we have further concluded that the amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 151.5(d) (4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of these amendments.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Date:
December 17, 1980 l
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References
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1.
Letter, J F Stolz (NRC) to T M Anderson '(Westinghouse) dated April 5, 1979 (Staff review of WCAP-8691)
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2.
Letter, L 0 Mayer (NSP) to Director of Nuclear Reactor Regulation (NRC) dated March 30, 1979 3.
Exxon Nuclear Company Topical Report, " Exxon Nuclear Power Distribution Control for Pressurized Water Reactors Phase II", IN-NF-77-57, Supplement 1, June 1979 4.
Exxon Nuclear Company Topical Report, " Fuel Rod Bowing for Exxon l
Nuclear Company Reload Fuel," IN-NF-79-43, May 1979 l
5.
Letter, G Lear (NRC) to W Nechodem (ENC), dated June 7,1978 l ?!3 6.
Exxon Nuclear Company Report, " Generic Mechanical and Thermal Hydraulic Design for Exxon Nuclear 14 x il Reload Fual Assemblies with Zircaloy Guide Tubes for Westinghouse 2-Loop Pressurized Water Reactors, XN-NF-78-34 [P], November 1978 (proprietary version), and IN-NF-78-34 l
[NP], January 1979 (non proprietary version) 7.
Exxon Nuclear Company Report, "ECCS Large Break Spectrum Analysis for
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Prairie Island Unit i Using ENC WEIM-IIA PWR Evaluation Model,"
XN-NF-78-46, November 1978 l ~
3.
Exxon Nuclear Company Topical Report, " Computational Procedures for Evaluating Fuel Rod Bowing ( AXIBOW)", IN-NF-75-32, Supplement 1, July 1979 9.
Exxon Nuclear Company Report, " Exposure Sensitivity Study for ENC XN-1 Reload Fuel at Prairie Island Unit 1 Using the ENC-WREM-IIA PWR Evaluation Model", XN-NF-79-18 (P), April 1980 (proprietary);
XN-NF-79-18(NP), April 1980 (non proprietary)
- 10. Interim Safety Evaluation Report on Effects of Fuel Rod Bowing on Thermal Margin Calcul.tions for Light Water Reactors - Revision 1 USNRC, February 16, 1977.
- 11. Letter, L 0 Mayer (NSP) to Director of Nuclear Reactor Regulation (KRC), dated October 30, 1979.
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- 12. NUREG-0452, " Westinghouse Pressurized Water Reactor Standardized Technical Specifications".
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4.
References (Cont'd) 14 XN-NF-77-57, Exxon Nuclear Company. " Exxon Nuclear Power Distribution Control for Pressurized Water Reactors, Phase 2 "
January 1978.
15.
U. S. Nuclear Regulatory Commission, " Amendment Nos. 35 and 29 to Facility Operating License Nos. DPR-42 and DPR-60 for the Prairie Island Nuclear Generating Plant, Unit Nos. I and 2, Respectively," April 30, 1979.
- 16. Memorandum, R. O. Meyer, NRC, to D. F. Ross, NP.C, March 2,1978, Revised Coefficients for Interim Rod Bowing Analysis.
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