ML20024G850
| ML20024G850 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/10/1975 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20024G851 | List: |
| References | |
| NUDOCS 9105010213 | |
| Download: ML20024G850 (6) | |
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Dear Mr. Ziemann,
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$TT'U' MONTICELLO NUCLEAR GENEPATING P1 ANT Docket No. 50-263 License No. DPR-22 Response to June 3. 1975 CETAB Questions This letter is in response to your June 3,1975 letter transmitting two questions concerning our GETAB Technical Specification change request.
The questions with their respect.ive answers are included below.
The analysis of Cycle 5, which will contnence this fa'.1, vill be b. sed on the GETAB analysis discussed in our License Amendment Request Dated March 12, 1975.
We therefore request that you uhedule complet ten of your review and issuance of these changes accordingly.
Questien No.
1.
The APPM flux scram trip setting and rod block equations in Icchnical specification 2.3 are the same as those used with the liench-Levy C11P correlation.
Either modify the equations or provide justification for retaining the equations based on critical heat flux rather than using units consistent with the GEXL/GETAB Analysis.
The trip setting and rod block equation constants for the 8 x 8 fuel are different frcnn those used by 7 x 7 fuel.
Explain the difference Response.
The present Technical Specification settings referenced are in terms of heat flux; the constants are the heat flux levels corresponding to the maximum peaking factor for 7 x 7 and 8 x 8 fuel respectively. As your question infers, it is appropriate that the settings be expressed in terms of peaking factor directly rather than extending the peaking factor to a heat flux value.
We under-stand that you are also reviewing, on a generic basis, a change in the slope of the flow biased APRM scram and rod block rettings.
This subject is addressed in Appendix A.
Since these changes effect four pages of our Technical Specifiestions we are including as Appendix E, the appropriate Technical Speciacation pages modified te reflect these changes, should you wish to effect tica at this time.
These pages would then serve as replacements and additions to Lxhibit B of our License Amendment Request Dated March 12, 1975.
Question No.
2.
Does the relative bundle to bundle power distribution used in the GEIAb statistict.1 analysis for Monticello remain fixed throughout the series of Monte Carlo simulationr? If not, how does it vary, and why?
Show tha:. the peak ram power factor used is the worst case that could occur during the cycle.
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NORThsCRN GTATED POWER COMPANY Mr. v. L. Zie:rann 2
July 10, 1975 Response. A series of questions on GETAB were answered in a January 20, 1975l Ic t te r f ro:a L.11. Frauenhoir of General Electric to A. J. Ignatonis of the Nuclear Regulatory Cotraission.
These answers were specific to Monticello, which was the icad plant GETAD analysis.
The bundic to bundle power distribution used in the Monte Carlo simulation to derive the safety limit and operating limit on MCPR is identified and justified in the detail in that document.
For your convenience,l l' ages 1-4 and figures 3-1 and 4-1, which answer the above question, are attached.
Yours very truly, j
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H(Cu muH: L-Ltr re our b-3-75 Itr furn responses to Appendix A-Justification For APRM Rod Block /
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I APPENDIX A M ONTIC ELLO JUST1FICATION FOR APPfi ROD BLOCK / SCRAM SE1 TING CIWm,I; To improve control rod operability in the core flow range above 207, of drive pump speed and below 50% of rated flow and to provide greater flexibility to accommodat situtations such as Xenon compensation during power ascermions with fixed control rod patterns, the APRM flow biased rod block (RB) and scram lines (S) should be redefined as shown belows R!i = 0.58 W + 50 S = 0.$8 W + 62 Where W is the recirculation locp flow in percent of rated flow, Ihese revised lines were selected on the following bases:
1.
The rod block lines intercept the rated power flow control line at natural circulation, thus raising the rod block set point by about 10% at low flows.
This APRM rod block setting will provide a reason-able range for maneuvering during plant startup.
i 2.
A6 part of the original design requirements, stability calculations were performed on the natural circulation line at 50% and 627, power (the new intercepts of the rod block and scram lines).
l 3.
At the rated flow conditions, the rod block and scram liin.: remain at 106% and 120% of rated power.
Discussion i
Stability calculations for Monticello have been performed and a;e presented in Section 7.2 of the FSAR (1) and were recalculated in cer. junction with the Thtrd Reload Submittal (2).
Figure 7-2-10 of the FSAR and rigitre 6-12 of the Third Reload Suhaittal show that the system is stable at the intersection of natural circulation flow and the nominal expected flow control line which is the new limit of the rod block line.
The least stable analyzed point is the 62% power-natural circulation flow point which is still cytremely stable and bounds the system stability as the Icast stable point.
Thus, while raising the APRM rod block and flow biased scram allowr operation in regions of reduced stability margin there is cicarly no threat to the ultimate stability 10mit of 1.0 decay ratio.
Analyses reported in the Third Reload Submittal and the FSAR, Section 7 demonstrate that with the scram trip set at 120% of rated power none of the abr.ormal operational transients analysed violate the fuci safety limit and there is substantial margin from fuel damage.
Credit is not taken in these analyses for the APRM flow-biased scram.
Thus, any setting for the AFPM flow-biased scrca provides additional margin from the Fuel Cladding integrity Safety Limit.
1 1
APPC; DIX A (CONTI!;t'ED) because C1. TAB analyser have not taken credit for the APti flow biased scrar, the derived operating limit MCPR is also valid for any APKM scram less than 120 percent of rated power. As with MCllFR, the worst case MCPR 100% of rated power so that maintaining the 108% rated power cccurs at sod bleer. setting assures no decrease in operating margin, (1) Monticello !;uclear Generatitt Plant, Final Safety Analysis Report, IMR-22, Docke t 50-263.
(2) I;orthern Stater Power Company, Montice,. O fiuclear Generating Plant.
Third Keload Submittal, December 11, 1974
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APPDiDIX B Appendi:, B, attached, consists of modified paEe5 for the Appendix A Technical Specifications as listed below.
These pager incorporate the changes discussed in the letter.
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