ML20210L933
| ML20210L933 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/12/1997 |
| From: | Hill W NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9708210364 | |
| Download: ML20210L933 (2) | |
Text
_ _ _ _
Northem States Power Company Monticello Nuclear Generating Plant 2007 Wr' Hwy 75 Monticek 4:nnesota 55362 9637 August 12,1997 I
US Nuclear Regulatory Commission I
Attn: Document Control Desk i
Washington, DC,?0555 1
MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR 22 Report of Corrections to ECCS Evaluation Models Pursuant to 10 CFR 50.46(a) the following is the required annual report of any change or error identified in ECCS analytical models or their application. The analysis of record for the Monticello reactor is docketed in the license amendment for plant rerate found in Reference 1. The most recent report on any change or error in analytical methods from the reactor vendor, General Electric, who performed the Monticello ECCS analysis, was submitted directly to the Nuclear Regulatory Commission as Reference 2 and was transmitted to Northem States Power with Reference 3.
Reference 2 discusses two items. The first item is an error in the application of the GEGAP code t
which results in a best estimate, rather than a bounding gap conductance. The effect is an underestimate of approximately 15"F in the calculated Peak Clad Temperature (PCT) of GE11 and GE13 fuel when analyzed using SAFE /REFLOOD. Since the Monticello analysis of record was done using SAFER /GESTR LOCA and not SAFE /REFLOOD, this error does not apply to Monticello calculations.
The second item is notification that General Electric has knowingly applied a conservatism of approximately 25'F in the ECCS evaluation models since they increased the density of fue! pellets in all their product lines in the middle 1980s. This does not constitute a change or error in the ECCS evaluation models and therefore need not be reported under 10 CFR 50.46(a).
The following table summarizes the calculated Peak Clad Temperature (PCT) for the analysis of record, Reference 1. Since this is a recent analysis, previous changes and errors affecting Monticello are incorporated into this analysis.
Fuel Type PCT ( F)
Reference
,f GE10 1922 1
[d l
GE12 Note B Note A: Monticello currently has 8 qualification fuelassemblies of the SPC 0x9-IX fuel type which are bounded by the GE10 LOCA analysis because of the following: (1) it has greater heat transfer area than the GE10 bundle, which improves heat transfer characteristics during a LOCA, (2) it has more fuel rods, which reduces the initial temperature and stored energy relative to the GE10 bundle, and (3) the larger water channelin the SPC 9x9-IX compared to GE10 provides a greater heat sink during a LOCA.
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Note B: Monticello currently has 4 lead use assemblies of the GE12 fuel type which are bounded by the GEt t LOCA analysis because of the following: (1) it has greater heat transfer l
area than the GE11 bundle, which improves heat transfer characteristics during a LOCA, (2) it has more fuel rods, which reduces the initial temperature and stored energy relative to the l
GE11 bund,e, and (3) the GE12 bundles used at Monticello are specifically designed to have lower linear heat generation rates than the coresident GE11 fuel.
Please contact Marcus Voth, Monticello Licensing Project Manager, at (612) 2715116 if you require further information. This letter contains no new commitments
$n f
l William J. Hill c:
Regional Administrator 111, NRC NRR Project Manager, NRC Sr Resident inspector, NRC State of Minnesota Attn: Kris Sanda J E Silberg
References:
- 1. General Electric Report NEDC-32514P,"Monticello SAFER /GESTR-LOCA, Loss-of-Coolant Accident Analysis," July 1996. This report is Exhibit G of Monticello License Amendment Request from William J. Hill (Northern States Power) to USNRC Document Control Desk, July 26,1996.
- 2. R. J. Reda (General Electric) letter to USNRC Document Control Desk, " Reporting of Changes and Errors in ECCS Evaluation Models," June 27,1997.
- 3. T. R. Brohaugh (General Electric) letter to K. S. Schnoobelen (Northern States Power), " Annual Report of Changes and Errors in ECCS Evaluation Models," July 14,1997.
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V GE Nuclear Energy s.we tw ca,,
t a su m m.wm sw June 27,1997 RJR-97-084 8
MFN-029-97 Document Control Desk US Nuclear Regulatory Commission Washington, DC 20555-0001 Attention: J. E. Lyons, Chief Reactor Systems Branch
Subject:
' Reporting of Changes and Errors in ECCS Evaluation Models
Reference:
Letter, R.J. Reda to the Document Control Desk (R. C. Jones,Jr.), Reporting of Changes and Erwrs in ECCS Evaluation Models, datedJune 28,1996 (MEN-088-96).
The purpose of this letter is to assist licensees with reporting, in accordance with 10CFR50.46 (a) (3) (ii), the impact of changes and errors in the methodology used by GE to demonstrate compliance with the Emergency Core Cooling System (ECCS) requiremenu of 10 CFR 50.46. This report covers the period from the last report (Reference) to the present.
It is noted that Peak Cladding Temperature (PCT) variations resulting from plant specific system or fuel changes are not addressed in this letter. These should be treated, as appropriate, on a plant specific basis in accordance with other sections of 10CFR50.
There have.been no changes or errors identified for the. SAFE /REFLOOD model desczibed in NEDE 20566-P-A, AnalyticalModelfor Loss-of-Coolant Analysis in Accordance with 10 CFR 50 Appendix K There hwe been no changes or errors identified for the SAFER /GESTR model described in NEDE 23785-1-P-A, The GESTR-LOCA and SAFER ModelsforEvaluation of Lass-of-Coolant Accidents, and NEDE 30996-P-A, SAFER-Modelfor Evaluation of Loss-of-Coolant AcendentsforJet Pump and Non-Jet Pump Plants.
During the reporting period an input error was discovered in the GEGAP gap conductance model which impacts ECCS/LOCA MAPLHGR margins in SAFE /REFLOOD plants using Gell or GEIS fuel. The nature of the input error in the GEGAP analysis was the use of a mean value of fuel pellet densification when a 95% confidence value should have been used.The expectation of the potential consequence of this type of error is a higher gap conductance between the fuel pellet and the cladding. This higher gap conductance would 1
c c
Document Control Desk U. S. Nuclear Regulatory Commission Page 2 result in a lower initial stored energy in the fuel pellet at the onset of the LOCA and, thus, result in the calculation of a lower PCT during the LOCA. An analysis showed that the new corrected inputs from GEGAP resulted in an increase in the calculated PCT of as much as 15*F.
In the mid-1980s, prior to the reporting requirements of 10CFR50.46, GE increased the manufactured fuel density for all fuels. This increased fuel der.sity was a recognized consenatism in the ECCS analysis, therefore no effon was made to redo all of the plant analysis, but rather to hold it as a known conservatirm in the analysis. This conservatism, were it to be implemented in an ECCS analysis would result in a calculated PCT decrease of 25*F and could be used to offset the PCT increase due to the GEGAP error. Thi-consenatism, which was the usa of a lower than actual fuel pellet density in the core heatup calculation, affects both the SAFE /REFLOOD and the S.AJER/GESTR models.
Most licensees have determined that they do not need to incorporate this known conservatism in their current ECCS analysis.
1 All utilities using these evaluation models have been notified of these changes.
I l
If you have any questions, please call me orj. L. Embley at (910) 675-5774.
Sincerely,
/'
A R.J. Reda, Manager Fuels and Facility Licensing (910) 675-5608 cc:
C.J. Monetta J. L. Embley
O
,...,, _ e GENuclear Energy -
ro.w n seesness umfueismas fuelPrject Manager GenenriElectre Company.
P 0= Bcu 180. M,C A33 Wdirungton, NC294014780 July 14,:1997 sr0675-5739 cc: C. A. Bonneau TRB:97-154
'" s;0s75-56s4 J. L Embley H. H. Paustian T. Slayton -
D. B. Waltermire D. G. Wegener Mr,' K. S. Schneebelen Fuel Engineer, Fuel Resources.
l Nonhern States Power Company 414 Nicollet Mall - Ren Sq _10 Minneapolis, MN 55401-1927
Subject:
Annual Report of Changes and Errors in ECCS Evaluation Models -
Reference:
Letter RHR-97-084, R. Jc Reda to the U. S. Nuclear Regulatory Commission,
'_' Reporting of Changes and Errors in ECCS Evaluation Models", dated June 27, 1997 (attached)
Dear Kirk:
Enclosed for your information is a copy of the referenced letter regarding the impact of changes and errors in the Emergency Core Cooling System (ECCS) evaluation methodology _ used by GE.
The annual ECCS reporting letter was sent to the NRC June 27,1997. It is being sent to you so that you remain abreast of the happenings on the annual reporting of ECCS per 10 CFR 50:46 (a)
(3) (ii).
_=
k Ifyou would like additional information, please contact me or John Embley at (910) 675-5774 Very truly yoursi_ r 7meu A T. R. Brohaugh