ML17264A113
| ML17264A113 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 07/17/1995 |
| From: | Mecredy R ROCHESTER GAS & ELECTRIC CORP. |
| To: | Charemagne Grimes NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9507250159 | |
| Download: ML17264A113 (9) | |
Text
PRIORITY 1 (ACCELERATED RZDS PROCESSING)
REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9507250159 DOC.DATE: 95/07/17
" NOTARIZED: NO DOCKET g
FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G
05000244 P
AUTH.NAME AUTHOR AFFILIATION MECREDY;R.C.
Rochester Gas
& Electric Corp.
RECIP.NAME RECIPIENT AFFILIATION GRIMES,C.I.
SUBJECT:
Forwards response to questions in ref 950711 ltr re methodology for determining LTOP sys setpoints.
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4ND ROCHESTER GASANDEIECIICCORK)RATION ~ 89 EASTAVENUE, ROCHESTER, N. Y Id6d9-0001 AREA CODE716 546-27OO ROBERT C. MECREDY Vice President Nvcteor operations July 17, 1995 U.S. Nuclear Regulatory Commission Document Control Desk Attention:
Mr. Chris I. Grimes Chief, Office ofTechnical Specifications Branch Mail Stop 011E22 Washington, D.C. 20555
Subject:
Technical Specification Improvement Program, Reactor Coolant System (RCS)
Pressure and Temperature Limits Report (PTLR)
Rochester Gas &, Electric Corporation R.E. Ginna Nuclear Power Plant Docket No. 50-244
References:
(a)
Letter from R.C. Mecredy, RG&E, to A.R. Johnson, NRC,
Subject:
Technical Specification Improvement Program, dated May 5, 1995.
(b)
Letter from C.I. Grimes, NRC, to R.A. Newton, Westinghouse Owners Group,
Subject:
Request forAdditionalInformation pAI)Regarding 5'CAP-14040, "Methodology Used to Develop Cold Overpressure MitigatingSystem Setpoints and RCS Heatup and CooldownLimit Curves," dated July 11, 1995.
Dear Mr. Grimes,
By Reference (a), RG&E submitted WCAP-14040 and a plant-specific methodology for determining Low Temperature Overpressure Protection (LTOP) system setpoints.
These items were proposed to be used as the basis for the PTLR which would be implemented as part of the conversion to improved standard technical specifications for Ginna Station. By Reference (b),
the NRC submitted questions with respect to both WCAP-14040 (Enclosure 1 to subject letter) and the RG&E methodology for determining LTOP system setpoints (Enclosure 2). The purpose ofthis letter is to respond to those questions provided in Enclosure 2. Responses to the questions provided in Enclosure 1, and to those questions in Enclosure 2 which are generic (i.e.,
questions in Enclosure 2 which are identical to those in Enclosure 1), are to be provided under separate cover by the Westinghouse Owners Group.
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h Section 3.1 should be modified to clearly state that the most limitingmass addition transient should be considered for design ofCOMS. Aninadvertent actuation ofsafety injection should be considered (assume all operable SIpumps deliver water into RCS) if itis more liiniting than the case ofafailure ofthe normal charging flo>vcontrols >vith letdoivn isolated RGB agrees that an inadvertent safety injection should be considered in the design of LTOP ifit is a more limitingmass addition transient.
However, the Ginna Station technical specifications require all three safety injection pumps to be inoperable when the PORVs provide for RCS relief capability and at least two safety injection pumps be inoperable when a 1.1 square inch relief path provides the RCS relief capability. These technical specification limits are in place since the installed LTOP system cannot otherwise mitigate an inadvertent actuation ofsafety injection. This approach has been previously reviewed and found acceptable by the NRC. Therefore, RGRE proposes to revise the last paragraph of Section 3.1 to read as follows:
Two specific transients have been defined, with the RCS in a water-solid condition, as the design basis for LTOPS. Each ofthese scenarios assumes no RHR System heat removal capability. The RHR System reliefvalve (203) does not actuate during the transients.
The first transient consists of a heat injection scenario in which a reactor coolant pump in a single loop is started with the RCS temperature as much as 50'F lower than the steam generator secondary side temperature.
This results in a sudden heat input to a water-solid RCS from the steam generators, creating an increasing pressure transient.
The second transient has Been defined as a mass injection scenario into a water-solid RCS()s',::eau's'ed:::b j
,AVERY YAVA) hWPAVh hVPP )'l.)4W/AVAPh)PAVPAPP/VP/P+Y+VP
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)PPPPVPPWACPA (PAVAVPPYAVAV}VAVAVPPV+WA)Pi 4)V)AVOCA'PPPA+Vh)P~VPP)P...).,.,'..; 4Y~4)i)) '.' )Yg s'sfctj)i6jcctioQ~~poiiipsjjiito!th8RCS!~Th'e:',:s'0
+ST )'A AM..4 VA'+)%Ah..CNiN, NPV)P)NNAVPPi")PPP44P')PFi4h VP)A') )WAP)))P'PA)P'PPPP') $'PPP)VAC N V, ')PP')i PPik)P simultaneous isolation ofthe RHR System, isolation ofletdown, and failure ofthe normal charging flow controls to the fullflow condition. Hitli~rjsceTiario':,pi'ag-:b'8 Slim'ifiateIj:,':fi'0m,:,cop'siike'ratio'id'ep)e'n) i'ng":on'.,:tfie";:p3'ant,":confi'gui rveist'ri'cted,;be'te'chai'c'a3'-,':spi"eoifi'Ca'tii'o'ns";:~:,':A'lS'O~'>'y, and safety injection flows may also be evaluated on a plant-specific basis.
The resulting mass injectio
'auses an increasing pressure transient.
2.
Provide basis ofassuming 800 psia as the PORVpiping limitin the COMS desigii.
This question is the same as Enclosure 1, question 4 (i.e., this is a generic question which applies to both WCAP-14040 and the RGB LTOP methodology).
As such, the Westinghouse Owners Group willrespond to this question.
3.
Section 3.2.5indicates thatin the selection ofthe PORV setpoints, the upper liinitsare specified by the mininumi ofthe steady-state cooldown curve. Please discuss why the heatup curve is not consideredin thisprocess.
This question is the same as Enclosure 1, question 8 (i.e., this is a generic question which applies to both WCAP-14040 and the RGB LTOP methodology). As such, the Westinghouse Owners Group willrespond to this question.
Section 3.2.5 indicates that the uncertainties in the pressure and teniperature instnunentation utilized by the COMS are not accounted forin the selection ofthe COMS PORV setpoints.
Thisis not acceptable to the staff. Please modify the methodology to consider the potential uncertainties in the instrumentation utilized by the COMS.
For determining a LTOP setpoint which is intended to protect only the 10 CFR 50, Appendix G limits, instrument uncertainty is not required due to the conservatism which is employed in the analysis.
However, the LTOP setpoint at Ginna Station must also protect against RHR overpressurization.
As such, instrument uncertainty does apply in the determination ofthe LTOP setpoint when using the RG&E methodology.
Temperature uncertainty is accounted for in the selection ofthe initial conditions for the transients while pressure instrument uncertainty is accounted for in the actuation setpoint selection.
Therefore, RGB proposes to delete the fourth sentence ofthe second paragraph of Section 3.2.5 which states that instrument uncertainty is not included in the analysis.
In addition, we propose to replace item q of Section 3.2.1 with "Instrument uncertainty for temperature (conditions under which the LTOP System is placed into service) and pressure uncertainty (actuation setpoint)" to clarify this position.
In Section 3.2.1, items n and q describe the same parameter.
Please correct this error.
As discussed in the response to question 4 above, item q is being replaced with "Instrument uncertainty for temperature (conditions under which the LTOP System is placed into service) and pressure uncertainty (actuation setpoint)".
In Section 3.2. I, itis indicated that the computer code BSÃT1KLAP5/MOD2-B&8'is used by RGd'cZ< forI.TOP design.
Please provide discussion on the applicability ofthis computer code forI.TOP desigi at Ginna. Also, discuss the staffreview status for this computer code.
The report referenced in the RGkE specified methodology (Reference
- 19) for computer code BWNTRELAPS/MOD2 has been reviewed and approved by the NRC. This referenced report documents the BkWNuclear Technologies (BWNT) adaptation ofthe Idaho National Engineering Laboratory (INEL)RELAPS/MOD2 Cycle 36.05 code.
The fundamental equations, constitutive models and correlations, and method ofsolution of Cycle 36.05 code are preserved in the BWNTversion with input options added to invoke several revised models.
These revised models were developed to: (1) address specific deficiencies in the base code, and (2) extend the capability ofthe code as required to model systems unique to certain designed PWRs (e.g., high elevation AFW injection lines). Application ofthis code to Westinghouse PWRs is documented in BAW-10169P-A.
RGEcE considers this code to be acceptable for the LTOP transients.
For the LTOP analyzed transients, the RCS fluid remains a single-phase liquid. Therefore, the important code process and closure models are: (1) state property search, (2) single-phase flow, (3) single-phase wall heat transfer, (4) RCS pump flow, and (5) choked flow through the PORV. These are discussed in more detail below with respect to the models used for Ginna Station.
The RELAPS property routines are designed to calculate any fluid state between atmospheric pressure and critical pressure.
Difficultyin resolving state properties is typically encountered where two-phase search inputs are calculated during a timestep that is out ofrange.
However, the single-phase conditions that are expected in the LTOP transients preclude this problem.
The governing field equations in RELAPS are formulated from conventually accepted forms ofthe conservative equations for nonequilibrium, nonhomogeneous two-phase flows. In the LTOP calculations, these coded difference equations will"collapse" to that for unsteady, one-dimensional single-phase flows. Except for the necessary correlated closure models, these forms are independent of pressure and temperature conditions and acceptable for use.
In RELAPS the wall frictionwillbe computed from a numerical fitto the Colebrook Correlation. Thewall frictionfactoriscalculatedusing A,=64/Re. Theplantinput model includes the necessary adjustments to ensure that the pressure drops and flows for other geometries are consistent with the target conditions.
Single-phase wall heat transfer under turbulent flow conditions willbe calculated using the Dittus-Beolter Correlation. This correlation is well accepted and has been extensively used for single-phase heat transfer without the restrictions regarding fluid pressure.
For lower flow rates, RELAP5 willuse the industry-standard laminar and free convection correlations.
The RELAPS pump process model is not used for the LTOP models.
Instead, field test data ofRCS flowversus time willbe input as a boundary condition.
The PORV choked flowcalculation willbe performed using the Henry-Fauske model which is widely accepted and which has been successfully benchmarked with the subcooled liquid over a range ofpressures.
In. summary, for the LTOP calculations, RELAPS/MOD2 Version 20.0HP has the necessary process and closure models to analyze the key phenomena.
The RCS remains subcooled, which allows the code to use the established single-phase models, where the accuracy is not a function ofpressure.
Furthermore, the pressures associated with this transient are high enough that the code could adequately calculate two-phase conditions ifthey existed.
RGB willprovide a corrected version ofthe LTOP system setpoint methodology following NRC acceptance of these responses and our response to any other potential future questions.
Please contact Brian Flynn at (716) 771-4805 ifyou have any questions related to this RGEcE specific methodology.
Very truly yours, Robert C. Mecredy
MDF3743 xc:
U.S. Nuclear Regulatory Commission Mr. Allen R. Johnson (Mail Stop 14B2)
PWR Project Directorate I-1 Washington, D.C. 20555 U.S. Nuclear Regulatory Commission Mr. Carl Schulten (Mail Stop 011E22)
Office ofTechnical Specifications Branch Washington, D.C. 20555 U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King ofPrussia, PA 19406 A
Ginna Senior Resident Inspector Mr. Jim Andrachek Westinghouse Electric Company Energy Center East 4-1 4350 Northern Pike Monroeville, PA 15146-2886