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Westinghouse Electric Co., - WCAP-10325-P-A Methodology Material Properties as Applied in the Watts Bar Containment Analysis.
	ML15209A892
Person / Time
Site:	Watts Bar
Issue date:	07/23/2015
From:	Gresham J; Westinghouse
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML15209A872	List: ML15209A891; ML15209A892;
References
	LTR-NRC-15-62, LTR-NRC-15-62 Attachment WCAP-10325-P-A
	Download: ML15209A892 (16)
	v • d • e

WESTINGHOUSE NON-PROPRIETARY CLASS 3 LTR-NRC-15-62 Attachment WCAP-10325-P-A Methodology Material Properties as Applied in the Watts Bar Containment Analysis (Non-Proprietary)

Westinghouse Electric Company LLC 1000 Westinghouse Drive Cranberry Township, Pennsylvania 16066

(*) 'Nedinghcuse LTR-NRC-1 5-62 Attachment

" Issue Statement

" Standard Review Plan

" WCAP-10325-P-A Methodology Background

WCAP-1 0325-P-A (SATAN/REFLOOD/EPITOME)

WCAP-8354-P-A (LOTIC1))

" IG-14-1 Discussion (InfoGram)

" WCAP-10325-P-A Conservatism Rack-up

" Comparison of Methodologies

" Watts Bar Analysis of Record Status

" Standard Review Plan Conformance

" Conclusions

Westinghouse 2

LTR-NRC-15-62 Attachment 9 The NRC has requested that Watts Bar 1 and 2 provide the results of the containment pressure, temperature, sump temperature responses and net positive suction head (NPSH) analysis using the ASME published volumetric heat capacity for the RCS metal including corrections of the errors reported NSALs.

Westinghouse 3

LTR-NRC-1 5-62 Attachment

" The objective is to conservatively calculate the containment pressure response following a LOCA to protect the health and safety of the public

" Standard Review Plan (NUREG-0800) Section 6.2.1.3

- Section IL.A Acceptance Criteria requires that containments are designed with sufficient margin to accommodate the temperature and pressure conditions following a LOCA

- Section II.B Acceptance Criteria states that additional conservatism should be included to maximize energy release during blowdown and reflood, maximizing stored sensible heat is cited as an example

Westinghouse 4

LTR-NRC-15-62 Attachment

" WCAP-1 0325-P-A documents a Loss of Coolant Accident Mass and Energy (LOCA M&E) release methodology

Built around several conservative assumptions

- Rapid non-mechanistic release of stored RCS energy

- Thermal conductors are single node (i.e. not conduction limited)

- Input parameters are skewed conservatively (e.g. core power, decay heat, initial conditions)

Westinghouse

LTR-NRC-1 5-62 Attachment WCAP-1 0325-P-A supports the Standard Review Plan acceptance criteria through the following:

- Conservatively fast stored energy release model

- Single node heat slabs (not conduction limited)

- Key inputs are biased conservatively

Fuel stored energy is maximized

Decay heat is maximized (ANS-1979+2sigma)

" RCS volumes are biased high

" Initial RCS temperatures are biased high

" Initial RCS pressure is biased high

" Uncertainty on core power is included

Westinghouse 6

LTR-NRC-15-62 Attachment WCAP-8354-P-A supports the Standard Review Plan acceptance criteria through the following:

- Containment heat sink effectiveness is biased low

Volume and surface area

Heat transfer from atmosphere

- Containment volumes are biased low

Upper compartment, lower compartment, and ice condenser

- No heat transfer to sump pool surface area is credited

- No heat transfer to ice condenser effluent is credited (LOCA)

- Various TS parameters biased in conservative direction (e.g.

UHS temperature, ice bed temperature)

Westinghouse 7

LTR-NRC-15-62 Attachment o Subsequent to issuance of the NSALs, further material property questions were raised

- The stainless steel volumetric heat capacity value in WCAP-10325-P-A analyses was noted to be lower than ASME published data

- WCAP-1 0325-P-A material properties are based on data generated prior to ASME data

Although not bounded by the ASME data, the values used were considered to be representative of available published data at the time

Westinghouse 8

LTR-NRC-15-62 Attachment

_;hous 2 *

g Elcr*i C LLC All R e ILOCA IM&E,:I Contain,]~limen*lt! Pressure*= Plo (Prelimi-narynF)]

WB1 WCAP-10325+NSALs WB1 WCAP-10325+NSALs+Cp+175k ce WB1 WCAP-10325+NSALs+Cp+200k ice WB1 WCT 14-_

12-cn

(: l_

u*8-0 2000 4000 6000 8000 10000 Time (s)

Westinghouse 9

LTR-NRC-15-62 Attachment

Known Conservatisms

NRC Concern

- Single node thermal conductors - Difference in volumetric heat

- Maximized stored metal energy capacity relative to ASME is non release rate conservative

- Maximized core power

- Bias on RCS volumes

- ANS-1979+2a decay heat

- Maximum RCS temperatures +

uncertainty

- Core stored energy maximized

(*) Westinghouse 10

LTR-NRC-15-62 Attachment The containment pressure comparison shows that the large peak containment pressure increase is a consequence of conservative assumptions in the WCAP-10325-P-A and WCAP-8354-P-A methodologies

- WCOBRA/TRAC is a more mechanistic LOCA M&E release tool

- The material properties in WCOBRA/TRAC, as submitted, more closely reflect the ASME data (future WCOBRA/TRAC analyses will use the ASME data plus conservatism)

- The increased time duration to ice melt seen with WCOBRA/TRAC reduces the effect of stored RCS metal energy contribution SWestinghouse 11

LTR-NRC-15-62 Attachment 9 Containment Analyses for Watts Bar 1/2 are in progress

- Supports dual unit operation with revised heat exchanger performance due to Unit 1 and Unit 2 shared systems (GDC-5)

° Reduction in component cooling water heat exchanger performance is considered

- The analyses are being finalized by Westinghouse

° This revisions include all updates required

- Analyses support Watts Bar Unit 2 startup

- Used WCAP-1 0325-P-A methodology SWestinghouse 12

LTR-NRC-15-62 Attachment Standard Review Plan (NUREG-0800) Section 6.2.1.3

- Section II.A Acceptance Criteria requires that containments are designed with sufficient margin to accommodate the temperature and pressure conditions following a LOCA Based on results calculated using WCOBRA/TRAC, the WCAP-1 0325-P-A methodology contains sufficient conservatism such that the acceptance criteria above is met SWestinghouse 13

LTR-NRC-15-62 Attachment

- Section IlI.B Acceptance Criteria states that additional conservatism should be included to maximize energy release during blowdown and reflood, maximizing stored sensible heat is cited as an example

Although the amount of stored RCS metal energy is potentially underestimated, the rate at which it is transferred to containment is highly conservative, and the net result is an overall conservative model with respect to containment integrity

Therefore, the acceptance criteria above is met

Westinghouse 14

LTR-NRC-1 5-62 Attachment We stigose No- Prpitr ~ Cls 3g 201 Wetngos Elcti Co pn LC. All Riht Reere.

" Watts Bar analyses fully comply with applicable General Design Criteria

" Standard Review Plan acceptance criteria are met

WCAP-10325-P-A has been demonstrated to be conservative

- Comparisons to WCOBRA/TRAC results demonstrate the level of conservatism in WCAP-10325-P-A

Westinghouse 15

ML15209A892

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