ML20217J714
| ML20217J714 | |
| Person / Time | |
|---|---|
| Issue date: | 04/01/1998 |
| From: | Craig C NRC (Affiliation Not Assigned) |
| To: | Essig T NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9804060363 | |
| Download: ML20217J714 (35) | |
Text
~
April 1, 1998 MEMORANDUM TO: Thomas H. Essig, Chief Generic issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation FROM:
Claudia M. Craig, Senior Project Manager Original Signed By:
Generic issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF MEETING WITH WESTINGHOUSE TO DISCUSS WCAP-12945, " WESTINGHOUSE CODE QUALIFICATION DOCUMENT FOR BEST ESTIMATE LOSS OF COOLANT ANALYSIS" The subject meeting was held at the Nuclear Regulatory Commission (NRC) offices in Rockville, Maryland on March 20,1998, between a representative of Westinghouse and the NRC staff. The meeting was held to provide the staff a copy of the approved version of the subject WCAP and discuss its contents. Attachment 1 is a copy of the non-proprietary presentation material. Attachment 2 is a list of meeting participants.
In a letter dated June 28,1996, the NRC forwarded to Westinghouse the safety evaluation report (SER) on WCAP-12945, " Westinghouse Code Qualification Document for Best Estimate Loss of Coolant Analysis." The SER advised Westinghouse that the subject topical report was I
acceptable for referencing with certain limitations and conditions. One of the principal I
conditions was the implementation of a documentation plan. The documentation plan consisted of three items. Westinghouse addressed the first portion, item "a", of the documentation plan by providing a detailed tracking system identifying where the responses to all RAls were docketed. This was provided to the staff in May 1996. The documentation plan also included an item to restructure the WCAP to reflect the approved methodology, item "b", and to provide all information between the original and final submittals, item "c".
I During the meeting Westinghouse discussed how the topical satisfied item "b" of the documentation plan. Westinghouse walked the staff through the WCAP, familiarized the staff with the layout, and used examples to demonstrate how the topical was structured.
Westinghouse reaffirmed the commitment to satisfy item "c" of the documentation plan within 6 months.
+\\
The staff plans to conduct audits of specific sections of the topical and document its findings.
I CENTER CDPy Dh Attachments: As stated cc w/atts: See next page DOCUMENT NAME: 3_20_98. MIN DISTRIBUTION: See next page OFFICE PGEBM g fi (A)SC:PGEB BC: SRXB NAME CCraig'sI MMbt$w TCollinsk DATE 3/)k/98 3 / y) /98 y / o/ /98 OFFICIAL RECORD COPY g 9804060363 980401 PDR TOPRP EMVWEST C
,~
f, gr:eg%;i UNITED STATES j
p j
NUCLEAR REGULATORY COMMISSION jo#g WASHINGTON, D.C. 20885-0001 g'%
pril 1, 1998 MEMORANDUM TO: Thomas H. Essig, Chief
' Generic issues and Environmental
~
Projects Branch _
i Division of Reactor Program Management Office of Nuclear Reactor Regulation,,
\\
I FROM:
Claudia M. Craig, Senior Project Mariage Generic lasues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation i
SUBJECT:
SUMMARY
OF MEETING WITH WESTINGHOUSE TO DISCUSS WCAP-12945, " WESTINGHOUSE CODE QUAL.lFICATION DOCUMENT FOR BEST ESTIMATE LOSS OF COOLANT ANALYSIS" The subject meeting was held at the Nuclear Regulatory Commission (NRC) offices in Rockville, Maryland on March 20,1998, between a representative of Westinghouse and the NRC staff. The meeting was held to provide the staf a copy of the approved version of the
{
subject WCAP and discuss its contents. Attachment 1 is a copy of the non-proprietary presentation material. Attachment 2 is a list of meeting participants.
In a letter dated June 28,1996, the NRC forwarded to Westinghouse the safety evaluation report (SER) on WCAP-12945, " Westinghouse Code Qualification Document for Best Estimate i
Loss of Coolant Analysis." The SER advised Westinghouse that the subject topical report was acceptable for referencing with certain limitations and conditions. One of the principal conditions was the implementation of a documentation plan. The documentation plan consisted i
of three items. Westinghouse addressed the first portion, itera "a", of the documentation plan by providing a detailed tracking system identifying where the responses to all RAls were docketed. This was provided to the staff in May 1996. The dxumentation plan also included an item to restructure the WCAP to reflect the approved methodology, item "b", and to provide all information between the original and final submittals, item "c".
During the meeting Westinghouse discussed how the topical satisfied item "b" of the documentation plan.. Westinghouse walked the staff through the WCAP, familiarized the staff with the layout, and used examples to demonstrate how the topical was structured.
Westinghouse reaffirmed the commitment to satisfy item "c" of the documentation plan wMhin j
- 6 months.
l
. The staff plans to conduct audits of specific sections of the topical and document its findings.
I 1
i Attachments: As stated
~ cc w/atts: See next page f
~ '
1
- r J
?
l I
i IMPLEMENTATION OF DOCUMENTATION PLAN REQUIREMENTS FOR WCAP-12945-P:
" CODE QUALIFICATION DOCUMENT FOR BEST ESTIMATE LOSS OF COOLANT ACCIDENT 4
ANALYSIS" MITCH NISSLEY WESTINGHOUSE NUCLEAR SERVICES DIVISION (412) 374-4303 nissieme@ westinghouse.com ATTACHMENT 1
MEETING OBJECTIVES DEMONSTRATE THAT WCAP-12945-P-A SATISFIES ITEM "b" l
OF THE DOCUMENTATION PLAN OUTLINED IN USNRC'S SER FAMILIARIZE THE STAFF WITH THE LAYOUT OF THE DOCUMENT RE-AFFIRM COMMITMENT TO SATISFY ITEM "c" OF THE DOCUMENTATION PLAN WITHIN 6 MONTHS (BY 9/20/98)
)
BACKGROUND INFORMATION WCAP-12945-P SUBMITTED AS A 5 VOLUME SET ('91 '93)
RIGOROUS REVIEW PERFORMED BY NRC/INEL/ACRS WESTINGHOUSE RESPONDED WITH > 60 ADDITIONAL SUBMITTAL PACKAGES NUMEROUS CODE & METHODOLOGY CHANGES RESULTED DOCUMENTATION ISSUES:
1)
VOLUME AND ORGANIZATION OF ORIGINAL SUBMITTALS MADE THEM DIFFICULT TO 1
FOLLOW / REVIEW 2)
TREMENDOUS PAPER TRAIL BETWEEN ORIGINAL AND FINAL SUBMITTALS
l DOCUMENTATION ISSUE RESOLUTION PRIOR TO SER:
1 NRC REQUIRED WESTINGHOUSE TO PROVIDE A DETAILED TRACKING SYSTEM, SHOWING WHERE RESPONSES TO ALL RAIs WERE DOCKETED WESTINGHOUSE PROVIDED THE REQUIRED e
INFORMATION IN MAY,1996 (NSD-NRC-96-4710) c ITEM "a" OF DOCUMENTATION PLAN FOLLOWING SER:
ITEM "b" jlE-STRUCTURE WCAP TO REFLECT APPROVED METHODOLOGY, SUBMIT PROPRIETARY AND NON-PROPRIETARY VERSIONS FOR NRC REVIEW (DETAILS TO FOLLOW)
ITEM "c" PROVIDE PROPRIETARY AND NON-PROPRIETARY VERSIONS OF ALL INFORMATION BETWEEN THE ORIGINAL AND FINAL SUBMITTALS
ITEM "b"(PAGES 13-14 OF SER)
"WCAP-12945 WILL BE RESTRUCTURED CONSISTENT WITH ITS REVISED METHODOLOGY. THE REVISED WCAP WILL PROVIDE UP FRONT A ROAD MAP DESCRIBING THE OVERALL WCOBRA/ TRAC EM APPROACH AND COMPARING IT TO THE ACCEPTABLE CSAU APPROACH. IT WILL ALSO PROVIDE IN l
AN ORDERLY AND UNDERSTANDABLE FASHION DESCRIPTIONS OF THE APPROVED INDIVIDUAL CORRELATIONS AND HOW THEY WERE DETERMINED TO BE APPROPRIATE, DESCRIPTIONS OF THE AS-APPROVED VALIDATIONS PERFORMED ON THE CODE, AND DESCRIPTION OF THE APPROVED UNCERTAINTY EVALUATION PROCESS.
IT WILL BE WELL INDEXED SUCH THAT INFORMATION IS READILY LOCATED. ALSO,IT WILL CONTAIN IN APPENDICES HISTORICAL REVIEW INFORMATION, SUCH AS QUESTIONS AND ACCEPTED RESPONSES, AND ORIGINAL REPORT PAGES j
TH.AT WERE REPLACED. THIS UPDATED VERSION OF WCAP-12945 WILL BE PROVIDED FOR STAFF REVIEW IN BOTH PROPRIETARY AND NON-PROPRIETARY VERSIONS WITHIN 6 MONTHS OF ISSUANCE OF OUR LETTER OF ACCEPTANCE."
IMPLEMENTATION OF ITEM "b" REQUIREMENTS "THE REVISED WCAP WILL PROVIDE UP FRONT A ROAD MAP DESCRIBING THE OVERALL WCOBRA/ TRAC EM APPROACH
)
AND COMPARING IT TO THE ACCEPTABLE CSAU APPROACH."
NUREG/CR-5249 DESCRIBES THE CSAU APPROACH BY BREAKING IT INTO 3 ELEMENTS CONSISTING OF 14 TOTAL STEPS SECTION 1-2 OF WCAP-12945-P-A WALKS THROUGH EACH CSAU STEP, COMPARING THE WCOBRA/ TRAC EM APPROACH WITH CSAU (see following pages 1-3 to 1-5)
SECTION 1-3-3-3 WAL.KS THROUGH THE PIRT, COMPARING THE WESTINGHOUSE RANKINGS WITH CSAU SECTION 1-3-5 DESCRIBES THE LAYOUT OF THE e
REPORT, AND RAI NOMENCLATURE (see following pages 1-48 to 1-51)
-]
l 21 Element I: Requirements and Code Capabilities j
The CSAU methodology begins with development of the Phenomena Identification and i
Ranking Table (PIRT) to identify the key thermal hydraulic phenomena which govem the f
transient of interest. A frozen code is selected, the documentation for the code is developed and the capabilities of the code are assessed against the key thermal hydraulic parameters identified in the PIRT, to demonstrate the code's applicability to the problem.
Step 1: Specify Scenario CEA_Q:
The scenario specified in CSAU was the large break LOCA.
Westinghouse:
The large break LOCA is the scenario assumed for the methodology described in this report.
A general description of a large break LOCA is presented in Section 1-3-1. Actual plant I
transient calculations are provided in more detail in Section 20.
Step 2: Select Nuclear Power Plant (NPP)
CSAU:
A Westinghouse four-loop Pressurized Water Reactor (PWR) with a 17x17 fuel design was selected.
Westinghouse:
Three and four loop operating Westinghouse PWRs with 15x15 and 17x17 fuel designs and l
with cold leg ECC injection were selected.
Step 3: Identify and Rank Phenomena C1.A_Q:
A A PIRT was developed to focus on the phenomena and processes which were important for the LOCA scenario (Boyack et al.,1989, Section 2.3). Experience and expert opinion were i
o V225.non\\sec t.non:lt431698 l-3
,j applied in ranking physical processes in order of importance. The following highly ranked phenomena were identified for assessment of uncertainty:
a)
Break mass flowrate b)
Pump head and torque degradation c)
Stored energy (gap conductance, fuel rod peaking factor, fuel conductivity, convective heat transfer) d)
Blowdown and rs Sood heat transfer (convective heat transfer, minimum rewetting temperature) e)
Delivery and bypassing of ECC f)
Steam binding (core entrainment to upper plenum and hot legs, boiling within U-tubes) g)
Noncondensable gases (partial pressure and dissolved nitrogen)
Westinnhouse:
- The modelling requirements needed to perform a best estimate calculation are identified and discussed (Section 1-3-3). In developing the requirements, the individual phenomena and processes which must be modelled to achieve an accurate estimate of the PCT are identified (Sections 1-3 3-1 and 1-3 3-2). A PIRT is developed, using the same process as described in the CSAU (Section 1-3-3 3). The following highly ranked models and phenomena are identified from the PIRT:
a)
Critical flow b)
Broken loop resistance c)
Fuel rod (fuel conductivity, gap conductivity, rod internal pressure, decay heat, cladding swelling and burst, zire water reaction, fuel relocation) d)
Core heat transfer o u 225 = = cimon w m es 1-4
e)
ECC bypass f) -
Entrainment/ steam binding g)
Condensation The CSAU and Westinghouse lists of dominant phenomena are similar, except that condensation is included in the Westinghouse list. In addition, the broken loop resistance (of which the pump is one component) is found to be important in the Westinghouse methodology. The fuel rod uncertainty includes contributions from cladding rupture t.nd fuel relocation. Finally, in the CSAU the noncondensables category deals with gases coming out of solution during ECC delivery while in the Westinghouse PIRT, nitrogen issuing from the l
accumulator after it has emptied is considered the important process.
The Westinghouse methodology includes an additional step in which important plant initial l
and boundary conditions whose uncertainty may affect PCT am also identified (Step 11).
These are considered as additional contributors to uncertainty.
Siep 4: Select Frozen Code CSAU:
ne TRAC-PF1 MOD 1, Version 14.3 code was selected for the CSAU studies by the NRC.
Westinnhouse:
Modelling requirements are identified based on the identification ofimportant LOCA processes (Sections 13-4-1 to 1-3-4-$).
Westinghouse selected ECOBRA/ TRAC MOD 7A for the best estimate methodology, based on an evaluation of the code's capabilities relative to the modelling requirements (Section 1-3 4-6).
(Note: The original version of WCOBRA/ TRAC used in the code assessment and methodology development was WCOBRAfrRAC MOD 7. During the USNRC review
{
WCOBRA/ TRAC MOD 7 was revised to improve the core entrainment model and correct o \\3225 nonWl.non.1b 031698 1-$
l
1 3
i
\\
Entrainment and de-entrainment Droplet flow I
I.3 5 Step 5: Provide Code Documentation This repon describes the models and correlations used in WCOBRA/ TRAC, the assessment performed to establish the code's ability to predict experimental data, and the PWR transient, the assessment performed to establish the range and distribution of the important variables affecting the peak cladding temperature, and the methodology used to combine uncertainties and biases. The report is divided into four broad areas: models and correlations, code assessment and ranging, PWR modelling, and uncenainty methodology. Each section addresses a specific step of the CSAU methodology in detail. The overall structure (i.e.,
number of sections and general section topic) of this revised repon is similar to the original repon submitted to the NRC; however, the following major revisions have been made:
l 1.
Each section is related to a specific element and step of the CSAU methodology.
2.
- Several sections have been significantly modified to reflect more clearly the final methodology as approved by the NRC. In all cases, the modifications include material already provided to the NRC via responses to requests for additional information (RAls), with minor text changes where necessary to improve the clarity of the presentation.
3.
Each section includes references to RAls pertaining to the subject being discussed in that section. In some of the later sections, significant changes have been made to more clearly describe the final methodology. In these sections, it is not practical to provide direct references in the revised text to all of the RAls.
In these cases, the RAI index at the end of the section contains a brief comment on why the RAI is no longer applicable, and references sections where the subject covered by the RAI is directly addressed.
'Ihe first pan consists of Sections 2 through 10. These chapters are the "Models and
. Correlations" pan of the repon. They identify the individual models and correlations in WCOBRA/ TRAC, give their technical basirland describe how they are programmed. Each of these sections also include a discussion of the scalability of each model and the suitability of each model for use in best estimate LOCA analysis. Reference is made to those simulations
. u ns. w w w m es 1 48
that will verify the scalability of the models and those that will incorporate the model into the overall code bias and uncenainty.
Sections 2 through 10 are organized according to thermal hydraulic topic. Section 2 describes the conservation equations and numerical methods. Flow regimes are described in Section 3, and the interfacial area for each regime is discussed. Section 4 provides information on momentum transfer, including the models and correlations used to determine interfacial shear, form loss and pressure drop, droplet breakup on structures and entrainment/de-entrainment phenomena. The relations used to evaluate interfacial heat and mass transfer are described in Section 5. The wall to fluid heat transfer models and correlations are discussed in Section 6, while the thermal-mechanical behavior of the structures used to model nuclear fuel rods and experimental fuel rod simulators is contained in Section 7. Each of the first seven sections use a common nomenclature. Section 8 describes the kinetics model and decay heat models in ECOBRA/ TRAC and uses a separate nomenclature. Special component models, used to model equipment such as pumps, steam generators, and safety injection, are described in Section 9. Finally, Section 10 provides information on calculation of the thermodynamic and transport properties of water and common fuel rod and RCS structural materials. In each section of this "Models and Correlations" part of the report, there are four elements that appear as subheadings. "Model Basis" identifies the model or correlation and gives reference to its origin and technical basis. "Model as Coded" provides specific information on how the models and correlations are programmed in the code. Numerical ramps, limits, and approximations of the true correlation are identified. " Scaling Considerations" discusses the range of scale over which the models apply or identifies the assessments that were performed in order to demonstrate scale independence. The " Conclusions" section describes the applicability of the models for best estimate LOCA calculations. Simulations that validate the models and correlations are identified.
Sections 11 through 16 describe the simulations of experimental tests and compare the calculated results to data. For each test simulated, the test facility is described and the noding diagram of the ECOBRA/ TRAC input model is presented. To maintain consistency between results, a " frozen" code version was used for the simulations. This is consistent with the CSAU approach, which emphasizes the use of a rigorously controlled code version for the simulations used to determine the code bias and uncenainty.
Section 19 includes results of sensitivity studies that were performed to examine timestep size and code convergence. These studies' were performed prior to other code validation o \\3225-non\\secI non.Ib 03160s
!-49
simulations in order to identify appropriate code convergence parameters for those calculations.
The simulations are grouped into the various sections by important LOCA phenomena identified in the PIRT. Blowdown and refill separate effects test simulations are described in Section 11. Section 12 repons the simulations of separate effects reflood tests including FLECHT-SEASET, FEBA, and G-2. A final assessment of the heat transfer models is performed in Section 13. Simulations of integral tests are an imponant pan of the assessment and validation of any best estimate thermal-hydraulic code. ECOBRA/ TRAC simulations of 2
the LOFT, CCTF, SCTF, and UPTF integral tests are reponed in Section 14. Section 15
)
repons simulations of experiments that validate the fluid flow models in ECOBRA/ TRAC.
{
The fuel rod, pump, accumulator, and break flow models are assessed by the simulations in Section 16. All of these simulations used a " frozen" code version. A final assessment of 1
ECOBRA/ TRAC is performed in Section 17 and Appendix A. Apper "x A is a study of compensating errors in ECOBRA/ TRAC.
J The scaling assessment and calculation of the overall ECOBRAfrRAC cede bias and uncenainty is described in Sections 18 and 19. Sections 20 to 23 describe PWR modelling and sensitivity studies performed to confirm significant contributors to uncenainty as identified in the PIRT. Sections 24 to 26 develop the method which will be used to combine uncenainties and biases. Section 27 demonstrates the methodology using a specific PWR.
Section 28 provides a summary and conclusion, including a discussion of compliance with 10 CFR 50.46 and Regulatory Guide 1.157.
There are two additional appendices provided in this report. Appendix B is a list of code modifications perfonned near the end of the USNRC review to correct minor code errors and include modifications required for revisions to the methodology. Appendix C is a record of all final responses to RAIs, with references to material formally submitted to the NRC. The RAIs referenced in the body of the repon are listed in the back of each section or sub-section.
The nomenclature used in the RAI listings is as follows:
RAll-x to RAI3-x: Final responses to original RAI regarding Volumes 1 through 3 of WCAP-12945 P (Collins,1994a), and additional review comments (Fineman,1995) regarding preliminary Westinghouse responses to those RAI
. :uus-aaawi=lumes 1-50
'e RAI4-x to RAIS-x: Final responses to original RAI regarding Volumes 4 and 5 of WCAP-12945 P (Collins,1994b), and additional review comments (Fineman,1995) regarding preliminary Westinghouse responses to those RAI RAIS-x: Final responses to " Supplemental" RAI regarding Volumes 1 through 3 of WCAP 12945-P (Collins.1994b)
RAIA-x: Final responses to informal RAI, issued by Westinghouse in NTD NRC 94-4599, November 22,1995 RAIB x: Final responses to informal RAI, issued by Westinghouse in NTD-NRC-96-4618, January 5,1996 RAIC x: Final responses to informal RAI, issued by Westinghouse in NTD-NRC-96-4629 January 24,1996 RAID-x: Final responses to informal RAI, issued by Westinghouse in NTD-NRC-96-4631, January 26,1996 RAIE x: Final responses to informal RAI, issued by Westinghouse in NSD NRC-96-4672, March 25,1996 RAIF-x: Final responses to informal RAI, issued by Westinghouse in NSD-NRC-96-4702, April 30,1996 RAIG x: Final responses to informal RAI, issued by Westinghouse in NSD NRC-96-4718, May 9,1996 RAIH x: Final responses to informal RAI, issued by Westinghouse in NSD-NRC 96-4744, June 12,1996 14 References 10 CFR Pan 50, Section 46, " Acceptance Criteria for Emergency Cooling Systems for Light Water Cooled Nuclear Power Plants," Federal Register 39, (3), Jan. 4,1974.
o u225.no.u.ci non.m.om98 1-5 I
l "IT WILL ALSO PROVIDE IN AN ORDERLY AND UNDERSTANDABLE FASHION DESCRIPTIONS OF THE APPROVED INDIVIDUAL CORRELATIONS AND HOW THEY
{
WERE DETERMINED TO BE APPROPRIATE,... "
1 A CONSISTENT APPROACH IS USED TO PRESENT THE e
APPROVED INDIVIDUAL CORRELATIONS IN VOL.1 (see following pages 6-2 to 6-6):
- 1) MODEL BASIS (PHYSICAL PROCESS, BASIC EQUATIONS, LITERATURE CITATIONS)
- 2) MODEL AS CODED (DESCRIBES ANY RAMPS, LIMITS, NUMERICAL DAMPING, ETC.)
- 3) SCALING CONSIDERATIONS ADDITIONAL ASSESSMENT OF KEY PHYSICAL e
MODELS (FROM THE PIRT) PERFORMED IN VOLUMES 2 & 3, WITH MAJOR CONCLUSIONS SUMMARIZED IN SECTION 25 (VOL 5)
"... DESCRIPTIONS OF THE AS-APPROVED VALIDATIONS PERFORMED ON THE CODE,..."
VOLUMES 2 & 3 REFLECT RE-ANALYSES WHICH WERE REQUIRED BECAUSE OF CODE REVISIONS
... AND DESCRIPTION OF THE APPROVED UNCERTAINTY f
EVALUATION PROCESS."
UNCERTAINTIES IN PLANT AND CODE RELATED PARAMETERS PRESENTED IN SECTIONS 21 AND 25 OVERALL UNCERTAINTY METHODOLOGY e
PRESENTED IN SECTION 26, AND DEMONSTRATED IN SECTION 27 I
a
Figure 6-2. The following list gives the heat transfer regimes used in the WCOBRA/ TRAC vessel component heat transfer package.
i
' Mode 1 Single phase liquid convection (SPL)
Mode 2 Single-phase vapor convection (SPV) i i
Mode 3 (currently not assigned)
)
J Mode 4 Subcooled nucleate boiling (SCNB) 1 Mode 5 Saturated nucleate boiling (NUCL)
Mode 6 Transition boiling (TRAN) l Mode 7 Inverted annular film boiling (IAFB)
Mode 8 Inverted annular dispersed flow (IADF) w Mode 9 Dispersed droplet film boiling (DFFB)
Figure 6-3 shows a heat transfer regime map, indicating where each of the modes apply.
l For each regime, three heat transfer coefficients are determined. These are: h, the heat transfer coefficient from the wall to vapor, h, the heat transfer coefficient from the wall to i
liquid for sensible heat, and h, the heat transfer coefficient from the wall to liquid for latent I
heat. He use of h, and h to partition the heat transfer to the fluid phases is discussed in a
Section 6-211. The following sections describe, by heat transfer regime, the correlations used by the vessel component to determine h, h,, and h.
a 6-21 Convection to Single-Phase Vapor
{
Model Basis Heat transfer to single-phase vapor (SPV) is assumed when % > [
]".
The WCOBRA/ TRAC vessel component uses a set of four correlations to determine the heat I
- oA3225wh6\\sec6 non.lb.03189s 6-2 1
'o 4
^
transfer coefficients for convection to single phase vapor. The maximum value of these four correlations is chosen as the heat transfer coefficient to be used to calculate the hea
' provide a continuous'and smooth transition between heat transfer regimes. These correlations are the McAdams (1954) correlation for turbulent natural convection, a constant Nusselt number value for laminar forced convection, the Dittus-Boelter (1930) equation, and an expression proposed by Wong and Hochreiter (1981) for turbulent forced convection. This section presents each correlation and describes its basis.
The McAdams correlation for turbulent free convection over vertical plates and cylinders is given by g,
h,, = 0.13 j> (Gr,Pr,) ass (6-1) r where the Grashof number (Gr,) is defined by
{
Gr' =
(6-2) l 2
w.
{
with the Prandtl number (Pr,) defined by Pr' = *'
(6-3) k, The form of the McAdams correlation results from the analysis of the boundary layer on a vertical surface, at uniform temperature and in an infinite fluid at rest. It is assumed that the flow in the boundary layer is buoyancy induced, and is primarily parallel to the surface.
Although the coefficients for this correlation were originally developed by fitting the equation to data from vertical flat plates in air,the McAdams correlation has also been found to provide good estimates of the heat transfer coefficients for vertical planes and short horizontal I
o U225=hecGesc6 non:It>031s9s 6-3
i I
surfaces in water, oils, alcohols, and air. This correlation is valid in the range 0
10* < GrPr < 10.
For laminar flow, the heat transfer coefficient for vapor is determined assuming a constant Nusselt number of 10. Thus, for laminar vapor flow the heat transfer coefficient is given by
'k' h,,,, = 10 (6-4)W
[nj where k, is the film thermal conductivity for vapor.
This expression for the laminar flow heat transfer coefficient is in the same form as that for fully developed laminar flow in a circular pipe with a constant wall heat flux. The Nusselt number for intemal tube flow with constant wall heat flux is 4.364. For laminar extemal flows, it has been shown that the calculated Nusselt number is higher. Kim (1979) showed that the Nusselt number for an infinite rod bundle with a square rod to pitch ratio of 1.33 is 7.86.
For forced turbulent flow, convective vapor heat transfer coefficients are determined by the Dittus-Boelter (1930) equation and a correlation proposed by Wong and Hochreiter (1981) that was based on experimental rod bundle data. The Dittus-Boelter equation was originally developed for turbulent flow within smooth tubes in automobile radiators. It has since proven acceptable for many other applications involving turbulent flows. It is given by h,,,, m = 0.023 p'
' G' D** (Pr,)a (6-5)
'k
< n, < v.
where n = 0.4 for heating and a = 0.3 for cooling. All vapor properties are evaluated at the mean film temperature.
oA3225=W non:Ib.03 tt9s 6-4
)
J
i 1
The expression proposed by Wong and Hochreiter (1981) is
)
1
'k i
h,,, = 0.0797 gG'D*'a8 (Pr,)*333 (6-6) s h>
r This correlation is a linear regression fit to experimental data obtained from steam cooling heat transfer tests run in a 17x17 rod bundle. This correlation predicts heat transfer coefficients that are larger than those predicted by the Dittus Boelter equation for Reynolds numbers less than 25,000.
Model as Coded The set of four correlations are coded as presented above, with all fluid properties evaluated at the mean film temperature, nese correlations are applied to both vertical and horizontal surfaces in the vessel and use the hydraulic diameter of the flow channel, D, as the characteristic length.
i For heated structures, the heat transfer coefficient to single-phase vapor is calculated as 1
'h4 h,g = maximunr (6-7)<2)
=, n h, (if Re, < [2000]*d)
{
When the Reynolds number is less than [
]", the McAdams correlation for turbulent i
natural convection is also considered.
I 1
Continuity between free and forced convection and between laminar and turbulent flow is assured by selecting the maximum value of the heat transfer coefficients. Figure 6-4
{
compares the expressions in Equation 6-7 for Pr = 1. The Dittus-Boelter equation is coded with the [
l 1
JM,.
o.V225w\\sec6\\sec6 nortIb-031s9s 6-5 l
{
If grids are present in the flow, the convective heat transfer to single phase vapor is enhanc This is accounted for by multiplying the convective heat transfer coefficient by a factor F g
that models the grid effect. Then,
. h, yy = Fg h
,y (6-8) ne effect of the grid on convective heat transfer and calculation of F is described in g
Section 6-2 8. For unheated stmetures, Fg = 0 and h, g is selected as the maximum of
' h,,,,, h,, a, and h,. Since the Wong Hochreiter correlation was developed for rod bundles, it is not used for unheated structures.
The single phase vapor regime is assumed when % > (
]". Only heat transfer to vapor is calculated, and for this regime, hg,,y = 0 (69) and h,yy = 0 (6-10)W a
Scaline Considerations Each of the four correlations used v calculate the single phase heat transfer coefficient to vapor scale by using an appropriate characteristic length. In ECOBRA/ TRAC, the channel hydraulic diameter is used for the characteristic length. The McAdams correlation is not affected by choice of the characteristic length since that term cancels out of the expression for the he~at transfer coefficient. The hydraulic diameter affects the calculation of the natural convection heat transfer coefficient only through its use in the -
Reynolds number in the selection logic to determine the appropriate heat transfer mode.
Therefore, the scale dependence of the McAdams (1954) correlation is not large.
The correlation by Wong and Hochreiter ( 981) was developed directly from experimental data from a full scale rod bundle. Therefore, the only scale dependent concern is over the oA3225=W non.Ib431898 6-6
O
\\
~
"IT WILL BE WELL INDEXED SUCH THAT INFORMATION IS READILY LOCATED. ALSO,IT WILL CONTAIN IN APPENDICES HISTORICAL REVIEW INFORMATION, SUCH AS QUESTIONS AND ACCEPTED RESPONSES, AND ORIGINAL REPORT PAGES THAT WERE REPLACED."
WHERE INFORMATION IN TEXT IS SUPPORTED BY A RESPONSE TO RAI, IT IS CROSS-REFERENCED AS "*",
AND "X" IS DEFINED IN A "RAI LISTING" SECTION, FOLLOWING THE REFERENCES (see previous pages 6-2 to 6-6
]
and following pages 6-103 to 6-105)
WHERE THE ORIGINAL TEXT HAS BEEN COMPLETELY REPLACED, THIS IS CALLED OUT AND l
THE PREVIOUSLY DOCKETED REFERENCE IS IDENTIFIED (see following page 25-4-1) 4 WHERE RAIs ARE NO LONGER APPLICABLE, OR TOPIC HAS BEEN MOVED, THIS IS IDENTIFIED IN THE RAI LISTING (see following pages 25-12-1 to 25-12-3)
. APPENDIX C (RAI QUESTIONS AND FINAL RESPONSES)
INCLUDES AN INTRODUCTION IDENTIFYING ALL RAI TRANSMITTALS FROM THE NRC TO W, AND THE PREVIOUSLY DOCKETED REFERENCE WHERE EACH WAS RESOLVED (see 1" two pages ofIntroduction to App. C)
. 6 6 RAI Listing 1.
RAll 1, part (gg) 2.
RAll-152 3.
RAll-153 4.
RAll-154 j
5.
RAll 155 6.
RAll-156 7.
RAll-157 8.
RAll-158 1
9.
RAll-159 10.
RAll-160 11.
RAll-161 12.
RAll-162 13.
RAll-163 14.
RAll-164 15.
RAll-165 16.
RAll-166 17.
RAll-167 18.
RAll-168 19.
RAll-169 20.
RAll-170 21.
RAll-171 (refers to page 6-29; now page 6-26) l 22.
RAll-172 23.
RAll-173 24.
RAll-174 25.
RAll-175 26.
RAll-176 27.
RAll-177 28.
RAll-178 29.
RAll-179 30.
RAll-180 31.
RAll-181 32.
RAll-182 33.
RAll-183
' 9 34.
RAll-184
.:o225 m nan:iw2tm 6-103
1 4
35.
RAll-185 36.
RAll-186
^
37.
RAll-187 38.
RAll-188 39.
RAll-189 (refers to pages 6-47 and 6-48; now pages 6-43 and 6-44) 40.
RAll-190 41.
RAll-191 42.
RAll-192 43.
RAll-193 44.
RAll-194 (refers to page 6-58; now page 6-53) 45.
RAll-195 (refers to page 6-61; now page 6-56) 46.
RAll 196 (refers to page 6-39; now page 6-36) 47.
RAll-197 48.
RAll-198 49.
RAll-199 50.
RAll-200 51.
RAll-201 (refers to page 6-71; now page 6-63) 52.
RAll-202 53.
RAll-203 (refers to page 6-77; now page 6-68)
~j 54.
RAll 204 (refers to page 6-77; now page 6-68) 55.
RAll-205 (refers to page 6-80; now page 6-71) 56.
RAll-206 (refers to page 6-82; now page 6-72) 57.
RAll-207.
58.
RAll-208 (refers to page 6 86; now page 6 76) 59.
RAll-209 (refers to page 6-88; now page 6-78) j 60.
RAll-210 (refers to page 6 91; now page 6-79) 61.
RAll-211 (refers to page 6-89; now page 6 79)
{
62.
RAll-212 (refers to page 6-89; now page 6-78) 63.
RAll-213 (refers to page 6 93; now page 6-81) 64.
RAll-214 (this response added to main text) 65.
RAll-215 (refers to pages 6-95 and 6-97; now pages 6-84 and 6-87) 4 66.
RAll-216 (refers to page 6-97; now page 6-87. This response added to main text) 67.
RAll-217 68.
RAll-218 69.
RAll-219 -
70.
not used I
ou 225. m = i w 3 m 6-104 o
e 71.
RAll-151 72.
RAll-1, part.(mm) 73.
RAll-1, part (hh) 1 1
ouns.mnon: 6.o3i99:
6-105
j 25-4 Stored Energy / Fuel Rod This component requires consideration of the initial reactor state in combination with the models involved in calculating fuel and cladding temperature. This information was originally provided in the Revised Methodology Report (Liparulo,1995), and the HOTSPOT Model Report (Lipamlo,1995a), as revised in Liparulo (1995b).
25-41 Initial Reactor State Uncertainties Reactor core power distributions are characterized by radial and axial power distributions, as discussed in Section 21-2. The steady-state radial distribution is established by core loading pattem, fuel enrichment, fixed bumable poisons, etc., and is not subject to wide variation during normal operation (Volume IV, Section 21-2-1-1). The maximum of the radial distribution is defined by Fm (hot rod average power divided by the core average rod average power). Predictions of F, are accurate to within [
]" probability (Section 21-2-1-3).
In core design, the calculated Fw is augmented by 4 percent to account for prediction and measurement uncertainty, and by an additional [
]" for " good measure".
Steady-stat. axial distributions are established by core loading pattem and bumup. The axial distribution tends to vary widely as a result of changes in extemal controls such as boron or l
control rods. The maximum of the radial distribution times maximum of the axial distribution is F (maximum linear heat rate divided by the core average linear heat rate). Predictions of o
F are accurate to within [
]" probability (Section 21-2-1-3). Local q
variations in pellet and subchannel geometry are also considered for the hot rod (additional
[
]" F uncertainty). Transients are simulated in the core design process, yielding a q
wide range of possible power distributions and F s. As described in Section 21, the axial o
distribution is further specified by (
]".
In core design, the calculated F for each power distribution is augmented by [
]"
q prior to comparing to the Technical Specification to bound ticulational, measurement, and local uncertainties.
o u:25 nonw25-4 non.:b.03is9s 25-4-1
)
4
?.
2512 RAI Listing Due to the significani restructuring of Sections 24 to 27, many of the RAI's applicable to the original version of these sections refer to text which has been deleted or significantly modified. Consequently, footnotes were not included in the main body of the text. Instead, reference is made to applicable RAI's in the text, or the text has been modified to include the
)
response to the RAI directly. In Section 25-12, the topic of each RAI or group of RAI's which referred to the original text is briefly described, and reference is made to the section or page where the topic is discussed in the_ main text.
RA15-1. Requests additional justification that the phenomena listed have been addressed in the validation data base (Section 24-3).
S RA15-2. Requests clarification of several items in the key LOCA parameters list for the reference case (Section 26-3-2 and Table 26-3-1).
]
i RAI5-3. Requests clarification for the value of PLHR used in the analysis (Section 25-4).
RAI5-4. Requests clarif
.on of the offsite power assumption. As indicated in Section 26-3-2. Item 3.0d, the linuting condition (offsite power available/not available) is determined on a plant specific basis.
RAI5-Sa. Asks how the code uncenainty (which deals with models such as lheat transfer
{
coefficient) can be considered independent of plant type. The code uncenainty is now used only as a lower bound; the effect of uncenainties in models is now evaluated on a plant-specific basis (Section 261-6).
RAI5-5b. Asks for further informr. tion supponing the claim of plant independent code uncenainty when applied to UPI plants. This RAI is no longer applicable; the methodology described in this repon does not apply to UPI plants.
I RAI5-6. Requests funher clarification on how the code uncertainty is applied to the hot rod.
This RAI is no longer applicable; the hot rod uncenainty is determined directly (Section 25-4-2).
o.u225.w2512.non:ib.o3:ses 25-12-1
c RAI5-7. Asks for clarification of the method used to combine several variables affecting the
. hot rod and hot assembly powers. See Section 25-4-2-1 for clarification.
RAIS-8. Asks for clarification of the range of variables used for the power distribution run matrix (Section 25-4-1).
RAIS 9. Points out incorrect reference. References have been corrected.
RAIS-10. Points out incorrect reference. References have been corrected.
RAIS-II. Asks why the effect of FDH.LOCA is only evaluated at two points compared with
{
other power distribution parameters. As described in Sections 21 and 25-4-1, the range of variation in FDH is narrow compared with the range of FQ, PBOT, and PMID; therefore, only two levels are evaluated in the power distribution run matrix.
l RAI5-12. Asks that the value of ERR (estimate of response surface fit error) be verified. This l
RAI is no longer applicable. The original method used the quantity ERR in the Monte Carlo analysis to estimate the uncertainty introduced by errors in the response surface fit. The final I
method accounts for response surface fit plus superposition error via the superposition validation step (Section 26-5-2-3).
RAIS-13. Asks why most of the first and second reflood peaks in the VRA analysis have the same PCT. This RAI is no longer applicable. The final methodology treats first and second reflood PCT separately (Section 26-5-2-1, Item 2).
RAIS-14. Asks if the choice of reference case affects the form of the derived response surface. The analysis presented in the response to this RAI remains valid for the response surfaces generated using the final methodology. As indicated in the response, choice of the
" reference" case does not affect the calculated result.
RAIS-15. Asks for clarification of how the Monte Carlo approach is implemented. The final method used is described in a step by step fashion in Section 26-5-2-2.
RAIS-16. Aske forjustification of the statement that the guillotine break is limiting. This RAI is no longer applicable. The split and guillotine breaks are treated separately, and the limiting case is determined (Section 26-1-5).
l oo225 w25-12.non.id-osis9s 25-12-2
2 RAIS-17 to RAI5-24. Request clarification of the equations used to estimate the loop resistance uncertainty, A more complete development of these equations is provided in Section 25-3-5.
RAIS-25. Asks how the break location affects the loop resistance. (
}"
)
RAI5-26 to RAI5-30. Request clarification of the range and stmeture of the run matrix used to estimate the effect of loop resistance uncertainty and break flow uncertainty. Section 25 3-6 develops the range to be used for the flow resistance parameters, Section 25 3-7 describes some simplifying assumptions, and Section 25-3-8 describes sensitivity studies supporting the assumptions. Section 26-4-4 describes how the loop resistance uncertainty is evaluated along with uncertainty in CD and condensation rate.
RAI5-31 to 35. Request clarification of the methods used to estimate the effect of initial condition uncertainties such as T,,.
Section 26-4-2-1 describes these methods more completely.
l 1
1 a:u225.s c2s.i2mm:iuns9s 25 12-3
g WESTINGHOUSE NON PROPRIETARY CLASS 3 APPENDIX C RESOLUTION OF REQUESTS FOR ADDITIONAL INFORMATION INTRODUCTION A large number of Requests for Additional Information (RAI's) were generated during the USNRC review of WCAP 12945-P. The majority of the RAl's were issued formally, as letters from the USNRC to Westinghouse. Late in the licensing process, additional RAl's were provided on a more informal basis. The following discussion is intended to provide a "roadmap"of the location where all RAl's were resolved. It is an expanded version of the information previously provided in Reference C-1.
Tables C-1 through C-3 identify the location of responses to questions on Volumes I through 3 of WCAP 12945 P. These RAl's were provided to Westinghouse in References C-2 and C-4. The identified references are listed after Table C 8.
Tables C 4 and C 5 identify the location of responses to questions on Volumes 4 and 5 of WCAP 12945-P. These RAl's were provided to Westinghouse in References C 3 and C-4.
Table C-6 identifies the location of responses to supplemental questions on Volumes I through 3 of WCAP 12945-P. These RAl's were provided to Westinghouse in References C-3 and C-4.
Table C 7 identifies the location of responses to questions on the Revised Methodology Report (Reference 10 in the list after Table C-8), provided to Westinghouse in Reference C-5.
Table C 8 identifies the location of responses to statistical methodology questions from Cory Atwcod 1
(INEL), provided to Westinghouse in References C-6 through C-11.
The final responses to the formal RAl's on Volumes I through 5 of WCAP-12925-P are provided in the sections following Tables C 1 through C-8. The first six sections correspond directly to the RAl's identified in Tables C-1 through C 6. The final eight sections are copies of the "RAIA" through "RA!H" i
submittals, where this nomenclature is consistent with that described on page I-51 of Volume 1.
REFERENCES
~
C 1)
Letter, R. C. Jones (USNRC) to N. J. Liparuto (W), January 24,1996.
C 2)
Letter, T. E. Collins (USNRC) to N. J. Liparulo (W), " Request for Additional Information, Re: WCAP 12945 P", April 21,1994.
C-3)
Letter, T. E. Collins (USNRC) to N. J. Liparuto (W), " Request for Additional Information, Re:
WCAP 12945 P", June 15,1994.
C 4)
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF-03 95, January 30,1995.
C 5)
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF-10-95, November 14,1995.
C 6)
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF-05 95/CLA-1, September i 1,1995.
C 7)
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF 06 95/CLA 2, September 13,1995.
C 8)
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF 08-95/CLA-3, September 29,1995.
I C-9)-
Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF 09-95/CLA-4, November 6,1995.
C 10) Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF 01 96/CLA 5, January 15,1996.
C 11) Letter, C. P. Fineman (INEL) to F. R. Orr (USNRC), CPF-02 96/CLA-7, January 24,1996.
I
5 TABLE C-1.
REQUESTS FOR ADDITIONAL INFORMATION: WCAP-12945 P, VOLUME 1 (Note: All questions in this Table are referred to by "RAll xx" in the report, excep where noted in the REFERENCE column)
QUESTION REFERENCE TOPIC la-e Ref.1, Att. A Volume I equations 1f Ref.1 Att. A & D ig il Ref.1. Art. A Imm Ref.1. Att. A & E Inn oo Ref.1 Att. A lpp Ref.1, Att. A & E Iqq-rr Ref.1. Att. A 2
Ref.1, Att. A PIRT Ref. 3, Att. EE 3a Ref.1. Att. A Range of test conditions vs PWR conditions Ref. 6, Att. LL Ref. 8 Att. SS 3b Ref.1, Art. A Applicacility to non W PWRs Ref. 4, Att. GG 4
Ref.1. Att. A Orthogonal vs transverse gaps 5
Ref.1, Art. A & D Equations 2 55 and 2 56 Ref. 2. Art. Z 6
Ref.1. Att. A Equation 2 62 7
Ref.1, Att. A Turbulence models 8
Ref.1, Att. A Equations 2-62 to 2 64 9
Ref.1, Att. A Equations 2 69 to 2-71 10 Ref.1, Art. A Equations 2 74 and 2-75 11 Ref.1. Att. A 12 Ref.1, An. A 13 Ref.1. Art. A & D Equations 2-77 and 2 78 14 Ref.1, Art. A Equations 2-79 and 2 80 15 Ref. I, Art. B Cell face discussion 16 Ref.1, Att. A Equations 2 !29 and 2132 17 Ref.1, Art. A Equation 2137 18 Ref.1, Att. B Effect of covviance terms on mom. flux derivatives 19 Ref.1, Art. B Equation 2136 20 Ref.1, Att. A Equations 3 2 to 3-11 21a Ref.1, Art. A Small bubble /large bubble transition 21b Ref.1 Art. I Effect of pipe diameter on flow regime maps 22 Ref. I, Att. A & D Equations 3-15 & 3-16 Ref. 2, Art. Y 23 Ref.1, Att. A, D & W Minimum bubble number density (Equation 3-18) 24 Ref.1, Art. A & D Equation 3 22 25 Ref.1. Art. A Interfacial area for superheated liquid 26 Ref. I, Att. B & D Equation 3-23 27 Ref.1 Art. D Equation 3-25 f
28 Ref.1, Att. B Equation 3 26 29 Ref.1, Att. B Equation 3 29 30 Ref.1, Au. A & D Minimum droplet diameter (Equation 3-40) 31 Ref.1. Art. A Equations 3 41,-46,-50 and -51 32 Ref.1. Art. B Slug diameter 33 Ref.1. Art. A Equation 3 63
a SECTIONS OF SPECIAL INTEREST REVIEW ISSUE LOCATION ROADMAP SECTION 1-2 PIRT SECTION 1-3-3-3 ENTRAINMENT MODEL SECTION 4-6-3 COMPENSATING ERRORS VOL 3, APPENDIX A f
SCALING SECTION 18 PLANT PARAMETER RANGING SECTION 21 CODE PARAMETER RANGING SECTION 25 (HTC, TMIN: SECTION 25-5)
UNCERTAINTY PROPAGATION SECTION 26 COMPLIANCE WITH RG 1.157 SECTION 28 i
i
~
a-i O
WESTINGHOUSE /NRC MEETING 3
WCAP-12945 MARCH 20,1998 MEETING PARTICIPANTS NAME ORGANIZATION.
Claudia Craig NRC/NRR/PGEB Frank Orr NRC/NRR/SRXB Lambros Lois NRC/NRR/SRXB Mitch Nissley
. Westinghouse /NSD/SAE Mohammed Shuaibi NRC/NRR/SRXB I
{
1 4
ATTACHMENT 2 s
Westinghouse Owners Group cc:
Mr. Nicholas Liparulo Westinghouse Electric Corporation Mail Stop ECE 4-15 P.O. Box 355 Pittsburgh, Pennsylvania 15320-0355 Mr. Hank Sepp Westinghouse Electric Corporation Mail Stop ECE 4-07A P.O. Box 355 Pittsburgh, Pennsylvania 15320-0355 Mr. Andrew Drake Westinghouse Owners Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, Pennsylvania 15320-0355 i
I
DISTRIBUTION: Mtg/ Westinghouse dated April 1, 1998 Hard Copy Central Fdes PUBLIC PGEB R/F MMalloy CCraig OGC ACRS E-mail SCollins/FMiraglia RZimmerman JRoe/DMatthews BSheron GHolahan/SNewberry TCollins EWeiss FOrr LLois MShuaibi D
. _ _. _ _ _