NSD-NRC-96-4716, Forwards Matl Presented to NRC Technical Staff on 960503 at Meeting to Further Discuss Thermal Hydraulic Uncertainty Issue.Matl Suppls Presentation Matl from 960229 Meeting & Written Submittal of 960412

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Forwards Matl Presented to NRC Technical Staff on 960503 at Meeting to Further Discuss Thermal Hydraulic Uncertainty Issue.Matl Suppls Presentation Matl from 960229 Meeting & Written Submittal of 960412
ML20117D662
Person / Time
Site: 05200003
Issue date: 05/03/1996
From: Mcintyre B
WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To: Quay T
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
DCP-NRC0511, DCP-NRC511, NSD-NRC-96-4716, NUDOCS 9605130207
Download: ML20117D662 (62)
v • d • e


Text

{{#Wiki_filter:O l l Westinghouse Energy Systems Box 355 Electric Corporation Pittsburgh PennsyNanta 15230 0355 NSD-NRC-96-4716 DCP/NRC0511 Docket No.: STN-52-003 May 3,1996 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTENTION: T.R. QUAY

SUBJECT:

MATERIAL PRESENTED AT MAY 3,1996 AP600 TIIERMAL HYDRAULIC UNCERTAINTY MEETING

Dear Mr. Quay:

The attached material was presented to the NRC technical staff on May 3,1996 at a meeting to further discuss the thermal hydraulic uncertainty issue. This material supplements the presentation i material from our February 29,1996 meeting and written submittal of April 12, 1996. Westinghouse expects the NRC to review this material and provide written agreement that the presented approach, if executed properly, will successfully resolve this issue. In addition, comments are expected on the PRA PIRTs and selection of benchmarking cases, along with specific details of any additional information the staff requires to clarify details of how this approach will be implemented. Please contact me if you have any questions on this material. ri A. McIntyre, Man er Advanced Plant Safety and Licensing '"J 130058 Atuichment cc: W. Huffman, NRC (w/o attachment) N. Liparulo, Westinghouse (w/o attachment) 9605130207 960503 PDR ADOCK 05200003 A PDR 2766A 1 I / I I i

4 i 4 Westinghouse / NRC Meeting on j MAA.P4 Benchmarking l for AP600 Level 1 PRA l (PIRTs and Case Selection) May 3,1996 Rockville, MD D. K. Ohkawa L. E. Hochreiter c:\\wp\\ap600V)503960.mtg May 2,1996

l 1 l AGENDA l l Introduction l Feedback from NRC i l Benchmarking Process l Status l 1 Overview of PRA Scenarios PRA PIRTs Selection of Benchmarking Cases Summary / Discussion of Open Items l i c:\\wpW600V)S03W.mtg May 2.1996 i

Benchmarking Process / Status c:\\wp\\ap6000503%n.mtg May 2,1996 Page 1

MAAP4 Benchmarking Process I 1 A B C D Understanding MAAP4 Code Understanding DBA SBLOCA of PRA Capabilities & t f OSU Test PlRT l Scenarios Limitations Results /

  1. 2
  2. 1 Definition of Preliminary

~ PRA PIRTs MAAP4/NOTRUMP Comparison i U y y Final Comparison of input Modelling

  1. 3
  2. 4
  3. 5 1

Selection Define NOTRUMP i of Final Comparison Applicability Benchmarking Process to PRA Cases Scenarios y Re-run WAAP4 5 NOTRUMP and NOTRUMP ~ 1 + a j d Ass NOT Differences my l t on U nol NOTRUMP N l m 4 Evoluote WAAP4 Code Results/ Umitations y l @\\ .1 internal "Y Revi U U U I B:nchmark T&H Final l R: port to NRC Uncertainty PRA Analysis D l

e e I i i Overview of PRA Scenarios c:\\wp\\ap600V)S03%n.mtg May 2,.1996 Page 3

l Focus of MAAP4 Analyses MAAP4 cases have been defined to support the PRA event trees for scenarios that require ADS actuation for successful core cooling Event trees are lumped into four groups: Loss of heat sink Transients Small LOCA (SLOCA) up to 2" l Intermediate LOCA (NLOCA) up to 6" Medium LOCA (MLOCA) up to 9" l j Initial focus was on a clear correlation between equipment assumed l in the event trees and the equipment assumed in the MAAP4 analyses The logic on the event trees defines minimum equipment that is l needed, such as: At least 1 CMT At least I accumulator At least 2 stage 4 ADS l At least 1 DVI line for IRWST injection l f cAwp\\ap600V)503hmtg May 2,1996 Page 4 i l

General Analysis (Scenario) Assumptions Minimal heat removal by " normal" methods: No main feedwater, no startup feedwater No PRHR 1 Either one CMT or one accumulator Functioning CMT allows automatic ADS actuation No CMT requires manual ADS actuation Minimal number of ADS valves Typically 2 out of 4 stage 4 ADS for IRWST gravity injection l Typically I stage 2,3 or 4 ADS for RNS pumped injection 1 DVI line for injection I Containment Isolation Failure is assumed Nominal conditions c:\\wp\\ap600\\0503%nmitg May 2,1996 Page 5 a

i Additional Scope of MAAP4 Analyses a i Break ;ize and location Number of tanks (CMTs and accumulators) J } Number of ADS lines l Operator action times i Effect of containment isolation i 1 l i i c:\\wpiap600V)503%n.mtg May 2,1996 Page 6

l i i Transients and SLOCAs High pressure scenarios that require stage 1,2, or 3 ADS prior to stage 4 ADS, due to the RCS pressure interlock (~1000 psia) on stage 4 ADS Loss of heat sink events, up to 2" break, where SG heat removal plays a role Inventory loss through pressurizer safety valve may occur Duration of event is 2 to 4 hours ADS success criterion I stage 2 or 3 ADS + 2 stage 4 ADS for IRWST gravity injection 1 stage 2 or 3 ADS for RNS injection Example 0.5" hot leg break to illustrate plant response l l t c:\\wp\\ap600T503%n.mtg May 2.,1996 Page 7 j

I r Transients and SLOCAs (Cont.) l 0.5" Hot Leg Break l Sequence of Events Time (sec) Reactor Trip on Low Pressurizer Level (or low 750 pressurizer pressure) CMT Actuation 750 Pressurizer Empties 1200 i Pressurizer starts to refill 4000 l SG empties 9300 Pressurizer SV Setpoint Reached (greater rat' of 10,700 e RCS inventory loss) l CMT draining begihs 11,500 l ADS-1 Actuation (Fails - nothing happens) 12,060 ADS-3 Actuation (1 valve opens) 12,300 l ADS-4 Actuation (2 valves open) 12,470 Top of core uncovers 12,500 CMT empties 12,750 IRWST begins to inject 12,850 Top of core recovers 13,000 l c:\\wp\\ap6000503%n.mtg May 2,1996 Page 8 I l l l l

18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFH0C l PPS 0 0 0 RCS Press

PBS 0

0 0 SG Pressure 3000 m o 2500 -;: = :.5 m o. v 2000 -E 1500 -E m

' 1000 -:

-"~~---~~~-~~~~~~~~~~------------w m

_i m

e 500 - : [. 6 Cl-0 O 2 0'0 0 4 0'0 0 6 0'0 0 8 0'0 0 10b00 12 BOO 14 BOO 16000 Time (s) 18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFHOC MTH00013 0 0 0 RCS Inventory 350000 m E 300000 -E ._a 250000 -E v 200000 -E m 150000 -E m 100000 -2 2 5 50000 l 'l l O 2000 4000 6000 8000 10b00 12 BOO 14 BOO 16000 Time (S) .I 9 l l l. l

1 ? 18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFH00 MTH00044 0 0 0 Int Przr Water Relie

MTH00045 0

0 0 Int Przr Vapor Relie 200000 150000 - 100000 -: ~ f I 50000 -: 1 0 ~ ' ' ' ' ' ' ' ' ' ' ' ' O 2 0'0 0 40'00 6 0'0 0 80'00 10b00 12 BOO 14 BOO 16000 Iime (S) 18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFH00 MWPZ 0 0 0 Pressurizer' inventor 70000 } 60000 - 4 50000 -E v 40000 -E 30000 -- m 20000 - m ] 10000 -f =' ' ' ' ' ' ' ''''''''''t 0 O 20'00 4 0'0 0 6 0'0 0 80'00 10 BOO 12 BOO 14 BOO 16000 Iime (S) 10

3 9 18-Apr-96 14:23:54 AP600 0.5" HL' AUTO ADS CASE AFHOC WWMT 1 0 0 CMT Inj - - - - WW C L M T I O O CMT Bal Water Inj

WGPSMT 1

0 0 CMT Bal Vapor Inj 100 ..i l } 80 -E Ill l 3, 60 -! l '""e I 40 -: L fo '~' 20 -5 -~~~ ~~ 0 ? = r 5 5 l l 5 'lfl 4 -60 *'l 'l l 'l l 0 2000 4000 6000 8000 10000 12000 14000 16000 Time (S) 18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFHOC MTH00033 1 0 0 CMT Level (FOI) MTH00034 1 0 0 CMT Mass (F01) 1.2 1 ~,, 5 8-- ~__ 6-- g s \\ 4-2 \\ \\ 2-2 \\ 0 0 20'00 4000 60'00 80'00 10b00 12dOO 14000 16000 l Time (s) \\\\ i i t l j

18-Apr-96 14:23:54 AP600 0.5" HL AUTO ADS CASE AFH00 WWGO 3 0 0 IRWST Inj 140 i 120 -! c - 100 -: 2 80 -E l p E 5 60 - 40 -~ 20 -E O 0 l l l l l l l 0 2000 4000 6000 8000 10000 12000 14000 16000 Iime (S) 18-Apr-96 14:23:54 AP600 0.5" H L A U T ') ADS CASE AFH00 ZWV 0 0 0 Mixture Lev I - - - - M T H 0 0 0 01 0 0 0 Top of Core 25

  • 20-15 --

h _c &jo_: c o ~ 5 l l l 'l l l l 0 2000 4000 6000 8000 10000 12000 14000 16000 Iime (S) e

Intermediate LOCAs Defined to be large enough that break will reduce pressure below ADS stage 4 RCS pressure interlock (~1000 psia) 2" to 6" breaks SG heat removal plays a small role Duration of event is I to 2 hours ADS success criterion: 2 stage 4 ADS for IRWST gravity injection I stage 2 or 3 ADS or 1 stage 4 ADS for RNS injection Example 5.0" hot leg break to illustrate plant response l l c:\\wp\\ap600T503W.mtg May 2.1996 Page 13 1

I l Intermediate LOCA (Cont.) l l 5.0" Hot Lee Break Sequence of Events Time (sec) l Reactor Trip on Low Pressurizer Level 10 CMT Actuation 10 Pressurizer empties 50 CMT draitling begins 200 Vessel mixture level below hot legs 210 ADS-1 Actuation (Fails - nothing happens) 624 ADS-4 Actuation (2 valves open) 1170 CMT empties 1550 i l Vessel mixture level below hot legs 1700 IRWST begins to inject 1725 i l l l c;\\wpiap600W503%n.mtg May 2,1996 Page 14

25-Apr-96 10:35:27 AP600 5.0" HL AUTO ADS CASE AFHSA PPS 0 0 0 RCS Press

PBS 0

0 0 SG Pressure 2500 m o I 2000 -: a 1500 -;i { 1000 -- m 500 -~ a 0 ~ l l l O 1000 2000 3000 4000 Time (s) 25-Apr-96 10:35:27 AP600 5.0" HL AUTO ADS CASE AFHSA - MT H0 0013 0 0 0 RCS Inventory 350000 E 300000 -~ _a - 250000 - v 200000 -E m 150000 -E m l o 100000 -E =E = Ml 50000 l 0 1000 2000 3000 4000 Time (s) i 16 I 1

l 25-Apr-96 10:35:27 AP600 5.0" HL' AUTO ADS CASE AFH5A WWMT 1 0 0 CMT Inj - - - WWC L M T 1 0 0 CMT Bal Water inj - --- - W G P S M T 1 0 0 CMT Bal Vapor Inj 100 l = 1 7 80 -E i i 5 60 -5 g 40 - Elli g i l 20 -jl ~ g o _ lN. "-W.AMA%MMb :- O I - -2 0 -E l +

-4 0 -5 s -60 l

l l 0 1000 2000 3000 4000 Time (s) l 25-Apr-96 10:35:27 AP600 5.0" HL AUTO ADS CASE AFHSA I MTH00033 1 0 0 CMT Level (FOI)

MTH00034 1

0 0 CMT Mass (F01) l 1.2 l 1-- \\ l 8-{ s l 6-5 4-! 's s 2-- 's s o 0 1000 2000 3000 4000 Ilme (S) \\&

i l \\ l l l 25-Apr-96 10:35:27 AP600 5.0" HL AUTO ADS CASE AFH5A WWGO 3 0 0 IRWST Inj .200 l l E I n , 150 -- % 100 -~ x 5 50 -- O 0 i i i 0 1000 2000 3000 4000 Time (S) l t 25-Apr-96 10:35:27 AP600 5.0" HL AUTO ADS CASE AFH5A ZWV 0 0 0 Mixture Lev 1 l - - - - M T H 0 0 0 01 0 0 0 Top of Core 1 i i ^ 25 v ) "20-- ~ l 15 - _c

  • 10 -

i i c l' CD [ J ~ 5 I i 1 0 1000 2000 3000 4000 IIme (S) Il l

Medium LOCAs i Defined to be large enough that break will reduce pressure below RNS shutoff head without any ADS l 6" to 8.75" breaks SG heat removal plays no role Duration of event is less than an hour ADS success criterion: l 2 stage 4 ADS for IRWST gravity injection No ADS for RNS injection Example 8.75" hot leg break to illustrate plant response l l The larger breaks do not need much " help" from the ADS to depressurize Main issue is whether CMT can inject fast enough, in absence of accumulator cAwp\\ap600W503hmtg May 2,1996 Page 18

l ^ l Medium LOCA (Cont.) 8.75" Hot Lee Break l Sequence of Events Time (sec) Reactor Trip on Low Pressurizer Level 5 CMT Actuation 5 CMT draining begins <100

  • Vessel mixture level below hot legs 120 ADS-1 Actuation (Fails - nothing happens) 480 ADS-4 Actuation (2 valves open) 1030 IRWST begins to inject 1100 CMT empties 1415 l

The time of CMT draining identified above may be sooner than realistic. l l c:\\wp\\ap6000503%.mtg May 2,1906 Page 19

18-Apr-96 14:24:26 AP600 8.75" HL AUTO ADS CASE AFH80 PPS 0 0 0 RCS Press

PBS 0

0 0 SG Pressure _ 2500 o '~ 2 0 0 0 -- n a 1500- _: o 1000 - l n m 500 -2 i l 0 i 0 500 1000 1500 2000 25'00 30'00 3500 IIme (S) i 18-Apr-96 14:24:26 AP600 8.75" HL AUTO ADS CASE AFH8D MTH00013 0 0 0 RCS Inventory 350000 _ E 300000 - .a - 250000 - i j v 200000 -- i m 150000 -i m 0 100000 - 50000 'l'l''''l'''i 0 500 1000 1500 2000 2500 30'00 3500 t Iime (S) i l \\ 1 ao

1 18-Apr-96 14:24:26 AP600 8.75" HL' AUTO ADS CASE AFH80 WWMT 1 0 0 CMT inj - - - - WW C L M T 1 0 0 CMT Bal Water Inj

WGPSMT 1

0 0 CMT Bal Vapor inj 100 i 80 -5 5 60 -f 1 40 -l l ll j 20 - 0-E l rn,---% .- -.-s n - o C -2 0 - -4 0 -5 4 2' -60 'l' 'l'l'l'l'l' 0 500 1000 1500 2000 2500 3000 3500 1 Time (s) 18-Apr-96 14:24:26 AP600 8.75" HL AUTO ADS CASE AFH8D MTH00033 1 0 0 CMT Level (F01)

MTH00034 1

0 0 CMT Mass (F01) 1.2 1-~ 8-E s s 6-E l 4-E 's s 2-: 's 's ~l i I I f f 1 I t I I i l i t i I I I I I t t I I I il 1 1 I I 0 0 500 10'00 15'00 2000 25'00 3000 3500 Time (S) 9.\\ l I

i l l 18-Apr-96 14:24:26 AP600 8.75" HL AUTO ADS CASE AFH8D WWGO 3 0 0 IRWST inj J A200 e - 150 -- / % 100 - = E 5 50 -- I 2 0 0 5b0 1000 15'00 20'00 25'00 30'00 3500 I me (S) l l t l 18-Apr-96 14:24:26 AP600 8.75" HL AUTO ADS CASE AFH80 l ZWV 0 0 0 Mixture Lev l - - - - M T H 0 0 0 01 0 0 0 Top'of Core 25 n 20 -- v 15 -3 l [ 10 -3 e 5 0 5d0 10'00 15'00 20'00 25'00 30'00 3500 Iime (S) 1 aa

Inventory Trends for PRA Scenarios With 1 CMT (Automatic ADS) N N k N c N I N I N-- Core Uncovery 5 /N E y Before ADS 'E N (no Accum)

  • j After ADS.

+SLOCA = l c NLOCA -

l

MLOCA H l l l 0 2" s' 8.75" Break Equivalent ID cB

Scenarios Without CMTs (Manual ADS Cases) If both CMTs fail, the operator must manually actuate ADS The operator action " clock" is started when the "S" signal fails to actuate CMTs SLOCAs are not challenging due to slow inventory loss, allowing ample operator action time (30 minutes is credited) Other LOCAs have 20 minute operator action time in PRA l l l l 1 i c:\\wp\\ap6000503%n.mtg - May 2.1996 Page 24 I

1 l 1 PRA Scenarios Without CMTs 1 Accumulator, No ADS 30 CORE / UNCOVERS 9o 20 E i .5 E v ' ACCUMULATORS ) CORE UNCOVERS IN M GJ o 10 .H

  • -- SLOCA ~1 :

NLOCA rI: MLOCA

i o

0 2 6 8.75 Break Equivalent ID (inches) i l N 1

Manual ADS Cases (Cont) Time (sec) Sequence of Events 3" HL 6" HL 8.75" HL Reactor Trip on Low Pressurizer Level 26 7 4 Vessel Mixture Level Below flot Legs 6(X) 170 Accumulator injection starts 2(X) 90 Accumulator empties 1025 400 Vessel Mixture Level Below flot Legs 1150 5(X) Top of core uncovers 790 730 Accumulator injection starts 940 Manual ADS-4 Actuation (2 valves open) 1226 1207 12(M Top of core recovers 13(X) Accumulator emptics 1425 Vessel Mixture Level Below flot Legs 1700 IRWST begins to inject 19(X) 14(X) 1205 c:\\wp\\ap600V)503% mig May 2,1996 Page 26

18-Apr-96 14:33:51 AP600 3.0" HL MANUAL ADS CASE MFH3A_T20 PPS 0 0 0 RCS Press PBS 0 0 0 SG Pressure 2500 m o } 2000 - v 1500 - : e 1000 - ~~~~~ 3 I m 500 -E u 0 I 0 1000 20'00 30'00 4000 Iime (S) 18-Apr-96 14:33:51 AP600 3.0" HL MANUAL ADS CASE WFH3A_T20 MTH00013 0 0 0 RCS Inventory 350000 y 300000 -_ " 250000 -5 v 200000 -E 150000 -E en 100000 -: 50000 - s 0 l 0 1000 2000 30'00 4000 Iime (S) 71

l i l l 18-Apr-96 14:33:51 AP600 3.0" HL MANUAL ADS CASE MFH3A_T20. WESFDC 0 0 0 Accum inj l l 700 e 600 -E e 500 -E = l 2 400 -E \\ i "'300-E m O ~ - 200 -E l 1 w

100 -E 2

0 '''l 0 1000 2000 3000 4000 Time (s) l 18-Apr-96 14:33:51 AP600 3.0" HL MANUAL ADS CASE MFH3A_T20 MACUM 0 0 0 Accum Mass 120000 m E 100000 -: l o l 80000 -: 60000 -: l l m 40000 -: m l C 20000 -: f s l ~ 0 I I i 1 0 1000 2000 3000 4000 Time (s)

18-Apr-96 14:33:51 AP600 3.0" HL MANUAL ADS CASE MFH3A_T20 WWGO 3 0 0 IRWST Inj 140 h 120 -! f - 100 -2 2 80 -E a 60 -E f 40-! 20 -E a o 'j 0 l l O 1000 2000 3000 4000 Time (S) 18-Apr-96 14:33:51 AP600 3.0" HL WANUAL ADS CASE WFH3A_T20 ZWV 0 0 0 Mixture Lev - - - - M T H 0 0 0 01 0 0 0 Top of Core 25 m 2 b

  • 20--

15 -: r ~ O 10 - c Q) 2 J 5 l l l O 1000 2000 3000 4000 l Iime (S)

18-Apr-96 14:34:21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 PPS 0 0 0 RCS Press PBS 0 0 0 SG Pressure 2500 m l o l % 2000 - a l 1500 - a>

1000 --

m 500 -E m 1 "I 1 l t I it i iiimi it t t I t it i;I f I I I it i1 i f 0 5d0 10'00 15'00 20'00 25'00 30'00 3500 Time (s) 18-Apr-96 14:34:21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 l MTH00013 0 0 0 RCS inventory 350000 m E 300000 -- _a - 250000 - l 200000 - g m 150000 -3 m o 100000 -: =E l 50000 l''l l''l'l' 0 500 1000 1500 2000 2500 3000 3500 Time (s) e 30

I 18-Apr-96 14:34:21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 i WESFOC 0 0 0 Accum inj .,2000 s e .o -, 1500 -- e 1000 - oa: = O E 500 -: I s t l i s ~ ' 0 ' ' ' 'l'l' l'''' 0 500 1000 1500 2000 2500 3000 3500 Time (S) l 18-Apr-96 14:34:21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 MACUM 0 0 0 Accum Moss 120000. : m E 100000 -: _a 800'00 -3 60000 -- m 40000 - m l 0 20000 -: ':E 0 ~'l' l'l'l'l' 0 500 1000 1500 2000 2500 3000 3500 l Time (s) 31

1 1 l 18-Apr-96 14:34i21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 WWGO 3 0 0 IRWST Inj 2 200 r m s e n ,150 -_ 1 % 100 - = 5 50 -- E i 3E 0 0 5b0 10'00 15'00 20'00 25'00 30'00 3500 Time (s) l 18-Apr-96 14:34:21 AP600 6.0" HL MANUAL ADS CASE MFH6A_T20 ZWV 0 0 0 Mixture Lev - - - - M T H 0 0 0 01 0 0 0 Top of Core f 25 m _ y i ~ 20 -- ( 15 -_ _c ~ i w 10 -: c c3 J " ''''''''''''''''''''''''ii 5 0 500 10'00 15'00 20'00 25'00 30'00 3500 l l Time (s)

._y _si o 18-Apr-96 14,34:31 AP600 8.75" HL MANUAL ADS CASE WFH8D_T20. PPS 0 0 0 RCS Press PBS 0 0 0 SG Pressure 2500 m o To 2000 -3 1500 - : 1000 - o a m 500 - o u Q, =g g g a e e e i t f f I f I I t I f f f f f I I l I l 0 5b0 10'00 15'00 20'00 25'00 30'00 3500 Iime (s) 18-Apr-96 14:34:31 AP600 8.75" HL MANUAL ADS CASE WFH80_T20 MTH00013 0 0 0 RCS Inventory 350000 _ ^ 300000 -E E 4 250000 - i v 200000 ;_ 150000 -5 m m 100000 - L 50000 - ~ c :,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 0 500 1000 1500 2000 25'00 30'00 3500 Time (s) n

o 1 18-Apr-96 14:34:31 AP600 8.75" HL MANUAL ADS CASE MFH80_T20 WESFDC 0 0 0 Accum inj l 1400 1200 -: f - 1000 -E 2 800 -E o 600 -: = 400 -E 1 200 -E O 0 ''''''''''''i>>ii'iiii' 0 5d0 10'00 15'00 20'00 25'00 30'00 3500 Iime (S) l 18-Apr-96 14:34:31 AP600 8.75" HL MANUAL ADS CASE MFH80_T20 MACUM P 0 0 Accum Moss 120000 n E 100000 - o 80000 -3 60000 -3 m 40000 -: m 20000 - 22 ~' ' ' 0 ''''''''''''''''''''''iii 0 500 10'00 15'00 20'00 25'00 30'00 3500 t Iime (S) f l I l

18-Apr-96 14:34:31 AP600 8.75" HL MANUAL. ADS CASE WFH80_T20 WWGO 3 0 0 IRWST Inj ,.200 s E $ 150 -{ l l E 100 - x 5 50 - 3' 0 i 0 5b0 10'00 15'00' 20'00 25'00 30'00 3500 i Time (s) 18-Apr-96 14:34:31 AP600 8.75" 'HL MANUAL ADS CASE WFH80_T20 ZWV-0 0 0 Mixture Lev - - - - M T H 0 0 0 01 0 0 0 Top of Core 25 ~ 20 -- v 15- [ _c ~

  • 10 -

C o J 5 0 500 1000 15'00 20'00 25'00 30'00 3500 Time (s) l J b

1 inventory Trends for PRA Scenarios Without CMTs (Manual ADS) j 5 \\ d I Core Uncovery E E N / = .5 After f p",", Before Accum (no CMTs) +SLOCA = l NLOCA

l

WLOCA H I l l O' 2" 6" 8.75' Break Equivalent ID l i 3b l

PRA PIRTs c;\\wp\\ap6000503%o.mtg May 2,1996 Page 37

PRA PIRT Process A group of experts were assembled who have experience in AP600 systems design, small-break LOCA, PRA, and PIRTs The different transients which are used to describe the plant performance for beyond design basis accidents were reviewed and contrasted to the AP600 small-break LOCA i Focus was the role of different equipment for preventing and mitigating core uncovery Discussion also focused on how MAAP4 does the calculations relative to NOTRUMP i The small-break LOCA PIRT was the starting point to identify the high ranked phenomena for the PRA scenarios i The PRA scenarios were categorizdd to develop two PIRTs: Scenarios with CMTs Scenarios without CMTs c:\\wp\\ap6000503hmtg May 2.1996 Page 38

PRA PIRT Process (Cont.) The "high" ranked phenomena were also ranked in a relative fashion j The differentiation between the "really" high ranked phenomena and the other highly ranked phenomena was the expected tolerance of the calculation to increased uncertainty in the lower ranked phenomena j The lower ranked phenomena (which are still important) are indicated as an "I" The small-break LOCA PIRT was then. evaluated in this fashion to create the PRA PIRT i The highly ranked phenomena were grouped, where logical, and the parameters which should be compared when benchmarking M AAP4 t to NOTRUMP were identified j The important PIRT items were cross-checked against the proposed + benchmarking cases to address the highly ranked phenomena i I cdwpbp600V)S0396o mtg May 2,1996 Page 39

Nomenclature for PRA PIRTs a H liigh Importance: Has controlling influence on minimum vessel inventory; high accuracy needed on prediction I High Interest: Phenomenon that is unique to AP600 and/or PRA scenarios that should be examined, but moderate differences in the predictions are not expected to have contro!;!ng influence on the minimum vessel inventory. These - phenomena were identified as high importance on the Chapter 15 SBLOCA PIRT. (Dash): Neither a high importance nor a high interest item for benchmarking. l O Qmitted: Same as Dash, but it was a high importance item on the Chapter 15 SBLOCA PIRT. Bold H or I indicates that item was not identified as high importance on the Chapter 15 SBLOCA PIRT. i 1 c:\\wphp600V)503hmtg May 2.1996 Page 40 i

TAI 4LE l A PIRT for PR A Scenarios with CMTs Conp>nent / Itenomena Blow-Nat. ADS IRWST Discussion of fligh !newtance and fligh Interest hents itenshm.uking thw down Circu-blow-Caavity lation down Drain Break IntegratcJ tweak water Break Critical How (in complex 11 11 li Ontical tweak flow avurs when the tucak is the main vent Integrated tweak v4=w geomeines) path from the reactor system. The tweak Nw rate RCS guessure determines the rate of invenhwy loss, the system depressurization, and the timing of the acddent gwogression. For larger tweaks, the predine of tweak flow and deptessuriza6on is most inputant during the idowdown ghase treause it can impad coolant invenusy in the cure region. For snaller tweaks, inaccuracies in tweak tiow gredictions may have a cumulative effect impacting the 6ndag of the accident progression. Subsonic How Line Resistance Discharge Coefficient CMT Recirculadon CMT Recirculation CMT water innwa tion rate Natural circulation of CMT and I I CMT recirculadon consists of cold water being injected to l$alance line water hw rate R balana leg the downcomer through the DVI line, and hat water CMT water mass invenkwy returning to the CMT via the cold les and balance line. This results in a small net injecuon to the RCS. CMT recirculation ocmts for a long period of 6me to snuller tweaks, controlling the 6 ming of the accident gwogression. Liquid mixing of a balance leg, I I 1hermal mixing and stratificadon was teserved in CMT tenenture condensate, and Chf!' liquid experiments, but code numerical diffusion is not ex[rcted to have a significant inet on the overall recirculating and draining tchavior. Hashing effects of hoa CMT liquid layer CMT wall heat transfer c:\\wp\\apHUpirt tla Page 41 May 2.1996

TABLE I A PIRT fm PRA Scenarios with CARS Comgunent / Phenomena Blow-Nat. ADS IRWST Discussion of liigh inputana and liigh Interest Items ItenchatuLingt h w down Circu-tilow-Gravity lanon down Drain CMT Balance Lines CMT Transition to Draining Halance hac water tiow rate Pressure Drop I I The gAenomena in the balance knes and cold legs Italance hoe varv flow rate deternune when vapr will enter the balance line, ending CMT teset Flow Composidon 1 I the recitalados period of the CNR. Phas separation Tanw recirmianon ends indumtes whea the CMT starts to drain. Dimining of the CMT initiates ADS. lhese phenomena are unique to the old bgs AP600 plant and have been the focus of tes6ag and PliL4o-Cold les Tee 1 I

s. Ilowever. effa s in h das d se a

transition from recirculanon to draining do not have a gg ,g;, g g controlling influence on core ctuling. Hashing Sured Energy Release CMT Draining Effects CMT Draining CMT water injection tiow rate Thermal stratification and mixing 1 I lhese phenomena are related to the deternunzion of the CMT nuss inventsry of warmer condensate with gressure at the top of the CMT which cuatrols the draining CMT level colder CMT water rate of the CMT. The impact of the interfacial CMT tengwrmure condensa6on is to reduce the pressure at the 19 of the lime draining starts laterfacial condensa6on on CMT II CMT such that the CMT drain flow is reduced; this is name water surface important for larger tweaks. The overall draining rate of the CMT is important since it detan6nes the 6nw of ADS adua6co. Condensa6cn on cold thick stect surfaces Transient conduction in CMT ~ walls Dynamic effects of steam O This is only a possible effect fir the larger tweaks; the injection and mixing with CMT CMT diffuur telps to nutigate this effect. liquid and condensate c:\\wp\\ap600\\pirt sla Page 42 May 2.1996

l l TA14LE l A PlRT for PRA Scenarios with Chffs Concinent / lhenomena IWw-Nat. ADS 1RWST Discussion of thsh inewtance and liigh laterest lienu BenchnwLing thus t down Circu-IWw-Gravity latwa down Ikain I I Ugper llead Ikaaning Effects L'gper !! cad (Cont) Hashing Mixtwe Level O O O O-Mixture level in the upper picaum is considered below; nuature level in the upper head is not a concern. Entrainment / De-entrainment Ugper Plenum Draining Effects Hashing Entrainmeni / De-entrainment Extwe Level 11 11 11 11 Core Coolina RCS mass inventury lhese phenotnena are ranked high since the two phase drift Vessel mass inventury flux and mixtwe level models determine the distratunite of Cae nustwe level a two phase mixtwe, which deternunes if the core windJ Cae adigsed level Vesselfure become uncovered and experience a dad temperague heat Mixture Level / Mass inventory. 11 II II - II up. These are the key phenomena for PRA suaess criteria. Decay lleat II-11 H 11 lhe decay heat to be removed is a sensitive twindary condition. Forced Convection Hashing - Natural Circulation How and !! cat Transfer Mass How How Resistance cAwp'apNXy irt.ala Page 43 p May 2.19)6

TAftI E I A 11RT for PRA Scenarios with CMTs Component / Phenomena filow-Nat. ADS IRWST INscussion of liigh Inyortana and liigh laterest items itenchmmLing F.rus &>wn Carcu-filow-Gravity lation down Drain Vessel / Core (Cont.) Ibweconrr RCS Pressure Wall Stored Energy H H he stored energy in the vessel wall can impact the Ibwnconw M.us inventuy pessure of the RCS during the IRWST gravay injectiin I "8Y " E'#" "## '# "d 'I Downcomer / lower Plenum Stared Energy Release / Boiling H H 8'"'" ' Y "'YI " # "dd"""*I ^^II'*8#5 to RCS venting capacity. - - - - =. kvel 11 11 his is highly ranked since it provides the gravity driving Ibwnconwr level head for flow into the core, It is specif;cally of greac>t interest during the IRWST injection penad. Fladung lap Asymmetry Effects lite legs Countercurtent Ilow Entrainrrent Flastung ~ liorizontal Huid Strardication H H AD 4 Integrated ADS-4 water ADS-4 is a Ley componeet Isr the PRA success criteria. Integrated AIE4 vapor lhase Separation in Tees (Ihw H H Ac reduced venting capacity (compared to DBA)is the RCS pessure Region) reason for the increased importana. He flow regime in llat leg water lewt the hot leg determines the mixture that is entrained into tha ADS 4 ADS stage 4 lines. He ADS stage 4 lines are the primar'y Critical Flow II H venting path to redace system guessure to achieve / I 8'*N'Y I' Subsonic Flow H Two-lhase Pressure Dnp H c:\\wp\\apNXFpirt.tla 1%ge 44 May 2. IW6

TABLE l A PIRT for PRA Scenarios with CMTs Congonent / Phenomena blow-Nat. ADS 1RWST Diumssion of liigh Ingxutance and liigh Interest items Headmasking inus down Circu-Blow-Gravity latxe down Drain ADSl1 lategrated ADS l t water ADS Stages 1 - 3 Craical How O O II In PRA full depressuriation scenarios Go IRWST grasity lategrated Alb l-1 sagwe injection), ADS stage I to 3 are only used in high pessure RCS pessure Two Phase Pressure Drop I scenarios to reduce the pressure below the 4th stage interlock ADS I - 3 do not have a controllag ir. fluence Valve Loss Coefficient O on the event progression. Single-Phase Pressure Drop IRWST IRWST IRWST flow ree Pool level 'the IRWST injection provides core cooling. The pool IRWST level levelis a tuundary condiuon that provides the elevation IRWST tenverature Gravity Draining 11 head to drive the inventary injedion. Gravity draining also RCS pessure depends on the primary system pressure, pessure drtps in Temperature H the vent paths, and hae resistances in the injecuan lines. DVI Line Pressure Drop Olow Resistance) Discharge Line Hashing How and Temperature Distribuuan in PR11R Bundle Region Vapor Condensation l c:\\wp\\arhUpirt.:la Page 45 May 2.1996 i

_m en i l P TABLE 1A PIRT for PRA Scenarios with CMTs 1 i down Cirm-, ADS IRWST Discussion of liigh importana and liigh interest items Bendinurking ihm Component / lhenomena Blow-Nat. Blow-Gravity l lation abwa Ikain IYessurizer Surge 1.ine lYessure Ikop 1 Ilooding / COL 1 I Pressuriier Pressurizer level he luessurizer of high interest because it can inquet the XYessurizer nuss inventury lYessurizer redistribuuon of mass in the RCS. Once ADS-4 is liashing 1 aauated, the pressurizer drains. Level (Inventory) I I level Swell I I COL t [ i Ennainmena / De-entrainment 1 Stured Energy Release i Vapor Space Behavior Steam Generator Steam Generatur SG Mass laventevy I 29 Natural Circulation lhe steam generators are the only source of energy tenawal SG lleat Transfer except the CMTs and the tweak flow. For tweaks too small I I Secondary Mass leventory to remove the decay heat,the steam generatius play a rule in the timing of the event. Steam Generator llent Transfer n Secondary Condeuons L U-tube Condensauon i se, a.7 Pressure Steam Generance Tube Draining i c-\\wp\\ap60mpirt.tla Page 46 May 2.1996

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8

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TABLEIB PIRT for PR A Scenarias werhuut CMTs Compoacat / Phenomena Blow. Nat. ADS IRWST Discussica of liigh Imputance aaJ liigh laterest Items llenchmarking Ikus down Circu-Ibw-Gravity lanon down Drama hreak Integrated tucak water Break Critical How (in complex 11 11 11 Crmcal treak hw occurs when the tucak is the maia vent lategrated tweak vage geometries) path from the reador system. De tweak hw rate RCS pessure determines the rate of saventury loss, the system depresswization, and the tuning of the accident gwsyressita lir larger tweaks, the predicsa of tweak hw and l depressarization is most ingwutant during the blowdown phase because it can impaa coolut inventory in the core 1 region. For smaller tweaks,inacturacies in tweak hw gwedictions may have a cuandative effect, impacting the timing of the saident progression. we g:3ow Ilae Resistance IGhge Coefficient Accumulators Accumulators i lajeasonIbw Rase II, 11 he accunadators provide the only source of reacter coolant make-up prior to ADS aduation. De rate of delivery can play a key role in the pimary inventory status. N basible Gas Easrainment Upper Head Draining Effeas Ugper IIcad (Cost) liashing Mixture Level O O O O Mixture level in the upper plenum is considered below: mixture level in the t;pper head is not a concern. Entrainment / De-entrainment cAwp\\npMAApirt.tla Page 48 May 2,1996 L-i

TABLliIB 11RT for PRA Scenarios without CMTs Gunpunent / I'henomena Blow. Nat. ADS IRWST Discussion of liigh Inqutance and liigh Interest items Itca tn w Ling l a u, down Circu-Blow-Gravity la6on down Drain Upper Plenum Ikaining Effeas Rasl6ag Entrainment / De<ntrainment Manture Level 11 11 11 Core Celing RG mass inventivy 'Ihese phenomena are rankcJ high sina the tw+ phase draft Vessel mass inventimy llua and mixture level models deternune the dastribution of Core nsttwe level Core coll wd level a two-phase mixture, whidi determines if the oee would 4 y become uncovered and experience a clad temperatwe heat Maxiure Level / Mass Inventory 11 11 11 11 up. These are the key phenomena for PRA suaess criteria Decay lleat 11 11 11 11 The decay hea to be removed is a sensitive tuundary condition. I'urced Convection Flashing Natural Carcuta6ca How and lleat Transfer Mass flow 11ow Resistance c:\\wp\\ap60ttpan.tla Page 49 May 2,1996

~---------..MM.:q W.E 6 .A eha. "------- ' - " - - - -- - ' ' " '"-"'- - - ' " - - - ' - - ~ - ' - ' ' - - - - - " - - - - - - - - - - ' - - - - - - - - - - - - - - - - " ' - ' - - ' - - - - - ' ' " - ' - - " - - - - - - - ~ ~ -~~ " ~ - - ' - - ' - ' ~ " " - M i TABLEIB PIRT for PRA Scenaram without CMTs L Component / Itenomena Blow. Nat. ADS IRWST Discussion of liigh Imputance and lingh lainest licms Bendmarking thias 1 down Circu-Blow. Grasity lation down Ikain VesselCore (Cont ) Dowacomer R(3 henure Wall Stwed Enagy H H Ihe sured enagy in the vessel wa!! can inect the ibwacono Mass Invenury guessure of the RCS during the IRWST gravity inycuan sured cangy is a smacaQ see d hand Dowacoma / Iewer Plenum steam genaation, whah may gwovide addisonal challenges Stwed Energy Release / Boiling H H to RCS venting apacay. level 11 11 lhis is highly ranked since it provides the gravity driving Dowacuaw level head for fbw into the cure. It is specifically of greatest interest during the IRWST injecuan gerk=1. Hashing tap Asymmetry Effects flot legs Casatercurrent ibw Earrainment Rashing liarizustal Huid Stratifacation H H ADS-4 lategrated Al&4 wata ADS-4 is a Ley courqu>nent for the PRA success aiteria. Integrated Al&4 vapr 1%ase Separation in Tees (Ibw H H lhe reduced venting capacity fcompared to DBA)is the RCS pessure Regica) reason for the increased ingmutance. The fbw regime in the leg wara level the tus leg determines the nutture that is catrained into the ADS 4 ADS stage 4 hoes. The ADS stage 4 lanes are the grimary CJitical Row H vesting path to reduce system guessure to adieve / 8'" Subsonic lbw H Two Phase Pressure Iktp H cAwp\\ar60thurt.tla Page 50 May 2 !W6

TABLEIB PIRT for PRA Scenarios wittunst CMTs Comp >ncat / Phemotacan Blow. Nat. ADS IRWST Discussion of liigh Inewtance and I!ngh laterest facias licadouu king lists dawn Carcu

  • Blow-Gravity lation down

. Ikaia ADS Stages 1 - 3 AIN I 1 lateg ated AlW I-3 water Cndcal Flow 0 0 11 la PRA full depressurization scenarios no IRWST gravisy lategrated Alb l-3 vapr injection). ADS stage I to 3 are only used in high pessure RCS penure Twerhase Pressure Drop I scenarios to reduce the pressure below the 4th stage interkrk. ADS I - 3 as out have a controlling influence Valve Loss Coefficient O on the event progression. Single-Phase Pressure Drop IRWST IRWST IRWST Nw rate Puol level Il lhe IRWST injection provides stre cooling. lhe guol IRWST level level is a houndary coastson that proviks the elevation IRWST tengerature Caavity Ikaising 11 head to drive the inventary injection. Gravity draining also RCS guessure depends on the primary sysica pressure, gressure drops in Teraperature H the vent paths, and line resistances in the injec6on lines. DVI Line Pressure Ikop Gbw Resistance) Ducharge Line Flashing Ibw and Teraperature Distritaation in PRHR Bundle Region Vapur Condensation cSwp\\ap600Tput tla Page 51 May 2.1996

TABili iB PIRT for PRA Scenarios without CMTs Component / Phenomena Blow-Nat. ADS IRWST Discussion of fligh Inpurtance and !!igh laterest items llenchnurLing Focus down Carcu-Blow-Gravity lados down Ikain IYessuriur Surge line hessure Ikup Floo&ng / CCIL I 1 Pressuriur liessuriur level lhe guessuriur of high interest twause it can invad the hessuriur nass inventury Pressuriur redistribution of mass in the RCS. Onm ADS-4 is Flashing I actuated. d e pressurizer drains. level Onventory) I I l level Swell I I mg i Entrainment I De-entrainment 4 Stured Energy Release Vapor Spee Behavior Steam Genermor Steam Generatar SG Mass leventwy 29 Natural Circulation I lhe steam generators are the only source of eneigy renmal SG lleat Transfer except the break flow. Since the actuaion of ADS is Secondary Mass inventory 1 controlled by operatar maion, the SGs play a snuller role in the timing of the event. Steam Generator lleat Transfer Secondary Condidons U tube Condensation Secondary Pressure Steam Generator Tube Drair.ing c:\\wpWprt.tla Page 52 May 2,194

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Selection of Benchmarking Cases 1 CSwpWOO503%n.mtg May 2.1996 l' age 55

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Summary / Open Items c:\\wpup600050396amtg May 2.1996 Page57

Summary PRA scenarios have been discussed by a panel of experts to develop the PRA PIRTs The key phenomena which significantly affect the core inventory have been identified for a range of break sizes and available passive safety system equipment Benchmarking cases have been selected which capture the key phenomena Benchmarking process between NOTRUMP and MAAP4 will verify the AP600 PRA success criteria NOTRUMP and M AAP4 will confirm successful core cooling for a spectrum of PRA scenarios that have been chosen to fully demonstrate the phenomena of interest MAAP4 will be used for additional sensitivities to support the PRA i l l c:\\wpbp6mM503hmtg May 2,1996 Page 58 I

s 'o OPEN ITEMS NRC Actions Feedback on 2/29/96 plan Review PRA PIRTs Review selection of benchmarking cases Further clarification of T&H uncertainty concerns Westinchouse Actions Continue with benchmarking activities Plan for resolution of long-term recirculation issues Joint Actions Next meeting c:\\wpbp60025039% meg. May 2.1996 Page 59}}

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