ML20136H908

Analysis of Station Blackout Transient for Bellefonte PWR, Draft Preliminary Rept for Comment

ML20136H908
Person / Time
Site:	Bellefonte, 05000000
Issue date:	04/30/1984
From:	Dobbe C EG&G IDAHO, INC.
To:	NRC
Shared Package
ML20136H886	List: IA-85-503, Responds to FOIA Request for Two Specified Repts to Be Placed in Pdr.App Identifies Two Repts Placed in PDR ML20136H882 ML20136H908 ML20136H916
References
CON-FIN-A-6354, FOIA-85-503, FOIA-850503, REF-GTECI-A-44, REF-GTECI-EL, TASK-A-44, TASK-OR NUDOCS 8508200542
Download: ML20136H908 (54)

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April 1984

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! DRAFT PRELIMINARY REPORT FOR COMMENT' ANALYSIS OF A STATION BLACK 0UT TRANSIENT FOR THE BELLEFONTE PRESSURIZED WATER REACTOR I

C. A. Dobbe 1

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! idaho National Engineering Laboratory i Operated by the U.S. Department of Energy I l

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U.S. NUCLEAR REGULATORY COMMISSION Under DOE Contract No. DE-AC07-76ID01570 N FIN No. A6354

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4 FIN No. A6354 DRAFT PRELIMINARY REPORT FOR CCMMENT 4

, ANALYSIS OF A STATION BLACKOUT

, TRANSIENT FOR THE BELLEFONTE PRESSURIZED WATER REACTOR

'l C. A. Dobbe 1

Published May 1984 i

EG&G Idaho, Inc.

Idaho Falls, Idaho 83415 i '

s Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Under DCE Contract No. OE-AC07-76ID01570

1 I ABSTRACT Analyses of a station blackout transient in support of the Nuclear Regulatory Commission's Severe Accident Sequence Analysis Program are presented. The RELAPS computer code was used to calculate the effects of concurrent loss of offsite power, onsite power, and emergency feedwater during full cower operation on the Bellefonte Babcock and Wilcox design pressurized water reactor. Results provide insight into timing of significant events and provide thermal-nydraulic bound &ry conditions for subsequent core performance and containment analyses.

FIN No. A6354--Severe Accident Sequence Analysis (SASA) Program 11

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SUMMARY

Analyses were performec in support of the Nuclear Regulatory Commission's Severe Accicent Sequence Analysis Program. The RELAPS

. computer code was used to calculate the effects of a station blackout transient at the Bellefonte pressurized water reactor during full power operation. Bellefonte is a Babcock and Wilcox raised loop design plant to be operated by the Tennessee Valley Authority. The purpose of the calculation was to determine the predicted timing of significant events and to provide thermal-hydraulic boundary conditions for subsequent core parformance and containment calculations.

The station blackout transient considered was the TMLB' sequence. The TMLB' sequence is def'ned as a concurrent loss of offsite power, onsite power, and emergency feedwater during full power plant operation. The TML3' sequence assumes that emergency feedwater is not restored and power is unavailable for one to three hours. Core heatup was calculated by RELAPS to occur 1680 s after transient initiation. The RELAPS calculation was terminated at 2854 s when steam temperatures reached the current code water properties limit of 2240*F (1500 K).

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O g 7 ACKNOWLEDGMENTS The author gratefully acknowledges the personnel of the Tennessee i Valley Authority for providing information needed for the analyses presented in this report. The author is thankful to J. E. Blakeley for his help in the RELAPS code modeling of the Bellefonte plant and analyses of the RELAPS calculations, Sindi Crowton for the development of the graphics presented, and Louise Judy and Joan Mosher for their timely text processing efforts required for completion of this document.

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l CONTENTS ABSTRACT ............ . .. . .... .... ...... ....... ......... ...... 11

SUMMARY

................... ... ... ....... ... ....................... iii

1. INTRODUCTION .................. .................................. 1

2. COMPUTER CODE DESCRIPTION ........................................ 3

3. INPUT MODEL DESCRIPTION .......................................... 4 4 S P ECI FICATION O F ANALY S I S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5. ANALYTICAL RESULTS ............................................... 18 1

6. CONCLUSIONS .............................................. ....... 30

7. REFERENCES ....................................................... 31 APPENDIX A--ADDITIONAL RESULTS OF THE SELLEFONTE STATION BLACKCUT . .. . . 32 FIGURES

1. RELAP5 model of the Bellefonte A cool ant loop . . . . . . . . . . . . . . . . . . . . 6

2. RELAPS model of the Bellefonte B coolant loop .................... 7

3. RELAPS mocel of the Bellefonte reactor ves sel . . . . . . . . . . . . . . . . . . . . 11 4 Steam generator secondary side pressures vs. time . . . . . . . . . . . . . . . 20

5. Primary system pressure vs. time .................................

20

6. Pressurizer liquid level from pressure drop vs. time . . . . . . . . . . . . . 22

7. Mass expelled from the crimary system through the PORV vs. time ......................................................... 22

8. Mass expelled from the primary system in excess of the rated PORV capacity for saturated liquid vs. time ...................... 24

9. Comparison of calculated and expected primary system mass expulsion through the pressurizer safety valves vs. time ......... 24

10. Hot leg mass flow rates vs. time ................................. 25

11. A loop hot leg void fraction vs. time ............................ 28

12. Upper head and upper plenum void fractions vs. time .............. 28 i

V

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13. Core void fractions vs. time .... ....... . .. ................... 28 14 Fuel rod cladcing surface temoeratures vs. time ................ . 29

15. Primary loop coolant temperatures vs. time ....................... 29 TABLES

1. Correspondence between the physical and mathematical components in the primary loops for the RELAPS model of Bellefonte .................................................... 8

2. Correscondence between the physical and mathematical components in the A and B loco steam generator secondarias for the RELAPS model of Sellefonte ............................... 10

3. Correspondence between the anysical and mathematical components in the reactor vessel for the RELAPS model of Bellefonte . . . . . . . . . 12 4 Comparison of computed and desired steady state parameters forSellefonte................................................... 15

5. Pressure relief valve characteristics used for Bellefonte . .. . . .. . 17

6. Seg'!ence of events for RELAPS calculation of Bellefonte station blackout ................................................. 19 I

i v1

ANALYSIS OF A STATION BLACKOUT TRANSIENT FOR THE BELLEFCNTE PRESSURIZED WATER REACTOR i

j 1. INTRCDUCTION i -

The Severe Accident Sequence Analysis (SASA) Program was formulated by the United States Nuclear Regulatory Commission (NRC) to evaluate

postulated reactor accidents during a broad spectrum of accident sequences. These postulated sequences may extend beyond the current design basis in terms of system failures, core damage, and release of fission

! products to the environment. The objective of the SASA program is to evaluate nuclear plant response for accident sequences that could lead to partial or total core melt and to evaluate potential mitigating actions.

The Idaho National Engineering Laboratory (INEL) pressurized water reactor (PWR) SASA effort includes the evaluation of a station blackout transient

, from transient initiation through severe core damage.

l The station blackout transient was selected from dominant core melt sequences identified by the NRC sponsored Accident Sequence Evaluation Program (ASEP). The base transient is iritiated by a loss of offsite power i

followed by a failure to provide onsite power and failure to provide steam generator cooling via the auxiliary feedwater system. This station blackout sequence assumes no operator intervention and is designated the

TMLB' sequence. The TMLB' sequence assumes no power for one to three hours and no restoration of auxiliary feedwater. The TMLS' sequence eventually results in core degradation and a challenge to the reactor containment 4 boundaries.

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The current analysis was performed for the Bellefonte Nuclear Steam

. Supply System (NSSS); a Babcock and Wilcox (B&W) design PWR with 205 fuel assemblies (205-FA) and raised coolant loops. Bellefonte is to be operated by the Tennessee Valley Authority (TVA). The thermal-hydraulic analysis for the TMLB' sequence through core uncovery was performed with the RELAP5/M001.6 computer code.1~9 The purpose of the analysis was to i

characterize the transient by determining timing of significant phenomena 4

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l observable by the oparator. The results of the RELAPS thermal-hydraulic analysis provide boundary conditions for separate comcuter code calculations of the core thermal-mechanical response and containment response to the station blackout following core uncovery. In particular, the core response from core uncovery to slumping of core material will be evaluated with the SCDAP 10 computer code. The results of the SCDAP analysis provide boundary conditions for additional RELAPS analysis to .

investigate fission product transport and structural heating in the primary coolant system during the core damage phase of the TML3', The effect of operator actions and equipment availability on the timing and eventual outcome of the TMLS' sequence will also subsequently be evaluated and successful plant recovery sequences determined.

The work reported here represents the initial thermal-nydraulic calculations of the TMLB' sequence for Bellefonte. A brief description of the RELAPS comcuter code is presented in Section 2 with the input model developed for the analysis described in Section 3. The specification of the analysis is presented in Section 4 and the analytical results are discussed in Section 5. Conclusions are given in Section 6.

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2. CCMPUTER CODE DESCRIPTICN The Bellefente TMLB' analysis was performed using the RELAP5/M001.6 computer code. The RELAPS/M001.6 comcuter code is an advanced computer

. code designed for best estimate thermal-hydraulic analysis of light water reactor transients. The code is a one-dimensional, two-fluid, nonequilibrium computer code utilizing a five equation hyd*odynamic model.

The five equations are a mass conservation equation and a momentum conservation equation for each phase and a single overall energy equation.

The use of a single energy equation requires the assumption that one of the phases within a control volume will be at saturation. Special process

, models are provided for abrupt area changes, branching, choking, pumps,

! accumulators, core neutronics, control systems, and valves.

The Bellefonte TMLB' analysis was performed with RELAP5/M001.6 Cycle 12. Cycle 12 of RELAP5/MC01.6 differs from the released version,

RELAPS/M001.5, in that selected models available in RELAP5/M002 (scheduled l for release in F(-84) have been incorporated. The models pertinent to the 1 subject analysis are (1) addition of the 1979 ANS standard for nuclear fuel 9

decay heat determination and (2) addition of a cross-flow junction model to approximate a two-dimensional system component.6 RELAPS/M001.6 Cycle 12 is filed uncer Idaho National Engineering Laboratory Computer

, Configuration Control Management Archival Number F01245.

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3. INPUT MCDEL CESCRIPTION The RELAPS model of the Bellefonte NSSS was constructed primarily from information provided to INEL by TVA. The information included detailed blueprints, thermal-hydraulic design specifications, descriptions of most plant subsystems, anticipated operating parameters, and copies of the Bellefonte Final Safety Analysis Report (FSAR). The following discusses the details of the Bellefonte RELAPS steady state full power model. The steady state and transient input decks for the Bellefonte TMLB' analyses, as well as the job control language (JCL) to run the RELAP5/M001.6 computer code, are filed under Idaho National Engineering Laboratory Computer Code Configuration Management Archival Numoer F01276.

The RELAPS Bellefonte model details all of the major system components required for the station blackout analysis. Features modeled incluce all major primary system coolant loop and reactor vessel flow paths, secondary system main feecwater paths downstream of the main feedwater isolation valve (MFIV), and the secondary main steam paths upstream of the turbine stop valves (TSV), including the main steam isolation valves (MSIV). The Bellefonte RELAPS steady state model utilized 183 control volumes, 190 junctions, and 185 heat structures to simulate the NSSS.

The nodalization scheme used for the Bellefonte RELAPS model is based on the Oconee RELAPS model developed at INEL.U The Oconee RELAPS model has been used to evaluate small breaks, steam line breaks, plant operational and plant overcooling transients. The nedalization has proven to be sufficiently detailed to provide satisfactory results over this broad analytical range and was chosen as the basis for the Bellefonte RELAPS model. Significant design differences do exist between the Oconee PWR (177 fuel assemoly plant with lowered loops) and the Bellefonte PWR ,

(205 fuel assembly plant with raised loops). The primary differences are:

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1. The steam generators in Seilefonte are raised relative to tne i reactor vessel, wntch eliminates the deep loop seal in the pump suctions of the Oconee cesign. This results in shcrter piping runs between the steam generators and the pumps and longer

. vertical runs of hot leg piping between the reactor vessel and the top of the hot legs for the Bellefonte model.

2. Bellefonte has larger diameter pump suction piping than does Oconee. This is related to the larger system flows of the Bellefonte design, i

3. Bellefonte uses' the B&W Mark C fuel assemblies with a 17 by 17 rod array, whereas Oconee uses the Mark B fuel i assemblies with a 15 by 15 rod array.

The two primary coolant loops for Bellefonte each consist of a hot leg, a steam generator, two pump suction legs, two reactor coolant pumps, and two cold legs. The loop containing the pressurizer, referred to as the ,

A loop, was nodalized as shown in Figure 1. The second coolant loop, referred to as the B loop, was nadalized as shown in Figure 2. Table 1 summarizes the relationship between the physical components of the Bellefonte coolant loops and the corresponding mathematical comoonents of the RELAP5 model.

The pressurizer is connected to the A loop as shown in Figure 1. The pressurizer surge line is connected to the hot leg at Component 108 utilizing the cross-flow model discussed in Section 2.1. This approach prevents partitioning the hot leg flow stream momentum into the pressurizer surge line and artificially elevating the pressurizer pressure. The spray line is connected between the pressurizer steam dome and the A loop cold leg through an inline check valve. Primary system pressure relief is provided by code safety valves and the power operated relief valve (PORV) connected to the pressurizer steam dome.

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TABLE 1. CORRESPON0ENCE SETWEEN THE PHYSICAL AND MATHEMATICAL COMPONENTS IN THE PRIMARY LOOPS FOR THE RELAPS MODEL OF BELLEFONTE physical Comoonent RELAp5 Comoonent(s)

Loco A Hot leg 100, 101, 105, 108, 110 Steam generator inlet plenum 115 Steam generator tubes 120 Steam generator outlet plenum 125 A-1 pump suction leg 160 A-2 pump suction leg 130 A-1 reactor coolant pump 165 A-2 reactor coolant pump 135 A-1 cold leg 170, 175, 180, 131 A-2 cold leg 140, 145, 150, 151 4

Loco 3 _

Hot leg 200, 201, 205, 208, 210 Steam generator inlet plenum 215 l Steam generator tubes 220 Steam generator outlet plenum 4

225 8-1 pump suction leg 260 B-2 pump suction leg 230 3-1 reactor coolant pump 265 B-2 reactor coolant pump 235 1 8-1 cold leg 270, 275, 280, 281 3-2 cold leg 240, 245, 250, 251

pressurizer l

Surge line 600, 601, 605 Pressurizer 610 Pressurizer dome 615 Soray line 620 Soray valve 616

, PORV 804, 805 Safety valve 802, 803 i

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The four reactor coolant pumps for Bellefonte are Bingnam-Willamette pumps. The single phase head and torque data as well as the puma rated-conditions were suoplied by TVA. Pump friction was based on assumed

friction torque equal to 2.25'.' of rated torque with l'.' static friction and

. 1.25'.' dynamic friction at rated conditions. These friction values are typical for this type of reactor coolant pump.

The Bellefonte steam generators are the B&W once-through design. The primary and secondary sides of the boiler region were nodalized witn twelve axial control volumes as opposed to the eight volume nedalization used for Oconee. The additional volumes were used to better define the calculated transition region between nucleate boiling and film boiling on the secondary side and thus improve stability of the heat transfer solution '

curing steady state calculations. Overpressure control for the steam generator secondary sice is provided by both ccde safety valves and modulating atmospheric dump valves (MADV) with secondary side isolation provided by turbine control valves (TCV) and main feedwater isolation valves (MFIV). The relationship between the steam generator secondary side physical components and the corresponding mathematical components of the RELAPS model are presented in Table 2.

The nedalization scheme used for the reactor vessel is shown in Figure 3. The model is similar to that used for the Oconee plant, although the flow paths in the upper plenum and upper' head are different. The flow between the inner upper plenum and outer upper plenum through the plenum cylinder was modeled with two junctions. Additionally, the upper head is modeled as a flow through volume instead of a dead end volu'me, as was cone for Oconee. The Bellefonte design utilizes a perforated solid plenum cover plate instead of an eggerate support, which would promote flow from the inner upper plenum region to the outer upper plenum region tnrougn the upper head. As is common to B&W design vessels, pressure relief f*om the upper plenum to the downcomer is provided by eight reactor vent valves that are fully open at a differential pressure of 0.125 psia (862. Pa).' The correscondence between the physical components of the reactor vessel and the RELAP5 mathematical components is given in Table 3.

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TABLE 2. CORRESPCNCENCE SETWEEN THE PHYSICAL AND MATHEMATICAL CCMPCNENTS IN THE A AND 8 LOOP STEAM GENERATOR SECONDARIES FOR THE RELAPS MODEL OF BELLEFONTE Physical Comoonent RELAPS Component Steam Generator A Feedwater line 700, 827 Main feedwater isolatien valve 705 Downcomer 300 Tube bundle 310 Steam cowncomer 315, 320 Maia steam line 325, 330, 3a0, . .

350, 360, 370 Turbine stop valve 365 Main steam isolation valve 335 Safety valves 311 Modulating atmospheric dump valves 809 Steam $enerator B Feecwater line 750, 927 Main feedwater isolation valve 755 Downcomer 400 Tube bundle 410 Steam downcomer 415, 420 Main steam line 425, 430, 440, 450, 460, 470 Turbine stop valve a65 Main steam isolation valve 435 Safety valves 911 Modulating atmospheric dump valves 909 i

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11

l TABLE 3. CORRESPONDENCE BETWEEN THE PHYSICAL AND MATHEMATICAL CCMPONENTS l IN THE REACTOR VESSEL FOR THE RELAPS MODEL OF SELLEFONTE l

1 Physical Component RELAPS Comoonent(s)

Inlet annulus 555, 557, 560, 562, 565, 567 Downcomer 570 Lower plenum 505, 575 Core 515 Core bypass 510 Upper plenum 520, 525, 530, 535, 538, 540, 545 Upper head 550 Vent valve 536 G

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Heat structures were used throughout the model to characterize the heat capacity of and resulting heat transfer from major structural masses in the Sellefonte NSSS. Included were structures to model loop piping,

steam generator tubes, shrouds anc vessel, pressurizer walls and heaters, reactor vessel walls, core barrel, core baffles and former plates, plenum cylinder, internal supports and guide structures, and the nuclear fuel.

The outside of the piping and vessel surfaces were treated as adiabatic boundaries eliminating environmental heat losses. The core fuel heat source was modeled using the RELAPS point kinetics package with Doppler and density reactivity feedback and control red insertion simulated.

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4 SPECIFICATICN OF ANALYSIS l

The evaluation of the TMLB' sequence involved two separate calculational steps. First, RELAPS calcu!ations were performed to produce a consistent set of steady state system parameters equivalent to the normal full power operating parameters of the Bellefonte NSSS. Second, appropriate boundary conditions were applied to the resulting RELAP5 steady state model via code restart to match the TMLB' base sequence assumptions.

The RELAPS analysis was terminated when core fuel heatup produced code calculated steam temperatures in excess of the current code water properties limit of 2240*F (1500 K).

4.1 Steady State Initial Conditions The initial conditions for the RELAPS TMLB' calculations were representative of the anticipated operating conditions of the Bellefonte NSSS at 100% of rated core power. Table 4 compares the values of selected plant parameters obtained from the Bellefonte FSAR for full power steady state operation with those calculated by RELAP5. The initial conditions were obtained from a RELAPS steady state calculation that used control systems to drive reactor coolant pumo soeed and main feedwater valve area to produce the desired loop mass flow rates and secondary side mass, respectively. The secondary side steam flow was adjusted to produce the desirec cold leg temperature. Adcitionally, the steam line pressure, feedwater temperature, pressurizer pressure, and core power were held constant. The comparison in Table 4 shows that the RELAPS calculated initial conditions were in excellent agreement with anticipated plant operating parameters. Differences between the desired and computed values are well within the uncertainty in the anticipated plant operating parameters.

For the RELAPS analysis of the TMLB' transient it was assumed the loss -

of station power resulted in simultaneous turoine trip, reactor scram, primary reactor coolant pump trip, and main feedwater valve closure l initiation. Turbine trip isolated the steam generators from the balance of plant by closing the turoine stop valves. The bottled up" steam generator 14

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TABLE 4 CCMPARISON OF COMPUTED AND DESIRED STEADY STATE PARAMETERS FOR BELLEFCNTE Parameter RELAPS Desired Core thermal power (MW)* 3600. 3600.

Pressurizer pressure (psia) 2210. 2210.

(MPa) 15.2 15.2 Pressurizer level (in.) 195. 195.

(m) 4.95 4.95 Hot leg temperature (*F) 627.4 627.5 (K) 603.9 604.0 Cold leg temperature (*F) 573.8 573.7 (K) 574.2 574.1 Total loop flow (1bm/s) 43724 43722.

(kg/s) 19833. 19832.

Reactor coolant pump head (psi) 121. 119.

(MPa) 0.83 0.S2 Steam generator pressure (psia) 1060. 1060.

(MPa) 7.31 7.31 Steam generator liquid mass (1bm) 32610. 33660.

(kg) 14792. 15268.

Steam generator feed (1bm/s)D 2280. 2236.

(kg/s) 1034. 1014.

Feedwater temperature (*F) 477. 477.

(K) 520. 520.

Steam superheat (*F)c 32. . 50.

(K) 18. 28.

a. Core axial power shaped based on 460 effective full power days.

b. Per steam generator. Steam flow set to same valve.

c. RELAPS calculated equilibrium temperature.

15

secondaries were proviced pressure relief via the modulating atmospheric duma valves (MADV) and the secondary coce safeties. The nonmodulating atmospheric cump valves were assumed nonoperational. The primary system pressure relief was provided by the PCRV and the code safety valves. The valves were sized to provide the rated flows of saturated steam shown in Table 5.

The initial core power profile was based on the Bellefonte FSAR puolished values for the end of the first cycle (460 effective full power cays). Reactor scram was assumed to occur simultaneously with transient initiation with best estimate delays for scram signal processing, control red drive electromagnetic field decay, and red droo times incorporated into the scram table. The ANS-79 standarc decay heat model was utilized with infinite coerating time assumed. The RELAPS kinetics package, a space incependent (point reactor kinetics) macel, was used to calculate both .

prompt and delayed neutron power contributions to the core power.

The pressurizer heaters were assumed to trip off at transient initiation. The pressurizer spray line was assumed to remain open during the transient as the assumed transient did not initiate a closure signal for the inline checx valve. Primary system coolant makeup and letdown systems were not modeled.

The TMLB' secuence does not include any ECCS injection er emergency feecwater injection. These systems are not modeled and no credit is taken for them in the subject analysis.

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a .

TABLE 5. PRESSURE RELIEF VALVE CHARACTERISTICS USED FOR BELLEFCNTE Pressure Setpoints'

[ psia (MPa))

b Rated Flow Valve Valve Ocen Valve Closed [lbm/s (ko/s))

e Steam Generator Code Safeties Bank 1 1287. (8.87) 1187. (8.18) 258.4 (117.2)

Bank 2 1318. (9.09) 1216. (8.38) 264.6 (120.0)

MADV 1220. (8.41) 1170. (8.07) 164.3 (74.5) 1 Primary System Coce Safeties 2500. (17.24) 2390. (16.48) 282.2 (128.0)d PCRV 2310. (15.93) 2285. (15.76) 44.4 (20.1)

a. Pressure setpoints differ from those published for Bellefonte. The values shown were obtained from the Tennessee Valley Authority.

b. Valve rated flow at full open pressure setpoint,

c. Per steam generator.

d. Total for two safety valves. Valve rated flow at 2590. psia (17.86 MPa).

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5. ANALYTICAL RESULTS The results of the TML3' station blackout transient analysis for the Bellefonte NSSS are presented in this section. The results of the system thermal-hydraulic analysis calculated with RELAP5 are presented below.

Additional plotted results of the RELAPS analyses are presented in Appendix A.

The system thermal-hydraulic response to a TMLB' station blackout sequence is characterized by a complete ooiloff of the steam generator secondary side water mass within the first few minutes of the transient.

The primary system then heats up and, as the coolant in the loops expands, pressurizes to the setpoint of the primary coolant system relief valves.

The primary system then saturates and natural circulation in the locos is lost when the upper portions of the hot legs void. The remaining fluid in the loops falls into the pump suctions and reactor vessel as the loop mass flow rates approach ze o. The fluid in the reactor vessel is then boiled off by the fission product decay heat generated in the core resulting in fuel cladding dryout and heatup.

The sequence of significant events for the TMLS' station blackout transient are summarized in Table 6. Initial overpressurization of the steam generator secondaries following loss of feedwater forced the MADV and coce safety valves open within 20 s. Figure 4 shows that the pressure in both steam generator seconcaries cycled between the opening and closing setpoints of the MADV [1223 psia (8.41 MPa) and 1170 psia (8.07 MPa),

respectively] until primary and secondary temperatures equilibrated following flow stagnation in the loops at 1050 s. The primary system pressure, shown in Figure 5 for the pressurizer steam come, initially dropped as the early portion of pump coastdown produced adequate loop flows to transport decay heat to the steam generators. The primary system then repressurized to the PORV opening pressure of 2310 psia (15.93 MPa) at 236 s as core decay heat exceeded the heat removed by steam generators.

Primary system cressure cycled between the PORV opening pressure and the i valve reseat pressure of 2285 psia (15.76 MPa) for the remainder of the transient.

18

e O TABLE 6. SEQUENCE OF EVENTS FOR RELAPS CALCULATICN OF BELLEFCNTE STATION BLACKOUT Time Event (s)

Scram signal 0.0 RCP's trip 0.0 Main feedwater begins 0.0 2.0 s coastdown TCV's start closing 0.06 (0.15 s closing time)

Control rod drop begins 0.4 MADV's open (both steam 3.0 l generators)

Contrel rods fully inserted 3.1 Steam generator safeties cycle both 4.5 to 8.5 S.G.'s (open-close) - 14.5 to 16.0 Effective heat sink lost 45 to 50 PORV initial opening 286.5 Primary saturates (hot legs) 900.

Loss of natural circulation 1050.

~

Fuel cladding heatup begins 1680.

Transient terminated 2854.

1~

19

1 I

I l

l I

i l

1 l

=0 , . . .o00 0 A loop O 8 10o0 q 1250 o S es00 g, w w e 1 -

I, 1200 e h i U

_b'-.

g g,000 .,

a. a.

2 E n00 e E 7500 o

3 o

> m

.m I f I f C SCO M ?S00 2000 2500 3000 rim. (3)

Figure 4. _ Steem generater sesondery :Ide preroo ,s. ttme.

'4300 . . .

l0 Pressuri zer l

,se000 ,. . m h YNSWW Wtk '2 #

• v

• ?S500 e

• w E t o 2200 j e 1S000 - -

g s i

'G. g ,

I s us00 . .

2 00 . .

5 E o o i

> 14000 1 -

i 2000 g , ,

O SCO 1000 1500 2000 2500 3000 l Time (s)

Figure S. Primary system pressure n. time.

l l

20 l

• i

l The response of the pressurizer licuid level to the TML9' is shown in Figure 6. The level, calculatec from the axial pressurizer pressure '

difference less the steam gravity head, shows the pressurizer full (level exceeds elevation of upper pressure tap) by 700 s and remained essentially

. full until approximately 1050 s. The pressuri:er level fluctuations between 1050 s (loss of natural circulation) and 1400 s paralleled draining of the A loop hot leg. When the pressurizer was filled with water, the primary system mass decreased at an accelerated rate as licuid was expelled through the PORV.

The mass expelled through the PORV during tne TMLB' is shown in Figure 7. The PORV mass flow rate implied by Figure 7 had a maximum value of 600 lbm/s (272. kg/s) between 1000 and 1100 s. The saturated liquid mass flow rate for the PORV was computed to be 88 lbm/s (40 kg/s) at 2310 psi (15.9 MPa)." The discrepancy in relief flow rates was the result of an error in the computation of the PORV full open area used for the RELAP5 model. The valve sizing error affects both the system pressure resconse and the pric.ary coolant mass discharge rate.

The effect on the primary system pressure response can be estimated from an energy and mass balance calculation. The difference between energy .

adced to the primary system in the core (de u y heat) and the energy removed i

from the system by the PORV (rated mass flow x specific enthalpy) can be used to compute the net change in primary system enthalpy over a given time period. Likewise, the PORV mass flow over the same period can be used to compute the change in primary system density. The resultant specific enthalpy and density then define a new primary system pressure and a primary system repressurization rate can be determined.

a. Based on valve rated flow for saturated steam shown in Table 5.

,, Saturated Henry-Fauske critical flow model used to compute change in mass flux between saturated steam and saturated liquid.

+

21

w e

14 i l0 Pressurtzer level I g- ,

. 40 m ^

E -

w v 10 - upper preneure to .

T> 30 e -

- 3 - -

g t _l . ,, T -

- lO I S g..

20 E -

0 4

~10 2

O S00 1000 1500 2000 2500 3000 Tim. (s)

FIpre 8. Pressurizer I1 quid level from preneure dreo vs.

tf me.

200000 , , , ,

lO Posry flew l 9 m'n}

6 -

~

,m _ _

B o

= 2.00,0-  ;

. se a

- - o f 100000 2.oo.,o a E l 1

n 1

l w U as 50000 - w i e -

-LOON 0 en i

-c E 00 0 0 C ' 2 ' '

O.00 0 SCO W ?SCO 2000 2500 3000 Time (s)

Figure 7. Ideas espelled from the primo.y system through the PCAV vs. time.

l l

l .

] .

. a 4

The energy balance calculation was initiated at the time the mass flow calculated by RELAP5 exceeded the rated mass flow for the PORV. Figure a shows the integratec result of the difference between the RELAP5 calculatec PORV flow and the maximum rated value of 88 lbm/s (40 kg/s). The relief capacity of the PORV was exceeced by the primary system expansion after 900 s. Starting at 900 s and using a time interval of 100 s, the primary system repressurization with the PORV flow limited to 88 lbm/s was calculated to be 0.65 psi /s. From Table 5, the opening pressure for the code safeties is 2500 osia (17.24 MPa). The time reouired to reach the code safety opening pressure would then be 292 s.

The total system relief capacity (PORV and code safeties) for saturated liquid at rated pressure is 650 lbm/s (295 kg/s).* Once the primary system reached the code safety setooint, the primary system pressure would stabili:e since the relief capacity exceeds the system expansion rate. Figure 8 indicates that the relief capacity of the coce safeties would be required until about 1900 s. Figure 9 shows a comparison of the current calculation of PORV integrated mass flow and the anticipated PORV and code safeties integrated mass flow. The results show that correcting the PORV valve area would result in a +292 s shift in time for events occurring after 900 s with a 200 psi increase in primary system pressure between 900 and 1900 s. The effect of tne PORV sizing error on the outcome of the current calculation should be inconsequential.

The loop mass flow rate for the hot legs response to the TMLB' is shown in Figure 10. The loop flow followed reactor coolant pump coastdown and established a natural circulation flow rate of ~1000 lbm/s (450 kg/s) per loop. The flow rate stagnated at 1050 s when hot leg saturation

• 1 1

1

a. Based on valve rated flow for saturated steam shown in Table 5.

Saturated Henry-Fauske crit'ical flow model used to compute change in mass flux between saturated steam and saturated liquid.

l 23 1

i 6

Integrated rnass tiow (kg) Integrated mass flow (kg)

N 0 3

I l

l 5

o 2 I. ,

.. . .. I. .

P P DO O n

j k -

<t I i=1 1 ni.

3 g i" gl

3! l <

~8 ea t' S ro I

f EI 7^

kE~3U a j3 i t.8 . .

7,g.$ . .

=

i[?

g*-

• 3]?

g,v i

7 3 '"

} h~ o -

si al

{I is u g] <

1. • 8 _ _

7Q l

3. *I

<1 j.

"i

= I .. .. . ;E

. l ..

i l--li s n ,,.

~

!-! !i integrated mass flow (Ibm) 11Integroled mass flow (Ibm) ,

e

=

t e

e

O s SCOC_- , , &

O A loop O a loop .nsoco 8000 - .

m M

7

\ - .iogoo cm 6 4000 ' -

e w

n a I

_O

-e2000"> 8detural ofreuleff en dest -5000 e

Q m.

2 -_ 4 e

-;--- - - yh . _ - -

2 0- r " - - . J ..o

-2000 O Soo 1000 1500 2000 ZS00 3000 Tim. (3)

Figure 10. Hot leg moss flow r a t es vs. time.

l l

l l

I 25 ,

I i

f

. ', o i

l produced voiding at the top of the hot leg. As shown in Figure 11, the  ;

voiding propagated frem the top of the hot leg to the elevation of the i reactor vessel hot leg nozzles between 1050 s and 1500 s as liquid drained back into the reactor vessel. The A loop hot leg flow indicated some net positive loop flow between 1050 s and 1500 s due to flow from the vessel to the pressurizer.

The voiding of the reactor vessel during the TMLB' is shown in Figure 12 for the upper head and upper plenum and in Figure 13 for the core. The upper head and upper plenum above the hot leg centerline (4.2 ft (1.3 m) above the top of the core) voided rapidly following system saturation at 850 s. Liquid draining back into the vessel frem the het legs nintained coolant above the top of the core until the hot legs completely crained at -1500 s. After the hot legs drainea, the remaining liquid in the core boiled off rapidly producing the top down dryout of the core snown in Figure 13. As shown in Figure 14, the clacding surface temperatures increased rapidly following dryout with the highest temperature predicted to occur 8.9 ft (2.71 m) to 11.2 ft (3.41 m) above the core inlet. The e,ladding temperatures were calculated to exceed the initiation temperature for potentially significant zircaloy oxidation of 1340*F (1000 K) by 2200 s at the hot spot. Since RELAPS does not contain models to calculate zircaloy-steam reactions, the cladding temperatures calculated beyond 2200 s are anticipated to be low. The calculation was continued beycnd 2200 s with l1 ELAPS to better define boundary conditions needed for the SCCAP core damage analysis. The cladding temperatures exceeded 1340'F (1000 K) in the top half of the core by 2350 s. The bottom node did not heatup above saturation temperature as liquid was still present at that elevation (see Figure 13). Dryout of the core resulted in superheated steam in the primary loops as shown in Figure 15. The loop heatup is asymmetric with the highest temperatures occurring in the A loop hot leg, the path between the core and the pressurizer PORV.

26

e

• • a 1.5 4 LS O Top of het leg C So tt om of ho t l eg c c C 0 o 1 .I

^

~ -

a

" C. 1.0 o O

C 7 A E T

T.

O o.

3 >

0.S -- l N -~ G.S $

$ 1 I

f 0..,.-.-- - .

A . .

C.0 0 500 1000 1500 2000 2500 3000 Time (s)

Figure 11. A toop het leg voic fraction vs. 'Irre.

J i,

i h

27

8 O Elevations relative to core outlet ts , , , , t.s C C '

O O

g t<- p  ; = = = -- to g h I 1  %

f f

2 0 1. peer "ood 1 o C 7.7 - 11.2 ft. O

1. f (2.3 - 3.4 m) 04 , l A 4.2 - 7.7 f t. -. o,3 g

'E ,

') (1.3 - 2.3 m) a o 0 2.1 - 4.2 ft. >

0

> f J (.84 - 1.3 m) j7f 7 0.0 - 2.1 f t. -

f (0.0 .44 m) 0: : C' c.0 0 500 '000 iS00 2000 2500 3000 rim . (3)

F1 pre 12. Uoper heed ems upper pioman weid frociloes vs.

time.

Elevations relative to core inlet ts , , , , , ts O ft2 - 13.4 f t.

(3.4 - 4.1 m)

C 8.3 - ft.2 ft.

$ (2.7 - 3.4 m) g

- a 8.7 - 8.9 ft. -

u 3, (2.0 - 2.7 m) - - - -

~ ~ to E O O 4.s - 8.7 ft. I T- O A (t4 - 2.0 m) D y 7 2.2 - 4.5 f t. y

(.87 - 1.4 m) -

O j X 0.0 - 2.2 ft. J' (0.0 .87 m) o M* -*-

0.5 a Q. 4 o.

O d 0 e a m

0: : =C': - O.0 0 S00 1000 1500 2000 2500 3000 Time (s)

Figure 13. Core veld fraetloce vs. time.

e 28 .

9

.L 4

Elevations relative to core inlet

• s00 , , . .

O tt2 - 12.s ft.

m (3A - 3.9 m) e g 1400 -

O 8.9 - tt.2 ft.

(2.7 - 3.4 m)

-2000 D

• A S.7 - B.9 f t. ,

s t200 . (2.0 - 2.7 m) -

s 0 4.5 - 6.7 f t. -

8 e

(t4 - 2.0 m) Z***Y'"'"

ts00 2*

7 2.2 - 4.5 f t.

200

• I" M

• U *" ~

(.67 - 1.4 m) f e X 0.1 - 2.2 ft. o

(.03 .67 m) e 800 "- - 200 ,

u o

?  ?

M a eem- -

= = = -l': '

x.

vi 3

, i ,

g ,

O SCO 1000 1500 2000 2500 3000 Time (s)

Flpsre 14 Fuel red eloddleg surf ace temperaturae vs. time.

1000 , , , , ,

• O Met tog A

• s O Het leg E s a Cold leg A1 'N -

s o Cold leg at u e e

c. o.

E E see -. noo 2

.E_ x /l,ld P - _lo

.5 700 - --800 .5 a a g-Q=

. g -= - - w .

, o k_ w_

.c--

_.e00 e E g 3 g ,

y 0 300 1000 300 2000 2500 3000 Time (s)

FIpere 15. Pritnery Ice, eeelet temperatures vs. time.

29

6. CONCLUSIONS A TML3' station blackout transient at the Bellefonte Naclear Pcwer Station was analyzed using the RELAPS computer code. The analysis showed primary system boiloff with subsequent core uncovery and dryout within -

1700. s of transient initiation. Events were calculated to occur about 292 s earlier than anticipated after the pressurizer refilled due to an error in PORV valve sizing but the effect on the overall calculation was expected to be minor. The calculation was carried out to the current RELAPS water properties limit of 2240*F (1500 K) to provide boundary conditions for subsequent SCDAP core performance analyses. The core fluid anc material temperatures presented are only valid below 1340*F (1000 k) as RELAPS coes not contain models to predict metal water reaction and the resultant energy deposition into metal and fluid.

i

=

l 30

7. REFERENCES

1. V, H. Ransom et al . , RELAP5/MCD1.5: Mocels. Develoomental Assessment.

and User Information, EGG-NSMD-6035, Octooer 1982.

2. D. M. Kiser, Imoroved Steady State Edit / Testing Scheme for RELAPS, IS-NSMD-83-010, April 1983.

3. R. J. Wagner, RELAP5/MCD2 Shaft Control Comoonent, IS-NSMD-83-014, April 1983.

4 J. A. Traop, RELAPS/M002 Turbine Comoonent Comoletion Reoort, IS-NSMD-83-015, Aoril 1983.

5. D. M. Kiser, Imoroved Wall Drao Model for RELAP5/M002, IS-NSMD-83-016, April 1983.

6. J. A. Trapp, Cross-Flow Junction and Seoarator Vograde Comoletion Recort, IS-NSMD-83-019, April 1983.

7. J. C. Lin, R. A. Riemke, J. A. Trapp, RELAPS/M002 Hydrodynamic Numerical Scheme and Noneouilibrium Constitutive Mocels, IS-NSMD-83-021, April 1983.

8. J. C. Lin, Time Steo Control for Heat Transfer, IS-NSMD-83-022, May 1983.

9. R. J. Wagner, Addition of ANS 1979 Standard Decay Heat to RELAPS, WR-NSMD-83-0003, January 1983.

10. G. A. Berna et al., SCDAP/ MOD 1/V0: A Comouter Code for the Analysis of LWR Vessel Benavior During Severe Accicent Transients, IS-SAAM-84-002, January 1984 -

11. C. D. Fletcher et al. , RELAP5 Thermal-Hydraulic Analysis of Pressurized Thermal Shock Secuences for the Oconee-1 Pressurized Water Reactor, EGG-NSMD-6343, July 1983.

31

APPENDIX A _

ACDITIONAL RESULTS OF THE BELLEFONTE STATION BLACK 0VT S

45' 32

• l .

APPENDIX A The following figures document the results of tne TMLB' calculation for Sellefonte. RELAP5 calculated values of system parameters not presented in the text are given.

S l

I 33 j l

I

. , l l

l i

l l

Elevations relative to core outlet 1400, , . ,

,g g

• o un er w 3 s C 7.7 - 112 ft.

N ~ (2.3 - 3.4 m) ~ 3w

• E A 4.2 - 7.7 ft.

g (t3 - 2.3 m) 1 E

o 2.1 - 4.2 f t. v

' '5" E

e (.s4 - t3 m) ~

=

- 1000 - ~

7 0.0 - 2.1 f t.

E7 (0.0 .s4 m) , Ep 3~ o lu .

li e00 -- - - 'c* li a e 3 3 7

• 7 mm;;; C 2 O 2 - -

g 500 g o . . . i y o

y g G 500 900 1500 2000 2500 30C0 Time (s)

Figure A-t Upper heed and weer pieman fluid temperatures vs.

time - ptLArs.

Elevations relative to core inlet 1800 , , , , ,

• O TL2 - 13.4 f t.

• 3 (3.4 - 4.1 m) s 1400 -

C a.s - It2 ft. -.g z gc u (2.7 - 3.4 m) 1 a 4.7 - B.9 ft. 1 E 1200 . (2.0 - 2.7 m) . g o 0 4.5 - 6.7 f t.

• o (t4 - 2.0 m) . . .ts00 pm 7 2.2 - 4.5 f t. -^

I 56 * -

X

(.57 - t4 m) 0.0 - 2.2 f f.

~

I k

4 (0.0 .67 m) a E 800-- IC00 E 3 3

- 7 7 e o

• I C O 7 A^

$00 'E [?T I - -

g ,

3 500

- .m O ' ' o

> 400 0 500 200  ?$00 2000 2500 3000 Time (s)

Figare 4-2. Core fluid temperGtures vs. time - RELAPS.

l 34 .

P i

i

e Elevations relative to core inlet 1200 , , , , ,

! O 11.2 - U.4 tt.

s (3.4 - 4.1 m) .isoc s g C 8.s - tt.2 ft. } 3w w

" ~

(2.7 - 3.4 m) ~

{ A 8.7 - 8.9 f t. E E (2.0 - 2.7 m) E*

e e 0 4.5 - 6.7 f t. ~

(t4 - 2.0 m) k ge 7 2.2 - 4.5 f t. ~.m00 s d 800 ,. (.67 - 1.4 m) E^D

.1 "C X 0.0 - 2.2 ft. - *

4 4 (0.0 .67 m)

= e- ' s g _

. g

,oo __ _

e 2 500 e 4

0 500 1000 1500 2000 2500 3000 Time (3)

FIpre A-3. Core trypees ffuld temperatures vs. time - RD.APS.

a00 , , , ,

O

• 5 O At het leg s O At pressuriser 3 s c t .M o u

=

c.

750 *. l, l'$

,,, rklI e

a.

S E

700 *  ?

(...) ~800  ?

E m

N g ^b v <

W.

3v j SSO y [g j. -

700

=

a.

:J j ll

=

a 3

E

-7: -

2

E o o y g n , i e y

0 SCO 1000 1300 2000 2500 3000 Time (s)

FIpre A-4 Pressurizer surge line fluid temperature vs. time

- REl.APS.

35

l Elevations relative to bottom of pressurizer 1 830 . . .

e a w b 3 3 c 640 0 -

' ^"^" ' - * " * ' '

420 -

, , , , _~_ - _ . - - . . . -

e E II E e e

e. <> *-

E '

O Steam dome -O 2.2 slo O 31.7 - 34.8 7t. -

3 (9.7 'O.6 m) 3 3 4 18.7 - 25.2 ft. E 3 (5.7 - 7.7 m) 3 a 600 - 0 S.7 - 12.2 f t. ~ 620 E

• * (1.7 - 3.7 m)

• 7 0.0 - 2.3 f t.

h (0.0 - 0.8 m) h o ' l c

> 590 0 300 1000 1500 2000 2500 3003 rime (s)

Figure A-S. Pressurizer fluid temperature vs. time - ;tELAPS.

W i . . 4 l lO Serey line l l 3

j h 3 620 -

.C

' ^

--O C- M W -

6S0 e

- .e.

gm e^

x 500 - -

g la-2*

w w V

4 a 3 600 3 3 3 5 SSC RJ) ~

e a .

E E 3 3 O ' ' ' ' ' o y 3,g . SSO >

0 SCO 900 1500 2000 2500 3000 Time (s)

Figure A-4. Pressurizer spray line fluid temperotare vs. time

- RELAPS.

36

a .

20000 , , , i i 9 O Core intet '0000 C Cor e ou tle t 1S000 -

m m 3CoC0 m a N N E

• - .a 6 0

, 2C000 0

• ! a 2

o SC00 y icooo E a o

• 0- C C C C C 3 -* O

. . . -50C00 0 SCO 20 1500 2000 2500 3000 Time (s)

Figure A-7. Core moes flew role ve. time - RELAPS.

c00 , , , ,

I 2000 d O Core bypese inlet C Core bypass ouH et ISOC - m n n N" 500 ,- N o

.x

-> coo E

.0 j O R i o

• 500 W G l 3 "I ~ '~ '---

N O y "- -

_ . - _e - --- -- '"-0

• a r 2

-500

, , -900 0 SCO 1000 1500 2000 2500 3000 Time (s)

Figure A-8. Core bypoes mese flow rate vs. time - RELAPS.

I 1

37 i e I

l

l

, e. ,

4000 i . . >

C O Inside pienum cylinder - 8000 0 Cutside plenum cyJr' der 3000 -

m 6000 e a N N E o

.as' 2000

.o-4000 v D 3 3,  ! o

@c ,t- -

2000

~

" n Q

• 2 - C 7 2 0- , C C C C C C-0

,g. , , , , , -2000 0 500 *000 1500 2000 2500 3000 J

Time (s)

Figure A-W. Idess flow rate between uooer plenum and upper hood vs. tf rme- RELAPS.

400 , ,

lO Vent volves l - 500 soo . -

^

500 7 N N cn E 6 200 -

400 -

0, 3 ..

o l D

=

• 00,-

i 3 200 1 a ,

n l l m o b n

3 l c l-i 3

CE M m l

il t Ilikl'"'*1 w L m. .kii

. . . O--0

,g< , i i . ,

.200 0 500 *000

. tS00 2000 2500 3000

! rim. (3) .

I Figure A-10. Reactor vent volves mass flow role vs. time

! - E APS.

l i

l t

y .

e .

I o

I

\ .

I 10000 , , .

O Het leg elevation 200C0 0 C Vent va!ve elevation a000 - -

G m

^ 150C0 "

N

)"

.as sc00 - -

.o E

v -

100C0

• I =

{ MM - -

y

.2 l

d!

l N O

= coo . ./5000 ,

n I l

2 O l

,. s _l 2

~ '~ " - ' " " ' '

0 Ig"w = - w w ". "-0

=

-2c00 ' '

O SCO 'C00 1500 2000 2500 3000 Time (s)

Figure A-ft. Idose Mow rate througn plenum eylleder Notes vs.

time - RELAPS.

20C00,; , , , ,

lO 3ewncomer l 4C000 s000 -

^

30000 7 4m N E }

d *0000 , ,

-Q 1 - 200C0 v R

o .

3 g j O 3CCO ,--

, - 10000 e n o n 3 0

c. -O C bN- 0 0 0 0 C O- 0

' - -10000

-5000* ' '

0 500 '000 1500 2000 2500 30C0 Time (s)

Figure A-12. Ovwecomer mass flow rote LD5 ft. (0.33 m) telew ,

the het leg centerlice vs. time - PE.AP5.

l l

~

39 F

. '* a i

i l

l l

l l

'30 , , , ,

O lO Norzte leewoos l 3*O m

n 10 0 - -

7

• 00 N **J o C d S w

l S0j- -

,00 3

= .2 E a o a 0,  ; __- - ' k_0_,.;,.4, ,

'__ . ; O--0 $

-50' ' ' '**

O SCO '000 iS00 2000 2500 3000 Tim. (3)

Figure A-13. Hot tog nozzle lookoge vs. time - RELAPS.

1000 , ,

2000 lO At het leg l g 500 -1000 S N

>c 6 e w

R 0 1- '- - ~

R _~} ",My'py ~""'7""""'V

8 O w 2 -500- .

J -50C0 g

- -2m 0 SCO EC 1500 2000 2500 3000 Tim. (s) .

Figure A-14. Pressurizer surge One moss flow ra t e vs. time

- RELAPS.

e

0 '* .

15 . . .

3 IO Sorav nn. l 8," 20 e

a

• l N

) 5 -

, -. to E D j

...._- .u .n i.;

, . (3 g 0(H3, " j  : -* 0 g g 't l 0

_S _ j' .. ->0 ,,

$ E 2

~

-10A -

" "IO <

-15 +

0 SCO 1000 1500 2000 2500 3000 Tim. (s)

FIpre A-15. Pressarf zer spray !!ne mass flow rate vs. time

- RELAPS.

400 , , ,

lO PCRV l . goo i ^

m s00 -

j

$o l 600 \

E 6 1 '. $s,) e w

i

$ 200 -

' di 3

g i i 400 o s

! L 1  :

a.  ;

_': g -

g j ,; b i o

~~

.6 E .

1 .

C C C C -

' " '  : 0 0 SCO 1000 1500 2000 2500 3000 Tim. (s)

Fipre A-16. PORY mass flow rate vs. time - RELAPS.

41 -

. a a

1000 . . .

O A loo # 2000 C B loco 800 -

n \ a i

$m (li 1500 6 s00 -

-3 w

.o.

I E 3 t 1000 o

' 400

- - O E #

c 2 3 500 200. - -

l 0,w ...

as ~a e

(I a ,.s n w w w

w w

n ems =

0 to . 20 30 40 50 Time (s)

Figure 4-f7. Steen generator secondary side code saf ety volves moes flow rate vs. tf rre - RELAPS.

15 0 i i O A loop 3no C 9 loco m -l *250 ^

n i g

Nm oc - -

C 6 200 w3 3

o i

= 15 0 o n

a 50 -

• O 10 0 #

3 0 i 2 -

l l gg O C' I I C' i

C'g9Ed C O 't C 0 0 500 1000 1500 2000 2500 3000 Time (s) -

l Figure A-18. Steam generator secondary side atmoscheric durnp volves mass flow rate vs. time - RELAPS.

l l l 1

42 -

I

[ 1

e ** .

Elevations relative to core ir ;;

ts . . . . .

LS O tt.2 - 13.4 f t.

(3.4 - 4.t rn)

O a.9 - 1t2 ft.

g (2.7 - 3.4 m) 8

~

A 6.7 - 8.9 it.  :::

i.. (2.0 - 2.7 m) , , . , , _ _ _--g-. to o 8 C 0 4.5 - 6.7 f t. / p 4 (t4 - 2.0 m) *

.g 7 2.2 - 4.5 f t. j .e

(.$7 - L4 m) J' j X 0.0 - 2.2 ft. $

(0.0 .67 m) g 0.5 -

0.s  ;

e. > a.

C O

> 4I >

0: 200': C' d O-  ? 10 0 500 10C0 1500 2000 2500 30C0 Tirne (s)

FIpre A-19. Core bypass void fractione vs. time - RELAPS.

0.05 , . . . 0.05 O Core inlet C Lower plenum e 0.04 * - 0.04 e O O u o

• C 0 t 0.03 - - 0.03 &

m u O O 0.02 - - 0.02 J

6 6 o o 0.01- -

, --- 0.01 I

t O SCO 1000 1500 2000 2500 3000 Time (s)

Fipre A-20. Core inlet ed lower pierunt void fractions vs.

time - RELAP5.

43

. ** e o

Elevations relative to core inlet 1 . . .

7 er 70 yg 4 1.0 O a. - itz ft. g (2.7 - 3.4 m) '

C s.7 - 3.3 ft. - as "3 " g g (2.0 - 2.7 m) ,

- A 4.3 - 6.7 ft. ,

o (14 - 2.0 m). o 0 3 0 2.2 - 4.5 f t. l A E8 ~ "" 08 ::

(.17 - 1.4 m)

.g 7 0.0 - 2.2 ff. .g o

(0.0 = .67 m) l o

0.4 - - 14 w w 0 o o

> u. 1, ..u>

(7 0""""' " " E ' '

O.0 0 500 M00 1500 2000 2500 30C0 Time (3)

Figure A-21. Downesmer void fractione vs. time - REI.APS.

Elevations relative to surge line 1 . . r

: .: 0 t.0 J O 55.2 - 60.2 f t.

a( i ( s.8 - 18.3 m) f C 36.8 - 55.2 ft. ~ as 5 as ~ l (tt2 - ts.3 m) g

U

A 18.4 - 36.8 ft. -

o '

l (5.5 - tt2 m) o 3

O l 0 5.0 - 18.4 f t.

D 18 ~ j (t3 - 5.6 m) -~ C 8 a 2 ,1 .-

o o j o a4 -

- 24 b 6 o o a2- -

il -- 0.2 09-4 : C' A

O.0 0 500 1000 1500 2000 1500 3000 Time (s) .

Figure A-22. A toop hot leg void fraction in upflow leg vs.

time - RELAPS.

44

s **a Elevations relative to surge line 1 . ,  :  : .:  : Lo O 55.2 - 60.2 f t.

(?$.8 - 18.3 m) 0 36.8 - 55.2 ft. ~"

M'" fy (11.2 - 16.8 m) g $

~

A 18.4 - 36.8 f t. -

f (5.5 - 11.2 m) o o O C 5.0 - 18.4 f t.

a 08~ (1.5 - 5.s m) - 0.8 a J

_o .-

o o 0.4 ~

• 0.4

- 1 -

o '5 o

@- a

> 0.2 - p n u>

00 : : '= f '

O.0 0 S00 1000 tS00 2C00 2500 30C0 Time (s)

FIpsre A-21 B leep het leg void fractiori in upflow leg vs.

time - RC.APS.

Elevations relative to lower luce sheet 1 4 , - -- C O O C . C L0 c 08- ~ ~ CA e o o u o Q l o

& Q.a - -- 0.8 &

3 0 2 o o 0.4 - - 0.4

. o O 32.2 - 35.4 f t. $

C. (9.8 - 10.8 m) 3.

$ U" 0 19.8 - 25.0 ft.

"' U $

^

(6.0 - 9.8 m) 0.0 - S.S f t.

(0.0 - 3.7 m) u 0 300 1000 1500 2000 2500 3000 Time (s)

Figure A-24. A lose steen gocerotor primary side vold fraction vs. time - RELAP5.

45

. ** a O

Elevations relative to lower tube sheet 3 ' ' ~ " LO Y .

c OJ-- hr "" 18 C

• C '

3

c o e u- pl -- 0.s e o h o *

> 0.4 _ .. c4

$ h O 32.2 - 35.4 f f. $

g (9.3 - 10.3 m) g y ,,

O 19.8 - 26.0 ft. ,

y (6.0 - 9.8 m) i 4 a 0.0 - 5.5 f t.

(0.0 - 3.7 m) 05 : C5'O O' Ak o

l' O.0 0 S00 *000  ?!00 2C00 2500 30C0 Time (s)

Figure A-25. B loeo steem generator primary side void fraction vs. time - RELAPS.

1 i i i , i 1.0 0 S. G. outlet C Pumo sueilon y OJ--

0 e -- 0.8 =

2 1 l1 2 zc I zo 2 U~ *M a T 7 i* / 3*

0.4 - 1 j -- 0.4 n- w 12 -

j ll -- 0.2 00 0 C' C O C C C 2 0.0 0 500 m 1500 2000 2500 3000 Time (s)

Figure A-26. A loop void fraction between stoom generator and cold leg - REl.APS.

G*N I

l 1

l l

I 1 . . i i to O S. C. ou tt e t O Pumo suction g u.. O% _. g,3 C

o o

u o g

O g, 0.8 -- - 0.8 e 7 7 0 o

• -. c.4 0.4

• 6 w 0.2 - - j -.u

• 00 0 0

C' 500 C'

1000 aO f 1500 C

2000 C C 2500

'O C 3000 0.0 Time (s)

Figure A-27. B looo vold fraction between steam generator and cold log - RELAP5.

Elevations relative to bottom of vessel '

C CCC'C '

O core side O Downcomer side '30 n8 - -

m E < 15 =

• v 20 0 3 8"- .

2  :

m 0"

5 d 4 13 ~

J

- i

. 10

_ )

- a

' ' ' ' 4 2

0 SCO 1000 1500 2000 2500 3000 Time (s)

Figure A-18. Cedarsed mixture levels in the downcomer and core vs. time - RELAP5.

l l

47 .

ada o Compensated f or steam head 20 .

! O Steam generator A 60 4

C Steam generator 5 i

15 -

- 50 9 =

v

= v l

- - 40 -

e e

! > -)

k >

3 -

e 10 m -

. 30 J n 1

-h 2o -

h Sk -

Il to i! fl

.s 0 _

0

- - _ 0 0 10 0 200 300 Time (s)

Figure A-29. Steem generster secondary side IIquid level from pressure drop - RC.APS.

48 -

.-. - . . . - - , - ,