NUREG/IA-0241

 International 

Agreement Report

Assessment of the TRACE Code Using

Transient Data from Maanshan PWR

Nuclear Power Plant

Prepared by:

1

Jong-Rong Wang, 1Hao-Tzu Lin, 2Chunkuan Shih

1

Institute of Nuclear Energy Research

Atomic Energy Council, R.O.C. 

1000, Wenhua Rd., Chiaan Village, Lungtan, Taoyuan, 325

TAIWAN

2

Institute of Nuclear Engineering and Science

National Tsing Hua University

101 Section 2, Kuang Fu Rd., HsinChu

TAIWAN

A. Calvo, NRC Project Manager 

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

June 2010 

Prepared as part of

The Agreement on Research Participation and Technical Exchange 

Under the International Code Assessment and Maintenance Program (CAMP)

 

Published by

U.S. Nuclear Regulatory Commission
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NUREG/IA-0241

Assessment of the TRACE Code Using Transient 

Data from Maanshan PWR Nuclear Power Plant

Manuscript Completed: May 2010 

Date Published: June 2010 

Prepared by: Jong-Rong Wang, Hao-Tzu Lin, Chunkuan Shih* 

Institute of Nuclear Energy Research, Atomic Energy Council, R.O.C. 

1000, Wenhua Rd., Chiaan Village, Lungtan, Taoyuan, 325, TAIWAN 

*Institute of Nuclear Engineering and Science, National Tsing Hua University, 

101 Section 2, Kuang Fu Rd., HsinChu, TAIWAN 

Antony Calvo, NRC Project Manager 

Prepared for:

Division of Systems Analysis 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001

iii 

ABSTRACT

This study consists of two steps. The first step is the establishment of TRACE (TRAC/RELAP 

Advanced Computational Engine) models for important components, such as pressurizers, 

steam generators, the feedwater control system, the steam dump control system, and so on, in 

Maanshan Nuclear Power Plant (NPP) using SNAP(Symbolic Nuclear Analysis Program)

/TRACE. These component models were tested and compared with Maanshan startup test data 

to verify their accuracy. Key parameters were identified to refine the models further. The next 

step is the incorporation of the above component models into the Maanshan NPP TRACE 

model. TRACE transient analyses of scenarios such as load reduction and turbine trip were 

performed and their results were compared with the corresponding plant data from Maanshan 

startup tests. The TRACE model of Maanshan NPP is also used to analyze Loss of Flow 

transient as defined in FSAR Chapter 15 which includes Partial Loss of Flow (PLOF), Complete 

Loss of Flow-Under Voltage (CLOF-UV), and Complete Loss of Flow-Under Frequency 

(CLOF-UF). Analysis results indicate that the Maanshan NPP TRACE model predicts not only 

the behaviors of important plant parameters consistent with the plant data, but also their 

associated numerical values with respectable accuracy. 
iv 
v 

FOREWORD

The USNRC is developing an advanced thermal hydraulic code named TRACE for nuclear 

power plant safety analysis. The development of TRACE is based on TRAC, integrating 

RELAP5 and other programs. NRC has determined that in the future, TRACE will be the main 

code used in thermal hydraulic safety analysis, and no further development of other thermal 

hydraulic codes such as RELAP5 and TRAC will be continued. A graphic user interface 

program, SNAP, which processes inputs and outputs for TRACE is also under development. 

One of the features of TRACE is its capacity to model the reactor vessel with 3-D geometry. It 

can support a more accurate and detailed safety analysis of nuclear power plants. TRACE has 

a greater simulation capability than the other old codes, especially for events like LOCA. 

Taiwan and the United States have signed an agreement on CAMP(Code Applications and 

Maintenance Program) which includes the development and maintenance of TRACE. INER 

(Institute of Nuclear Energy Research, Atomic Energy Council, R.O.C.) is the organization in 

Taiwan responsible for the application of TRACE in thermal hydraulic safety analysis, for 

recording users’ experiences of it, and providing suggestions for its development. To meet this 

responsibility, we built a TRACE model of TPC (Taiwan Power Company) Maanshan PWR 

NPP. In this report, TRACE models of components or control systems such as pressurizers, 

steam generators, the feedwater control system, and the steam dump control system in the 

Maanshan NPP were developed first. Startup tests of Maanshan NPP were utilized and 

conducted to confirm the accuracy of these TRACE component models. Then, the models were 

integrated into a whole-plant TRACE model. Finally, the accuracy of the whole-plant TRACE 

model was evaluated using Maanshan NPP startup tests and FSAR data. 

 
vi 
vii 

CONTENTS

Page

Abstract ....................................................................................................................................... iii 

Foreword...................................................................................................................................... v

Executive Summary ................................................................................................................... xi 

Abbreviations ............................................................................................................................ xiii 

1. Introduction ........................................................................................................................ 1-1 

2. Methodology ....................................................................................................................... 2-1 

3. Establishment and verification of TRACE model for important components of 

Maanshan NPP ................................................................................................................... 3-1 

3.1 Pressurizer and its control systems ............................................................................ 3-1 

3.2 Steam generator with feedwater control system ..................................................... 3-10 

3.3 Steam dump control system ...................................................................................... 3-13 

4. TRACE Modeling of Maanshan NPP ................................................................................. 4-1 

4.1 Model description ........................................................................................................ 4-1 

4.2 Results and discussions ............................................................................................ 4-4 

4.2.1 Large-load reduction at 100% power (PAT49) ...................................................... 4-4 

4.2.2 Net-load trip at 100% power (PAT51) ................................................................... 4-4 

4.2.3 Turbine trip test from 100% power (PAT50) .......................................................... 4-5 

4.2.4 Partial Loss of Flow (PLOF) .................................................................................. 4-5 

4.2.5 Complete Loss of Flow-Under Voltage (CLOF-UV) .............................................. 4-5 

4.2.6 Complete Loss of Flow-Under Frequency (CLOF-UF) .......................................... 4-5 

5. Conclusions .................................................................................................................. 5-1 

6. References .................................................................................................................... 6-1 
viii 

Figures

Page

Fig.1 The TRACE model of Maanshan NPP.................................................................. xii 

Fig.2.1 The flow chart of establishing and verifying the TRACE model of Maanshan NPP2-2 

Fig.3.1 The TRACE model of the pressurizer for Maanshan NPP.................................. 3-5 

Fig.3.2 Water level during the 100 % turbine trip test ..................................................... 3-5 

Fig.3.3 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % turbine trip test ........................................................................ 3-6 

Fig.3.4 Water level during the 100 % large-load reduction test ...................................... 3-6 

Fig.3.5 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % large-load reduction test ......................................................... 3-7 

Fig.3.6 Water level during the 100 % net-load trip test ................................................... 3-7 

Fig.3.7 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % net-load trip test ...................................................................... 3-8 

Fig.3.8 Water level during the 50 % net-load trip test ..................................................... 3-8 

Fig.3.9 Comparison of the measured and calculated pressurizer pressure histories 

during the 50 % net-load trip test ........................................................................ 3-9 

Fig.3.10 The TRACE model of the steam generator and feedwater control system in 

Maanshan NPP ................................................................................................. 3-11 

Fig.3.11 The feedwater flow comparison between TRACE and the measured value of 

Maanshan NPP ................................................................................................. 3-11 

Fig.3.12 The steam flow comparison between TRACE and the measured value of 

Maanshan NPP ................................................................................................. 3-12 

Fig.3.13 The S/G water level comparison between TRACE and the measured value of 

Maanshan NPP ................................................................................................. 3-12 

Fig.3.14 The TRACE model of the steam dump control system for Maanshan NPP ..... 3-14 

Fig.3.15 The first set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control 

system .............................................................................................................. 3-14 

Fig.3.16 The second set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control 

system .............................................................................................................. 3-15 

Fig.3.17 The third set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control 

system .............................................................................................................. 3-15 

Fig.3.18 The fourth set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control 

system .............................................................................................................. 3-16 

Fig.4.1 The TRACE model of Maanshan NPP................................................................ 4-3 

Fig.4.2 The comparisons of power and Tavg between TRACE model and Maanshan NPP 

(PAT49) ............................................................................................................... 4-9 

Fig.4.3 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT49) ............................................................................. 4-9 

Fig.4.4 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT49) ................................................................ 4-10 

Fig.4.5 The comparisons of power and Tavg between TRACE model and Maanshan 

NPP (PAT51) .................................................................................................... 4-10 
ix 

Fig.4.6 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT51) ........................................................................... 4-11 

Fig.4.7 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT51) ................................................................ 4-11 

Fig.4.8 The comparisons of power and Tavg between TRACE model and Maanshan 

NPP (PAT50) .................................................................................................... 4-12 

Fig.4.9 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT50) ........................................................................... 4-12 

Fig.4.10 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT50) ................................................................ 4-13 

Fig.4.11 Comparisons of the power and core flow of PLOF among FSAR, RETRAN and 

TRACE .............................................................................................................. 4-13 

Fig.4.12 Comparisons of the pressurizer pressure and Tavg of PLOF among FSAR, 

RETRAN and TRACE ....................................................................................... 4-14 

Fig.4.13 Comparisons of the power and core flow of CLOF-UV among FSAR, RETRAN 

and TRACE ....................................................................................................... 4-14 

Fig.4.14 Comparisons of the pressurizer pressure and Tavg of CLOF-UV among FSAR, 

RETRAN and TRACE ....................................................................................... 4-15 

Fig.4.15 Comparisons of the power and core flow of CLOF-UF among FSAR, RETRAN 

and TRACE ....................................................................................................... 4-15 

Fig.4.16 Comparisons of the pressurizer pressure and Tavg of CLOF-UF among FSAR, 

RETRAN and TRACE ....................................................................................... 4-16 

Fig.4.17 Animation of Maanshan NPP model ................................................................. 4-16 
x 

Tables

Page

Table 3.1 The parameters of the pressurizer for Maanshan NPP ...................................... 3-4 

Table 4.1 The comparison between the steady state data of TRACE and the measured 

values from the power plant ............................................................................. 4-2 

Table 4.2 The large load reduction sequences in TRACE model and Maanshan NPP ..... 4-7 

Table 4.3 The net load trip sequences in TRACE model and Maanshan NPP .................. 4-7 

Table 4.4 The turbine trip sequences in TRACE model and Maanshan NPP .................... 4-7 

Table 4.5 The sequences of PLOF in FSAR, RETRAN and TRACE ................................. 4-8 

Table 4.6 The sequences of CLOF-UV in FSAR, RETRAN and TRACE .......................... 4-8 

Table 4.7 The sequences of CLOF-UF in FSAR, RETRAN and TRACE ........................... 4-8 
xi 

EXECUTIVE SUMMARY

An agreement which includes the development and maintenance of TRACE has been signed 

between Taiwan and USA on CAMP. INER (Institute of Nuclear Energy Research Atomic 

Energy Council, R.O.C.) is the organization in Taiwan responsible for applying TRACE to 

thermal hydraulic safety analysis in order to provide users’ experiences and development 

suggestions. To fulfill this responsibility, we will establish a TRACE model of TPC (Taiwan 

Power Company) Maanshan PWR nuclear power plant (NPP). 

Maanshan NPP is the first PWR in Taiwan. Its reactor is made by Westinghouse Company and 

has the rated power of 2775 MWt. The reactor coolant system has three loops and each loop 

has a reactor coolant motor and a steam generator. Besides, the pressurizer is connected with 

the hot-leg piping in loop 2. 

The codes used in this research are SNAP v 1.1.8 and TRACE v 5.0p1. The methodology of 

Maanshan NPP TRACE model is described as follows: First, collecting the power startup tests 

and FSAR data [7]-[12] from Maanshan NPP. Second, establishing the Maanshan TRACE 

models of several important components such as pressurizer, steam generators, the feedwater 

control system, the steam dump control system, etc. by SNAP/TRACE. Then, the startup tests 

of Maanshan NPP will be used to verify the accuracy of the TRACE models. Third, adding other 

necessary components (e.g., the vessel and the main steam piping) into the TRACE model 

mentioned above to construct the Maanshan NPP TRACE model. Finally, testing the 

convergence of steady state of the Maanshan NPP TRACE model, comparing the TRACE data 

in a steady state, analyzing the transients, and comparing the TRACE data of the transients with 

the startup tests and FSAR data of Maahshan NPP. The TRACE model of Maanshan NPP is 

shown in Fig. 1. 

Analysis results indicate that the Maanshan NPP TRACE model predicts not only the behaviors 

of important plant parameters consistent with the startup tests and FSAR data, but also their 

associated numerical values with respectable accuracy. 
Fig. 1 The TRACE model of Maanshan NPP 

xii 
xiii 

ABBREVIATIONS

CAMP Code Applications and Maintenance Program 

CLOF-UF Complete Loss of Flow-Under Frequency 

CLOF-UV Complete Loss of Flow-Under Voltage 

FSAR Final Safety Analysis Report 

INER Institute of Nuclear Energy Research Atomic Energy Council, R.O.C. 

LOCA Loss Of Coolant Accidents 

NPP Nuclear Power Plant 

NRC Nuclear Regulatory Commission 

PLOF Partial Loss of Flow 

PORVs Power-Operated Relief Valves 

S/G Steam Generator 

SNAP Symbolic Nuclear Analysis Program 

SVs Safety Valves 

TPC Taiwan Power Company 

TRACE TRAC/RELAP Advanced Computational Engine 

US United States 

 

 

 

 

 

 

 

 

 

 

 

 
xiv 

 

 
1-1 

1. INTRODUCTION

The US NRC (United States Nuclear Regulatory Commission) is developing an advanced 

thermal hydraulic code named TRACE for nuclear power plant safety analysis. The 

development of TRACE is based on TRAC, integrating RELAP5 and other programs. NRC has 

determined that in the future, TRACE will be the main code used in thermal hydraulic safety 

analysis, and no further development of other thermal hydraulic codes such as RELAP5 and 

TRAC will be continued. A graphic user interface program, SNAP, which processes inputs and 

outputs for TRACE is also under development. One of the features of TRACE is its capacity to 

model the reactor vessel with 3-D geometry. It can support a more accurate and detailed safety 

analysis of nuclear power plants. TRACE has a greater simulation capability than the other old 

codes, especially for events like LOCA. Accordingly, an increasing number of researchers is 

using TRACE code to analyze test facilities and nuclear power plants. Gonza’ lez et al. [1]-[2] 

established a TRACE model for Almaraz NPP and analyzed the Loss of Residual Heat Removal 

System (RHRS) event under midloop operating conditions. Their results revealed that the 

TRACE model can simulate the event accurately. Jasiulevicius et al. [3] also constructed a 

TRACE model of a Large-Scale Test Facility (LSTF), and confirmed its accuracy against data 

on the small-break loss of coolant accidents (SB-LOCA). Jaeger et al. [4] adopted a TRACE and 

PARCS model of Bulgarian nuclear power plant Kozloduy unit 6, and verified its accuracy using 

data from OECD/NEA VVER-1000 Coolant Transient Benchmark Phase 2. Barten et al. [5] 

established the TRACE model of UMSICHT water hammer experiments and the analysis results 

showed good agreement with the experiments data. Xu et al. [6] used TRACE/PARCS to do the 

validation of the stability analysis of Ringhals. Their results showed good agreement with the 

plant data. These investigations demonstrate that the TRACE code predicts results that agree 

reasonably with plant data. 

Taiwan and the US have signed an agreement on CAMP which includes the development and 

maintenance of TRACE. INER is the organization in Taiwan that is responsible for the 

application of TRACE in thermal hydraulic safety analysis, for recording users’ experiences of it, 

and providing suggestions for its development. To meet this responsibility, we built a TRACE 

model of TPC Maanshan PWR NPP. In this report, TRACE models of components or control 

systems such as pressurizers, steam generators, the feedwater control system and the steam 

dump control system in the Maanshan NPP were developed first. Startup tests data [7]-[11] of 

Maanshan NPP were utilized and conducted to confirm the accuracy of these TRACE 

component models. Then, the models were integrated into a Maanshan NPP TRACE model. 

Finally, the accuracy of the Maanshan NPP TRACE model was evaluated using Maanshan NPP 

Startup tests and FSAR data [7]-[12]. 
2-1 

2. Methodology 

The code versions used in this research are SNAP v 1.1.8 and TRACE v 5.0p1. The 

methodology of Maanshan NPP TRACE model as follows: First, collecting the power startup 

tests and FSAR data [7]-[12] from Maanshan NPP. Second, the Maanshan TRACE models for 

several important components such as pressurizer, steam generators, feedwater control system 

and steam dump control system etc. are established by SNAP/TRACE. Then the startup tests of 

Maanshan NPP will be used to verify the accuracy of the TRACE models. Third, the other 

necessary components (e.g. vessel and main steam piping) were added into the TRACE model 

mentioned above to construct the Maanshan NPP TRACE model. Finally, testing the 

convergence of steady state, comparing the TRACE data at steady state, analyzing the 

transients, and comparing the TRACE data at transients with the startup tests and FSAR data 

for Maahshan NPP TRACE model are performed. The complete process is presented in Fig. 

2.1. 
Collecting the system operating data, actual cases 

testing data, and FSAR data from Maanshan NPP. 

2-2 

Building the TRACE model of several 

components by SNAP/TRACE. 

Steam generator Feedwater control 

system 

Steam dump 

control system 

Pressurizer 

Verifying the TRACE model for several 

components 

Start up tests 

data: 

z large-load 

reduction 

z net-load trip 

z turbine trip 

FSAR data: 

z Loss of flow 

Deficiency

Yes 

The TRACE model of Maanshan NPP 

Verifying the TRACE model of Maanshan NPP 

Testing the convergence of steady state and 

comparing the data at steady state with the 

startup tests and FSAR data 

Fig. 2.1 The flow chart of establishing and verifying the TRACE model of Maanshan NPP 

Deficiency 

Yes 

Analyzing the transient and comparing the data 

at transient with the startup tests and FSAR data 
3-1 

3. Establishment and verification of TRACE model for important 

components of Maanshan NPP 

Maanshan NPP is the only Westinghouse-PWR in Taiwan. The rated core thermal power is 

2775 MW. The reactor coolant system has three loops, each of which includes a reactor coolant 

pump and a steam generator. The pressurizer is connected to the hot-leg piping in loop 2. 

Because of the complexity of the equipment and systems at the Maanshan NPP, establishing 

component models first, for integration into a whole plant model, is the most effective approach. 

With reference to the TRACE user manual [13], and related information [7]-[12], component 

models of the pressurizer, steam generator, control system and steam dump control system 

were established. 

3.1 Pressurizer and its control systems [14]

The pressurizer is made up of steel tank which contains saturated water in the lower section 

and saturated steam in the upper section in normal operation. It is connected to the hot leg of 

loop 2 through a surge line. The important components of the pressurizer include a sprayer, 

electric heaters, power-operated relief valves (PORVs), safety valves (SVs), a surge line, and a 

relief tank. The sprayer, the PORVs and the SVs are equipped at the top of the tank, while 

electric heaters are immersed in the water. The sprayer and the electric heaters are used to 

control the system pressure while load transients. While the reactor power increases, the 

coolant volume increases correspondingly such that the coolant surges into the pressurizer. In 

such a case, the sprayer is activated to spray water from the top of the tank to limit the pressure 

by condensing the steam. While the reactor power decreases, the coolant volume decreases 

and the coolant surges out the pressurizer. At this time, some of the water flashes to steam due 

to pressure drop. The electric heaters are activated to heat up the water in the tank to maintain 

the desired operating pressure. 

The sprayer is activated by the pressure-difference setpoint. In normal operating condition, a 

low fluid flow rate of 2 gpm is sprayed into the pressurizer. When the pressure difference 

exceeds 25 psi, the flow rate starts to increase. The flow rate increases linearly from 2 gpm 

(1.00E3 lbm/hr) to 700 gpm (3.49E5 lbm/hr) as the pressure difference increases from 25 psi to 

75 psi. The electric heaters can be classified into a proportional heater and a backup heater. 

The control of the proportional heater and backup heater is based on the pressure-difference 

setpoints and water-level setpoints. The proportional heater adds half of the rated heat to the 

liquid in normal operation, generates heat of 376 KW at a full rate as the pressure error signal is 

less than -15 psi, and is turned off completely as the pressure error signal is greater than +15 

psi. The backup heater can only be fully turned on or off, and is controlled by the pressure error 

signal together with the level error signal. The backup heater is turned on completely only when 

the level error signal exceeds the setpoint by +5 % and the pressure error signal is less than the 

setpoint of -25 psi. On the other hand, the backup heater may be turned off completely if the 

pressure error signal is greater than -17 psi. The proportional heater and backup heater are 

totally turned off as the water level is lower than 14 %, no matter the pressure is high or low. 

Therefore, the water level for heater cutoff is 5.095 ft. 

The PORVs are open when the pressure-difference setpoint 100 psi is reached, and the PORVs 

are closed when the pressure difference drops down to 80 psi. The release capability for each 

of the three PORVs is 210,000 lb/hr. The SVs are open when the pressure-difference setpoint 
3-2 

235 psi is reached, and the SVs are closed as the pressure difference is lower than 235 psi. 

The release capability for each of the three SVs is 380,000 lb/hr. Table 3.1 presents its 

important design parameters. 

The pressurizer model was built by SNAP/TRACE. TRACE includes several hydraulic 

components such as PIPEs, PLENUMs, PRIZERs (pressurizers), CHANs (BWR fuel channels), 

PUMPs, JETPs (jet pumps), SEPDs (separators), TEEs, TURBs (turbines), HEATRs (feedwater 

heaters), CONTANs (containment), VALVEs, and VESSELs. Powered and heated components 

are denoted by POWER, FLPOWER (fluid power), and HTSTR (heat structure) in TRACE. FILL 

and BREAK components supply the coolant-flow and pressure boundary conditions. Therefore, 

the PIPE component is used to model the feature of the pressurizer. The FILL component 

models the phenomena of insurge and outsurge at the surge nozzle, the spray mechanism 

through the spray nozzle, and the pressure relief by letting steam exit through the 

power-operated relief valves (PORVs) and safety valves (SVs). The HTSTR component is 

added at the bottom of the pressurizer to model the heaters. To fulfill the control procedures of 

the open position of the spray valve, the opening and closing of PORVs and SVs, the 

proportional heater and backup heater, the control systems (trips, signal variables, control 

blocks, and component action tables) are properly combined for TRACE to follow. The fill table 

of the FILL component is edited to simulate the flow insurge and outsurge as the boundary 

condition of the pressurizer model. Therefore, the mass flow rates relative to time must be 

initially given. However, flow meters were not installed along the surge line to measure the flow 

rates during the tests conducted in 1985. We managed to adjust the mass flow rates at the 

surge nozzle by matching the calculated water level inside the pressurizer with those from the 

test data. Thus, trial and error is applied to search out the proper inputs of the mass flow rates. 

All of the plant tests collected in this study have the records of the variations in water level. 

Consequently, the time-varying mass flow rates input to the fill table for each test are 

successfully obtained. After the pressurizer model is constructed and the boundary conditions 

are given, each test retrieves its fluid initial conditions using the steady-state calculation function 

in TRACE. 

The TRACE model of the pressurizer is shown in Fig. 3.1. Besides, the turbine trip test at 100% 

power (PAT50), the large-load reduction at 100% power (PAT49), and the net-load trip at 100% 

power(PAT51) transients [7]-[11] were used to verify the TRACE model of the pressurizer. 

The turbine trip test was initiated by manually tripping the turbine while the plant was operating 

at full power. As a result, the reactor was directly tripped with control rods in full-in position. The 

decrease in the reactor coolant temperature led a large flow outsurge of the pressurizer. To 

simulate this transient, the mass flow rates relative to time are given in the fill table of FILL 

component as the boundary conditions. It is adjusted so that the calculated water levels match 

those in the plant test data. The solid line in Fig. 3.2 shows the water levels during the 100% 

turbine trip test. The circles in Fig. 3.2 represent the resultant water level after the mass flow 

rates of the FILL component are well adjusted. Fig. 3.3 plots the calculated pressurizer pressure 

histories together with the measured pressure histories. This figure reveals that the pressure 

histories in the pressurizer predicted by TRACE are in agreement with the plant test data. 

The large-load reduction test was initiated by reducing the steam flow passing through the 

turbine from 100 to 50% of the rated capacity. This test is used to verify that the rod control 

system and the steam dump system can be automatically initialized, and the reactor power can 

be reduced from 100 to 50% corresponding to the reduction in steam flow. To simulate this 

transient, the mass flow rates related to time at the surge nozzle are also properly given. The 

given inputs result in that the calculated water levels meet the measured water levels, as shown 
3-3 

in Fig. 3.4. Comparison between the measured and calculated pressurizer pressure during the 

transient is shown in Fig. 3.5. It can be seen that the calculated pressure histories follow the 

plant test data, caused by a combination of insurge, outsurge, spray actuation, and electric 

heater action. However, a discrepancy between the calculated and the measured pressure 

histories is observed. In this simulation, the pressure response seems over-reactive when the 

pressure is increasing. 

The 100 % net-load trip test was initiated by manually rejecting load while the plant was 

operating at full power. All the control systems were in auto mode. Fig. 3.6 shows that the 

calculated water levels meet the measured water levels. The calculated and the measured 

pressurizer pressures during the transient are plotted in Fig. 3.7. As revealed from this figure, 

the calculated pressure histories follow the trend of the plant test data. The calculated pressure 

in this net-load trip test reaches the sprayer setpoint plus 25 psi at time 175 sec. Therefore, the 

sprayer starts to spray cool liquid into the pressurizer to suppress the pressure. 

The 50 % net-load trip test was initiated by manually rejecting load while the plant was 

operating at 50 % power. All the control systems were in auto mode. Fig. 3.8 shows that the 

calculated water levels meet the measured water levels. The calculated and the measured 

pressurizer pressures during the transient are plotted in Fig. 3.9. The calculated pressure 

histories follow the plant test data, caused by a combination of insurge, outsurge, spray 

actuation, opening of PORVs and electric heater action. However, a discrepancy between the 

calculated and the measured pressure histories is also observed. 

This study develops a pressurizer model for the Maanshan NPP, and the predicted results of 

TRACE are compared with the startup tests data. The results show that the comparisons are in 

reasonable agreement. 
3-4 

Table 3.1 The parameters of the pressurizer for Maanshan NPP 

Parameter

Pressurizer volume 39.64 m3

Full power water level 56.5 % 

Pressurizer flow length 11.74 m 

Sprayer valve max. flow rate (total 2 valves) 44 L/sec 

Heater (proportional heater and backup heater) 1400 W 

Safety valve setpoint 1.7236×107

Pa 

Power-operated relief valve setpoint 1.6202×107

Pa 
The control of pressure 

The control of proportional heater 

The control of water level 

The control of backup heater

PORV Sprayer SV 

Fig.3.1 The TRACE model of the pressurizer for Maanshan NPP 

Fig. 3.2 Water level during the 100 % turbine trip test 

3-5 
Fig. 3.3 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % turbine trip test 

Fig. 3.4 Water level during the 100 % large-load reduction test 

3-6 
Fig. 3.5 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % large-load reduction test 

Fig. 3.6 Water level during the 100 % net-load trip test 

3-7 
Fig. 3.7 Comparison of the measured and calculated pressurizer pressure histories 

during the 100 % net-load trip test 

Fig. 3.8 Water level during the 50 % net-load trip test 

3-8 
Fig. 3.9 Comparison of the measured and calculated pressurizer pressure histories 

during the 50 % net-load trip test 

3-9 
3-10 

3.2 Steam generator with feedwater control system [15]

The steam generator of the Maanshan power plant is a Model F, vertical U-tube heat 

exchanger, with a total of 5,624 U-tubes. The establishment of the TRACE model of the steam 

generator was based on the TRACE V5.0 user manual [13], and the INER report [10]. Wang 

and Wang [10] employed RETRAN to carry out the simulation and analysis of the steam 

generator, and compared the feedwater flow thus obtained with the plant test data. No 

significant difference between the results obtained using RETRAN and the plant data was 

found. 

Fig. 3.10 displays the TRACE model of the steam generator in Maanshan. According to Fig. 

3.10, the U-Tube at the primary side is separated into 18 volumes. A FILL component 

represents “HOT-LEG fluid inflow”, and a BREAK component is used to represent “COLD-LEG 

fluid outflow”. Their inputs were derived from the real plant temperature and pressure time 

histories [7]-[11]. Then, at the secondary side, the region of the boiler is separated into seven 

volumes; the region of the downcomer is separated into 13 volumes, and the region of the 

steam dome and the separator is separated into 13 volumes. Next, a FILL component is added 

to represent “feedwater inletflow”, and a BREAK component is added to represent “steam 

outflow”. The plant data for feedwater flow and other input parameters derived from velocity, 

temperature and pressure were used to set the initial conditions. The feedwater flow was then 

controlled by a three-element feedwater control system after the transient began. In Fig. 3.10, 

components in red represent in which heat conductions or heat exchanges exist. The most 

important heat exchanges in the steam generator take place between the primary side and the 

secondary side. 

Fig. 3.10 depicts the TRACE component model of the feedwater control system in the 

Maanshan NPP. The model was established according to the INER report [7]. The main function 

of the feedwater control system is to maintain a fixed water level of the steam generator at the 

secondary side when it is operating normally. The feedwater control system controls the main 

feedwater control valve using three signals including the water level error signal, the steam flow 

signal, and the feedwater flow signal. The water level error signal is calculated as the difference 

between the actual water level and the preset water level (typically 50%). Another value is 

calculated as the difference between the steam flow and the feedwater flow. These two 

differences are taken as the control signals of feedwater valve. 

The TRACE model of the steam generator and feedwater control system was verified with a 

large-load reduction at 100% power test at Maanshan NPP (PAT49). Fig. 3.11 shows the 

comparison between the results for feedwater flow from the TRACE model and from the plant 

data. Fig. 3.12 and Fig. 3.13 compare steam flows and water levels in the steam generator. The 

results of TRACE are almost the same as the measured values from power plant, except when 

larger fluctuations occur. 

In brief, the results of the steam generator and feedwater control system in the TRACE 

component model agree closely with the plant data and exhibit respectable accuracy. 
Fig. 3.10 The TRACE model of the steam generator and feedwater control system in 

Maanshan NPP 

0 50 100 150 200 250 300 350 400 450

Time (sec)

0

200

400

600

800

Feedwater flow (kg/sec)

PAT49

Plant data

TRACE data

Fig. 3.11 The feedwater flow comparison between TRACE and the measured value of 

Maanshan NPP

3-11 
0 50 100 150 200 250 300 350 400 450

Time (sec)

0

200

400

600

800

Steam flow (kg/sec)

PAT49

Plant data

TRACE data

Fig. 3.12 The steam flow comparison between TRACE and the measured value of 

Maanshan NPP 

0 50 100 150 200 250 300 350 400 450

Time (sec)

0

20

40

60

80

100

S/G liquid level (%)

PAT49

Plant data

TRACE data

Fig. 3.13 The S/G water level comparison between TRACE and the measured value of 

Maanshan NPP

3-12 
3-13 

3.3 Steam dump control system [15]

The steam dump control system is composed of ten atmospheric venting valves, six turbine 

bypass valves and the associated piping control apparatus. Fig. 3.14 shows the TRACE model 

of the steam dump control system. This model was established and described in the INER [7]. 

The ten atmospheric venting valves and six turbine by-pass valves are grouped into four sets in 

this model. Three turbine bypass valves comprise the first set and the other three as the second 

set. Five atmospheric venting valves are considered as the third set and the rest as the fourth 

set. 

When the turbine trip occurs, an electrical signal converted from the error signal between the 

highest Tavg and Tnoload is sent to the turbine trip controller. Through the P/I controller, air that 

flows from the air supply piping is directed to the first and second sets of turbine bypass valves 

to control the degree of valve openings. 

For the load rejection of load reduction, an electrical signal converted from the error signal 

between the highest Tavg (maximum) and Tref (converted from first-stage steam pressure) is 

sent to the load rejection controller. Through the P/I controller, air that flows from the air supply 

piping is directed to the turbine bypass valves and atmospheric venting valves (the first through 

fourth sets of valves) to control the degree of valve openings. 

The TRACE model for the steam dump control system was confirmed using the large-load 

reduction at 100% power test (PAT49) in Maanshan. Figs. 3.15-3.18 compares the results of the 

openings between the TRACE model and the plant data; they generally agree closely. Notably, 

in Fig. 3.15 and 3.16, the first and second sets of valves were closed at 375s and remained 

closed afterwards. However, the simulated results of TRACE indicate that the first and second 

sets of valves open again. The temperature difference from the plant testing records reveals 

that the first and second sets of valves should have opened again. Hence they are suspected to 

have been manually closed during the test. Fig. 3.16 demonstrates that the valve opening in 

TRACE reduces to 0% (200s to 400s), but was in fact about 4.5% in the plant data. In the steam 

dump control system, Tavg signal activates the valves. All of the second set of valves should 

close, according to the Tavg difference records, but in fact, they close only to around 4.5%. 

Therefore, the second set of valves could not be fully closed or were poorly calibrated in the 

testing process. The results for the steam dump control system obtained using the TRACE 

model are thus concluded to agree closely with the plant data. 
Fig. 3.14 The TRACE model of the steam dump control system for Maanshan NPP 

0 50 100 150 200 250 300 350 400 450

Time (sec)

0

20

40

60

80

100

120

Steam dump 1 position (%)

PAT49

Plant data

TRACE data

Fig. 3.15 The first set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control system 

3-14 
0 50 100 150 200 250 300 350 400 450

Time (sec)

0

20

40

60

80

100

120

Steam dump 2 position (%)

PAT49

Plant data

TRACE data

Fig. 3.16 The second set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control system 

0 50 100 150 200 250 300 350 400 450

Time (sec)

0

20

40

60

80

100

120

Steam dump 3 position (%)

PAT49

Plant data

TRACE data

Fig. 3.17 The third set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control system

3-15 
0 50 100 150 200 250 300 350 400 450

Time (sec)

0

20

40

60

80

100

120

Steam dump 4 position (%)

PAT49

Plant data

TRACE data

Fig. 3.18 The fourth set comparison between the steam dump analysis results of TRACE 

model and the measured values by Maanshan NPP for steam dump control system 

3-16 
4-1 

4. TRACE Modeling of Maanshan NPP 

4.1 Model description 

The TRACE component models of the pressurizer, steam generator, feedwater control system, 

and steam dump system were illustrated and verified against the turbine trip, net-load trip, and 

load reduction startup test data. These models were then integrated into a TRACE model of 

Maanshan NPP, as presented in Fig. 4.1. It is a three-loop model, and each loop has a 

feedwater control system. The main structure of this model includes the pressure vessel, 

pressurizers, steam generators, steam piping at the secondary side (including four sets of 

steam dump and vent valves) and the steam dump system. The pressure vessels are 

cylindrical, and its divisions are as shown in Fig. 4.1. It is divided into 12 levels in the axial 

direction, two rings in the radial direction (internal and external rings) and six equal azimuthal 

sectors in the “θ” direction. The control rod conduit connects the 12th and 7th layers of the vessel 

from end to end. The fuel region is between the third and sixth layers, and heat conductors were 

added onto these structures to simulate the reactor core. 

Before any transient analysis can begin in the TRACE model of Maanshan NPP, a consistent 

set of parameters used in TRACE must be obtained in the process of steady-state 

initialization. In TRACE, steady-state initialization was performed with real plant power input 

[7]-[11]. The resulting calculated parameters such as the feedwater and steam flows of the 

steam generators, the water levels in the steam generators and the pressurizer, the pressure of 

the pressurizer, and the hot-leg temperatures were then compared with data from the startup 

tests [7]-[11]test data. Table 4.1 shows the comparison between the steady-state results of the 

TRACE model and the measured values in Maanshan. The results are clearly mutually quite 

consistent, except in the case of the steam generator feedwater flow, which exhibits about 

6.67% differences. We suspect that this deviation is probably caused by the larger 

measurement errors in the startup tests. 
4-2 

Table 4.1 The comparison between the steady state data of TRACE and the measured 

values from the power plant 

Parameter (PAT49) Plant data TRACE data Error (%) 

Power (W) 2.8026×109 2.8026×109 0.00 

Tavg (K)* 582.90 582.63 0.05 

Pressurizer liquid 

level (%) 

57.04 56.59 0.79 

Pressurizer pressure 

(Pa) 

1.5334×107 1.4972×107 2.36 

Steam generator 

liquid level (%) 

48.94 50.10 2.37 

Steam generator 

feedwater flow 

(kg/sec) 

541.50 505.37 6.67 

Steam generator 

outlet steam 

pressure (Pa) 

6.8465×106 6.9327×106 1.24 

*Tavg = (Hot-leg temperature +Cold-leg temperature)/2 
Fig. 4.1 The TRACE model of Maanshan NPP 

4-3 
4-4 

4.2 Results and discussions [15]-[17]

Following the steady state initialization, the TRACE model of Maanshan NPP was verified using 

three startup test transients [7]-[11] including the large-load reduction at 100% power (PAT49), 

the net-load trip at 100% power (PAT51) and the turbine trip test at 100% power (PAT50), and 

three FSAR transients [12] including Partial Loss of Flow (PLOF), Complete Loss of Flow-Under 

Voltage (CLOF-UV) and Complete Loss of Flow-Under Frequency (CLOF-UF). 

Besides, in transient analysis, there are two methods to simulate or calculate power in 

Maanshan NPP TRACE model. One is to input the power curve by “power table” into the 

TRACE model of Maanshan NPP which is the same as the startup tests data to simulate the 

power for the transient analysis. Another is to use “point kinetic” data (e.g., the delay neutron 

fraction, Doppler reactivity coefficient, and Void reactivity coefficient) in the Maanshan NPP 

TRACE model and let TRACE to calculate the power for the transient analysis. The first method 

is used in the PAT49 and PAT51 transients and the second method in the PAT50, PLOF, 

CLOF-UV, and CLOF-UF transients. 

Tables 4.2-4.7 present the sequence of each transient and the timings of events predicted by 

TRACE. The transient sequences of TRACE arose from the actuation of the related control 

system, which in turn had to be actuated by physical parameter signals. If the parameters 

predicted by TRACE differ from the plant data, then the event sequences will also differ. Such 

deviations can be observed in the comparisons of transient event analyses. For example, the 

variation of Tavg affects the opening times of the turbine bypass valves and atmospheric valves. 

4.2.1 Large-load reduction at 100% power (PAT49)

Table 4.2 shows the Large-load reduction sequences of Maanshan NPP startup test data and 

TRACE. It can be observed that these sequences of the plant data and TRACE are roughly the 

same. Fig. 4.2 plots the core power curves of the Maanshan NPP and TRACE in the case of 

PAT49. In TRACE, the core power can be specified by a power table, and is essentially the 

same as that given by the plant data. Fig. 4.2 compares Tavg from the plant data with that from 

TRACE predictions. The temperatures calculated by TRACE almost equal the measured values 

in Maanshan NPP. Fig. 4.3 compares the water levels and pressures in pressurizer, revealing 

that the water level calculated by TRACE is slightly lower but follows the trend of the plant data. 

The pressure calculated using TRACE also follows the trend of the plant data, with larger 

fluctuations. Fig. 4.4 plots the results for steam generator feedwater flow and water level. The 

feedwater flow is in good agreement with the plant data except for the period between 50 sec. 

and 150 sec. The water level calculated by TRACE is close to the measured values of the plant, 

but with smaller fluctuations. 

4.2.2 Net-load trip at 100% power (PAT51)

Table 4.3 shows the Net-load trip sequences of Maanshan NPP startup tests data and TRACE 

model. It can be seen that these two sequences are approximately the same. Figs. 4.5-4.7 

present the verified results for case PAT51. The predicted Tavg are approximately the same as 

those from the plant data, except in the period between 320 sec. and 400 sec. Fig. 4.6 

compares the water levels and pressures in the pressurizer indicating that the water level 

calculated by TRACE is slightly lower than that in the startup tests data. The pressure of TRACE 

is also lower at most of the time, but with larger fluctuations. The trends of pressurizer water 

level and pressure are quite similar between predictions and startup tests data. Fig. 4.7 

compares steam generator feedwater flows and water levels. The feedwater flow of TRACE is 
4-5 

close to the measured value in the tests, except between 60 and 120s. The water level 

calculated by TRACE is close to that given by the plant data, but with smaller fluctuations. 

4.2.3 Turbine trip test from 100% power (PAT50)

Table 4.4 shows the Turbine trip test sequences of Maanshan NPP startup tests data and 

TRACE. It indicates that these two sequences are approximately the same. Fig. 4.8 plots the 

power curve of the Maanshan NPP and that calculated from TRACE in the case of PAT50. In 

TRACE, the core power can be specified by a power table, which is essentially the same as that 

given by the plant data, or by calculation using the built-in point kinetics model. As a result, the 

power calculated from TRACE includes decay heat, and stays at a level higher than the neutron 

flux-determined power from plant after 10 sec. The comparison of Tavg is also shown in Fig. 4.8. 

The temperature calculated by TRACE approximately follows the trend of the test data, but at a 

slower pace. Fig. 4.9 compares the pressures and water levels of the pressurizer and suggests 

that the water level calculated by TRACE approximately follows the trend of the plant data but 

decreases slower. Fig. 4.10 compares the steam generator feedwater flows and water levels. It 

reveals that the feedwater flow predicted by TRACE agrees closely with the results of the tests, 

except between 10 sec. and 30 sec. However, the water level calculated by TRACE falls 

gradually and then down to 0 at about 70 sec., while the level in the test declines rapidly after 10 

sec. and then down to 0 at about 35 sec. Therefore, a large difference exists between the 

predicted and actual steam generator water levels. 

4.2.4 Partial Loss of Flow (PLOF) 

Table 4.5 shows the PLOF sequences of FSAR, RETRAN and TRACE. It can be observed that 

these three sequences are approximately in good agreement. Besides, it displays the slower 

time response in TRACE. As for the verification of PLOF cases, Fig. 4.11 compares the power 

and core flow of FSAR, RETRAN and TRACE. It displays that the power curve of TRACE is 

almost the same as those of FSAR and RETRAN. It also shows that the core flow curve of 

TRACE approximately follows the trends of FSAR’s and RETRAN’s. Fig. 4.12 compares the 

pressurizer pressure and Tavg among FSAR, RETRAN and TRACE. The pressure curve of 

TRACE generally follows the trends of FSAR’s and RETRAN’s. It also can be found that the 

Tavg of TRACE and RETRAN are almost the same. 

4.2.5 Complete Loss of Flow-Under Voltage (CLOF-UV) 

Table 4.6 shows the CLOF-UV sequences of FSAR, RETRAN and TRACE. It can be seen that 

these three sequences are roughly the same. In the verification of CLOF-UV cases, Fig. 4.13 

shows the powers and core flows of FSAR, RETRAN and TRACE. In this figure, the TRACE 

curve is nearly similar to FSAR’s and RETRAN’s. It also reveals that the core flow curve of 

TRACE approximately follows the trends of FSAR’s and RETRAN’s. Fig. 4.14 shows the 

pressurizer pressures and Tavg of FSAR, RETRAN and TRACE. The pressure curve of TRACE 

generally follows the trends of FSAR’s and RETRAN’s but shows a difference from RETRAN’s 

curve after 5 sec. It also displays that the Tavg of TRACE and RETRAN are almost the same. 

4.2.6 Complete Loss of Flow-Under Frequency (CLOF-UF) 

Table 4.7 shows the CLOF-UF sequences of FSAR, RETRAN and TRACE. It can be shown that 

these three sequences are approximately the same. In the verification of CLOF-UF cases, Fig. 

4.15 plots the power curves of FSAR, RETRAN02 and TRACE, and the TRACE curve is nearly 

similar to FSAR’s and RETRAN’s. Fig. 4.15 also shows the core flows of FSAR, RETRAN and 

TRACE. It can be observed that the core flow curve of TRACE approximately follows the trends 

of FSAR’s and RETRAN’s. Fig. 4.16 plots the pressurizer pressures of FSAR, RETRAN and 
4-6 

TRACE. The pressure curve of TRACE generally follows the trends to FSAR’s and RETRAN’s 

but shows bigger differences from FSAR’s and RETRAN’s after 5 sec. It also reveals the Tavg 

of TRACE and RETRAN. It can be found that the temperatures of TRACE are almost the same 

a RETRAN’s. 

In summary, after the comparisons of all the LOF events shown in above figures including all 

cases of PLOF, CLOF-UV and CLOF-UF, the variation trend of each important thermal 

parameter calculated by the TRACE model of Maanshan NPP could conform to the results of 

FSAR and RETRAN. However, it shows that there is a larger difference in the pressurize 

pressure. We suspect that the differences of the results among FSAR, RETRAN and TRACE 

are caused by the difference of the calculation procedure or modeling of FSAR, RETRAN and 

TRACE. Furthermore, the animation of this model is presented using the animation function of 

SNAP/TRACE interface with above models and analysis results. The animation model of 

Maanshan NPP is shown in Fig. 4.17. 
4-7 

Table 4.2 The large load reduction sequences in TRACE model and Maanshan NPP 

Large load reduction (PAT49)* Plant data 

Time(sec) 

TRACE 

Time(sec) 

Initial load reduction to 50% 10.0 10.0 

T/B bypass valves fully open 20.0 19.2 

T/B atmospheric valves fully open 38.0 28.9 

*On steady status at first 10sec 

Table 4.3 The net load trip sequences in TRACE model and Maanshan NPP 

Net load trip (PAT51)* Plant data 

Time(sec) 

TRACE 

Time(sec) 

Initial load rejection 10.0 10.0 

T/B bypass valves fully open 14.0 11.8 

PZR spray valves fully open 17.8 16.1 

T/B atmospheric valves fully open 18.0 18.2 

*On steady status at first 10sec 

Table 4.4 The turbine trip sequences of TRACE model and Maanshan NPP 

Turbine trip (PAT50)* Plant data 

Time(sec) 

TRACE 

Time(sec) 

Manual T/B trip 10.0 10.0 

T/B stop valve full closure 10.1 10.1 

Reactor trip 10.1 10.1 

T/B bypass valves fully open 12.0 10.7 

Feedwater pump trip 28.5 29.0 

*On steady status at first 10sec 
4-8 

Table 4.5 The sequences of PLOF in FSAR, RETRAN and TRACE 

FSAR 

time 

(sec) 

RETRAN 

 time 

(sec) 

TRACE 

time 

(sec) 

One RCPs coastdown begins 0 0 0 

Low flow scram setpoint reached 1.4 1.47 1.68 

Rods begin to drop (scram) 2.4 2.47 2.68 

Table 4.6 The sequences of CLOF-UV in FSAR, RETRAN and TRACE 

FSAR 

time 

(sec) 

RETRAN 

 time 

(sec) 

TRACE 

time 

(sec) 

All RCPs coastdown begins 0 0 0 

Undervoltage scram signal 0 0 0.13 

Rods begin to drop(scram) 1.5 1.5 1.63 

Table 4.7 The sequences of CLOF-UF in FSAR, RETRAN and TRACE 

FSAR time 

(sec) 

RETRAN time 

(sec) 

TRACE 

time 

(sec) 

All RCPs coastdown begins 0 0 0 

Undervoltage scram signal 0.6 0.6 0.65 

Rods begin to drop (scram) 1.2 1.2 1.25 
0 60 120 180 240 300 360 420

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Normalized power

560

570

580

590

600

610

Tavg (K)

PAT49

Power-Plant data

Power-TRACE data

Tavg-Plant data

Tavg-TRACE data

Fig. 4.2 The comparisons of power and Tavg between TRACE model and Maanshan NPP 

(PAT49) 

0 60 120 180 240 300 360 420

Time (sec)

1.1x107

1.2x107

1.3x107

1.4x107

1.5x107

1.6x107

1.7x107

1.8x107

PZR pressure (Pa)

0

20

40

60

80

100

120

PZR liquid level (%)

PAT49

Pressure-Plant data

Pressure-TRACE data

Liquid level-Plant data

Liquid level-TRACE data

Fig. 4.3 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT49) 

4-9 
0 60 120 180 240 300 360 420

Time (sec)

0

100

200

300

400

500

600

700

Feedwater (kg/sec)

0

20

40

60

80

100

SG liquid level (%)

PAT49

Feedwater-Plant data 

Feedwater-TRACE data 

Liquid level-Plant data

Liquid level-TRACE data

Fig. 4.4 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT49) 

0 60 120 180 240 300 360 420

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Normalized power

560

570

580

590

600

Tavg (K)

PAT51

Power-Plant data

Power-TRACE data

Tavg-Plant data

Tavg-TRACE data

Fig. 4.5 The comparisons of power and Tavg between TRACE model and Maanshan NPP 

(PAT51) 

4-10 
0 60 120 180 240 300 360 420

Time (sec)

1.1x107

1.2x107

1.3x107

1.4x107

1.5x107

1.6x107

1.7x107

PZR pressure (Pa)

0

20

40

60

80

100

120

PZR liquid level (%)

PAT51

Pressure-Plant data

Pressure-TRACE data 

Liquid level-Plant data

Liquid level-TRACE data

Fig. 4.6 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT51) 

0 60 120 180 240 300 360 420

Time (sec)

0

100

200

300

400

500

600

700

Feedwater (kg/sec)

0

20

40

60

80

100

SG liquid level (%)

PAT51

Feedwater-Plant data 

Feedwater-TRACE data 

Liquid level-Plant data

Liquid level-TRACE data

Fig. 4.7 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT51) 

4-11 
0 20 40 60 80

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Normalized power

540

550

560

570

580

590

600

Tavg (K)

PAT50

Power-Plant data

Power-TRACE data 

Tavg-Plant data

Tavg-TRACE data

Fig. 4.8 The comparisons of power and Tavg between TRACE model and Maanshan NPP 

(PAT50) 

0 20 40 60 80

Time (sec)

1.1x107

1.2x107

1.3x107

1.4x107

1.5x107

1.6x107

1.7x107

PZR pressure (Pa)

0

20

40

60

80

100

120

PZR liquid level (%)

PAT 50

Pressure-Plant data

Pressure-TRACE data 

Liquid level-Plant data

Liquid level-TRACE data 

Fig. 4.9 The comparisons of the PZR’s water level and pressure between TRACE model 

and Maanshan NPP (PAT50) 

4-12 
0 20 40 60 80

Time (sec)

0

100

200

300

400

500

600

700

Feedwater (kg/sec)

0

20

40

60

80

100

SG liquid level (%)

PAT 50

Feedwater-Plant data

Feedwater-TRACE data

Liquid level-Plant data

Liquid level-TRACE data

Fig. 4.10 The comparisons of the SG’s feedwater flow and water level between TRACE 

model and Maanshan NPP (PAT50) 

0 2 4 6 810

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Normalized power

0

0.2

0.4

0.6

0.8

1

1.2

Nominal Core flow 

PLOF

Power-FSAR

Power-RETRAN

Power-TRACE 

Core flow- FSAR

Core flow- RETRAN

Core flow- TRACE

Fig. 4.11 Comparisons of the power and core flow of PLOF among FSAR, RETRAN and 

TRACE 

4-13 
0 2 4 6 810

Time (sec)

14

15

16

17

Pressurizer Pressure (MPa)

550

575

600

625

650

Tavg (K)

PLOF

Pressure-FSAR

Pressure-RETRAN

Pressure-TRACE 

Tavg-RETRAN

Tavg-TRACE

Fig. 4.12 Comparisons of the pressurizer pressure and Tavg of PLOF among FSAR, 

RETRAN and TRACE 

0 2 4 6 810

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Nominal Power

0

0.2

0.4

0.6

0.8

1

1.2

Nomial Core Flow

CLOF-UV

Power-FSAR

Power-RETRAN

Power-TRACE

Core flow-FSAR

Core flow-RETRAN

Core flow-TRACE

Fig. 4.13 Comparisons of the power and core flow of CLOF-UV among FSAR, RETRAN 

and TRACE 

4-14 
0 2 4 6 810

Time (sec)

14

15

16

17

Pressurizer pressure (MPa)

550

575

600

625

650

Tavg (K)

CLOF-UV

Pressure-FSAR

Pressure-RETRAN

Pressure-TRACE

Tavg-RETRAN

Tavg-TRACE

Fig. 4.14 Comparisons of the pressurizer pressure and Tavg of CLOF-UV among FSAR, 

RETRAN and TRACE 

0 2 4 6 810

Time (sec)

0

0.2

0.4

0.6

0.8

1

1.2

Nominal Power

0

0.2

0.4

0.6

0.8

1

1.2

Nominal Core flow 

CLOF-UF

Power-FSAR

Power-RETRAN

Power-TRACE

Core flow-FSAR

Core flow-RETRAN

Core flow-TRACE

Fig. 4.15 Comparisons of the power and core flow of CLOF-UF among FSAR, RETRAN 

and TRACE 

4-15 
0 2 4 6 810

Time (sec)

14

15

16

17

Pressurizer pressure (MPa)

550

575

600

625

650

Tavg (K)

CLOF-UF

Pressure-FSAR

Pressure-RETRAN

Pressure-TRACE

Tavg-RETRAN

Tavg-TRACE

Fig. 4.16 Comparisons of the pressurizer pressure and Tavg of CLOF-UF among FSAR, 

RETRAN and TRACE 

Fig. 4.17 Animation of Maanshan NPP model 

4-16 
5-1 

5. CONCLUSIONS

By using SNAP/TRACE, this study developed a TRACE model of the Maanshan NPP. 

Effectiveness of the proposed model was verified with the large-load reduction at 100% power 

(PAT49), the net-load trip at 100% power (PAT51), the turbine trip test at 100% power (PAT50), 

Partial Loss of Flow (PLOF), Complete Loss of Flow-Under Voltage (CLOF-UV), and Complete 

Loss of Flow-Under Frequency (CLOF-UF) in Maanshan startup tests and FSAR data. 

Analytical results indicate that the Maanshan NPP TRACE model predicts not only the 

behaviors of important plant parameters in consistent trends with the startup tests and FSAR 

data, but also their numerical values with respectable accuracy. The TRACE model of 

Maanshan NPP can be used in future safety analysis with confidence, such as the applications 

for power uprating, life extensions, and design modifications. 
6-1 

6. REFERENCES

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