Annals of Nuclear Energy 40 (2012) 122–129

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Annals of Nuclear Energy

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Introducing PCTRAN as an evaluation tool for nuclear power plantemergency responses

Yi-Hsiang Cheng a,⇑, Chunkuan Shih b, Show-Chyuan Chiang c, Tung-Li Weng c

a Material and Chemical Research Labs, Industrial Technology Research Institute, Building 52, No. 195, Chung-Hsing Road, Sec. 4, Chutung, Hsinchu 31040, Taiwan, ROCb Institute of Nuclear Engineering and Science, National Tsing Hua University, No. 101, Kuang-Fu Road, Sec. 2, Hsinchu 30013, Taiwan, ROCc Department of Nuclear Safety, Taiwan Power Company, No. 242, Roosevelt Road, Sec. 3, Taipei 10016, Taiwan, ROC

a r t i c l e i n f o

Article history:Received 9 November 2010Received in revised form 19 October 2011Accepted 21 October 2011Available online 1 December 2011

Keywords:Accident evaluation toolNuclear emergency responseProtective actions

0306-4549/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.anucene.2011.10.016

⇑ Corresponding author. Tel.: +886 3 5914789; fax:E-mail address: yhcheng@itri.org.tw (Y.-H. Cheng)

a b s t r a c t

Protecting the public from radiation exposure is important if a nuclear power plant (NPP) accident occurs.Deciding appropriate protective actions in a timely and effective manner can be fulfilled by using aneffective accident evaluation tool. In our earlier work, we have integrated PCTRAN (Personal ComputerTransient Analyzer) with the off-site dose calculation model. In this study, we introduce PCTRAN as anevaluation tool for nuclear power plant emergency responses. If abnormal conditions in the plant aremonitored or observed, the plant staffs can distinguish accident/incident initiation events. Thus, theresponsible personnel can immediately operate PCTRAN and set up those accident/incident initiationevents to simulate the nuclear power plant transient or accident in conjunction with off-site dose distri-butions. The evaluation results consequently help the responsible organizations decide the rescue andprotective actions. In this study, we explain and demonstrate the capabilities of PCTRAN for nuclearemergency responses, through applying it to simulate the postulated nuclear power plant accidentscenarios.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Radioactive materials are produced in nuclear reactor opera-tions, and may be released into the atmosphere if an accident oc-curs. The event of an accidental release of radioactive materialsresults in dangerous levels of radiation, harm the populationaround the plant, and damage the environment. Therefore, theresponsible organizations should take the responsibility to protectthe public from radiation exposure by initiating appropriate pro-tective actions in the event of a nuclear power plant accident(CFR, 2004). The US NRC has examined that the plant licensee musthave adequate protective measures which can and will be taken inthe event of a radiological emergency.

In Taiwan, there are three operating nuclear power plants, Chin-shan, Kuosheng, and Maanshan, and a fourth plant, Lungmen, iscurrently under construction. The responsible organizations,including the central government and the local government (muni-cipal government and country government), shall cooperate to en-act emergency countermeasures in the event of a nuclear accident(AEC, 2003). Protective measures, such as sheltering, distributingpotassium iodide, evacuation and accommodation, temporary relo-cation, and others, are taken in the emergency planning zone (EPZ).

ll rights reserved.

+886 3 5820001..

The range of EPZ of each operating nuclear power plant in Taiwanextends 5 km in radius around the plants. On-site and off-site re-sponse measures must be taken promptly and effectively in theevent of an accident.

To respond to the nuclear emergency, the plant licensee evalu-ates plant conditions and recommends appropriate actions to theplant-site response organizations, the central government andthe local government. The central government overall analyzes, as-sesses, and manages the nuclear accident, as well as plans andsupervises all other work. The local government implement theirresponse support and provide resources. The public protective ac-tions should be determined in accordance with the plant condi-tions. To enhance the process of deciding and recommendingprotective actions, some studies have evaluated the nuclear acci-dent sequence and the dose consequences under the accident sce-narios (FZK and NRPB, 1991; Haste et al., 2006; Wu et al., 2006).Other studies developed tools or simulation systems to strengthenthe training of all emergency response organizations (Crichton andFlin, 2004; Kurfess et al., 2003; Ha et al., 2006), to ensure that theresponsible organizations are familiar with the emergency re-sponse plan.

In our earlier works, we have integrated the nuclear powerplant simulation software, PCTRAN (Personal Computer TransientAnalyzer), with an atmospheric dispersion algorithm to efficientlyevaluate a nuclear power plant accident and its off-site doseconsequences (Cheng et al., 2007, 2008). The developed dispersion

Y.-H. Cheng et al. / Annals of Nuclear Energy 40 (2012) 122–129 123

algorithm, including a modified atmospheric diffusion model andthe programming method, can satisfy the application requirementsduring nuclear emergency. Herein, we further introduce PCTRAN asan evaluation tool of nuclear power plant accident and the doseconsequences for nuclear emergency responses. We explain anddemonstrate the capabilities of PCTRAN by applying it to simulatethe postulated nuclear power plant accident scenarios.

Fig. 1. Graphical user interface of PCTRAN

2. Descriptions of evaluation tool

The nuclear power plant simulation software, PCTRAN, is aproduct of Micro-Simulation Technology (MST) Inc., which can per-form nuclear power plant transient and accident simulation on apersonal computer (MST Inc., 2007). The windows-based graphicaluser interfaces allow users interacting with the simulation

: (a) Main Mimic and (b) Dose Mimic.

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software through directly manipulation of the graphical elements.The major advantage of PCTRAN is that it can be operated easilyand is capable of running faster than real time (Po, 1981, 1988).The latest version of PCTRAN updated by MST Inc. contains the se-vere accident model comprised of core meltdown, vessel penetra-tion and corium–concrete interaction.

The software has several features that are suitable for beingused as the evaluation tool for the emergency responses:

� The software is a windows-based product with graphical userinterfaces, as shown in Fig. 1a and b, individually named asMain Mimic and Dose Mimic. The system components and fea-tures of a nuclear power plant are modeled as graphical ele-ments, which are arranged systematically on the interfaces.Therefore, users can interact with the simulation softwarethrough direct manipulation of the graphical elements, and eas-ily give commands to the calculation center through manipula-tion of the interfaces.

Fig. 2. Evaluation tool for nuclear po

� All input data of the software are organized into MS Accessdatabase, for the purpose of easy editing and management.The basic plant data, geometric, physics, trip set-points andother characteristic data, are saved in the MS Access databasein advance. Furthermore, initial conditions, such as the reactorthermal power, core pressure, core temperature, fuel-life cycle,and so forth, are also saved in database. In addition, a variety ofmalfunctions, such as loss of coolant accident, steam line break,fuel failure during power operation, anticipated transient with-out scram, etc., are collected in the database for the malfunctionsettings of the nuclear components and features.� The plant mimics are displayed on the computer screen as the

computation is processing, and important plant parametersare digitally displayed on the mimics. The modeled graphicalelements of nuclear components also dynamically reflect theplant status. For example, on the Main Mimic, the water levelsin the reactor vessel dynamically rise and fall, and the coolantvoid fraction is reflected by changing colors as it is calculated.

wer plant emergency responses.

Y.-H. Cheng et al. / Annals of Nuclear Energy 40 (2012) 122–129 125

On the Dose Mimic, the molten fuel collapses to the bottom ofthe reactor vessel, and the collapsed core drops to the contain-ment cavity floor.� The software can run in real-time, two-times, four-times, eight-

times, or sixteen-times faster than real time. Therefore, the soft-ware has the ability to perform an analysis or a prediction aheadof the actual events unfolding.� The software has the ability to execute an accident simulation

according to the time-sequenced scenarios. As the simulatedaccident events unfold in sequence, important plant parame-ters, such as core power, core pressure and temperature, down-comer water level, fuel and cladding temperatures, drywell andwetwell pressures, flows of ECCSs, and so on, are calculated bythe PCTRAN main routine. Furthermore, the time-varying activ-ity of fission products released from the reactor core, throughthe leakage path, to the environment is also calculated. Theamount of these fission products escaping from the failurephysical barriers can be known.

Two major functions have been embedded to PCTRAN, such thatits application capabilities to nuclear emergency responses havebeen reinforced. PCTRAN was being integrated with off-site dosedispersion model and network functions, as described in Fig. 2.The embedded two major functions are helpful to the nuclearemergency responses. The off-site dose dispersion model isresponsible for the calculations of dose distributions within theEPZ, while the network functions can display and distribute thecalculated plant parameters and dose levels to all responsibleorganizations.

When PCTRAN is integrated with the off-site dose dispersionmodel, the subroutine of the dose calculation acquires the activityof fission products from the main routine of PCTRAN, and then pro-jects the off-site dose distributions according to the meteorologicalconditions (wind direction, wind velocity, and stability category).The dose dispersion model was based on the Gaussian puff model,and we utilized the software development techniques to accommo-

Fig. 3. Puff Mimic being extended i

date a rapid and long-term assessment of the radioactive effluentdispersion and the dose levels in the EPZ. Therefore, the improvedPCTRAN has the capability of conducting a rapid and long-term cal-culation. In addition to the Main Mimic and the Dose Mimic, a PuffMimic, as shown in Fig. 3, is further added into PCTRAN.

PCTRAN was also being set up its internet functions to developits data and information communication capability. MySQL was se-lected as the database engine and TOMCAT was selected as theWeb server. Thus, the plant parameters simulated by PCTRANcan be stored in the MySQL database and shown on the Web,and all personnel involved in the emergency responses can lookup the simulated plant parameters from the Web. Furthermore,we applied the VNC (Virtual Network Computing) framework tofulfill the remote control of the PCTRAN host computer. The tech-nical personnel can remotely operate the PCTRAN host computer,and all personnel from different sites can instantly access the sim-ulated plant parameters.

In summary, the upgrade PCTRAN has several major capabili-ties, of which it can be used as the evaluation tool for nuclearemergency responses. First, PCTRAN can be executed immediatelyto simulate the whole plant transient and the dose consequencesduring a nuclear emergency. Second, PCTRAN has the capabilityof long-term simulation in the event of a severe accident. Third,PCTRAN has the capability of rapid assessments for pre-analysisor forecast purposes. Fourth, PCTRAN provides data and informa-tion communication functions for different responsible organiza-tions through networks. Therefore, PCTRAN acts as an accident/incident simulator for experienced analyst, a supervisor tool forthe emergency executive committee and a data exchange systemfor all related personnel.

3. Nuclear emergency responses

The Nuclear Power Plant Emergency Response Plan (NPP-ERP)establishes all emergency response organizations and defines

n PCTRAN for dose calculation.

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their role to a nuclear power plant accident. The central govern-ment has commanded that the NPP-ERP shall be drilled and exer-cised periodically to make sure that protective actions can bedecided and activated immediately and all responsible organiza-tions can cooperate timely and effectively in the event of anaccident.

In Taiwan, the central government periodically selects one EPZto conduct its Nuclear Power Plant Emergency Response Plan Exer-cise (NPP-ERPE). The NPP-ERPE is designed to test the capability ofon-site and off-site response organizations in protecting publichealth and safety through the implementation of the NPP-ERP un-der the simulated conditions. To conduct the NPP-ERPE, the plantlicensee designs a series of accident events under which the emer-gency executive committee and the on-site or the off-site responseorganizations will be activated.

This study introduces PCTRAN as an evaluation tool of nuclearpower plant transient and accident predictions during nuclearemergency. To ensure the practicality of PCTRAN during nuclearemergency, we applied it to simulate the postulated time-se-quenced nuclear power plant accident scenarios. We use PCTRANto assess the consequences of the nuclear accident scenarios andthus to support the decision-making of rescue actions. Importantplant parameters, including core power, core pressure, core tem-perature, core water level, cladding temperature, containmentpressure, temperature, etc., are calculated such that the competentauthority and the responsible organizations can understand theplant conditions. Furthermore, radiation dosages on the popula-tion, such as whole body and thyroid dosages, are also assessedsuch that the potential magnitude and locations of radiologicalhazards can be determined.

Table 1Emergency accident scenarios and corresponding settings in PCTRAN.

Real time (min) Event

t + 0 (09:00) Full power normal operationt + 10 (09:10) Low voltage alarm on 4.16 kV bus; EDG-B startt + 30 (09:30) Automatic scram (logic card malfunction)t + 40 (09:40) Main feedwater pump A vibration; 3 SG levels

mismatcht + 50 (09:50) Fuel fail detector slight elevated reading 0.5E4 CPM

t + 60 (10:00) Seismic monitor triggered 0.27 g; reactor scram

t + 75 (10:15) Motor-driven AFW pump B tripped

t + 85 (10:25) Motor-driven AFW pump A tripped

t + 95 (10:35) CCP-B uncouplingt + 105 (10:45) 2 RCP vibration, trippedt + 115 (10:55) Fuel failure high alarm: core activity 2E4

t + 125 (11:05) Loss of 161 kVt + 135 (11:15) Pump B-EF-P105 uncouplingt + 150 (11:30) SG B tube rupture 250 gpm (60 m3/h); RC coolant

sampling: core activity 200 lCi/g

t + 270 (13:30) Fuel fail reactor coolant activity 120 lCi/g

t + 280 (13:40) SG B auxiliary FW pump steam supply valve failedopen; steam leak 4E5 kg/h

t + 310 (14:10) Pump B-EF-P106 breakdownt + 340 (14:40) CCP-A breakdownt + 360 (15:00) RHR pump A tript + 370 (15:10) SG-B break outside containment 4E5 kg/h

unisolablet + 390 (15:30) End

3.1. Application of PCTRAN to nuclear emergency responses

If abnormal conditions in the plant are monitored or observed,the plant staffs will distinguish accident/incident initiation events.Accordingly, these accident initiation events can be set up in thesoftware and thus the consequences of the events are simulated.To explain and demonstrate how PCTRAN can be applied for nucle-ar emergency responses, PCTRAN was used to conduct the de-signed time-sequenced nuclear power plant accident scenarios.The major events in the scenarios involved:

(1) Slight fuel clad failure.(2) Seismic event manual scram.(3) Motor-driven SG AFW-B pump tripped.(4) 2 RCPs tripped.(5) Loss of off-site power, and DGB starts.(6) SG tube rupture.(7) More fuel failure.(8) Isolate faulted SG steam and AFW lines.(9) Cooldown the reactor using the good SG’s.

(10) Steam supply valve to FW pump B open, but unisolablesteam line leak outside the containment.

(11) Maximum reactor coolant 120 lCi/gm; increasing off-siteExclusion Area Boundary (EAB) and Low Population Zone(LPZ) integrated dose.

The accident can be summarized as a series of accident initia-tion events that can be set up in the software. We propose thatthe technical personnel operate PCTRAN and sequentially set upthose accident initiation events during the nuclear emergency.

PCTRAN time (s) PCTRAN action

�3000 IC1: 100% power steady state�2400 No action�1200 No action�600 No action

0 MF17: set 0.2% fuel failureCore activity changed from 1.2E3 to 5.2E3 CPM

600 Seismic monitor triggered 0.27 g > OBE (0.2 g).Action: Manual scram

1500 Motor-driven AFW pump B trip. Action: trip AFWpump B

2100 Motor-driven AFW pump A trip. Action: trip AFWpump A

2700 Fail CCP-B3300 2 RCP vibration. Action: trip ‘‘B’’ side RCP3900 MF17: set 1.5% fuel failure

RC coolant sampling: core activity 2.27 E4 CPM4500 345 kV available; no action5100 No action6000 1. MF10: ‘‘A’’ side SGTR 70%. Isolate ‘‘A’’ AFW &

MSIV; start depressurization and cooldown (byusing Tavg controlled cooldown rate 50C/h). Mustactivate TBV to allow steam dump to turbine2. Enter MF17 = 2%, activity = 4.39 E6 Bq/g = 118.53 lCi/g

13,200 RC coolant sampling: core activity 4.4 E6 Bq/g = 118.8 lCi/g

13,800 1. MF4: 400% steam line break outside containment2. Fail turbine-driven AFW pump

15,600 No action17,400 Fail CCP-A; only CCP-S operating18,600 Trip RHR A19,200 MF4: steam line break 1200 cm2; off-site radiation

monitor increases20,400 End

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Therefore, PCTRAN can conduct the simulation and reported plantparameters following the accident scenarios. Table 1 presents boththe designed time-sequenced accident scenarios and the corre-sponding time-sequenced settings in PCTRAN. In the first 3000 s(50 min), there are no actions for PCTRAN to operate. Therefore,

Fig. 4. Important plant parame

the time sequence of the PCTRAN operation has 50 min time delaycomparing to the real time.

To demonstrate the simulation capabilities of this evaluationtool, we used it to simulate a series of accident sequences ofWestinghouse 3-loop PWR. In the software, it has been defined

ters reported by PCTRAN.

128 Y.-H. Cheng et al. / Annals of Nuclear Energy 40 (2012) 122–129

that ‘A-loop’ is one of the three loops, and ‘B-loop’ refers two of thethree loops. Fig. 4 plots the important plant parameters reportedby PCTRAN. At time 10 min, the reactor is scrammed by manualtrip. Therefore, the core neutron flux and thermal power decrease

Fig. 4 (continued)

instantly to about 5%. The feedwater pumps and the recirculationpumps remain working to remove the residual heat and maintainthe reactor water level. The B-loop motor-driven feedwater pumpmalfunctions at time 25 min, and then the A-loop motor-drivenfeedwater pump malfunctions at time 35 min. At time 55 min,two recirculation pumps at B-loop trip. Consequently, the core in-let flow decreases. At time 100 min, one SG tube ruptures. The bro-ken SG is isolated by closing the AFW and MSIV. The reactor iscooled down using the other good 2 SGs, and thus the RCS andSGs pressures and temperatures decrease. At time 230 min, theFW pump steam supply valve fails open, such that steam leaks out-side the containment.

Under the accident scenarios, the fuel failure was detected attime 0 min, and fuel failure high alarm was reached at time65 min. The release of fission products to the environment started

Fig. 5. Distributions of dosages within 1 km radius of the plane at the end ofsimulation.

Y.-H. Cheng et al. / Annals of Nuclear Energy 40 (2012) 122–129 129

at time 100 min due to one steam-generator tube rupture. As wehave mentioned, PCTRAN also provides the estimation of ground-level dosages, including the thyroid and whole body dose ratesand their accumulations. The designed meteorological conditionsof were the Pasquill stability category D with a northeast windvelocity of 4 m/s. The technical personnel set up the meteorologi-cal conditions from the Puff Mimic of PCTRAN, and then theground-level dosages were estimated. The distributions of the inte-grated whole body and thyroid dosages within 1 km radius of theplane at the end of the simulation are displayed in Fig. 5.

During the simulation, those calculated plant parameters andoff-site dose distributions were both saved in the MS Access andupdated to the network database. The network functions ofPCTRAN is deigned to retrieve, present, and traverse all the evalu-ation data. Thus, the plant conditions and the dose levels in the EPZcan be looked up from different sites through the web browser.This information helps the responsible organizations decide theirrescue or protective actions.

4. Conclusions

This study introduces PCTRAN for use as an evaluation duringthe nuclear power plant emergency responses. We applied PCTRANto simulate the postulated nuclear power plant accident scenarios.The accident scenarios were summarized as a series of accident ini-tiation events, and were set up in the software. To enhance thecapabilities of PCTRAN to nuclear power plant emergency re-sponses, it has been integrated with off-site dose dispersion modeland network functions. Therefore, PCTRAN conducted the simula-tion and reported plant parameters and off-site dose distributionsfollowing the accident scenarios. Furthermore, the simulated plantparameters can also be looked up from different sites through theweb browser. From the demonstration, we confirmed that PCTRANcan conduct a rapid and long-term simulation in the event of a nu-

clear accident. It also provides data and information communica-tion functions for different responsible organizations throughnetworks. Therefore, the improved PCTRAN can act as an acci-dent/incident simulator and a data exchange system for nuclearpower plant emergency responses.

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