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Nuclear Engineering and Design 265 (2013) 932– 937

Contents lists available at ScienceDirect

Nuclear Engineering and Design

j ourna l h om epa ge: www.elsev ier .com/ locate /nucengdes

nalytic study for physical protection system (PPS) in nuclear powerlants (NPPs)

ae Ho Woo ∗

epartment of Nuclear Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea

i g h l i g h t s

The physical protection system (PPS) is investigated.General NPPs are modeled in the study.Possible terror cases, likelihood, and consequence are studied.PPS is constructed by analytical methods.

r t i c l e i n f o

rticle history:eceived 28 April 2013

a b s t r a c t

The nuclear safeguard is analyzed in the aspect of the physical protection system (PPS) in nuclear powerplants (NPPs). The PPS is reviewed and its related terror scenarios are investigated. The PPS is developed

eceived in revised form 31 August 2013ccepted 19 September 2013

using analytical methods. In the terror scenarios, there are 8 possible cases for the terror attacks tothe NPPs. Then, the likelihood of terror is classified by the general terror incidents. The consequenceof terror is classified by Design Basis Threat (DBT) of the International Atomic Energy Agency (IAEA)scale. The physical protection method is suggested by defense-in-depth constraints and severe accidentcountermeasures. Finally, the advanced PPS is constructed, which could be used for the preparation forthe possible terror attacks in the NPPs.

. Introduction

The commercial nuclear power plants (NPPs) are operated nor-ally, if any kinds of accidents by the terror or sabotage are not

appened, because the well equipped safety systems of NPPs couldontinue the normal operations. Hence the analysis of terror orabotage in physical protection system (PPS) of NPPs’ security ismportant in the country like the Republic of Korea where the mil-tary enemy is under confliction.

As it is seen in Fukushima accident at March 11, 2001, the NPPsan produce steam explosion, radioactive material release, andnternational panics by the natural disaster like the earthquake.his caused the national economic stagnation and internationalnti-nuclear movement. The suicide airplane crash terror tohe World Trade Center (WTC) and the Department of DefenseDOD) building provoked panics and worries, which happened in

eptember 11, 2001. If this terror happened in NPPs, much moreorrible results could be produced.

∗ Tel.: +82 2 880 8337; fax: +82 2 889 2688.E-mail address: thw@snu.ac.kr

029-5493/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.nucengdes.2013.09.025

© 2013 Elsevier B.V. All rights reserved.

It is necessary to estimate the stability of the plant securityby the monitoring systems for NPPs. Serious attack like the ter-ror or sabotage is not notified before an incident. So, it is neededto analyze by indirect method like the terror or sabotage relatedalgorithm. The Design Basis Threat (DBT) has been introduced forthe terror or sabotage case which was constructed as the similarconcept to the Design Basis Accident (DBA). It was also analyzedthat the safeguards meant the regulations of the related systems.The safeguard regulations had been prepared simultaneously withthe commercial NPPs business from the mid 20th century.

It is very important to study analytically in order to strengthenthe safeguard of NPPs’ terror. That is, it is necessary to analyzehow the terror and sabotage can happen in normal operation andhow to prepare. This could be estimated by the analytic methodbased on the opinions of experts. The purpose of the safeguardwas that the trade did not go to the supply of nuclear bombs andthe importance of the perceptions is that pending nuclear disarma-ment, world security is better served with fewer rather than morenuclear weapons and nuclear weapon states (IAEA, 2004).

The DBT has been introduced to make the protections of NPPs.DBT is the response against the potential threat in which the radi-ation sabotage, theft, and usage could be done against the PPS andthis is a part of section 73.1 of the Code of Federal Regulations Title

T.H. Woo / Nuclear Engineering and Design 265 (2013) 932– 937 933

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Fig. 2. Physical protection system.

cations (NCPA, 2001). There is a list of terror scenarios in Table 1.These scenarios are analyzed in this study. The contents are asfollows:

Table 1List of terror scenario.

Sort Number Event

Explosion 1 A truck bomb

Armed attack 2 Attack by boat3 Suicide attack by small

aircraft4 Frontal assault with small

arms5 Attack with rockets or

medium artillery

Etc. 6 Sabotage to the power lines

Fig. 1. Flowchart of study.

0 (10 CFR) in Nuclear Regulatory Commission’s (NRC’s) regula-ions after 1979 (US NRC, 2012). In addition, the INFCIRC/225/Rev.

(Corrected) of nuclear material and facility describes the DBT fol-owing the International Atomic Energy Agency (IAEA), which was

ade in 1999. The object is to describe the reason, intention, andositional possibility against the production and estimation of pro-ection system (IAEA, 2009). The major objects of DBT are impurendividual and group in internal and external part, material lost andabotage, prohibited actions, PPS related arms, utensil, technology,esign and estimation of DBT, etc. (IAEA, 2012a).

Although this study has a difficulty in finding the internal NPPs,he large scale light water reactor (LWR) near seashore is modeled.he terror scenarios could be obtained by literature survey andxpert opinions. The likelihood, consequence, and PPS for ter-ors can be studied. In the past studies, Borrelli studied that Higheliability Safeguards (HRS) approach in a series of quantitativeodeling efforts to develop methodologies for demonstrating the

afeguardability of these facilities (Borrelli, 2013). In addition, Parkt al. worked for a graded approach to cyber security in a researcheactor facility (Park et al., 2013).

The object of the study is how to construct the protections inPPs where the analytic method is done. There are 8 exampled ter-

or cases, likelihoods, and consequences which are analyzed andhe strategies are introduced. Since terror cases in NPPs are prohib-ted to open to public following DBT, the previous general terrorases are considered as the likelihood investigation. The conse-uences are estimated by the damage of power lines, psychological

anic disorder, and so on. The strategy of protection is done byetection, delay, and response of PPS. The flowchart of study ishown in Fig. 1. There is the background for the modeling whichs shown in Section 2. Section 3 explains the method of the study.

Fig. 3. Directions of terror attacks.

Section 4 describes results of the study. There are some conclusionsin Section 5.

2. Background

In order to investigate the terror cases which are related withthe PPS, the possible events are considered. There are 3 kinds ofclassifications in PPS which are in Fig. 2 (Rico and Beasley, 2006).There are 8 possible scenarios for the terror attacks to the NPPsincorporate with a report (NCPA, 2001). Fig. 3 shows the direc-tions of terror attacks. There are 3 ways as land, sea, and air. Inthe terror scenarios, the 8 possible scenarios are considered for theterror attacks to the NPPs with several subjectively modified appli-

7 Infiltration and sabotage8 Suicide crash to the reactor

building or spent-fuelstorage by airliner

934 T.H. Woo / Nuclear Engineering and Design 265 (2013) 932– 937

Table 2Situation of world terror occurrence.

Sort 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Total

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There could be many works that are damaged by the infiltra-tion and sabotage. Usually a labor striking or civilian’s intrusioncould be an angry demonstrator who can destruct anything in thesite. Therefore this kind of case could be severer than the case of

Table 3Likelihood of event occurrence.

Likelihood Frequency (1/year)

Explosion 209 334 487 1111 1569

Armed attack 222 281 323 548 1030

Etc. 2 9 2 29 45

A truck bomb Attack by boat Suicide attack by small aircraft Frontal assault with small arms Attack with rockets or medium artillery Sabotage to the power lines Infiltration and sabotage Suicide crash to the reactor building or spent-fuel storage byairliner

The nuclear terror is analyzed by the aspect of nuclear bombanufacturing. Nuclear weapons are inherently terrifying due to

heir lethality (PROS, 2012). The nuclear, chemical, and biologicaltuffs have been tried to be used in the terrorist related groups. It isaid that the nuclear terrorism is initiated from buying the nuclearomb in the black market or stealing for the nuclear facilities likehe NPPs.

In the past time, the terrorist organizations and individuals havettempted to make use of the biological weapons which could pro-uce the destructions. The notorious incident, the anthrax letterttacks in the United States showed the public and social confu-ions widely. Especially, the nuclear terror is a method of attackingo NPPs, stealing nuclear material from NPPs, and producing nuclearombs by the nuclear material like the Pu-239 or Pu-241.

. Method

These 8 kinds of terror scenarios are analyzed to examine theangerousness which is analyzed by modified terror consequencend defense-in depth level of terror attacks to nuclear power plants.here are 8 possible cases for the terror scenarios in the exampledPP.

.1. Scenario #1: a truck bomb

It is considered that the truck bomb could affect on the externalart of the site and the least damage on the reactor containmentuilding and nuclear fuel storage facility. Hence, it is less dangeroushan the other scenarios. If the terrorist would like to select therucial method with this method, it is needed to prepare againsthe possible attack.

.2. Scenario #2: attack by boat

Considering the location of NPPs which are installed near theeashore, the possibility of the attack by boat in the sea is verymportant. This could be happened in some countries where thelant sites are located on the seashore like the case of the Republicf Korea. The foreign ship and submarine can get to the plant placeomparatively easily. The marine police should guard from the ter-or attack from the sea. However, the guarding could be failed

ollowing the situations. Especially, when the weather is very bad,t is very difficult to detect the strange substance in the sea. If the

issing of the unidentified object in the sea, the terror attack coulde possible easily.

1649 1630 1680 1664 1768 12,1011510 1343 1486 946 1302 8991

13 10 14 88 110 322

3.3. Scenario #3: suicide attack by small aircraft

This case could be a stronger method to the reactor building,dry storage cask and nuclear fuel storage pool by aircraft crashmethod (NCPA, 2001). The most plausible target is nuclear fuelstorage pool by airplane collision. According to General Electric’sstudy, although several thousand bomb installed crash would behappened, the radioactive material contaminations are negligible(NCPA, 2001).

3.4. Scenario #4: frontal assault with small arms

With small arms, the NPP could be attacked by the terrorists.Once this case happens, the site is in emergency situation and thesecure procedures are in action. The plant is in maximum alertstates by Trip and Shutdown methods in order to stop the oper-ations. This case is considered less dangerous than the case of‘infiltration and sabotage’ and ‘suicide crash to the reactor buildingor spent-fuel storage by airliner’, because the containment buildingcan withstand against the small arms.

3.5. Scenario #5: attack with rockets or medium artillery

This is an attack case comparing to the previous one withstronger arms attack. For example, the portable rocket or bazookafor tank attack is considered. However, this case could be protectedby the containment building by the concrete steel materials. It iscertain that the attacked building should be recovered as soon aspossible for stability.

3.6. Scenario #6: sabotage to the power lines

It is very easy to make this attack, because all power lines arenot protected from plant site. It is nearly impossible to protect allpower lines thoroughly, because the power lines are installed nearthe lower populated areas. Due to the NIMBY (Not In My Backyard)phenomena for the NPP, the plant site is located around seclusionplaces. If the external load supply line is disconnected, turbine tripvalve is activated to stop the steam supply to turbine and the elec-tricity generation stops. In addition, the battery or diesel drivenmotor is installed. This is also useful for the motor operation likethe case of Fukushima’s flooded motor in order not to happen thecoolant supply failure.

3.7. Scenario #7: infiltration and sabotage

Rare 0–100Often 101–1000Frequently 1001–10,000Very frequently >10,000

T.H. Woo / Nuclear Engineering and Design 265 (2013) 932– 937 935

Table 4Likelihood of terror occurrence of scenarios.

Sort Scenario number Likelihood Related example

Explosion 1 1210.1/year, frequently Explosion in Oklahoma government complex in April 19, 1995

Armed attack 2 899.1/year, often USS Cole was attacked in Aden, Yemen at October 12, 20003 Small airplane crashed to the Internal Revenue Service (IRS) building

in Austin, Texas at February 18, 20104 Gun shooting in Holocaust Museum near the White House by a white

people with white supremacy in 20065 Rocket attack to Untied States chancellery in Benghazi, east Libya at

September 11, 2012

Etc. 6 32.2/year, rare Disconnection and abstraction to the power lines with attacks byrocket and vehicle by resistance in recovery site in Iraq

7 Occupation and strike in Pyung Tack complex of Ssangyong Motorsagainst the restructuring from May 22, 2000 to August 6, 2000

8 Airliner crash terror to World Trade Center and Department of Defensebuilding in September 11, 2001

Table 5Classification by terror attack.

Level Consequence

7 Major accident Accident High6 Serious accident5 Accident with wider consequences Medium4 Accident with local consequences

3 Serious incident Incident Low2 Incident

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Table 7Defense-in-depth by level.

Consequence Level Defense-in-depth condition

Low 1 Conservative design and high quality inconstruction and operation

Low 2 Control, limiting and protection systemsand other surveillance features

Low 3 Engineered safety features and accidentprocedures

Medium 4 Complementary measures and accident

Even if it is easy to approach to the spent fuel storage facility,the jet fuel of the crashed airliner is floated on the water of the stor-age and the water is not to be steamed (NCPA, 2001). However, if

Table 8Strategy by combinations of detection, delay and response.

1 Anomaly

0 Deviation Deviation

/11 terror attack (NCPA, 2001). Since the attacks inside of thelant could provoke the damage of facility, this would be consid-red to be severer than the outer attack of 9/11. The reason the/11 case is compared is that this is imagined as the worst terrorase in the history considering unexpected and innocent deaths.ut, it is not possible for the intruder or demonstrator to reacho reactor core, because there are many gates to the reactor coren which the permission is necessary to pass each gate. If there isne person who knows well the plan situation, it is easy to geto the reactor core. Even though one could get to the place, it ismpossible to steal the nuclear fuel without the suitable equip-

ents. The person could be dead by high radiation exposures ifhe coarse equipments are used. However, if a guy would like to

ake a suicide attack in the reactor core, it is very clear the cases the 2nd Fukushima disaster where the building destructions andnvironmental contaminations would be produced.

.8. Scenario #8: suicide crash to the reactor building orpent-fuel storage by airliner

Although this case has not been studied by Nuclear Regula-ory Commission (NRC), if airliner crashes to the rector building,he reactor core vessel could not be broken, but be cracked in theontainment building significantly (NCPA, 2001). The fire by crash

able 6onsequence of terror attack.

Scenario Consequence

1 Low2 Medium3 Medium4 Medium5 Medium6 Medium7 High8 High

managementMedium 5 Off-site emergency response

could make the steam explosion which can release the radioac-tive material like the Iodine, Cesium, and noble gases and the coredamage can start (NCPA, 2001). Eventually, eternal core damagecan start like the cases of the Fukushima, Chernobyl, and ThreeMile Island (TMI) cases. If the crash attack is expected, the con-tainment building ventilation should begin to remove hydrogengas to inhibit the steam explosion. Certainly, the control rod andshutdown system should be operated immediately.

If the spent fuel storage facility is attacked, the situation isdifferent from the case of the containment building, because theradioactive material could be released to the atmosphere, althoughthe energy of spent fuel is lower. Usually, the spent fuel is cooledin the storage facility where it is 9–10 feet’ height and 5–10 years’period. Then, it is sent to the dry cask (NCPA, 2001).

Defense-in-depth condition Strategy by combinations of detection,delay and response

Conservative design and highquality in construction andoperation

Detection in initial stage of event regardingHuman factor

Control, limiting and protectionsystems and other Surveillancefeatures

Detection by surveillance facility (corestability and thermal inertia, inherentplant facility like abnormal operationcontrol system)

Engineered safety features andaccident procedures

Delay of plan deterioration

Complementary measures andaccident management

Delay of plan deterioration. Emergencyresponse of inner-plant part

Off-site emergency response Delay of plan deterioration. Emergencyresponse of external-plant part (externalemergency response is a preventionsmethod of accident)

936 T.H. Woo / Nuclear Engineering and Design 265 (2013) 932– 937

Table 9Strategy for physical protection.

Scenario Consequence Method

Detection Detection Detection

1 Low CCTV, guard Barricade Security, police, troops2, 3, 4, 5, 6 Medium CCTV, guard (including

coastguard), radar, residualcurrent protective

Floating barriers,coastguard boat,anti-aircraft gun, barricade,wire entanglement

Security, boat, helicopter,fighting airplane, police,repair

7, 8 High CCTV, guard, radar Barricade, anti-aircraft gun,airport security

Security, police, troops,fighting airplane

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Dry cask could make many radioactive material releases. Espe-ially, the Iodine-131 can affect to the thyroid (NCPA, 2001). Caskhould be strong to the airplane crash due to the thick concreteteel. If the airliner’s crash is expected, the cask should be hided ort is installed in the underground.

More severe case is mental and psychological panic to the peo-le. Angst, fret, and melancholy could be the big handicaps. Anyocial and economical behaviors are stopped. As time goes on, theituation is going to be normal by dispersion and diffusion of theadioactive materials.

Then, the likelihood of terror is obtained by the general terrorncidents which are announced by several agencies. Using theseata, the likelihood of terror is made. Also, the consequence of ter-or is classified by the IAEA scale by DBT. The physical protectionethod is produced where the defense-in-depth constraints and

evere accident countermeasures are considered. Eventually, thePS is constructed.

. Results

It has been known that it is necessary to strengthen the prepa-ation of the intentional approach and damage in the consequencef safety following the physical damage of the facilities in theperating NPPs after the Fukushima accident. Terrorists attack sce-arios are analyzed in this work to their likelihood and potentialafety impact on large light-water cooled NPPs, based on pastttacks on large-scale public facilities. By qualitative research onPS, terrorists attack scenarios and safety impacts have been exam-ned for the case of large light water reactors operating in sea shorenvironments.

The study for safeguard in operation is developed using analyt-cal methods which is in Fig. 1. The terror scenarios are introducedy 8 cases. Then, the likelihood of terror is classified by the gen-ral terror incidents. The consequence of terror is classified by theAEA scale by DBT. The physical protection method is suggestedy defense-in-depth constraints and severe accident countermea-ures for PPS constructions.

An analysis for terrorists attack to nuclear power plants isocused on the likelihood and potential safety impact for each sce-ario, in which these large light water cooled reactors are mostly

ocated on sea shore. IAEA event scale is employed to classify theeverity of potential attacks on safety ramifications. As potentialounter-measures, phased response options are studies. Based onhe likelihood of occurrence of terrorists attack scenarios and con-

equence on the plant safety, three phases of counter actions areonsidered for physical protection. The detection phase is per-ormed where the sensor respond to attempts and initiates anlarm. Various information from sensors is reported and analyzed

strengthening

for potential scenarios. Detected information is assumed to be sub-jected to personnel assessment and judgment to determine if thealarm reflects true situations. The delay phase provides means ofdelaying adversary actions. Delaying an adversary action is an effec-tive method of giving the security forces necessary time to respondand to interrupt the adversary attacks. The response phase con-sists of the actions taken by the counter-terrorism force to preventfull adversary impact based on responding measures, contingencyplanning, communication and interruption.

The situation of world terror occurrence is obtained by the 3classifications as explosion, armed attack and which are in Table 2(Terrorism Information Integration Center, 2012). The likelihood ofevent occurrence in Table 3 is decided basically by expert judgment.For example, the similar system is shown in the risk frequencyof the general event (Berg, 2010) which is analogized for thelikelihood of event occurrence for terror incident. The commoncharacteristics of the accident in general event and terror in thispaper are ‘failure incident’ and ‘unusual incident’. As it is known,the incident in NPPs happens with uncertainty which could pro-duce the failed and unusual event. Table 4 shows the likelihood ofterror occurrence of scenarios where related examples are listedby general cases (Chosun Ilbo, 2012; Hankook Ilbo (USA), 2010;Joongang Ilbo (LA), 2006; Joongang Ilbo, 2009, 2012; Wikipedia,2012a,b, 2013). The classification by terror attack is done by severaldocumentations which are in Table 5 (Hagemann, 2009; IAEA, 1999,1980, 2012b). Table 6 has the consequence list in each scenario.There is the defense-in-depth by level in Table 7 and the strategyby combinations of detection, delay and response in Table 8 (IAEA,1996). The strategy for physical protection is shown in Table 9(KINS, 2011).

5. Conclusions

The severe damage to NPPs by terror could produce the danger-ous situation like the case of Fukushima disaster. Therefore, it isa conclusion to study the protection systems in security methods.By this background, this work modeled 8 cases of terror incidents.The likelihoods and occurrences of the 8 terror cases have beenanalyzed. The likelihoods are obtained by the general terror cases,because the data of terror cases in NPPs are not opened to pub-lic. So, the likelihood is analyzed by the general terror cases. Tomake the objective standards of the classification of occurrences,DBT is sorted as IAEA scale. This DBT is categorized as the energy ofnuclear material and consequently the destructive degree is clas-sified. Like this situation, IAEA level could show the consequencesfor how event or accident is destructed in NPPs. That is to say, the‘terror attack’ is sorted as ‘destructive degree’, then this ‘destruc-

tive degree’ can be implied by ‘consequence degree’. ‘A truck bomb’case is low in consequence. ‘Attack by boat’, ‘Suicide attack by smallaircraft’, ‘Frontal assault with small arms’, ‘Attack with rockets ormedium artillery’, and ‘Sabotage to the power line’ have medium

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evel consequence. ‘Infiltration and sabotage’ and ‘Suicide crash tohe reactor building or spent-fuel storage by airliner’ have highestevel in consequence.

The IAEA level of DBT is used for the strategy for physicalrotection which is concluded for the final protection strategiesKINS, 2011). Severity of potential progresses of an initiating acci-ent is taken into consideration to identify appropriate emergencyesponse treatment to minimize hazard to site personnel and theublic. It has been suggested to implement a variety of counter-errorism methods including barricade reinforcement, coastguardtrengthening, airport security strengthening, anti-aircraft defenseystem, anti-missile defense as well as measures to counteractotential sabotages.

In addition, the international cooperation is needed for success-ul PPS. Especially, there were announcements in Nuclear Securityummit as control and unification of nuclear security structure,trengthening of IAEA role, usage minimization and safe manage-ent of high enrichment uranium and plutonium, safe control

f radioactive material, unified approach of nuclear security andafety, strengthening of carrying security, prohibition of illegaluclear bargaining, developing and cooperation of nuclear iden-ification, and international cooperation (NSS Seoul, 2012; Chun,012).

The data in this paper are used by general event cases. Hencet is needed to study using the revised data where the possibleerror cases in NPPs have tendency of rare, limited, and overwhelm-ng affected damages. It is important to make a successful PPS bydjusting the discrepancy between the real data in NPPs and theeneral terror data. Additionally, it is suggested to make the newlyeveloped NPPs where the PPS is equipped from the construction.lso, the education of the operating personnel preparing for theossible terror attacks. Finally, the national agency is proposed toontrol the terror incident in NPPs. The new agency for manage-ent in terror of NPPs is imagined under the United Nation (UN),

ecause the cooperation with IAEA, an organization of the UN, isasy. The technology transfer for terror protection to other indus-ries is an advice for the future work.

cknowledgements

The author thanks to Dr. I.S. Hwang, Dr. M.S. Jae, and Dr. H.G. Jooor their research discussions.

Design 265 (2013) 932– 937 937

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