Physical protection measures

DiD concept applied as a basic principle for PP design should provide several layers of protection (security zones and structural barriers between them) and protection methods to prevent threats and mitigate potential consequences of intrusion. To achieve this protection measures of detection, delay, and response are used in a complementary manner. Also, preventive measures such as deterrence and access control are used against threats. Both technical organizational aspects are important when these are implemented. (IAEA 2018b, 38,40, 66-68, 76-82).

Detection is accomplished by using hardware (sensors, monitoring, and communication systems) and human surveillance (guard patrols). Detection is not instantaneous since an alarm triggered by a sensor (or human observation) must be transmitted, reported, and eventually assessed by security personnel before the process is complete. The time needed for detection is defined as detection time. The shorter the detection time, the more likely the response is to be executed in time. Diversity is achieved by using different sensors, which do not respond to the same nuisance alarms. Redundancy is provided using multiple complementary sensors and human surveillance. The central alarm station (CAS) is established to enable monitoring, assessment of alarms, and communication between both guards and response forces. The reliability of communication and alarm transmission is ensured by using redundancy (multiple communication systems and secondary alarm station SAS), diversity (different physical paths), and separation. (IAEA 2018b, 60, 66, 76-78).

The purpose of the delay is to slow an adversary’s progress towards a target, thereby providing time for a response to be initiated. Delay is accomplished by distances and areas that must be crossed without getting detected and by using barriers that need to be bypassed or defeated (e.g., fences, gates, doors, locks). The use of multiple layers of diverse physical barriers complicates the attempted intrusion and increases delay time. Detection systems and barriers should be used in a complementary manner to enable immediate detection of intruders before the barrier is reached to provide time to respond after detection is completed.

(IAEA 2021b, 97-98; IAEA 2018b, 67-68,78-79).

The response aims to interrupt and neutralize an adversary and mitigate the potential consequences of an act. The response forces consist of persons on-site (nuclear security officers) and off-site (law enforcement agencies) who are properly trained, appropriately

equipped, and armed to manage the threats. The guards, in turn, are responsible for monitoring and assessing alarms, patrolling the area, controlling access, and providing detection of intrusion. However, guards may also provide an initial response depending on national legal practices. A command center is established for communication between on-site response forces and CAS, plant operations, and off-on-site response forces. (IAEA 2018b, 68, 80-82; STUK 2021, 11,13-14, 19).Figure 14 demonstrates the relation between functions of detection, delay, and response.

Figure 14. The relation between detection, delay, and response. The adversary task time is the time adversary needs to complete the act. The PPS response time is the time needed from the first successful sensing until the adversary can be interrupted. In this figure, first sensing occurs early enough to allow the interruption. (IAEA 2018b, 59).

Deterrence can be used as a preventive protection measure by promoting the effectiveness of PPS. This may lead the NPP to be an unattractive target as the low probability of success and possible negative consequences may override benefits. The drawback is that some security-related information may require to be made public to communicate adversaries about the effectiveness of PPS. Concerning insider threats, deterrence can be a way to protect against malicious acts (e.g., promoting continuous monitoring and surveillance of activities, and using the two-person rule for entry into a vital area). (IAEA 2021b, 4-5; IAEA 2018b, 66; IAEA 2019b, 125-126).

The access control of people, material, and vehicles can be seen as a preventive measure since its main objective is to allow only authorized persons and vehicles to enter certain areas and to ensure that access rights are granted only for those whose trustworthiness and actual

need are confirmed by following appropriate procedures (e.g., trustworthiness check, identification measures, surveillance, and records). However, access control also provides detection for unauthorized access and prohibited or stolen material/equipment (e.g., alarm and identity verification systems, search systems for explosives, NM and metal detection, guard surveillance) and delay by use of barriers such as portals, turnstiles, and vehicle gates.

(IAEA 2021b, 73-97; IAEA 2018b, 79-80; IAEA 2013b, 32-33; IAEA 2011a, 23,25,55).

The PP measures indicate an analogy between security and safety in respect to the functional DiD concept, which for safety aims to maintain the integrity of structural barriers using functional measures aiming for prevention and mitigation. The delay (area and structural barriers) and detection (hardware and human observation) could be thought of as similar

‘barrier’ which ‘integrity’ (to keep adversaries from progressing towards HRC targets) is aimed to be maintained by functional measures such as prevention (e.g., deterrence and access control) and mitigation (response). Deterrence, delay, detection, and response could also be thought of as fundamental security functions.

In respect to nuclear security, adversaries can be seen as challenges for which PP measures are implemented to cope with and to ensure the integrity of the barrier (security zone and its surrounding physical barriers) used to keep threat from progressing towards higher level (targets with HRC). Adversaries as challenges to the PPS are induced by their capabilities and preventive measures are established as provisions to prepare for these. Similar objective tree could be drawn for security as it was previously presented for safety (figure 15).

Figure 15. The interrelation between protection measures, challenges (adversaries), and provisions for a threat level or a security zone.

Figure 16 demonstrates such DiD concept and provides some examples for each protection measure.

Figure 16. The PPS design in respect to DiD concept with example protection measures.