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atw Vol. 63 (2018) | Issue 1 ı January ENVIRONMENT AND SAFETY 22 | | Fig. 1. Schematic showing the general ranges of applicability of the 3 methods of Fault Analysis 2,3 . attitudes in organizations and individuals which establishes that, as an overriding priority, protection and safety issues receive the attention warranted by their significance” [9]. The development of a good safety culture requires a transparent approach to information sharing and dissemination. This helps ensure that incident reoccurrences can be prevented, and others who may be using the same or similar equipment, techniques or procedures can review their arrangements to prevent a similar incident. “The existence of a good safety culture is a prerequisite for the implementation of a good safety case. The converse is also true” [10]. This enables a good safety case to be translated into beneficial changes in behaviour associated with the existing safety culture and arrangements for the management of safety. Practicing a graded approach to safety ensures that the effort expanded is proportionate to the possible consequences. Figure 1 is from the Office for Nuclear Regulation Safety Assessment Principles [11] and shows the applicability for the methods of fault analysis; PSA, DBA and SAA. Thus more assessment effort is expended on those higher consequence and higher frequency events. 2) Office for Nuclear Regulation [11]. 3) Target 4 (BSL): ‘ Target 4 is intended to provide a broad indication of where DBA might be expected to be applied’ [11]. BSL – Basic Safety Level 4) Based upon a Sandia National Laboratories diagram | | Fig. 2. Design and Evaluation Process Outline 4 . techniques to demonstrate the effectiveness of defence in depth, such as: • Design Basis Analysis (DBA): to ensure that the design is robust, fault tolerant and has effective safety measures; • Probabilistic Safety Analysis (PSA): to ensure risks are acceptable, understand inter-dependencies and to evaluate failures; and • Severe Accident Analysis (SAA): to determine further practicable measures to improve defence in depth. The hierarchical view deviations, incidents and accidents for nuclear facilities is compared against five levels of defence in depth [7] for safety: • Preventing deviations from normal operations; • Controlling deviations from operational states; • Controlling accidents within the design basis; • Mitigating accidents and ensuring confinement of radioactive materials; and • Mitigating the radiological consequences of radioactive releases. This hierarchical view allows designers, operators and others to identify where they can most effectively contribute to maintaining safety. The Safety Case is a well-documented approach normally used by regulators for proportionally assessing the safety submissions against the radiological hazards presented. Safety cases are typically defined as a “ structured argument, supported by a body of evidence that provides a compelling, comprehensible and valid case that a system is safe for a given application in a given operating environment” [8]. For the safe operation of a nuclear site, facility or activity an effective safety culture needs to be in-place and fostered. Safety culture is defined as “The assembly of characteristics and 4.2 Security A number of methodologies are used in security to increase the likelihood of creating and maintaining secure operations. An example holistic approach is the Design and Evaluation Process Outline (DEPO) (Figure 2) [12]. The physical protection system (PPS) is developed from determining the targets to be protected from the postulated malicious capabilities, and then designing for delay, detection, assessment and response. Vulnerability assessment is undertaken to ensure that the PPS is likely to be effective and depending on the outcome the design will be refined or implemented. However, a number of assessment techniques need to be deployed and the associated performance measures calculated and considered for operational acceptance. For example, a sensitive detector with a high probability of detection may detect all intrusions but have a high false alarm rate such that responders ignore the alarms being received. Defence in depth for security [7] comprise layers of physical and Environment and Safety Nuclear Safety, Security and Safeguards: An Application of an Integrated Approach ı Howard Chapman, Jeremy Edwards, Joshua Fitzpatrick, Colette Grundy, Robert Rodger and Jonathan Scott
atw Vol. 63 (2018) | Issue 1 ı January | | Fig. 3. Schematic showing the general ranges of applicability for 3 security assessment methods. technical measures, along with operational and procedural protection that have to be overcome or circumvented by an adversary. The defence in depth approach should be applied in the following order: • Detecting a potential malicious act; • Delaying the adversary to allow an appropriate response; and • Responding to or neutralising the attack. Risk management techniques also need to be used to balance investment required to prevent high consequence low probability events and low consequence high probability events without putting an unnecessary burden on operational processes. A State’s Design Basis Threat (DBT) [13] details the capability and capacity of the malicious actors that any PPS should counter to maintain the security of nuclear material and other radioactive materials. Using that as a basis for the threats, scenarios should be developed that will be used in vulnerability assessments to determine how effective the security arrangements are likely to be in practice. Any weaknesses should be identified so that compensatory or enhancements in the arrangements can be implemented. The type and quality of assessment techniques that should be undertaken is suggested in Figure 3. The Nuclear Security Case 5 , part of the Nuclear Site Security Plan, is a more recent development than the Safety Case. Like the safety case the security case “should justify the claims, arguments and rationale for the ‘duty holders’ security regime by substantiating the security arrangements for a site, plant, activity, operation or modification. It should provide written evidence that the relevant security standards have been or are going to be met. It should also demonstrate that the risk posed by malicious activity has been reduced as far as could be reasonably expected” [14]. As with the safety case effort should be expended to reviewing security as a system rather than as individual components. Risk management techniques are used to manage any variations between the optimal arrangements and what is in currently in place, particularly when a possible vulnerability is identified. Vulnerability assessment techniques to determine the performance of security arrangements involve many aspects of the system performance including the probability of detection, probability of interruption, probability of neutralisation and probability of effectiveness. The IAEA Nuclear Security Assessment Methodology (NUSAM) Co-ordinated Research Programme (CRP) has been establishing a risk-informed, performance-based methodological framework for nuclear security assessment at sites, facilities and activities so that practitioners will be better informed of the approaches and techniques that can be used, and those that provide the most effective assessment and value for the different facility type. The CRP also allows the different methods to be compared and helps to identify the comparative strengths, weaknesses and limitations of the alternative approaches. This should ensure a consistency of approach in security assessment, and therefore by implication a baseline standard for international approaches. As in the case of safety for the secure operation of a nuclear site, facility or activity, an effective security culture needs to be in-place and fostered. Security culture is defined as “The assembly of characteristics, attitudes and behaviour of individuals, organizations and institutions which serves as a means to support and enhance nuclear security” [15]. Security and safety culture are both based upon the principles of adopting a questioning attitude, rigorous and prudent approaches, and effective communication. 4.3 Safeguards Underpinning and implementing the principles within the Non-Proliferation Treaty (NPT) the main approaches used by the safeguards community for the protection of civil nuclear material preventing it from being redirected into weapons activities is ‘Safeguards by Design’ [16] and nuclear materials accountancy and control (NMAC). The physical arrangements including Tamper Indicator Devices, multiple barriers, NMAC and facility arrangements such as Material Balance Areas provide additional measures for defence in depth aiding the inspection of material and the ability to detect potential diversion. Inspection and material characterisation activities are used in decision analysis to determine whether the plant or facility is operating to specification and agreement. Safety, security and safeguards broadly follow the same principles to achieve protection. 5 3S synergies The synergies and major considerations in the nuclear 3S are shown in Figure 4 [17]. This identifies the main issues and considerations within the 3S and where they intersect and overlap, irrespective of the type of regulatory regime. 5.1 Triple S Moving into the practice of 3S, through the applications of methods and techniques we use the term Triple S. Thus, when Figure 4 is revised with a selection of typical, but not exhaustive, activities and assessments 5) Part of NNL’s approach to demonstrating compliance with ONR’s Nuclear Security Assessment Principles (SyAPs). ENVIRONMENT AND SAFETY 23 Environment and Safety Nuclear Safety, Security and Safeguards: An Application of an Integrated Approach ı Howard Chapman, Jeremy Edwards, Joshua Fitzpatrick, Colette Grundy, Robert Rodger and Jonathan Scott
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