Материал: Крючков Фундаменталс оф Нуцлеар Материалс Пхысицал Протецтион 2011

Two steps are involved in efficiency assessment. Step 1 is a preliminary PPS efficiency assessment based on an engineering analysis. Step 2 is the final PPS efficiency assessment using dedicated software.

The work sequence is as follows:

∙formation of the work unit and a meeting of experts on the NI PPS efficiency assessment;

∙acquisition of initial data for the NI PPS efficiency assessment;

∙development of a formalized NI description;

∙NI PPS efficiency assessment as applied to an external threat;

∙NI PPS efficiency assessment as applied to an internal threat;

∙formulation and analysis of the NI PPS efficiency assessment results.

The PPS efficiency is assessed separately for external and internal threats.

For external threats, the PPS efficiency is assessed as applied to all NI vulnerabilities, given the attacker models developed in the NI vulnerability analysis and updated at the initial data acquisition and formalized site description stages.

When the efficiency indicator is estimated, it is assumed that the attacker, to defeat each PPS barrier, is free to choose one of the two following options:

∙option 1 – the external attacker, where possible, d efeats a PP barrier by stealth. This option is characterized by a low probability of detection and a long PB defeat time;

∙option 2 – the external attacker, where possible, d efeats a PP barrier rapidly, including using special force tools or explosives to destroy the PB. This option is characterized by a high probability of detection and a short PB defeat time.

For external threats, the PPS efficiency shall be assessed for both of the attacker action options.

The integrated indicator of the NI PPS efficiency for an external threat (Рext) is estimated from the expression:

where J is the number of the attacker targets within the nuclear site; j is the weight factor that reflects the significance (category) of the j–th target;

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and Рext.j is the differentiated PPS efficiency indicator, i.e. the probability of the attacker act against the j-th target to be suppressed.

The weight factor j is determined by the work unit using the expert evaluation method.

The differentiated PPS efficiency indicator is estimated from the expression:

k =1

where K is the total number of separate response force groups (the perimeter alarm group and others) involved in the conflict developments when the nuclear site is intruded; and Рext.jk is the probability of the external attacker act against the j-th target to be suppressed by the k–th response force group.

Where several scenarios of the attacker actions against the j–th target are considered, the differentiated indicator of its protection efficiency is assumed to be equal to the minimum value for all considered scenarios.

The attacker action scenario that matches the value of the minimum probability of the action against the j-th target to be suppressed is assumed as critical.

The probability of the external attacker act against the j-th target to be suppressed by the k–th response force group is in a general case the function of:

where L is the total number of the PPS lines to be defeated by the outside attacker to reach the j–th target; Рdjl is the probability of the attacker act against the j–th target at the l–th PPS layer to be detected; and Рseiz.jkl is the probability of the attacker committing an act against the j-th target to be seized by the k–th response force group acting in response to sign als starting with the l–th PPS layer.

The probabilities of detection are assumed to be equal to the values of performance characteristic for the respective EPPFs as shown in specifications.

The probabilities of the attacker to be seized are determined from the following condition:

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The PPS efficiency for an internal threat is assessed as applied to all NI vulnerabilities, given the powers of different site personnel groups. A personnel group shall be understood as a group of the nuclear site staff members having similar rights of access.

Efficiency should be estimated separately for each personnel group. When the efficiency indicator is calculated, it is assumed that the

insider, to defeat each PPS layer, may choose any of the following two options:

option 1 – the insider clears a PP layer by virtue of his/her capacity using authorized access routes. In doing this, for a lower probability of the act suppression, the insider may attempt to throw prohibited items out of/into the PP area via channels not accessible to humans (piping, upperstory windows, mesh holes and so on);

option 2 – the insider defeats a PP layer “by force ” using the same unauthorized intrusion channels as the external intruder. It is assumed that the attacker defeats the subsequent PP layers also “by force”.

The PPS efficiency is assessed for an internal threat assuming that the attacker action scenario consists of two steps: he/she first enters a PP area by virtue of his/her capacity and then breaks through “by force”. Sometimes, the attacker action scenario may not include step 2.

Different combinations of tools and materials the attacker may carry into the site and use to break through to the target or to commit an act are considered during the assessment.

It is assumed during the assessment that the attacker, to commit an unauthorized action, may employ tools and materials present at the site for production or other purpose.

For each of the targets, the integrated indicator of the NI PPS efficiency as applied to an internal threat (Рint.) is estimated from the expression:

where I is the number of the onsite personnel groups attached to the target under consideration; γi is the weight factor equal to the relation of the number of the persons in the i–th group to the total number of the site personnel; Рint.i is the differentiated indicator of the PPS efficiency as applied to an internal threat, i.e. the probability of an act by anyone in the i- th access group against the target under consideration to be prevented.

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The differentiated NI PPS efficiency indicator is estimated from the expression:

where L is the number of the PP layers cleared by the insider by virtue of his/her capacity; Рint.il is the probability of the insider carrying prohibited or stolen items on him/her to be detained at the access control point of the l–th PP layer; and Рli is the probability of the insider acting “by force” from a sector beyond the l–th PP layer to be detained.

Where more than one scenario of the insider acts against the j–th target are considered, the differentiated indicator of its protection efficiency is assumed to be equal to the minimum value for all considered scenarios.

The probability of the insider carrying prohibited items or materials to be detained at an access control point is estimated, in a general case, from the expression:

where Р*sear is the probability of the insider to be searched; Рsear is the probability of prohibited items to be detected by search; Р*met is the probability of the insider to be searched with the aid of a metal detector; Рmet is the probability of metallic items to be detected with the aid of a metal detector during the search; Р*exp is the probability of the insider to be searched with the aid of an explosive detector; Рexp is the probability of explosives to be detected with the aid of an explosive detector; Р*NM is the probability of the insider to be searched with the aid of an NM detector; and РNM is the probability of NM to be detected with the aid of an NM detector.

Note. If the insider does not have a prohibited material or item on or with him/her, the probability of detection for the respective detector is assumed to be equal to “0”.

The probabilities of the insider acting “by force” to be seized (Рli) are found in the same way as the probabilities of seizing the outside intruder. This does not take into account the PP layers cleared by the insider

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