Checking incoming correspondence for the presence of explosive devices and radioactive substances.

Checking incoming correspondence for explosive devices and radioactive substances.

CHECKING INCOMING CORRESPONDENCE (LETTERS, PARCELS)
FOR EXPLOSIVE DEVICES AND RADIOACTIVE SUBSTANCES

Source: Special Equipment magazine

1. INTRODUCTION

One ​​of the main channels for delivering sabotage and terrorist weapons worldwide is the postal channel. Special postal items equipped with explosive devices (ED) are manufactured for mailing.

Mail or other means of delivery of correspondence is an almost ideal method of delivery of explosive devices to the target. This is determined by two reasons:

• wide possibilities of camouflage and technical design of explosive devices;
• confidentiality of messages protected by law or moral and ethical standards.

This allows terrorists to choose the most effective way to achieve their goal: the order of delivery, the type of mail, the design of the explosive device, the method of its activation.

Many countries have created services to combat terrorism in the postal channel, statistics are kept on the use of the postal channel for terrorist purposes, which for obvious reasons are not widely published. Only the most notorious cases become known to the public. The number of explosive postal items (EPI) sent by mail in Western European countries in the 1980s amounted to several dozen per year (International Security Review).

Therefore, in the system of comprehensive protection of protected facilities from the use of sabotage and terrorist means (STM), an important place is occupied by control of the postal channel. For this purpose, a control point must be organized and equipped with special equipment, through which all correspondence arriving at the protected facility passes.

This article presents the main approaches to solving this issue, gives recommendations on the selection of technical means, technology for examining incoming correspondence, training personnel, and ensuring explosion protection.

2. DESCRIPTION OF TYPICAL EXPLOSIVE POSTAL ITEMS

Based on the general purpose of using explosive postal items, they are divided into the following main groups:

• explosive postal items with explosive devices intended to defeat the addressee when opening the package or removing the contents; when examining the item using organoleptic and instrumental methods;
• explosive postal items with explosive devices intended to defeat the control system;
• VPO with explosive bookmarks (without detonating devices), intended for the manufacture of sabotage and terrorist means (STM).

A wide range of circuit solutions, design elements and substances can be used in the manufacture of VPO.

The general scheme for constructing VPO contains the following main parts:

• camouflage;
• actuator (detonator);
• initiation means;
• warhead.

The interaction of the specified parts consists of transmitting such initial effects on camouflage as opening the package, probing, X-ray irradiation, etc. through the fuse to the initiating means, the activation of which sets the warhead into action.

Knowledge of the basic diagram of the VPO and their specific implementations allows for a targeted examination of the PO and the correct correlation of the identified elements in the controlled objects with their role in the design of the VPO.

Below we consider realistically feasible typical VPO containing the most common types of explosive devices and explosives.

One ​​of the main parts of the VPO intended for direct destruction of an object is the warhead, which is, as a rule, a concentrated charge of explosives. The destructive effect, characterized by such factors as a shock wave, fragments, high-temperature impact, depends on the design of the VPO, the mass and type of explosive charge, and the conditions for the activation of the VPO.

Excitation of explosives occurs in the form of a self-propagating chemical transformation with the formation of highly heated and high-pressure gases. Such chemical transformation of explosives is usually called explosive transformation. Explosive transformation, depending on the properties of the explosive and the type of impact on it, can occur in the form of an explosion or combustion.

The explosion spreads through the explosive at a high speed, measured in hundreds or thousands of meters per second. The process of explosive transformation caused by the passage of a shock wave through the explosive and proceeding at a constant (for a given substance in a given state) supersonic speed is called detonation.

The process of explosive transformation caused by the transfer of energy from one layer of explosive to another by thermal conductivity and radiation of heat by gaseous products is called combustion.

This process proceeds relatively slowly, with speeds not exceeding several meters per second.

In the manufacture of VPO warheads, high explosive (the most common group) or propellant (gunpowder) explosives are used.

High explosives include compositions whose characteristic type of explosive transformation is detonation. The following individual explosives are most widely used in such compositions: hexogen, PETN, octogen, tetryl, trinitrotoluene (TNT), nitroglycol, nitroglycerin.

In combination with various additives, the compositions can be solid (finely dispersed pressed or bulk mixtures), plastic, elastic, pasty (sheets, tapes, cords, other arbitrary shapes) in their aggregate state.

High explosives are not very sensitive to various types of external influences and detonation is initiated in them by an explosion of an initiating explosive, which is part of the initiating devices of the high explosive.

Propellant explosives include gunpowder and pyrotechnic compositions, which are characterized by explosive transformation in the form of combustion. The most common of these substances are nitrocellulose gunpowder (used in the manufacture of ammunition), black powder (hunting weapons), mechanical mixtures of oxidizer-fuel with various additives (pyrotechnic means). Propellant explosives are more sensitive to external influences and combustion is usually initiated by the combustion of elements of the means of initiating the explosive.

For known VPO, the initiation means are special assemblies made in the form of a cap-igniter, an electric igniter, a cap-detonator and an electric detonator. Industrially produced initiation means were mainly used, although the possibility of making homemade initiation means is not excluded, for example, in the form of an incandescent bridge or a spiral of a light bulb from a pocket flashlight. The purpose of the initiation means is to excite the warhead.

A primer-igniter, consisting of a cap filled with a special primer composition, closed with a copper cup, when pierced or struck on the bottom of the cap, produces a fire that is capable of igniting explosives.

For the same purposes, an electric igniter is used, consisting of a cylindrical body in which a plastic sleeve, an igniter composition and a glow bridge with current leads are placed.

The heating bridge is made of nichrome, platinum-iridium or constantan wire with a diameter of 9 to 50 microns. The mass (weight) of the cap composition for the indicated means of initiation is 0.02 — 0.15 g. The composition is a mechanical mixture of initiating explosive (up to 40%) with additives in the form of potassium chlorate, antimony, aluminum alloy with magnesium, barium salts, etc.

Unlike primers and electric igniters, detonator primers and electric detonators have a large explosive charge (up to 1.5 g) and, accordingly, large overall dimensions and weight.

The charge consists of layers of pressed initiating (up to 80%) and high explosive. The activation of the specified initiating means causes detonation of the explosive of the warhead.

A characteristic feature of initiation means is the presence of initiating explosives in the composition. Such substances are capable of explosive transformation from a minor mechanical (impact, injection) or thermal (heating of the coil) impulse. Of these substances, the most common at present are heavy metal compounds (mercuric fulminate, lead azide, lead trinitroresorcinate) and organic compounds (tetrazene and diazanitrophenol).

To activate the means of initiation, actuators are used that respond to certain actions with the explosive device. Such devices, called fuses, are divided into contact and non-contact. Contact fuses are triggered by mechanical action on the explosive device packaging (opening, probing the explosive device) or when removing the contents from it. In the overwhelming majority of explosive devices, contact fuses are made in the form of various types of devices for connecting electric igniters and electric detonators to the combat circuit. Such prevalence is due to the simplicity and relative safety of the design, easy accessibility of their elements, which are various contactors, current-carrying conductors and small-sized current sources. The specified fuses convert a certain impact into an electrical impulse.

Contact contactors, which are a mechanism for activating the igniter cap or detonator cap, are much less common. Such fuses are made in the form of a metal housing containing a spring mechanism for a movable pointed cylinder (striker). These fuses convert a certain mechanical impact on the explosive device into a kinetic impulse of the striker.

Non-contact fuses are devices that react to X-ray radiation and are designed to operate when X-ray methods are used to control explosive devices. Such fuses consist of a sensor (photodiode, photoresistor or small Geiger-Muller counters), a power amplifier (a set of radio components such as microcircuits, transistors, resistors, capacitors) and a contactor (electromagnetic relays, electronic keys). Non-contact fuses have been used very rarely (no more than a few times) throughout the history of using explosive devices.

The camouflage of most VPO consists of standard mass-produced envelopes (sometimes 2-3 envelopes nested inside each other), in which the combat chain is hidden by several layers of thick paper or cardboard. Another, also common method of camouflaging VU is a hollow niche in a hard cover (book, notebook) placed in a paper bag. Previously, various boxes were used, also placed in homemade paper bags. To protect against accidental damage on the mail channel, VPO are carefully sealed, sometimes additionally using adhesive tape and twine.

A wide range of people know about the use of X-ray control equipment. Certain methods of concealing the VU can be expected, such as camouflage with household items, sometimes sent in letters (keychains, badges, pens, musical greeting cards, etc.).

Concealment of a certain amount of explosives is carried out in such household items as chewing gum, packages with soft drink extract, perfume accessories, etc. A detonating cord with a core of heating element or hexogen enclosed in a protective shell was used as a warhead in a number of explosive devices, including in explosive devices. It is possible to send this cord without initiation means.

3. CHARACTERISTIC SIGNS OF EXPLOSIVE MAILINGS

Typical explosive devices belong to the class of explosive devices of the mine-blasting direction and are specially manufactured devices with a set of features indicating their applicability for producing an explosion. These features make it possible to distinguish explosive devices from a variety of ordinary explosive devices.

The following should be attributed to the generalized features due to the possibility of detecting explosive devices by organoleptic and instrumental methods:

• appearance and weight and dimensions of the packaging;
• presence of metal parts;
• characteristic shape of the elements of the VU and their relative position;
• presence of concentrated areas with a certain chemical composition.

The features that allow detection of explosive ordnance include features determined by their functional purpose and construction methods. These features pertain to such main parts of explosive ordnance as initiation means, fuses, and warheads. The design of these units and the method of their connection determine the functional diagram, operation mode, and type of explosive ordnance.

Tables 1 and 2 present generalized characteristic features of explosive ordnance in relation to detection methods and design features of the elements included in their composition.

Table 1 ORGANOLEPTIC METHODS OF SELECTION OF EXPLOSIVE ORDINARY ORDINARY PRODUCTS

Table 2. HARDWARE METHODS FOR DETECTING VPO

4. ORGANIZATION AND TECHNICAL EQUIPMENT OF CONTROL POSTS

When organizing a post for checking incoming correspondence for the presence of explosives, the following factors must be taken into account:

• average daily volume of incoming correspondence;
• composition of incoming correspondence: only paper bags, paper bags and packaging made of other materials, presence of large-sized packaging;
• possibility of the appearance of an explosive object.

These factors are decisive when choosing the location of the post, the area for it, the type and nature of the placement of special equipment.

The most difficult task is to control large flows of correspondence (tens of thousands per day). Solving this task requires a great deal of effort, the use of modern, productive control equipment. Usually, such flows also involve a significant number of large-sized packages.

Therefore, the control technology must be designed for high productivity, the ability to inspect large-sized packages, and ensure the protection of personnel from the possible explosion of large quantities of explosives (up to several hundred grams).

Figure 1 shows an approximate layout of the equipment of the premises of such a control post and the placement of equipment in them. In the case under consideration, it is better to equip the control post in a separate building. A storage facility for temporary storage of suspected explosive items before their transfer to the competent authorities can also be created here.

The figure does not show the location for provoking X-ray-sensitive detonators of the explosive device.

Recommended composition of the control post equipment:

• conveyor X-ray television introscope (RTI) with video control device (VKU);
• desktop metal detector for packages;
• desktop fluoroscope for packages;
• explosive vapor detector (portable device not shown in the figure);
• chemical kit for detecting microquantities of explosives (not shown in the figure);
• stationary or portable radiometer (dosimeter);
• explosion-proof container.

The list of equipment, its purpose and technical characteristics are given in Table 3.

Table 3

The task of controlling the mail flow is significantly simplified when several hundred mail items are received per day or per day. In this case, there is no need for a separate building. A separate room on the ground floor with windows that, if possible, do not overlook a crowded street is sufficient.

The bulk of the mail flow in this case, as practice shows, consists of paper bags and packages.

Large packages can be checked directly at the moment of acceptance using a portable rubber goods inspection device. If there is a suspicion of explosion hazard, they can be placed in a specially designated place in the courtyard. The placement of equipment for checking paper bags is shown in Figure 2. A special explosion-proof container of the ET-Ts-2 type should be used to store suspicious packages.

5. TECHNOLOGY FOR CONTROL OF INCOMING CORRESPONDENCE

Based on the proposed organization and equipment of checkpoints, the following mail inspection technology can be adopted for a mail flow of thousands and tens of thousands of units per day. Large-sized packages and paper bags in sacks or boxes are delivered to the RTI conveyor. The video control device (VKU) from the RTI and the operator are located in the adjacent room behind the explosion-proof wall. If there is no suspicion of explosion hazard, the mail that has passed through the RTI is transferred further for undelivering. If suspicions arise, large-sized packages undergo additional inspection using an explosive vapor detector and a chemical kit. If the suspicions are confirmed, the package will be placed in a temporary explosion-proof storage facility until the arrival of the competent authorities.

If a suspicious paper package is found in a sack or in a box, by successively dividing the entire number of packages in half and conducting additional checks for rubber products, a suspicious pack of envelopes or a suspicious package is identified, which are sent for additional checking with a metal detector and fluoroscope.

If the package is confirmed to be suspicious after fluoroscopy, it is also transferred to the VPO storage facility until the competent authorities arrive.

With a correspondence flow of no more than several hundred packages per day, it is possible to organize individual control of each package at once. With such a flow, large-sized packages will constitute units and, as already noted, can be controlled using cheaper portable RTI. When using the recommended equipment, the estimated time for one controlled unit will be 20 seconds.

Simultaneously with monitoring the mail flow for the presence of VPO, it is recommended to conduct monitoring for the presence of radioactive substances (RS).For its implementation, both stationary and portable radiometers can be used. The control process easily fits into the technology of checking for the presence of explosives. It can be carried out by monitoring the radiation background near the place of mail reception (in the case of large flows), or by measuring the radiation from each package. If you use radiometers with a response time of 1 — 2 seconds, then the performance of the control will remain virtually unchanged.

When checking an object on a rubber or fluoroscope, the operator observes its contents on a shadow X-ray image. The operator's task is to identify the explosive or its elements on this image.Considering that objects can have complex contents, and the explosive devices can be camouflaged, this task can be quite difficult. Therefore, the operator must undergo special training in working with X-ray images and acquire the appropriate skills. Then, during the work process, he also needs constant training in recognizing the elements of the explosive devices.

To prepare and train operators, it is necessary to have special test samples — models of the explosive devices elements.

Test samples may not repeat the design of the explosive devices completely, since this is not an easy task, but only reproduce their individual units in combination with extraneous camouflaging objects.

The operating procedures for the explosive vapor detector, the chemical rapid analysis kit, and the desktop metal detector are detailed in their operating manuals. Operators also need training to master these devices. However, there is no subjectivity in decision-making when working with them.

6. SAFETY MEASURES WHEN WORKING WITH THE EQUIPMENT AND HANDLING MAIL

When organizing mail flow control, sufficient safety measures must be provided to protect the working personnel in the event of a detonation of a detonator located in the VPO. An explosion may occur due to the impact of some random causes from the inadvertent activation of a detonator during manipulations with the VPO or, finally, if the VPO is equipped with a detonator that is triggered by the impact of search equipment. Detonators may be sensitive, for example, to the impact of X-ray radiation.

Therefore, to ensure the safety of personnel, the following organizational measures are necessary:

• all work on checking mail items must be carried out either in special explosion-proof rooms or in rooms in which the impact of an explosion on other rooms is minimized (a separate building, a room with one or two adjacent load-bearing walls, etc.);
• any technological operation must be carried out by the necessary minimum of service personnel;
• no unauthorized persons must be present in the mail control rooms;
• technical protective measures must be provided when using X-ray control equipment.

Explosion-proof rooms are built according to special designs based on the maximum possible explosion power. Such a room is shown schematically in Figure 1.

To reduce damage from the explosion of explosive devices when exposed to X-ray radiation during the control of large mail flows, provocation of X-ray-sensitive fuses can be used. For this, mail in bags or boxes is exposed to relatively powerful X-ray beams. After this, the mail is transferred for control for the presence of explosive devices.

In case of small flows, X-ray control is performed on a desktop X-ray fluoroscope. This device must have technical means of protection: a reinforced front panel, a knock-out rear wall, a remote control.

The desktop fluoroscope recommended in this manual provides protection against an explosion of an explosive charge with a power equal to 60 g of TNT.

The correct installation of this device is opposite a window facing an inner courtyard or a sparsely populated area of ​​the street. A special storage facility for temporary storage of mail items selected as suspicious for the presence of explosive devices should be provided. For large-sized mail items, it can be equipped in an explosion-proof room, as shown in Figure 1, or in the yard.

The simplest temporary storage facility can be a hole in the ground up to 1 m deep at a distance of at least 1.5 m from buildings.

A special explosion-proof container can be used for temporary storage of packages weighing up to 100 g and with dimensions not exceeding 615x412x400 mm.

7. CONCLUSION

Among the existing channels for covert delivery of TDS to a protected facility, mail is one of the most attractive for terrorists.

Because of this, the mail channel has always received much attention when organizing comprehensive protection. Therefore, it should be considered one of the most well-studied. The equipment created to monitor mail effectively solves the problem of detecting malware.

Properly organized control equipped with this technology can ensure almost 100% detection of malware.

When organizing mail control, special attention must be paid to the safety of personnel from a possible explosion. All available opportunities must be used for this: organizational, technical, personnel training.

Persons with secondary education are involved in the work of controlling mail items. But they must undergo serious special training.

The program of such personnel training includes:

• familiarization with the design features and characteristic elements of malware;
• mastering special technical means and technology for examining postal items;
• studying safety measures when handling controlled postal items and the procedure for action in case of suspected detection of malware;
• acquiring practical skills in working with equipment to identify characteristic signs of malware.