1. Radio Frequency (RF) Hazards
INTRODUCTION AND PRINCIPLES: (4 SLIDES, 14 MIN)
SLIDE 1 of 4: INTRODUCTION (2 min)
There has been a significant global increase in the use of electronic communication and detection devices. Examples are personal items such as mobile telephones and wireless communication links, to larger scale and therefore higher-powered transmitters for voice communication, electronic data transmission, asset tracking and radar.
These items produce and receive Radio Frequency (RF) fields of varying intensity. This intensity is controlled by their output power and antenna gain. It will vary from system to system.

2. Principles
Electrical Equipment Radio Frequency (RF) Electro-Explosive Device (EED) Ammunition functions unintentionally
INTRODUCTION AND PRINCIPLES: (4 SLIDES, 14 MIN)
SLIDE 2 of 4: PRINCIPLES (6 min)
RF is potentially hazardous when used in close proximity to explosives that have an installed electrical means of initiation. The electrical initiation method is generally through the use within the ammunition of an electro-explosive device (EED). An example of a type of ammunition which is an EED is an electronic time fuze.
Because most EED function as a direct result of heating the initiating material by an input of electrical energy, the presence of an RF field can induce the required charge into the EED, and so the ammunition may function unintentionally.
(Instructor: If possible, demonstrate RF by placing a mobile phone near to a stereo set while it is playing the radio. A buzzing should be heard, this is the RF interfering with the electrics. Now suggest that a similar thing may occur with items of ammunition. One wouldn’t want to initiate a missile while standing over it because you contravened the contraband rules and brought some prohibited equipment into the ammunition store. Note that the interference – and by inference the actual RF field – weakens as the phone is moved away from the radio, and it gets stronger as the phone is moved towards the radio. The RF strength weakens as the distance increases. Get students to try this too to involve them.).

3. Principles INTRODUCTION AND PRINCIPLES: (4 SLIDES, 14 MIN)
SLIDE 3 of 4: PRINCIPLES (4 min)
How does this happen? Any piece of wire, when subjected to RF, will pick up energy from the RF field around it. This is particularly true if the wires coming out of the EED from a ‘T’ shape – this is called a dipole antenna and is particularly susceptible to receiving RF. If this wire is part of an EED, then it is possible that the current may be sufficient to induce the required charge. Only relatively low amounts of RF may be required to function an EED.
The simplified illustration shows an electric detonator with the wires splayed – these effectively form a dipole antenna. The mobile phone is emitting an RF field. This may well be picked up by the detonator leads, and so the detonator may function.
This hazard can be minimised by intrinsic design characteristics of ammunition, screening and specialised packaging. However, these measures should not be seen as a guarantee of complete mitigation for accidental initiation. Note that the use of metallic ammunition containers does not automatically provide sufficient attenuation for EED in isolation.
There are also situations when EED’S are vulnerable to unintended initiation such as during transportation, removal or replacement procedures.
We know that we are endeavouring to achieve an ALARP status for risks that the ammunition that we are managing.
Unintentional initiation of ammunition due to RF poses a hazard. We should attempt to mitigate this risk as far as practicably possible. This should help us to keep our ‘duty of care’ to our employees, other people who may be at the explosive facility, and the general public.
IATG 05:60 covers the topics of Radio Frequency (RF) hazards.

4. Principles INTRODUCTION AND PRINCIPLES: (4 SLIDES, 14 MIN)
SLIDE 4 of 4: PRINCIPLES (3 min)
Would you want to start testing this theory in an ESH you just walked into to find barrels of nitrocellulose, boxes of pyrotechnics, igniferous initiators, and electrically operated squibs, ie EEDs? There is a complete explosive train here, and you may initiate a massive explosion because you were idle or careless and brought a mobile phone into the ESH.
(Instructor: click mouse now to reveal images of a 122mm multiple launch rocket system (a “Grad 1” or “BM 21” system).
Would you want to ‘push your luck’ and endanger the lives of you and your colleagues, for example, if you had to do an ammunition investigation on this system, with a random wire sticking out the back of the stuck-fast rocket?

5. Exposure Levels EXPOSURE LEVELS: (1 SLIDE, 3 MIN)
SLIDE 1 of 1: EXPOSURE LEVELS (3 min)
Interestingly, there are recommended exposure for people.
The responsibility for setting these limits would usually lie with the National Technical Authority.
There are different figures for workers and members of the general public.
This is likely to be especially important at sites like airfields which have high power radar systems. Best practice suggests the limits laid out in the table on the screen. These should meet the requirements of ALARP.
The limits shown in the top table meet the occupational exposure limits of healthy adults working under controlled conditions. These conditions include the opportunity to apply engineering and administrative measures and to provide personnel protection.
Members of the general public, where controlled exposure and protection is not possible, are covered in the lower table. These levels are lower than those recommended for the workforce.
There is a little more detail, including these figures, in IATG 05:60.

6. Safe Separation Distances
Circular ends =
a right cylinder
SAFE SEPARATION DISTANCES: (5 SLIDES, 23 MIN)
SLIDE 1 of 5: SAFE SEPARATION DISTANCES (5 min)
A wide range of communication equipment emitting RF fields may be found near ammunition items which contain EED's. Examples of such items are data-loggers, mobile phones, pagers, radios etc.
This means safe distance restrictions are required.
EEDs and/or weapons which are being handled or are under preparation, test or maintenance, are susceptible to much lower levels of RF. Therefore, controls are required to ensure they remain safe.
The hazard area for transmitters using omni-directional or rotating antennae is often defined as a right-cylindrical volume of air space centred on the transmitter. This is simply a cylinder with round (as opposed to, say, oval shaped ends). This is shown on the slide. The cylinder on the left is a right cylinder. Now imagine that this is notional area of space around an item ,for example a mobile phone. (Instructor: click mouse to reveal a purple box to represent a phone). The notional cylinder around the phone is considered to be the hazard area (for an omni-directional transmitter).
Oval (or otherwise not circular) ends =
NOT a right cylinder

7. Safe Separation Distances
SAFE SEPARATION DISTANCES: (5 SLIDES, 23 MIN)
SLIDE 2 of 5: SAFE SEPARATION DISTANCES (4 min)
For single and multi transmitter sites that have fixed directional beams radiating predominately in the same direction such as satellite tracking sites, the hazard area is mainly in the direction of the beam. The magnitude of a RF field decreases with increasing distance from the source. The simplified illustration shows a possible hazard area for the significant RF hazard associated with this equipment. If this system were pointed directly at our ammunition, we would be more concerned than if it were pointing away from it.
(Instructor: click mouse to remove satellite image, and replace with a building and waves).
It should be assumed that the field strength that exists inside a building or vehicle is the same as that of any external field. It is unlikely that a building will routinely mitigate the risk of RF hazards on a reliable and quantifiable basis.
Hazards external to the perimeter:
Outside the ESA and at least 100m from a processing building, radios with a power output of Q50W or with no significant antenna gain may be safely used.
For higher power radios or radars an assessment should be made to determine the possible field strength in processing areas. For some very high power broadcast transmitters, air traffic control radars or military radars this may require knowledge of their location out to distances of 3 km. In cases such as this, specialist assistance should be sought
Note that IATG 05:60 provides more detail on the requirements for transporting ammunition as well.

8. Safe Separation Distances
Emergency Situations:
Radius of 10m: No RF transmission
Radius of 50m: No vehicle-borne sets on transmit
(eg emergency services)
Emergency instructions issued to crews of vehicles transporting EED
SAFE SEPARATION DISTANCES: (5 SLIDES, 23 MIN)
SLIDE 3 of 5: SAFE SEPARATION DISTANCES (4 min)
Emergency situations:
In the event of an incident during the movement of ammunition, items which do not normally present a high RADHAZ risk may become vulnerable if there is damage to their inherent protection be it structural or packaging.
In such a situation the use of RF transmissions in the immediate vicinity should be imposed immediately:
No RF transmission shall be allowed within a radius of 10m from the EED;
Any emergency services using vehicle borne sets with ERP greater than 5W should not transmit within 50m of the damaged equipment; and
Drivers and/or escorts in vehicles transporting EED should be issued with emergency instructions as approved by the national technical authority

9. Calculation of Safe Separation Distances
Calculating transmitter field strength:
Type of aerial (directional or omni-directional)
Mean power supplied to antenna
The frequency or frequency band
The antenna gain
And if the transmitter has a pulse waveform:
The pulse repetition frequency (pulses per second)
The pulse width in seconds
SAFE SEPARATION DISTANCES: (5 SLIDES, 23 MIN)
SLIDE 4 of 5: CALCULATION OF SAFE SEPARATION DISTANCES (7 min)
Where no safety data exists for a particular piece of transmitting equipment the safe distance should be determined using the simplified method outlined in Annex C to IATG 05:60. The formulae and graphical methods have been developed to facilitate the determination of safe distances when the output characteristics of transmitters and susceptibility characteristics of EED are known.
Radios being used by establishment personnel or contractors should ideally not be used in areas where ammunition is being handled or in the vicinity of routes when ammunition is being handled, during loading or unloading operations or close to ammunition being loaded onto a firing platform or launcher. Where this cannot be avoided a safe distance shall be calculated and applied.
Calculation of field strength should only be undertaken by qualified personnel and the national technical authority should be consulted.
However to illustrate the process that is gone through to determine safe separation distances, consider the following.
Any radios being used should be of known field strength as supplied by the manufacturer or the national technical authority. A graph of field against distance is the preferred data format.
The following information is the minimum required to calculate transmitter field strength:
Type of aerial, directional or omni-directional
The mean power being supplied to the transmitter antenna in Watts
The frequency or frequency band of the transmitter
The antenna gain
If the transmitter has a pulse waveform and the EED is one whose thermal time constant is small (i.e. energy sensitive) the following is also required:
The pulse repetition frequency (PRF) in pulses per second
The pulse width (PW) in seconds
This information is normally found in the equipment handbooks, from equipment manufacturers or from the national technical authority.

10. Calculation of Safe Separation Distances
SAFE SEPARATION DISTANCES: (5 SLIDES, 2 MIN)
SLIDE 5 of 5: CALCULATION OF SAFE SEPARATION DISTANCES (3 min)
Where the transmitter information and the susceptibility of the EED are known then the calculation can be done using either a mathematical formula, or by using the radio density hazard graph (see the graph in the slide, for illustration purposes, which is from IATG 05:60, Annex C) or to determine the safe distance for the operation of radios or other equipment emitting RF.
There will generally be a number of minimum distances, which will take into account the specific activity being undertaken.

11. Questions
Are there any questions? 1 slide, 5 minutes