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Safety and Security of Radiation Sources


Radiation safety refers to protection of personnel against harmful effects of ionizing radiation by taking steps to ensure that people will not receive excessive doses of radiation and by monitoring all sources of radiation to which they may be exposed. Radiation safety measures are taken when working with radioactive substances and other sources of ionizing radiation to reduce the total dose from all types of ionizing radiation to the maximum permissible dose. Security means measures to prevent unauthorized access or damage to, and loss, theft or unauthorized transfer of, radioactive source. The meaning of “The safety of radiation sources and the security of radioactive materials” is to take steps to ensure the existence within their territories of effective national systems of control for ensuring the safety of radiation sources and the security of radioactive materials.

Activity of sources

When there is a correct number of neutron and proton in the nucleus of an atom, the nuclide is stable. However, many nuclides is unstable because they do not have the appropriate number of protons and neutron and they transform spontaneously into nuclides of other elements to achieve stability. In doing so, they emit radiation. This property is called radioactivity. The transformation is called ‘decay’ or disintegration and the nuclide is said to be a radionuclide. The activity of a radionuclide is the rate at which it undergoes spontaneous decay or disintegration. It is expressed in a unit called Becquerel (Bq). The Becquerel (Bq) is a unit or measure of actual radioactivity in material, with reference to the number of nuclear disintegrations per second (1 Bq = 1 disintegration/sec). Quantities of radioactive material are commonly estimated by measuring the amount of intrinsic radioactivity in becquerels – one Bq of radioactive material is that amount which has an average of one disintegration per second, i.e. an activity of 1 Bq. Activity was formerly expressed in a unit called Curie (Ci). One curie was originally the activity of one gram of radium-226 and represents 3.7 x 1010 disintegrations per second (Bq).

1 becquerel = 27 picocuries or 2.7 x 10-11 curies


Figure 1: Radioactivity of some natural and other materials

Why we need security controls?

When radiation passes through a material, it causes ionization which can damage chemical structures. If the material in question is biological material (such as the cells that make up human organs and tissues) and if the damage occurs to critical chemicals within the cells (such as the DNA molecules making up the chromosomes within the cell nucleus), the cell itself can be damaged. It has been known for many years that large doses of ionizing radiation, very much larger than background levels, can cause a measurable increase in cancers and leukaemia (‘cancer of the blood’) after some years delay. It must also be assumed, because of experiments on plants and animals, that ionising radiation can also cause genetic mutations that affect future generations although there has been no evidence of radiation-induced mutation in humans. At very high levels, radiation can cause sickness and death within weeks of exposure. By looking at these possible effects that will cause harm to human, we really need a security control to achieve an appropriate level of protection and safety for radiation sources which used in medicine. Ensuring safety in the use of radiation sources and operation of related facilities is of paramount importance for the protection of people and the environment from any associated radiation risks. In order to ensure radiation safety, a cradle-to-grave system for the control of radiation sources should be established. Another area of concern is to ensure that the radioactive sources are not lost, stolen and abandoned after not being used anymore. The fundamental safety objective is to protect people and the environment from harmful effects of ionizing radiation”. This objective must be achieved without unduly limiting the operation of facilities or the conduct of activities that give rise to radiation risks. Therefore, the system of protection and safety aims to assess, manage and control exposure to radiation so that radiation risks, including risks of health effects and risks to the environment, are reduced to the extent reasonably achievable.

Radioactive security alert!

Because exposure to high levels of ionizing radiation carries a risk, should we attempt to avoid it entirely? Even if we wanted to, this would be impossible. Radiation has always been present in the environment and in our bodies. However, we can and should minimize unnecessary exposure to significant levels of man-made radiation. Radiation is very easily detected. There is a range of simple, sensitive instruments capable of detecting minute amounts of radiation from natural and anthropogenic sources. A closed source of radiation by virtue of its design— hermetically sealed sources of radioactive radiation, X-ray machines, and accelerators—prevents radioactive substances from entering the environment. Only external irradiation acts on the body during exposure to closed sources. The dose of external irradiation may be reduced by spending the minimum possible amount of time in the radiation field, by placing the maximum possible distance between the source and object of irradiation, and by shielding either the source of radiation or the object irradiated. Proximity to open sources of radiation poses the danger that radioactive substances may enter the body through the respiratory tract, alimentary canal, and skin; that is, the danger of internal irradiation arises. To reduce the dose of internal irradiation, measures are taken to decrease the amount of radioactive substances entering the body. Such measures include hermetically sealing equipment and places of work, installing filters in exhaust systems, rationally planning radiochemical laboratories, utilizing means of individual protection, and observing the rules of radiation hygiene. The radiation safety service inspects all establishments where radioactive substances and other sources of ionizing radiation are used. It monitors compliance with radiation safety norms and health regulations and obtains information on the irradiation doses received by the personnel and by individuals living in the area. Depending on the nature of the job, the radiation safety service monitors the dose rate of all types of ionizing radiation (except ultraviolet) in places of work and adjacent areas, health protection zones, and the general work area. It also measures the contamination of places of work, of the personnel’s clothing and skin, and of environmental objects outside the work area. It inspects the collection and removal of solid and liquid radioactive wastes and measures the emission of radioactive substances into the atmosphere and the level of irradiation of the personnel and of individuals living in the area. Depending on the nature of the job, personnel monitoring also includes measurement of doses of external ß-radiation, neutrons, and X- and ?-radiation and the monitoring of the level of radioactive substances in the body or individual organs.

Security challenges

One major security challenge should be noteworthy is to create a “security culture.” Safety culture means the assembly of characteristics and attitudes in organizations and individuals which establishes that, as an overriding priority, protection and safety issues receive the attention warranted by their significance. As we know that good security needs both: strong, strictly enforced regulations and actively participating licensees. Strong regulations are required because investments in security usually don’t generate profits for the businesses. But no security system can work effectively without a vigilant staff that understands the terrorism risk is real. Much like the long-established “safety culture” that has almost certainly prevented many serious radiation accidents, a new “security culture” is needed. This means that businesses, regulators, and government agencies are all aware of security threats, understand their individual responsibilities, and adapt their practices accordingly. Another challenge of the security of radioactive material are how to factor in the ease of access to and transport of various sources. Devices containing sources with relatively high amounts of radioactivity such as research irradiator (category 1 source) tend to weigh much more than devices with lower level sources such as brachytherapy device weighs much less than a kilogram and is only millimetres in length. Both types of sources can be found in hospital settings. Assuming terrorists could access a hospital that has these sources, they would have a far easier time carrying brachytherapy sources. If terrorists wanted the larger amount of radioactivity resident in the irradiator, by knowing the specific design of the device possess the proper tools to break they could try to cut into the device to remove the radioactive material. These sources are designed for commercial use and many are used daily in hospitals, universities, and other open access settings where a “gates, guards, and guns methodology” or mentality is not feasible.


Figure 2: Categorization of Radioactive Sources.

What we learn from Fukushima

The Fukushima Daiichi nuclear disaster was a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tohoku earthquake and tsunami on 11 March 2011. The accident at Fukushima Daiichi nuclear power plant in Japan released about 940 PBq (iodine-131 equivalent) of radioactive material, mostly on days 4 to 6 after the tsunami. In May 2013, United Nation Scientific Commission on the Effects of Atomic Radiation (UNSCEAR) reported that “Radiation exposure following the nuclear accident at Fukushima-Daiichi did not cause any immediate health effects. It is unlikely to be able to attribute any health effects in the future among the general public and the vast majority of workers.” The lessons that we should be learned from the accident at Japan’s Fukushima-Daichii nuclear power plant, are that emergency generators should be better protected from flooding and other extreme natural events and that increasing the spacing between reactors at the same site would help prevent an incident at one reactor from damaging others nearby. The result from that event we should strengthen capabilities for assessing risks from events that could challenge the design of structures and components which lead to a loss of critical safety functions. The emergency response organizations should examine and, as needed, revise their emergency response plans, including the balance among protective actions, to enable effective responses to severe nuclear accidents. We should maintain and continuously monitor a strong nuclear safety culture in our safety-related activities and should examine opportunities to increase the transparency of and communication about our efforts to assess and improve the safety of the radioactive material. Looking at the causes of the Fukushima nuclear accident, particularly with respect to the performance of safety systems and operator response following the earthquake and tsunami, we should re-evaluate the studies on safety and security of radioactive material and high-level radioactive waste storage, particularly with respect to the safety and security of current storage arrangements and alternative arrangements in which the amount of commercial stored in premises is reduced. Another lesson that can be learned is to improve the radiation sources safety and security regulations, including processes for identifying and applying design-basis events for accidents and terrorist attacks to existing radioactive material storage.


The uses of radiation sources are worldwide, and their applications are nearly universal. Further, accidents involving radiation sources do occur. Some accidents have resulted in serious, even fatal, radiation exposures. When radioactive materials are involved, radioactive contamination of the environment can also occur. The major applications in which most major accidents have occurred are irradiation, industrial radiography, brachytherapy, and teletherapy. Accidents with radiation sources are also a worldwide problem, for example of an accident which happen in Brazil in 1987, and in Thailand in 2000—when unsuspecting scavengers who dismantled old radiotherapy machines exposed themselves and their families to very high doses of radiation. Four of the exposed people died in Brazil, and three in Thailand and more were seriously injured. The cost of cleanup and recovery for their communities was substantial. In 1996 at a hospital in San Jose 114 people received an overdose of radiation from cobalt-60 in therapy, about half suffering from Acute Radiation syndrome (ARS), and 13 died of ARS. Within the radiation protection community, the security of radioactive materials is always an integral part of the normal radiation protection program for radioactive materials. Historically, thefts of radioactive sources or devices are not unknown, but most such thefts were motivated by misguided thoughts on the part of the thieves that the stolen radioactive sources or devices had a monetary value similar to that of metals or specialized equipment. Such motivation for thefts continues today. Unfortunately, when thieves learn that the stolen items cannot be sold, they often discard them in trash or metal scrap, creating radiological risks for people who handle and dispose of trash or process and use recycled metal scrap.

How safe is safe enough?

In order to answer the question of whether medical radiation is safe, safety must be defined. What does safe mean? Does it mean that there is no risk? Or the risk is very small? Or the benefit exceeds the risk? Many activities carry some kind of risk. To call something safe usually means that it carries a low risk, not zero risk. Zero risk is almost impossible. Safety is different for everyone. For example, people with asthma do not tolerate pollution well. What is for people without asthma is not necessarily safe for people with asthma. An action or product is deemed safe as long as the risk associated with it is very low. This is true for medical x-rays, medication or any medicine. Even so, only patients who need diagnostic imaging should have imaging exams. Background radiation naturally exists everywhere in the environment. These levels of radiation are clearly safe. If they were not, life on Earth would not flourish. Yet, we know radiation has the potential to cause cancer. The degree of safety depends on the level of exposure. Ultra-high levels of radiation (levels far above background radiation or in amounts well in excess of those used in diagnostic imaging) may cause cancer to develop later in life. Only a small percentage of people who are heavily exposed to radiation develop radiation-induced cancer later in life. This includes people who are exposed to radiation from nuclear weapons, people involved in radiation accidents and people treated for existing cancer. The potential for radiation-induced cancer depends on the amount of radiation exposure and accumulation of exposure over a long time. Lower exposure levels—background radiation, nuclear medicine exams, computed tomography (CT) scans, or diagnostic x-rays—carry low risks. Nevertheless, a large volume of circumstantial evidence suggests that diagnostic levels of radiation probably are associated with a low level of risk for inducing disease many years after exposure. Such an event would be very infrequent. Benefits to patients who are sick or injured are so substantial that the radiation risk becomes a minor factor in their healthcare. When used in large quantities or when many examinations are performed, the risk from exposure to x-rays increases. In some instances, the accumulated dose from multiple examinations can reach levels where the risk of induced cancer has been identified. This can occur after certain types of CT examinations are repeated five or six times in some adult patients. For some very serious medical conditions, multiple exams are necessary, and the benefits far outweigh the risk. Safety is a priority. To be safe, medical practitioners should use radiation sources only in quantities sufficient for medical care. Benefits from the medical procedure greatly outweigh any potential small risk of harm from the amount of radiation used. There is no conclusive evidence of radiation causing harm at the levels patients receive from diagnostic x-ray exams. Although high doses of radiation are linked to an increased risk of cancer, the effects of the low doses of radiation used in diagnostic imaging are not known. No one is certain if any real risks are involved. Many diagnostic exposures are similar to the exposure that we receive from natural background radiation found all around us. Nevertheless, benefits of diagnostic medical exams are vital to good patient care. Safe levels of radiation are well understood and have been evaluated and agreed upon by many independent panels of experts. Daily exposure to low levels of radiation is a normal part of life on planet Earth. Every day we are exposed to radiation that is produced by the sun, radioactive materials in the earth and the air, and even trace amounts of naturally radioactive potassium and carbon contained in our own bodies. In some areas of the world natural background radiation is higher than the limits currently set for the workers at the Fukushima plants, due to natural radioactive materials in the ground. Residents have experienced no ill effects from this increased radiation exposure.


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Last Reviewed : 19 February 2016
Writer : Nurul Diyana bt. Shariff
Accreditor : Adzlin Hana bt. Mohd Sari