RADIATION EMERGENCY : LOST OF CONTROL OF SEALED SOURCES

INTRODUCTION

WHAT IS A SEALED RADIOACTIVE SOURCE ?

A sealed radioactive source is radioactive material that is permanently sealed in a capsule or bonded and in a solid form. The capsule of a sealed radioactive source is designed to prevent the radioactive material from escaping or being released from encapsulation under normal usage and probable accident conditions

Sealed radioactive sources such as the sources involved in the Indian accident are used widely in medicine, industry, and agriculture. The radioactive substance within a source is sealed within a protective container. Radioactive substances emit energetic particles or waves, which is called ionizing radiation. Radiation from the sources is used for a specific purpose. For instances, Sealed radioactive sources use by doctors to treat cancer, by radiographers to check welds in pipelines, or by industrial specialists to irradiate food to prevent it from spoiling.

When these sources are lost or stolen, however, they can fall into the hands of persons who do not have such training and knowledge or who wish to use them to cause harm intentionally. In such circumstances, radioactive sources may be a serious risk to anyone who comes too close to them, touches them, or picks them up, particularly if the sources are damaged.

WHAT ARE THE DANGERS OF SEALED RADIOACTIVE SOURCES?

In most countries, the use of sealed radioactive sources is regulated and users are required to be properly educated and trained in radiation safety and protection. The manufacture of the equipment itself is also regulated, so that radiation doses received by users, bystanders, and patients are tightly controlled.

Dose limits for individuals have been adopted by the International Community in the Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards for protecting people and the environment (Interim edition), General Safety Requirements Part 3, No. GSR Part 3 (Interim) (2011).

 The major risks from these sources occur when the source is lost, stolen, forgotten, or otherwise outside of regulatory control. These so-called orphan sources (orphan meaning they are no longer under proper control) can pose a significant danger if someone obtains or finds such a source and does not realize that it is radioactive. Injuries or death are possible when a source is found and someone unknowingly takes it home or tries to open it

PRECAUTIONS TO PREVENT THE LOST OR STOLEN SEALED SOURCE

To inform people of the presence of radiation, radioactive sources have special labels. The trefoil is the international symbol that appears on all containers, materials, or devices that have a radioactive component. The word “radioactive” and the number I, II, or III may also appear on the packaging used to transport radiation sources.

Sources are sometimes lost on construction sites or when old equipment is thrown away. Lost or discarded devices containing sealed radioactive sources can end up in scrap metal yards. People who collect scrap metal need to know how to recognize a device containing a sealed radioactive source. Old equipment, particularly if it is unusually heavy for its size, should be checked for the radiation symbol and other warning symbols.

REDUCING RISKS FROM LOSS OF CONTROL OF SOURCES

Devices containing sealed radioactive sources, when used as intended, are designed to limit radiation exposure to users to inconsequential levels. Despite their design safety features, some sealed radioactive source devices may produce a potentially lethal amount of radiation if used improperly. People using devices containing sealed radioactive sources must be trained and knowledgeable about proper use from both a safety and security perspective in accordance with relevant regulatory requirements. When used improperly or maliciously, such devices can cause injury or death. Acquisition and malevolent use of radioactive sources may cause radiation exposure or dispersal of radioactive material into the environment. Such an event could also cause significant social, psychological and economic impacts.

 If a source becomes too weak for its intended use, it does not mean that the source is harmless. Many accidents have resulted from sources that are no longer being used for their original purpose, but which still emit a significant amount of radiation.

Physical protection and proper security measures should be implemented for all sources to avoid the possibility of theft. However, a graded approach needs to be applied in which the most dangerous sources are defined so as to provide higher security and more stringent safety measures than is done for less dangerous sources.

REPORTS OF THE ACCIDENTS INVOLVING LOSS OF CONTROL OF SEALED RADIOACTIVE SOURCES

A ) Sources Abandoned in Turkey

A company stored two packages containing cobalt-60 radiotherapy sources in their general purpose warehouse in Istanbul, Turkey. When the warehouse was full, the packages were moved to an adjoining empty storage space that was later transferred to new owners who did not realize what was in the packages. In December 1998 and January 1999, both were sold as scrap metal, after which the purchasers broke open the shielded containers in a residential area.

Ten persons who had spent time in proximity to the dismantled containers became ill. Although they sought medical assistance, the cause of the illness was not recognized until almost four weeks after the symptoms appeared. A total of 18 persons (including seven children) were admitted to hospitals, with ten adults exhibiting symptoms of radiation sickness. When the injuries were eventually suspected as having been caused by radiation exposure, the doctor immediately alerted national authorities.

When the authorities responded, one unshielded source was quickly discovered at the scrapyard and safely recovered, preventing further radiation exposure. The source capsule had not been damaged and there had been no leakage of radioactive material. The source that had supposedly been in the second container was never found. After thorough investigation, it appears that there had been no source in the second container, but this could not be demonstrated unequivocally.

Investigations found that there were several contributing factors to the accident, including inadequate security and inadequate inventory control that allowed unauthorized sale of the packages to take place. Lack of recognition of the radiation symbol was also an important factor. Furthermore, transfer of the sources to a qualified and licensed waste operator would have prevented the accident.

B) Source Melted with Scrap Metal in Spain

In May of 1998, an unnoticed caesium-137 source was melted in an electric furnace of a stainless steel factory in Spain. The vapours were collected in a filter system, resulting in contamination of the collected dust, which was removed and sent to two factories for processing as a part of routine maintenance. One factory used the contaminated dust in a marsh stabilization process, resulting in contamination being spread throughout the marsh. The first warning of the event was from a gate monitor that alarmed on an empty truck returning from delivering the dust. Several days later elevated levels of caesium-137 were also detected in air samples in Southern France and Northern Italy. The radiological consequences of this event were minimal, with six people having slight levels of caesium-137 contamination. However, the economic, political and social consequences were significant. The estimated total costs for clean-up, waste storage, and interruption of business exceeded $25 million US dollars.

C) Source Lost in Honduras

On 28 October 2010, elevated radiation levels were detected from an underground source in a courtyard in a Honduras medical facility. Initial actions were taken to shield the area and install appropriate barricades and warning signs. The facility owners conducted an inventory of sealed radioactive sources that were in storage and Exchange container (IAEA).14 found that a caesium-137 brachytherapy source was missing. The source was safely recovered from a depth of approximately 2 cm below the soil surface. Source encapsulation remained intact, so the retrieved source was placed in a dedicated shielding facility with other brachytherapy sources. Although neither the source nor the area in which it was found was controlled, individual overexposure was extremely unlikely, based on the location and measured radiation levels.

PREVENTING LOSS OF CONTROL OF SEALED RADIOACTIVE SOURCES

Government programs can minimize the chance that sealed radioactive sources will be lost, stolen, or improperly discarded. Governments should also be able to respond to accidents or incidents when there has been a loss of control of sealed radioactive sources. Government Infrastructure

Devices containing sealed radioactive sources are used in virtually all countries of the world. Governments must ensure that the use of radioactive sources within their jurisdiction is performed according to laws and regulations. If requirements do not exist, radioactive sources might be imported and used without any type of regulatory control over safety, security or plans for appropriate disposal. To prevent such occurrences, national authorities should establish an infrastructure with laws and regulations and governmental organizations with responsibility for safe and secure importation, use and disposal of sealed radioactive sources, as well as provide emergency planning and response for accidents or incidents involving such sources. Users are responsible for complying with the laws and regulations governing safe and secure use and storage of sources. Laws and Regulations

Comprehensive national laws and regulations need to be in place to establish requirements for the safe and secure use of sealed radioactive sources. Laws provide for the establishment of the legal authority through which a national regulatory authority can be established to authorize, inspect and enforce compliance with regulations that control the sale, import, export, use and disposal of sealed radioactive sources. These regulations may specify the type of facility or individual permitted to possess and use a sealed radioactive source and may require all users to obtain an authorization, usually called a license, for possession and use of a source. The authorization process specifies the education and training required for those responsible for the proper use of the source and the requirements that a facility must meet with respect to physical protection to prevent its loss, theft, or unauthorized transfer. Procedures must also be in place for monitoring radiation when the source is stored, used or transported. The user must notify the regulatory authority of any changes in use of sources at the facility (including when sources are removed from active use). Regulatory Authority

A regulatory authority is usually empowered to authorize and inspect regulated activities and to enforce laws and regulations. The regulatory authority needs to have adequate legal authority for its activities (either through laws or regulations), properly trained staff, and a sufficient budget to undertake its duties, including regular inspection of facilities using radioactive sources and review of applications for permits or licenses to use sealed radioactive sources. The size of the staff required is dependent on the number and types of sealed radioactive sources that are in use. Most countries in the world will have several facilities using sources in medical and industrial applications. Inspections are the primary means to verify safe practices and adequate security measures. National Register of Radioactive Sources

In order to ensure that radioactive sources can be tracked throughout their lifetime, a national register of sealed radioactive sources, covering all sources should be established. Each facility using a sealed radioactive source should be required to maintain an inventory of sealed radioactive sources on its premises, and a national register of sources should also be maintained by the regulatory authority to ensure that sources can be traced if ownership changes. Such an inventory can help maintain regulatory control of a source throughout its lifetime and help to identify any sources for which control has been lost. Emergency Preparedness and Response

National authorities must be prepared to deal with emergencies that can arise when control over sealed radioactive sources is lost. Regulatory authorities must not only have procedures in place to respond to such 15 —SEALED RADIOACTIVE SOURCES — Issues for Government Agencies emergencies, but must require all users and facilities to have appropriate emergency plans and emergency reporting mechanisms in place. Depending on the nature and activity of the source involved, such accidents or incidents could have fatal or life-threatening consequences and cause widespread radioactive contamination and panic as well as financial losses to businesses and people. Clean up and monitoring of exposed persons requires significant resources, careful planning, and coordination between a variety of government agencies such as environmental protection, health and social services. Prevention is far more cost effective.

With the recent rise in terrorist activity, the possibility that a terrorist group will use a source for malicious purposes such as in a radioactive dispersal or exposure device must be included in emergency preparedness both by the regulatory authority and the facilities where sources are used or stored. High activity industrial radiography, irradiators, thermoelectric generators and tele therapy machines all use sealed radioactive sources that may be the target of terrorist activity. The extent of the provisions to protect sources from those with malicious intent should be applied according to a graded approach commensurate with the hazard of the source. Some provisions are intended to prevent the theft a source, to detect any unauthorized access, and to delay thieves until law enforcement agencies respond. Other provisions are intended to facilitate locating and recovering a lost or stolen source. Sealed radio-active sources may be smuggled across national borders; therefore, customs officers should be given clear guidance on how to respond when sealed radioactive sources are identified at a border control point. Similarly, national regulatory and police authorities should be prepared to respond to such situations.

Life cycle of sealed radioactive sources.

The life cycle of sealed radioactive sources, from the radioactive source production to its eventual disposal is represented in Fig. VI-1. Once sealed sources become disused (e.g. once they cannot accomplish their intended purpose anymore due to radioactive decay), if they are not managed safely and securely, they may leak, become abandoned or be lost, stolen or misused by unauthorized persons, causing radiation incidents or accidents. The IAEA defines a ‘disused source’ as “a radioactive source that is no longer used, and is not intended to be used, for the practice for which an authorization has been granted”2 . ‘Spent sources’ (a sub-set of disused sources) are those that are “no longer suitable for [their] intended purposes as a result of radioactive decay” 3. The term ‘disused source’ (or DSRS, disused sealed radioactive source) is used as defined above throughout this document.

Some of the challenges involved in the industrial and medical use of high activity sources, mainly cobalt-60 sources, include the existence of a limited number of suppliers, security concerns and frequent transport delays. Furthermore, in light of the widespread use of radioactive sources around the world and their long half-lives, the safe management and disposal of DSRS needs to be ensured. Partly as a result of these challenges, there has been a shift from the use of radioactive sources to electron accelerators in industrial applications, and to X-rays in research and development (R&D) work in radiation chemistry and biology. This shift away from cobalt-60 based teletherapy can also be observed in radiation medicine and is a consequence of the proven superiority of linear accelerator (linac)-based radiation therapy. Nonetheless, cobalt-60 sources are still preferred for many applications, and there is a continuing need for new sources to either replace or to replenish disused sources in existing cobalt-60 based systems

According to Basic Safety Standard (BSS), it states that there have been many instances in recent years of serious accidents, injuries and loss of life occurring as a result of failure to organize the prompt and formal decommissioning and disposal of devices containing sealed sources. The Code of Conduct on the Safety and Security of Radioactive Sources expects that every State should ensure that sealed sources are not stored for extended periods of time in facilities that have not been designed for the purpose of such storage. The Code of

Conduct also expects each State to ensure that, before the regulatory body authorizes receipt of a sealed source, arrangements, including financial provisions, have been made for its safe management once it becomes a disused source. The IAEA has developed guidance on measures to be taken to reduce the risk of accidents associated with disused sealed sources and on methods of identifying and locating disused and lost sources.

The management options for disused sources may be available to the principal party:

(a) Storage prior to disposal;

(b) Transfer to another authorized user;

(c) Return to the manufacturer and/or supplier;

(d) Decommissioning and disposal.

The facility in which a radiation source has been used may not be suitable for the safe and secure handling and storage of unshielded sources. The extent of the decommissioning activities at the user’s premises should therefore be minimized. In many cases, the source holder forms an integral part of the approved transport container and removal of the source from the holder should not be necessary.

As the source holder is likely to have details of the contents engraved on it, including the radionuclide content, activity, reference date and serial number, removal of the source from the holder would introduce the potential for loss of accountability. The small size of many sources can introduce the possibility of a source being dropped or mislaid without this being noticed. Instances have also occurred in which sealed sources have been inadvertently damaged while being removed from housing, resulting in significant contamination. Consequently, if it is not necessary to remove the source from the equipment at the point of use, such removal should be avoided.

REFERENCE

AMERICAN SOCIETY FOR NON-DESTRUCTIVE TESTING, ASNT Handbook on Radiographic Testing, 3rd edn, Vol. 4, ASNT, Columbus (2002).  

Board of Radiation & Isotope Technology. Blood Irradiator. Mumbai, India. http://www.britatom.gov.in