The fundamental objective of the regulatory supervision over the various uses of atomic energy is to avoid any damage to the people and environment, without unduly limiting the operation of facilities and performance of activities entailing risks. The fundamental objective applies to every facility and activity, the whole lifetime of the facilities and activities, including fabrication, construction, commissioning, operation, decommissioning, dismantling and closure. Additionally, the activities include the transport of radioactive materials and the management of radioactive wastes.
APPLICATIONS OF ATOMIC ENERGY UNDER REGULATORY SUPERVISION
Pursuant to the definition of the Atomic Act the application of the atomic energy means activities in connection with nuclear and other radioactive materials, equipment and facilities generating ionizing radiation and serving for the use of nuclear and other radioactive materials.
Operation of nuclear facilities
Among the facilities serving for the application of atomic energy, the Atomic Act defines the nuclear reactors using nuclear materials and the facilities storing nuclear materials as nuclear facilities. Altogether, four nuclear facilities operate in Hungary.
The most important facility of the Hungarian electric power generation fleet is the Paks Nuclear Power Plant. It consists of four VVER-440 type reactor units, each having a rated capacity of 500 MW. The Budapest Research Reactor operated by the HAS Institute of Energy Research is one of the most significant research equipment of the Hungarian physics. The most important practical area of utilization of the research reactor is the production of radioactive isotopes primarily for medical (diagnostic) purposes. The main mission of the Training Reactor is to educate the students and PhD students of the Budapest University of Technology and Economics and of other higher education institutes. The Spent Fuel Interim Storage Facility is established for the 50 year long interim storage of the spent fuel assemblies of the Paks Nuclear Power Plant.
Application, transport and storage of nuclear materials
The nuclear materials are such radioactive materials, in which the process of nuclear fission can be sustained (i.e. fissile materials) or which can be transformed to such materials (i.e. nuclear source materials).
In Hungary, the majority of the nuclear materials are used and stored in nuclear facilities.
It is less known that the company cleaning the water under the closed uranium mines produces a few tones of yellow cake every year. The uranium inventory under the ground is cc. 20,000 tone.
Besides reactor technology, nuclear materials are used, even if in small quantity, by 45 licensees mainly in research and industry, and in certain services.
Application, transport and storage of radioactive sources
The applications of radioactive isotopes and ionizing radiations extend over the areas of medical services, industry, agriculture, scientific research and education. In the field of industrial applications, the most widely used applications are tracing, process control and defectoscoping. Among the agricultural and food industrial applications, besides tracing, the preservation and sterilization (e.g. elimination of salmonellosis of import spices in everyday use) becomes more and more relevant. Diagnostic and therapy procedures using radioactive isotopes extend, the sterilization of medical products with high activity radioactive sources becomes a part of our current technology.
The magnitude of such applications is well shown by the data of the central register of the Hungarian Atomic Energy Authority. Accordingly, currently cca. 500 licensees use cca. 7000 radioactive sources in Hungary.
Processing, transport and storage of radioactive wastes
The solid and liquid, small and medium level radioactive wastes generated during the operation of the nuclear power plant shall be disposed. These wastes are, until their final disposal, temporarily stored at the nuclear power plant. The majority of the solid wastes are stored in steel drums of 200 litres, in compressed form. The liquid wastes are collected in containers. The wastes can be disposed only in solid form; the solidification of the liquid wastes therefore is performed at the plant before transportation to the repository. Such wastes are generated during dismantling of the nuclear power plant, which are to be disposed after processing, in solid form, together with the operational wastes.
The smaller radioactive waste producers, being outside of the nuclear fuel cycle, like hospitals, laboratories and industrial companies, annually produce low and intermediate level waste of 10-20 m and 1000-3000 of spent radioactive sources. The most radioactive waste, including the disused nuclear and radioactive materials, is produced by medical, industrial and research applications. The two most often used isotopes having the largest inventories are the Co-60 and Ir-192. These are used in medical and industrial radiography.
Operation of equipment generating ionizing radiation without containing radioactive material
The equipment generating ionizing radiation without containing radioactive material (e.g. X-ray machines) are widely used in medical diagnostic purposes. The X-ray examinations are essential methods and tools of modern medical practice. Currently, several thousands of such equipment operate in Hungary.
The Cyclotron Laboratory of the ATOMKI operates the largest particle accelerator equipment in Hungary. The MGC-20 type cyclotron has been providing accelerated particle beams for basic and applied research projects, as well as for medical and industrial applications since November, 1985.
HOW THE IONIZING RADIATION MAY CAUSE HARM?
The above described applications of atomic energy may cause harm in three specific ways. The risks accompanying the conduct of these activities are described by the first way: the damage occurs during the operation and conduct of activities by technical/safety related events. The second way of causing harm, when a sabotage is committed against the facilities or materials, or such materials are theft and then used for causing damage to the public and the environment. The third way is when the license holders use such materials, facilities or equipment for malevolent purposes.
Technical/safety related events in operation
Incidents and accidents in nuclear facilities
The events occurring at nuclear facilities and having impact on safety are classified based on the seriousness of the consequences they lead to. In order to identify such events, the analyses of the potential initiating events are analysed taking into account the probability of their occurrence. The identified list of internal and external events, together with the belonging initial and boundary conditions are grouped depending on whether they may lead to operational incident, design basis accidents or beyond design basis events. Within a certain group of initiating events, the initiating event having the most adverse consequences is considered as the characteristic initiating event.
In the case of operational events the consequences are limited by the systems of the facility so that the conditions of normal operation and the operational limits and conditions are still met. Operational events are e.g. load change of the plant, its shutdown or start-up, fuel movement, maintenance or testing.
The anticipated operational occurrences present a narrower scope. They do not belong to the scope of operational events, however their occurrence probability is relatively high but it is sufficient to assume a single failure (i.e. a randomly occurring loss of function and its consequences) during their analysis. Such events are e.g. the protection actuations, which occur in case of deviations and shut down the operating reactor.
The design basis accidents are processes induced by initiating events having lower probability (i.e. 10E-2–10E-6/year) than the anticipated operational occurrences; single failure is sufficient to be assumed during their analyses. It should be noted that the (release) limits established for normal operation shall be complied with by the facility in such events. Examples of design basis accidents are the largest assumed loss of coolant accident for nuclear power plant or the rupture of a fuel assembly for the spent fuel interim storage facility.
If multiple failures are also assumed after a postulated initiating event, a condition entailing consequences beyond the design basis may appear.
Postulated initiating events having even lower probability than those described above may lead to nuclear accidents. In such cases, radioactive materials above the regulatory limits may be discharged to the environment and cause radiological consequences. The severe accidents compose a separate category within the nuclear accidents, in the case of which the nuclear fuel is significantly damaged, melted and a significant release of radioactive materials occurs to the environment.
Safety events during the use, storage and transport of nuclear materials, radioactive sources and radioactive wastes
Certain unexpected, extraordinary events may occur during the use, storage and transport of nuclear materials, radioactive sources, and during the processing, storage or transport of radioactive wastes, which may cause that the personnel or the public in the endangered environment are exposed to higher doses that the established limits. Radiological accidents are those severe events, when dangerous radioactive materials are released to the environment. Such events may occur at any locations, where such materials are in use, storage or transport, such as hospitals, universities, research laboratories, industry facilities, as well as public, rail and water transport routes.
Incidents of equipment generating ionizing radiation without containing radioactive materials
The majority of the incidents occurred so far is in connection with operation of X-ray machines. The extraordinary operation of microtron, cyclotron, betatron should also be mentioned here.
Sabotage against nuclear facilities and radioactive materials
The sabotage is such an action when the adversary disturbs the normal operation of the facilities by intentionally damaging the operation of equipment in a way that environmental release occurs. The other case of sabotage is when the local explosion of radioactive material being in use, storage or transport causes the release of radioactive materials to the environment. Accordingly, the main targets of sabotage are the main safety systems of facilities and such high activity radioactive materials, the explosion of which may release significant amount of radioactivity.
Non-peaceful application of nuclear facilities, nuclear and other radioactive materials, and equipment generating ionizing radiation without containing radioactive material
Due to its damaging impact, the explosion of a nuclear weapon is the most significant action. The development of such a weapon from ore needs very complex technology, including the extraction of nuclear material from the ore, its enrichment to weapon level, conversion to metal, preparation of the necessary electronics. The theft of nuclear material in enriched form or the theft of a nuclear weapon highly simplifies this action.
The radioactive material dispersal devices cause less significant effects, but can be developed easier than the nuclear weapons. They can be different based on their operational principle. Their goal might be to contaminate drinking water sources or an element of the food chain, or disperse radioactive materials in a densely populated area. The equipment used for such purpose can be twofold: traditional explosive may disperse radioactive materials in powder or liquid form, or a device dispersing radioactive materials as e.g. a spray or sprinkler. Due to the small average particle size and particle weight, the release in powder form is the most efficient, since the slow deposition allows longer time for intake and longer dispersion route. Significant effects may be induced by small quantity of certain radioactive materials.
In addition, the harmful effects may appear through direct radiation, when a high activity sealed or partially unsealed radioactive source or equipment generating ionizing radiation is used to expose people e.g. in a frequently used location.
The above mentioned way can be further divided depending on whether the materials and equipment are obtained by unauthorized removal or the owner/licensee uses the materials and equipment for adversary purposes.
HARMFUL EFFECTS OF IONIZING RADIATION
The biological and environmental effects play relevant roles from the regulatory oversight point of view; however other consequences should also be mentioned in relation to an event having environmental effects.
Ionizing radiations have deterministic and stochastic effects.
The deterministic radiation effects appear only above a certain threshold dose (generally 1 Gy), and such effects induces more serious harms to the exposed person with the increase of the dose. The deterministic effects always appear above the threshold dose and never below that. The severity of the induced effect is proportionate to the dose. Such harms are e.g. skin burns, decrease of blood cells, oligo and aspermia.
In the case of stochastic radiation effect, not the severity of the biological effects, but the probability of their appearance depends on the dose. Accordingly, it cannot be forecasted in advance whether the radiation effects appear and when they appear in a given person, but this appearance is a probabilistic value for all those exposed. Stochastic biological effects may appear even for low doses, thus threshold dose value does not exist for such effects. It is a recognized assumption that the probability of the appearance of the effect linearly increases with the dose. Such effects are e.g. leukaemia or a tumour.
Environmental impacts are the increase of activity concentration and dose rate in the environment, contamination of the environment, which all may indirectly induce biological effects in the human body.
Events having no biological and environmental effects may have such significant impacts as the loss of public confidence in the safe and secure applications of nuclear energy and their supervision.
In the case of a more serious environmental release, panic and then long term fear may happen. Several years or decade long global social and psychological effects should be managed; the recovery is complicated, time consuming and very expensive.
GOALS AND TOOLS OF REGULATORY SUPERVISION
The prevention aims at avoiding any harm and deviation. Preventive regulatory tools include:
· establishment and promulgation of regulatory requirements and procedures, continuous development of the requirements system based on international experience and the technical and scientific development;
· establishment and promulgation of enforcement procedures and sanctions,
· licensing and authorization of activities in connection with the construction and operation of facilities, as well as the use, storage and transport of nuclear and other radioactive materials;
· accountancy for and registration of nuclear and other radioactive materials, and authorized persons;
· establishment, development and maintenance of nuclear safety and security culture;
· provision of guidance on the compliance with requirements and by cooperation with the users of atomic energy.
The detection/recognition aims to recognize the deviation or harm in due time. The regulatory tools of detection/recognition include:
· inspection/verification of the compliance with preventive measures;
· environmental monitoring;
· personal monitoring;
· inventory taking and verification,
· operation of remote observation and detection systems;
· evaluation of regular and eventual reports, public calls.
The response aims to eliminate the deviation and mitigate the harm. Three levels are distinguished: operative measures, joint measures and emergency management.
Certain deviation can be eliminated by operative measures, including:
· supervision of actions implemented by the users according to pre-established procedures;
· evaluation of an event investigation report, regulatory event investigation;
· conduct of an enforcement procedure.
Certain deviations can be eliminated or harmful consequences mitigated by the joint effort of several authorities, including:
· common site investigation and measures;
· police and nuclear forensics;
· recovery of lost or missing nuclear or other radioactive materials;
· safe and secure transport of found nuclear or other radioactive materials.
Emergency response measures must be applied if the environment is significantly contaminated or significant public exposure occurred. Such measures include:
· activation of the nuclear emergency response plan;
· recovery of the environment.