[en] The analysis of a radioactive sources inventory in countries with a nuclear programme usually comprises nearly all possible man-made sources available today, from sources related to nuclear power plants to calibration sources used for educational purposes. The risk based licensing process of radiation sources and exposures is a demanding task which could be internationally harmonised by introducing sources and practice related categorisation. The detailed categorisation of radioisotopes, replacing [1], was recently published [2]. The activity ratio (A/D ratio) is used as a basic parameter which is proportional to a risk involved in a use of a radioisotope. Radioisotopes as well as related practices are categorised. No categorisation of ionising sources related to electrical apparatus producing ionising radiation without radioisotopes has been given in literature. In addition, licensees usually perform many different activities with a specific source, so the categorisation of practice should be done, based on a risk involved with a specific practice. The risk is related to the probability of a specific event as well as to the consequences of that event. It is strongly related to the categorisation of source. The main issues related to a licensing process of sources and practices are presented. The review of possible categorisation of radioisotopes and related practices is given and a proposal of a combined harmonised approach of categorisation of sources and practices, based on risk, is given. (Author) 19 refs

[en] The Krsko NPP is a Westinghouse pressurised water reactor (PWR) with electrical output of 700 MW. In the year 2000 it performed a comprehensive maintenance after nearly 20 years of operation. The modernisation also included the replacement of two steam generators. The implementation of radiation protection standards given in (1-The Council of the European Union, Council Directive of 13 May 1996 Laying down Basic Safety Standards for the Protection of the Health of Workers and the General Public against the Danger Arising from Ionising Radiation, Council Directive 96/29/Euratom, Official Journal European Communities L 159, 1996.) is very important especially during a comprehensive maintenance of the NPP. As shown in the ISOE database (2-Nuclear Energy Agency, Occupational Exposures at Nuclear Power Plants, Eleventh Annual report of the ISOE Programme, 2001, OECD; 2002.), the general downward trend of the average collective effective dose of workers at PWRs in the recent years is mainly due to the implementation of work management principle and the reduction in outage duration. The analyses of the workers' exposures in the Krsko NPP are presented and the comparison with the worldwide trends is done. The standards established in (1) and (2) together with the lifetime cycle of the nuclear installation require development of the suitable performance indicators, which can be used as a evaluation tool in the radiation protection. Some of those indicators are already internationally used (2). The detail analysis of the trends of workers' doses requires also a comprehensive analysis of the jobs performed at the site of the nuclear installations. The analysis of the doses at the Krsko NPP shows the expected decrease after the modernisation of the NPP in the year 2000. (author)

[en] The wide spread use of radioactive and particularly of nuclear materials which started in the last century very quickly also demonstrated negative sides. The external exposure and radiotoxicity of these materials could be easily used in a malevolent act. Due to the fact that these materials could not be detected without special equipment designed for that purpose, severe control over their use in all phases of a life cycle is required. An orphan source is a radioactive source which is not under regulatory control, either because it has never been under regulatory or because it has been abandoned, lost, misplaced, stolen or transferred without proper authorization. In the last ten years a few international conferences were dedicated to the improvement of the safety and security of radioactive sources. Three main tasks are focused, the maintenance of data bases related to events with orphan sources and the publications of such events, the preparation of recommendations and guidelines to national regulatory bodies in order to prevent and detect the events related to orphan sources as well as to develop the response strategies to radiological or nuclear emergency, appraisals of the national strategies of radioactive sources control. Concerning Slovenia, strengthening control over orphan sources in Slovenia started after the adoption of new legislation in 2002. It was carried out through several tasks with the aim to prevent orphan sources, as well as to identify the sources which could be potentially orphan sources. The comprehensive methodology was developed by the Slovenian nuclear safety administration (S.N.S.A.) based on international guidelines as well as on the study of national lesson learned cases. The methodology was developed and used in close cooperation with all parties involved, namely other regulatory authorities, police, customs, agency for radioactive waste management (A.R.A.O.), technical support organisations (T.S.O.), users of source, authorised transporters etc. In the years 2003-2005 around 40 inspections resulted in regaining control over around 200 orphan sources. Three main cases could be identified, among them the majority of incident cases were related to sources which have never been under control. Such sources were very often used in past activities which were stopped without a proper termination of activities. Other two cases are related to illicit trafficking and lost of a control over sources which were under control in the past. (N.C.)

[en] Many countries, particularly in Europe, started with nuclear programs in the fifties of the last century. As a consequence nuclear research institutes were established, among them also the Institute Jozef Stefan (IJS) in Slovenia. The nuclear activities at the IJS were related to the development of uranium ore processing technology and technologies comprising uranium oxide and hexafluoride. After very intensive period of nuclear activities the decline began step by step due to different reasons. Various approaches of the termination and decommissioning of facilities were used. The inspectors of the Slovenian Nuclear Safety Administration (SNSA), the responsible authority, started intensive activities at the IJS at the end of 2004. All together 22 research laboratories or research units were included in the inspection program and around 50 researchers of the IJS were involved into the inspection procedures. The inspection was very intensive in the laboratories and storages where past nuclear activities took place and were later on abandoned. As a result several contaminated equipments and sites in addition to around 200 unregistered sources were found. The majority of these sources is related to past nuclear activities. The inspection program related to the terminated research activities is still in progress. The IJS immediately started with the remediation activities including the development of methodology related to decontamination of radioactive liquids. The decontamination of two nuclear laboratories and three different storages of radioactive waste at its sites is in progress. Sixty of the above mentioned sources have been already stored in the Central Interim Storage for Radioactive Waste. (author)

[en] Full text: The automatic radiation monitoring system in Slovenia started in early nineties and now it comprises measurements of: 1. External gamma radiation: For the time being there are forty-three probes with GM tubes integrated into a common automatic network, operated at the SNSA. The probes measure dose rate in 30 minute intervals. 2. Aerosol radioactivity: Three automatic aerosol stations measure the concentration of artificial alpha and beta activity in the air, gamma emitting radionuclides, radioactive iodine 131 in the air (in all chemical forms, - natural radon and thoron progeny, 3. Radon progeny concentration: Radon progeny concentration is measured hourly and results are displayed as the equilibrium equivalent concentrations (EEC), 4. Radioactive deposition measurements: As a support to gamma dose rate measurements - the SNSA developed and installed an automatic measuring station for surface contamination equipped with gamma spectrometry system (with 3x3' NaI(Tl) detector). All data are transferred through the different communication pathways to the SNSA. They are collected in 30 minute intervals. Within these intervals the central computer analyses and processes the collected data, and creates different reports. Every month QA/QC analysis of data is performed, showing the statistics of acquisition errors and availability of measuring results. All results are promptly available at the our WEB pages. The data are checked and daily sent to the EURDEP system at Ispra (Italy) and also to the Austrian, Croatian and Hungarian authorities. (author)

[en] Radiation protection and nuclear safety of nuclear installations have a common objective, protection against ionising radiation. The operational safety of a nuclear power plant is evaluated using performance indicators as for instance collective radiation exposure, unit capability factor, unplanned capability loss factor, etc. As stated by WANO (World Association of Nuclear Operators) the performance indicators are 'a management tool so each operator can monitor its own performance and progress, set challenging goals for improvement and consistently compare performance with that of other plants or industry'. In order to make the analysis of the performance indicators feasible to an operator as well as to regulatory authorities a suitable database should be created based on the data related to a facility or facilities. Moreover, the international bodies found out that the comparison of radiation protection in nuclear facilities in different countries could be feasible only if the databases with well defined parameters are established. The article will briefly describe the development of international databases regarding radiation protection related to nuclear facilities. The issues related to the possible development of the efficient radiation protection control of a nuclear facility based on experience of the Slovenian Nuclear Safety Administration will be presented. (author)

[en] Full text: In early 1999s the SNSA started to develop a computerised registration system of occupational radiation exposure for workers in a nuclear fuel cycle in Slovenia, which arises from four nuclear facilities: nuclear power plant, research reactor, storage facility and uranium mine. In the period 1985-2000 about 5000 workers altogether were monitored due to exposure in a nuclear fuel cycle in Slovenia (about 1200 employees and 3800 outside workers), with an average of 1000 workers being assessed each calendar year. Four dosimetric services regularly perform personal monitoring of the occupational exposure and all of them have been requested to provide data to the SNSA electronically. The computerised register was put into operation in 2000 enabling prompt control of personal exposures, including annual, 5-year and lifetime doses. Besides individual exposure also collective doses can be evaluated, together with size and time distributions and trends over certain periods. Apart from the total dose, the doses received due to external radiation (gamma, neutrons) and due to internal radiation have been separately recorded into the register. In addition, personal data of workers as well as employee and facility data have been also recorded. Some statistics of dose distributions have been evaluated and the results have been compared to international data. More than 80% of workers from the register have been exposed in the NPP. Workers received the major part of their exposure during the annual outage works. It is found out that in recent years, the average individual and collective doses have shown a rising trend. (author)

[en] The site-specific concentrations of the fission radionuclide ¹³⁷Cs, an activation radionuclide ¹³⁴Cs and the naturally occurring radionuclides ⁴⁰K, ²³⁸U, ²²⁶Ra and ²³²Th were determined by γ-spectroscopy in periphyton and sediment samples collected from the Kolubara River and its tributaries. Various concentration ratios were calculated in order to explain the bioaccumulation and distribution of radioisotopes in the Kolubara River ecosystem. The total γ activities of river sediments collected at the selected locations were also calculated. The concentrations of radiocesium per square meter of sediments were compared to the concentrations of ¹³⁷Cs for the regional soil after the Chernobyl accident. The presence of radioactive isotopes such as ¹³⁷Cs and ¹³⁴Cs, in the Kolubara River environment from the Chernobyl fallout was evident. (Author)

[en] A new technique for radon measurement in the natural environment was investigated. It is based on the use of activated charcoal and a track-etch detector. The charcoal acts as a radon collector from the air and the track-etch detector as a recorder of the alpha particles emitted by radon and its decay products. Our preliminary results show that the response of the new dosimeter to radon, using Deodorant activated charcoal (TOK, Yugoslavia) and a CR-39 track-etch detector, is 1.4 tracks cm^-2/Bqm^-3d, which is about eight times higher than that obtained with a standard track-etch dosimeter. (author)

[en] The level of radioactivity in discharges from a nuclear power plant (NPP) is a subject of strict control during the operation of an NPP as well as during its decommissioning. The control over radioisotopes in effluents of NPPs in the European Union (Eu) is a subject of the EURATOM Treaty signed in 1957. In addition, the European Commission published in 2004 a recommendation on standardised information on radioactive airborne and liquid discharges into the environment from nuclear power plant reactors and reprocessing plants in normal operation. In 2004, 157 NPPs were in operation in the Eu, the majority of these NPPs, namely 86 were pressurised water reactors (PWRs). On average they entered operation 22 years ago. These reactors already went through a few steps of the life cycle of an NPP: start - up phase, modernisation, upgrading etc. The effect of those steps on effluents has been studied for four Westinghouse NPPs in four different states in Europe, namely Slovenia, Spain, Sweden and Switzerland. Great discrepancies in activities of group of radionuclides in airborne and liquid effluents were found for a particular year. Only for specific radionuclides such as C-14 in airborne effluents and H-3 in liquid effluents these discrepancies were not found out. The study of the lifetime cycle from 1983 till 2004 of the Krsko NPP is reflected on its effluents. Five periods in its lifetime are identified showing also that due to the leakage of fuel elements in the years from 1993 to 1997 a substantial increase of activity of noble gases in effluents could be observed in that period. The operational regime of an NPP as well as the availability of best available technologies for treatment of effluents could drastically influence the absolute values of activities of some radionuclides in effluents. While no general study of operational regimes, pre-treatment technologies and subsequent effluents for NPPs in Europe is available yet, a first study identifying the life cycle of an NPP and effluents could be done. In addition, it should be emphasised that no harmonised approach to the measurement techniques including sampling procedures for determination of effluents in NPPs is in place and neither harmonised reporting. Furthermore also a scope of a control over effluents has not been harmonised yet. (author)