Nuclear Safety Authority Research Articles

Non-targeted effects of ionising radiation (NOTE) – an ongoing European Integrated project, 2006-2010

The general objectives of the NOTE project are: (1) to investigate the mechanisms of non-targeted effects, in particular, bystander effects, genomic instability and adaptive response; (2) to investigate if and how non-targeted effects modulate the cancer risk in the low dose region, and whether they relate to protective or harmful functions; (3) to investigate if ionising radiation can cause non-cancer diseases or beneficial effects at low and intermediate doses; (4) to investigate individual susceptibility and other factors modifying non-targeted responses; (5) to assess the relevance of non-targeted effects for radiation protection and to set the scientific basis for a modern, more realistic, radiation safety system; (6) to contribute to the conceptualisation of a new paradigm in radiation biology that would cover both the classical direct (DNA-targeted) and non-targeted (indirect) effects. The NOTE brings together 19 major European and Canadian groups involved in the discovery, characterisation and mechanistic investigation of non-targeted effects of ionising radiation in cellular, tissue and animal models. The NOTE research activities are organised in six work packages. Four work packages (WPs 2-5) are problem-oriented, focussing on major questions relevant for the scientific basis of the system of radiation protection: WP2 Mechanisms of non-targeted effects, WP3 Non-cancer diseases, WP4 Factors modifying non-targeted responses, WP5 Modelling of non-targeted effects. The integration activities provided by WP6 strengthen the collaboration by supporting the access to infrastructures, mobility and training. WP7 provides dissemination and exploitation activities in the form of workshops and a public website. Managerial activities (WP1) ensure the organisation and structures for decision making, monitoring of progress, knowledge management and efficient flow of information and financing. Coordinator of the NOTE project is Prof. Sisko Salomaa, STUK - Radiation and Nuclear Safety Authority, Helsinki, Finland. The project is supported by the European Commission under the Euratom specific programme for research and training on nuclear energy, 6th Framework Programme. Please visit the project website http://www.note-ip.org to obtain more information or contact us by e-mail note@stuk.fi. Progress of the first year of the project will be described.

Feedback from IAEA TranSAS appraisal mission in France

In 2002, France requested the International Atomic Energy Agency (IAEA) to organise a mission to assess its organisation for the control of transport of radioactive materials and its implementation of international regulations. The Transport Safety Appraisal Service (TranSAS) mission was conducted in 2004 by a team composed of thirteen independent experts. The scope of the appraisal was broad and covered all aspects of the implementation of regulations for the safe transport of radioactive materials. The main conclusion is that the implementation of the Transport Regulations is performed in accordance with IAEA requirements. Nevertheless, this mission issued three recommendations and sixteen suggestions. It led France to strengthen its control of non-competent authority approved. Moreover, the findings include twelve good practices that can serve as a model for other competent authorities, in particular in the area of maritime transport. The present paper presents the French Nuclear Safety Authority's feedback from this mission, in order to reach a high safety level in the field of transports.

Improvement of the measuring equipment used in the assessment of internal doses in emergency situations

Emergency response plans have long been focused on accidents at nuclear power plants. Recently, the malevolent use of radiation aimed at creating disruption in the society has been considered as a possible threat. In this kind of emergency situations casualties will most likely be members of the public and the number of affected people can vary from a few to mass casualties. There is an evident need for rapid measurements of large groups of internally contaminated people. Radiation and Nuclear Safety Authority (STUK) in Finland has obtained new monitors for thyroid and simple whole-body measurements in field conditions as a part of the continuous improving of emergency preparedness. The new monitors consist of a NaI(Tl) detector and a control unit. The monitors work as spectrometers allowing real-time spectrum analysis in the field.

Diagnostic reference levels for thorax X-ray examinations of paediatric patients

Based on the Medical Exposure Directive of the European Commission, 97/43/Euratom, The Radiation and Nuclear Safety Authority (STUK) in Finland has the responsibility for setting national diagnostic reference levels (DRLs) for the most common radiological examinations. Paediatric patients deserve special attention because of the higher radiation risk compared with adults. The purpose of this paper is to present a method that takes into account patient size when setting DRLs in paediatric patients. The overall data consisted of patient doses collected from six hospitals during the years 1994-2001, and new measurements in two hospitals in 2004. In total, there were 700 chest examinations. The method established by the National Radiological Protection Board (UK) for setting DRLs was not considered feasible in Finnish practice. Patient doses correlated exponentially with the projection thickness, which was measured directly for each patient. Since 1 January 2006, paediatric DRLs for conventional chest examinations have been specified in Finland as a DRL curve by using both dose quantities (entrance surface doses (ESD) and dose-area product (DAP)) as a function of patient projection thickness.

A risk-risk analysis-based socio-legal abstraction approach to complex decision making in nuclear systems

Complex risk-based decisions in nuclear systems are largely guided by probabilistic safety assessments and established legal precepts, such as ALARA. Typically, however, there exists a gap between the risk perceptions of experts and those of the public, which adversely affects the societal acceptability of these decisions. Often this gap is amplified by the media and campaign rhetoric, leading to controversies and even societal rejection of some of these decisions. Sifting through the rhetoric and objectively incorporating the underlying societal risk perceptions in decision-making will arguably contribute towards improving the societal acceptability of such risk decisions. To achieve such an improvement in social acceptability, this paper proposes a risk-risk analysis-based socio-legal abstraction approach within a fuzzy decision making framework. As an illustration, the deep geological repository decision-making problem of ASN, the French Nuclear Safety Authority, is abstracted and solved with hypothetical triangular fuzzy number rank preferences, and the advantages of using such a methodology are demonstrated.

EPR Becomes Reality at Finland's Olkiluoto 3

The EPR is a third-generation pressurized water reactor (PWR). Its development was started in 1992 by Framatome and Siemens within a Franco-German partnership. Since 2001 this work has been continued by Framatome ANP, which was formed when the two companies merged their nuclear businesses. The French company AREVA, world market leader in nuclear technology, holds a 66% share in Framatome ANP, with Siemens owning 34%. From the very start, development of the EPR was focused on improving plant safety and economics even further. The new reactor development was jointly financed together with the leading power utilities of both countries. The first steps towards realization of an EPR nuclear power plant were taken at Olkiluoto, Finland in 2004 [1][2], consisting of initial preparation of the construction site. By mid-February 2005 the local municipality – Eurajoki – had issued a construction permit, and the Finnish Government a construction license pursuant to the Finnish Nuclear Energy Act. This had been preceded by a preliminary safety assessment prepared by the Finnish Radiation and Nuclear Safety Authority (STUK) for the Finnish Ministry of Trade and Industry in which STUK verified that it did not see any safety-related issues opposing issuance of the nuclear construction license. STUK emphasized that the evolutionary design of the EPR had been further improved by AREVA compared to the previous product lines. Concreting work began this spring and the unit will start commercial operation in 2009. Construction of an EPR has also been given the political go-ahead in France. According to the utility Electricité de France (EDF) the new reactor will be built as a forerunner of a later series at the site of Flamanville in Normandy. Construction is scheduled to begin in 2007. An EPR nuclear power plant has a rated electric capacity of around 1600 MW, depending on specific site conditions. Being the product of intense bilateral cooperation the EPR combines the technological accomplishments of the world's two leading PWR product lines – France's N4 and Germany's Konvoi. At the same time it incorporates a new class of safety: its highly advanced safety systems represent a further enhancement of the high safety level already provided by nuclear plants currently in operation in Germany and France. To attain the specified safety goals, measures have been taken to further reduce the probability of occurrence of core damage and to also ensure that all consequences of a (hypothetical) accident involving core melt remain restricted to the plant itself. The EPR has additionally made great progress in terms of low power generating costs, conservation of natural resources, and minimization of waste volumes. From the viewpoint of the European nuclear community, it therefore demonstrates nuclear energy's excellent prospects for the future as an economical option for carbondioxide-free base-load power generation in our liberalized power markets.

SU-FF-I-54: Some Physical Factors Which Affect the Patient Doses and the Radiological Images Quality

Purpose: The purpose of this paper is the analysis of the console set parameters, the shape and the composition of the X-ray spectrum that is generated by the Roentgen device and the estimation of the organ doses and the effective dose involved in several radiological examinations using Monte-Carlo simulations. Method and Materials: The quality of X-ray beam, is usually expressed in terms of HVL. The HVL method consists in several measurements of the radiation dose, free in air, using a set of aluminum filters and a RADCHECK 06-256-dosimeter. First, a spline interpolation on the mmAl-dose plot has been made. Then, the HVL1 (the added filtration that correspond to the dose reduction by 1/2) and QVL (quarter value layer, which is the added filtration that correspond to the dose reduction by 1/4) factors are estimated by solving the corresponding cubic spline equations using the classical Cardano formulas. The HVL2 factor is calculated as HVL2=QVL−HVL1. Results: For comparison, the theoretical values at the same settings, regarded as those values corresponding to an adequate radiological device, HVL1 and HVL2 were computed, using the XCOMP5R software provided by University of Vienna. The effective dose was calculated, using the PCXMC, a Monte-Carlo based software, provided by STUK (Radiation and Nuclear Safety Authority in Finland). HVL and homogeneity factor values for theoretic and experimental mode are presented below (mmAl) Conclusion: The experimental HVL1 and HVL2 values are significant smaller then the theoretical values. that, all console set parameters are correct, we can conclude that patient doses should be greater then the corresponding doses generated by an appropriate X-ray device, due to the strong photons absorbtion at low energies.

Interlaboratory comparison and accreditation in quality control testing of diagnostic X-ray equipment

The University of Tartu provides a quality control service to the majority of diagnostic X-ray departments in Estonia. Its methodology has been adopted from the IEC and other relevant standards. Recently the Testing Centre of the University of Tartu was accredited on this methodology by ISO/IEC 17025. Besides the implementation of the quality management system, participation in interlaboratory comparison (ILC) was one of the prerequisites for the accreditation. Tests for estimating reproducibility of tube voltage and dose rate, accuracy of the voltage and accuracy of exposure time were carried out on a diagnostic X-ray unit in the Radiation and Nuclear Safety Authority in Helsinki. The measurement performance was judged by calculating deviation E(n) normalised with respect to the stated uncertainties. E(n) values for all tests were less than unity and by the common ILC criteria the testing performance could be considered as acceptable.

Prospects of nuclear desalination in Morocco

In the last few years, Morocco has faced a continuous series of dry seasons, which has put a great stress on its limited water resources. Hence, for some time now Morocco has been considering desalinating seawater to supply fresh water to some areas. In the early 1980's, due to limited energy resources, Morocco was obliged to consider other alternatives to meet its energy demands. A feasibility study for the introduction of a nuclear power plant into the national electrical grid was launched. Even though the study showed that the commercially proven, large size reactors could not be integrated into the grid due to their limited capacity, the national electrical utility continues to pursue its efforts to introduce nuclear energy into the country. Presently, the feasibility study is being updated and a bid invitation specification is being prepared with the help of the IAEA experts. In response to the increasing need for energy and water, Morocco and some North African countries participated in the IAEA regional project on the feasibility study on using nuclear energy for seawater desalination. Subsequently, Morocco carried out a feasibility study for the construction of a demonstration plant for seawater desalination using a 10 MW Nuclear Heating Reactor with China and IAEA. As part of its interest in nuclear energy, Morocco is setting up the nuclear infrastructure that could help in the implementation of the nuclear power programme. The construction of a nuclear research centre which is to be commissioned in a couple of years, and the establishment of the nuclear safety authority and the radiation protection authority are part of the programme.

Methods and practices used in incident analysis in the Finnish nuclear power industry

According to the Finnish Nuclear Energy Act it is licensee’s responsibility to ensure safe use of nuclear energy. Radiation and Nuclear Safety Authority (STUK) is the regulatory body responsible for the state supervision of the safe use of nuclear power in Finland. One essential prerequisite for the safe and reliable operation of nuclear power plants is that lessons are learned from the operational experience. It is utility’s prime responsibility to assess the operational events and implement appropriate corrective actions. STUK controls licensees’ operational experience feedback arrangements and imlementation as part of its inspection activities. In addition to this in Finland, the regulatory body performs its own assessment of the operational experience. Review and investigation of operational events is a part of the regulatory oversight of operational safety. Review of operational events is done by STUK basically at three different levels. First step is to perform a general review of all operational events, transients and reactor scram reports, which the licensees submit for information to STUK. The second level activities are related to the clarification of events at site and entering of events’ specific data into the event register database of STUK. This is done for events which meet the set criteria for the operator to submit a special report to STUK for approval. Safety significance of operational events is determined using probabilistic safety assessment (PSA) techniques. Risk significance of events and the number of safety significant events are followed by STUK indicators. The final step in operational event assessment performed by STUK is to assign STUK’s own investigation team for events deemed to have special importance, especially when the licensee’s organisation has not operated as planned. STUK launches its own detail investigation once a year on average. An analysis and evaluation of event investigation methods applied at STUK, and at the two Finnish nuclear power plant operators Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy (Fortum) was carried out by the Technical Research Centre (VTT) on request of STUK at the end of 1990s. The study aimed at providing a broad overview and suggestions for improvement of the whole organisational framework to support event investigation practices at the regulatory body and at the utilities. The main objective of the research was to evaluate the adequacy and reliability of event investigation analysis methods and practices in the Finnish nuclear power industry and based on the results to further develop them. The results and suggestions of the research are reviewed in the paper and the corrective actions implemented in event investigation and operating experience procedures both at STUK and at utilities are discussed as well. STUK has developed its own procedure for the risk-informed analysis of nuclear power plant events. The PSA based event analysis method is used to assess the safety significance and importance measures associated with the unavailability of components and systems subject to Technical Specifications. The insights from recently performed PSA based analyses are also briefly discussed in the paper.

INES Scale: French Application to Radioactive Material Transport

After gaining control of radioactive material transport in June 1997, the French Nuclear Safety Authority (ASN) decided to apply the International Nuclear Event Scale (INES scale) to transport events. The Directorate General for Nuclear Safety and Radioprotection (DGSNR) requests that radioactive material package consignors declare any event occurring during transport, and has introduced the use of the INES scale adapted to classify transport events in order to inform the public and to have feedback. The INES scale is applicable to events arising in nuclear installations associated with the civil nuclear industry andevents occurring during the transport of radioactive materials to and from them. The INES scale consists of seven levels. It is based on the successive application of threetypes of criterion (off-site impact, on-site impact and degradation of defence in depth) and uses the maximum level to determine the rating of an accident. As the transport in questiontakes place on public thoroughfares, only the off-site impact criteria and degradation ofdefence in-depth criteria apply. This paper deals with DGSNR's feedback during the past 7 years concerning the French application of the INES scale. Significant events that occurred during transport are presented. The French experience was used by the International Atomic Energy Agency (IAEA) to develop a draft guide in 2002 and the IAEA asked countries to use a new draft for a trial period in July 2004.

The French Nuclear Safety Authority's Experience with Radioactive Transport Inspection

AbstractAbout 300,000 radioactive material packages are transported annually in France. Most consist of radioisotopes for medical, pharmaceutical or industrial use, but the nuclear industry deals with the transport of fuel cycle materials (uranium, fuel assemblies, etc.) andwaste from power plants, reprocessing plants and research centres. France is also a transit country for shipments such as spent fuel packages from Switzerland or Germany, which are bound for Sellafield in the United Kingdom. The French nuclear safety authority(DGSNR, Directorate General for Nuclear Safety and Radioprotection) has since 1997 been responsible for the safety of radioactive material transport. This paper presents DGNSR's experience with transport inspection: a feedback of key points based on 300 inspections achieved during the past 5 years is given.

The first digital reactor protection system in China

The reactor protection system (RPS) used in the 10 MW high-temperature gas-cooled reactor is the first digital RPS designed and operated in China. In order to ensure its safety and reliability and to reduce the development risk and cost, some measures had to be taken. The measures adopted in the development process include the architecture of defense-in-depth, commercial grade hardware, prototype development model, separation of safety class software and non-safety class software, deterministic behavior of safety software, etc. The measures adopted in the verification and validation (V&V) process include effective dedication on the commercial grade hardware, emphasis on the assessment of the requirements and specifications, emphasis on the demonstration and testing, thorough testing for the safety function, long period demonstration operation, application of automatic test system to improve the efficiency of V&V processes, etc. As a result, this first digital RPS has passed the safety assessment of the National Nuclear Safety Authority. Its performance and safety are proven to be confident and assuring through the demonstration and testing. Thus, the design and V&V process of the first digital protection system in China was successful.

Radon mapping strategy in Finland

Since 1986, the Radiation and Nuclear Safety Authority (STUK, Finland) has performed systematic indoor radon mapping with municipal health authorities. STUK has made radon measurement plans and radon risk maps to identify radon-prone areas. In the most radon-prone area, there are about 260,000 low-rise dwellings. In this area, it is expected that in 37,000 homes, the action level of 400 Bq/m 3 will be exceeded. We have detected about 4800 of them. In the rest of Finland, the numbers are: 1,000,000 low-rise dwellings, 31,000 expected and 1800 detected cases exceeding the limit, respectively. The most active search for high radon houses should be focused on Southern Finland. The search is easiest in areas of permeable soil types like esker areas and other sand and gravel deposits because they are easy to locate from geological maps. It is cheaper and easier to take preventive measures when building new houses than to take mitigation measures later. Due to high indoor radon concentrations, it is reasonable to build radon-safe dwellings in all esker areas throughout the country and on other building sites in most parts of Finland.

Estimation of consequences following an atmospheric radioactive emission in a forest ecosystem

Forests represent very efficient filters of atmospheric aerosols. Radionuclides that are fixed on those aerosols fall on the aerial part of trees and understorey (leaves, branches and trunks) and on the soil (litter, mosses and first soil layers). Due to the high content of organic matters in the forest soils and the existence of a nutrition cycle by the humification process, radionuclides show a higher biodisponibility than in agricultural soils. IPSN developed, in collaboration with a finnish team from STUK (Finnish Nuclear Safety Authority), a model to assess the consequences of an atmospheric radioactive emission in a forest ecosystem. This dynamic compartment model has been developed with a simple and operational objective of crisis management. This model needs data relative to dry and wet depositions that are distributed in the ecosystem to trees, understorey and soil. Calculation of transfers between the different compartments of the ecosystem are used to calculate concentrations in forest products and external exposure. Then, ingestion dose and external exposure are calculated for several population groups : six age groups for the population, forest workers, hunters and mushroom and berry pickers. Calculations are made for iodine, caesium, strontium and plutonium isotopes and for three generic forest types : coniferous, deciduous and mixed forests. Forest structures vary in Europe with climate and soil type and also due to forest management. Many parameters in the model database are regional and should be adapted in order to substantially improve the estimations.

Occupational exposures of nuclear power plant workers in Finland.

In Finland, the Radiation and Nuclear Safety Authority (STUK) maintains a central dose register where all occupational doses of radiation workers are recorded. The computerised register enables easy control of personal doses, including annual, 5 year and lifetime doses. The type of radiation work is also recorded in the dose register. Finland was one of the first countries in the world to introduce dose limits based on the recommendations of ICRP 60. In this article, the radiation dose data of the Finnish nuclear power plant workers are analysed. The majority of the radiation doses are received during the maintenance outages. The trend of the 5 year doses and their distribution are presented. Doses received during different work assignments were averaged over the years 1996-1999 and they are also discussed in this article.

Implementation of Quality Standards in an Individual Monitoring Service

In this paper the implementation of a quality system to the procedures of an individual monitoring service (IMS) is described from the practical perspective. The IMS of the Radiation and Nuclear Safety Authority (STUK) is used as an example. The IMS of STUK monitors about 8500 persons mainly working in hospitals, industry and research centres. The current thermoluminescence dosemeter (TLD) system was introduced in 1992 and the whole service changed to TLDs in 1995. The quality system compatible with the quality standards was introduced in 1999. An application for accreditation to fulfill EN45001 and ISO/IEC Guide 25 was made in December 1999, accreditation was achieved in August 2000 by the Finnish Accreditation Service (FINAS). The considerations needed for the quality system to fulfill the requirements of the quality standards are reported.

Un outil peu connu mais efficient au service du principe ALARA : ISOE (Information System on Occupational Exposure)

An efficient but little known tool for the application of the ALARA principle: ISOE (Information System on Occupational Exposure). The Information System on Occupational Exposure to ionizing radiation (ISOE) is a program launched by the Nuclear Energy Agency (NEA) in 1992. It was developed to address the needs of nuclear power plants and safety authorities as a comparison and information tool on practices in terms of optimization (ALARA principle), in NEA member countries. To date, more than 90% of the operating nuclear power plants in the world are participating in this program, which is organized in a decentralized form, with a steering group and four technical centers (Europe, Asia, north America and IAEA). The ISOE program includes an occupational exposure database and an information exchange and communication network. The databases permit the preparation of studies and comparisons of practices, either in a factual or analytical way. Thus, the ISOE program favors exchanges to the benefit of all participants and helps to bring operational radiation protection ever closer towards the achievable of ALARA.

USE OF THE COMPLEX BETWEEN PROSTATE SPECIFIC ANTIGEN AND α1-PROTEASE INHIBITOR FOR SCREENING PROSTATE CANCER

We assess whether the complex between prostate specific antigen (PSA) and alpha1-protease inhibitor in serum can be used to reduce further the number of false-positive PSA screen results independent of total and free PSA. Sera from 304 consecutive screen positive subjects, including 78 with and 226 without prostate cancer, and serum PSA of 4 to 10 microg./l. or higher in the Finnish, randomized, population based prostate cancer screening trial were analyzed for PSA-alpha-protease inhibitor, and total and free PSA. Main outcome measures were specificity, sensitivity and area under receiver operating characteristics curve for proportions of free PSA and PSA-alpha 1-protease inhibitor, and for a combination of these among screen positive cases. The proportion of serum PSA-alpha 1-protease inhibitor of total PSA was lower in cancer cases than in controls (0.9% versus 1.6%, p <0.001). Logistic regression analysis of total PSA, free PSA and PSA-alpha 1-protease inhibitor showed that PSA-alpha 1-protease inhibitor in serum was an independent variable for discrimination between subjects with and without prostate cancer (p = 0.006) in the PSA range of 4 to 10 microg./l. The proportion of PSA-alpha 1-protease inhibitor alone improved specificity less than the proportion of free PSA but when these were combined by logistic regression they performed better than the proportion of free PSA alone at sensitivities of 85% to 95% (p <0.001). Serum PSA-alpha 1-protease inhibitor improves the specificity of total and free PSA in a screening population with total PSA 4 to 10 microg./l.

Erythemally Weighted Radiometers in Solar UV Monitoring: Results from the WMO/STUK Intercomparison

ABSTRACTThe first international intercomparison of erythemally weighted (EW) broadband radiometers was arranged in 1995 to improve the accuracy and comparability of the measurements carried out by solar UV monitoring networks. The intercomparison was arranged at the Radiation and Nuclear Safety Authority in Helsinki, Finland, in cooperation with the University of Innsbruck and with support from the World Meteorological Organization. Altogether 20 EW meters of six different types from 16 countries were (1) tested in the laboratory by measuring the spectral and angular responsivities and (2) calibrated in solar radiation against two reference spectroradiometers. Calibration factors (CFs) for the EW meters were determined by using simultaneously measured EW solar UV spectra as a calibration reference. The CFs averaged over solar elevations higher than 35° varied from 0.87 to 1.75, with the estimated uncertainty being ±10%. As a result of this intercomparison, for the first time the calibrations of more than 100 EW radiometers around the world are possible to trace to the same origin. The present experience indicates that the accuracy of temperature‐controlled EW radiometers is not significantly lower than the accuracy of spectroradiometers provided that strict quality assurance/quality control procedures are followed.