Nuclear Power

Excerpt from the IAEA Annual Report for 1994

Programme overview

A major conference entitled The Nuclear Power Option, held in September, confirmed the viability of nuclear power for future growth as an economic and environmentally sound technology. One conclusion was that it could be used in conjunction with other energy resources to provide a reliable supply of energy in the event of disruptions in fossil fuel supply and prices. The actions which should be taken by governments to maintain the nuclear power option were identified.

The training and qualification of nuclear power plant personnel were identified in 1993 as areas requiring greater attention from the Agency. In 1994, the first meeting of an International Working Group was held to formulate recommendations on the programme of work to be undertaken over the next few years. The initial emphasis will be on a training methodology, i.e. a systematic approach to training, the general objective being to help utilities become self-sufficient in identifying and satisfying their training needs.

A revised Power Reactor Information System (PRIS) database was completed and will be made available to Member States in 1995. This database is now accessible on-line to anyone using a PC with the appropriate software. The revision of the Agency's Quality Assurance Code and Safety Guides within the NUSS programme advanced to the point where final drafts were sent to Member States. Completion and publication of these documents is planned for 1995.

In its activities on advanced reactors the Agency continued to monitor and document trends in the development and design of next generation reactors, with special attention given to the status of small and medium sized reactors and their application for the desalination of sea water. The availability of potable water is an emerging issue in many Member States and the Agency was requested at the regular session of the General Conference to study options for the demonstration of nuclear reactors coupled to seawater desalination processes.


Nuclear Power Planning and Implementation

Development of an integrated package approach to energy, electricity and nuclear power programme planning

The planning methodologies developed by the Agency for energy, electricity and nuclear power planning continued to receive wide acceptance among Member States and international organizations. New developments in 1994 included the following:

Assistance in nuclear power programme planning

Support was given to technical co-operation projects in developing Member States, especially for nuclear power programme planning and development, including energy and nuclear power planning studies, project feasibility studies and infrastructure development planning:

General activities

The migration of the Energy and Economic Data Bank (EEDB) from the mainframe to the PC environment has been accomplished. Following the completion of improvements to the EEDB - planned for the first half of 1995 - various PC application packages from EEDB will become accessible through the LAN to Agency staff. An electronic version of the publications Reference Data Series No. 1, Energy, Electricity and Nuclear Power Estimates for the Period up to 2015, and Energy and Economic Tables, will be made available to Member States by early 1995.Also, an updated PC version of the Micro-EEDB package will be made available to Member States upon request in 1995.

Following a review of training needs, an International Working Group on Nuclear Power Plant Personnel Training and Qualification (IWGT&Q) was established. The Group met during 1994 and adopted terms of reference and proposed areas for further work, including a systematic approach to the training of nuclear power plant personnel, the use of simulators for training and the importance of management involvement in and support for training for the safe, reliable and economic operation of nuclear power plants.

The training and qualification of personnel continued to be emphasized as a key element in ensuring the safe and reliable operation of nuclear power plants. A preliminary draft was prepared, with extrabudgetary support from the USA, of a technical document on the training and evaluation of nuclear power plant personnel; this is a revision of an earlier publication (IAEA-TECDOC-525) on the systematic approach to training.

A major conference entitled The Nuclear Power Option was held in September. A positive future for nuclear power was foreseen. It was felt that the demand for more electricity would be concentrated in areas of rapid economic and population growth. Many countries recognized that there were environmental and public health benefits to be gained from the use of nuclear power. The use of a balanced mix of energy resources was generally considered to be necessary to protect economies against delivery or price disruptions in fuel supply. The consensus reached at the conference was that nuclear power was not only a viable option, but the preferred option in many countries, being a proven, economically competitive and environmentally sound technology. However, the safe and reliable operation of nuclear power plants, convincing solutions for waste storage and disposal problems, and a regular licensing process were considered to be pre-requisites for the revival and expansion of this source of power. The reduction in available qualified nuclear power plant staff was identified as an area requiring attention. Government action, and a supportive policy consistently applied, were also needed to achieve positive public acceptance.


Assessment and Improvement of Nuclear Power Plant Performance

Analysis of nuclear power plant performance

The PRIS database continued to be maintained and updated. Information services were provided to Member States by way of on-line access to PRIS and with the distribution of a subset of the MicroPRIS databank to PC users. PRIS has also been redesigned and migrated to the LAN environment with the objectives of making it available on-line, improving the flexibility of data entry, reducing the complexity of information retrieval, and making it more user friendly. The system is already available in-house and a group of trial users was established in Member States. Access to external users in Member States will be available at the beginning of 1995. Currently, there are 73 on-line users of the original mainframe version in 29 Member States and 4 international organizations, but this access will be discontinued in 1995 when the new system becomes fully available to Member States. Improvements are also being introduced by expanding the database to include more information on plant site and characteristics.

Co-operation with WEC and UNIPEDE continued, with Agency participation in the Committee on Performance of Thermal Plants, and work also progressed on the promotion and harmonization of internationally compatible terminology and definitions.

Work continued on the establishment of country nuclear profiles, covering a country's energy and economic situation, forecast of nuclear energy and main organizations and institutions playing a role in the nuclear area. Information was provided by several Member States, and the structure and contents of the profile were designed; a database will be finalized in 1995.

A technical document on the analysis of the performance of WWER-440 units was completed and is being prepared for publication.

Nuclear power plant life management

At a meeting of the International Working Group on Life Management of Nuclear Power Plants (IWG-LMNPP), national and international programmes on the subject of plant life management were discussed and recommendations developed on the priority, scope and content of publications and meetings to be organized by the Agency.

Quality management and quality assurance

Drafts for the revised framework of the NUSS Quality Assurance Code and 14 related Safety Guides were completed. The complete set will be submitted for approval and issue in 1995.

Three assessment and review missions on quality management and quality assurance were carried out under technical co-operation projects at Paks (Hungary) and Bohunice and Mochovce (Slovakia).


Advanced Reactor Developments

Review of general developments

An Advisory Group meeting was convened in Vienna to review the final draft of a status report on small and medium size reactors (SMRs). The purpose of this document is to provide up to date information so that design approaches and features of SMRs can be made more transparent, in particular with respect to their simplicity and flexibility for various applications, and the incorporation of passive safety systems. Part of the report is addressed to policy makers who are planning to evaluate SMRs, giving them an overview of the present status of SMR development, and the requirements and preconditions that would make their deployment beneficial.

An Advisory Group meeting on the technical feasibility and reliability of passive safety systems, held in Juelich, Germany, provided a forum for discussing the present situation in this area. Passive systems and components have been deployed in present reactor designs and some data on reliability, common mode failures and common cause failures should be available; the need for a joint effort to collect and validate such data is under consideration in several countries. One conclusion from the meeting was that a mixture of passive and active systems would provide the best solution for safety issues, taking into consideration cost, reliability and safety.

The services of consultants were used for a meeting on the feasibility of nuclear reactors with unattended operation. The aim was to decide on the scope and structure of the working programme for a Technical Committee meeting on this subject that will take place in 1995. Since the number of reactor concepts designed for unattended operation is quite small, it was concluded that the scope of the meeting should be expanded to include small reactor designs which feature a minimum of staff, or have remote monitoring which contributes to the operational mode of these reactors. It was concluded that the review of applications of these reactors in remote areas for many different purposes (e.g. heating, communication, power generation or desalination) could provide important feedback for potential users.

Water cooled reactors

Within the framework of the International Working Group on Advanced Technologies for Water Cooled Reactors (IWGATWR), the Agency organized a Technical Committee meeting and workshop in Moscow on comparison of advanced LWR design approaches. The meetings provided an opportunity to discuss, review and compare different design approaches for advanced pressurized LWRs, with the objective of further improving the common understanding of the respective rationales for selected design features. A further meeting was convened to summarize the findings and recommend follow-up activities.

The emergence of a large variety of advanced design concepts has prompted the use of different technical terms. Since such inconsistencies may create confusion, the Agency initiated work on a draft document on the definitions of terms describing features of advanced reactors. This draft, in the IAEA-TECDOC series, will be distributed to the International Working Groups on water cooled, gas cooled and fast reactors, as well as to the International Fusion Research Council, for review and comments. A final version will be prepared in late 1995.

A Technical Committee meeting and workshop on a comparison of best estimate methods for judging the design margins of advanced water cooled reactors were held in Lyon, France, to discuss the status and further needs forther development of best estimate methods, and specifically to identify factors which determine key margins, to examine differences in licensing and best estimate approaches and to identify the means of reducing the uncertainties of predicted margins. It was concluded that best estimate approaches can be used to significantly increase thermal margins and the resulting increased margins can be used to enhance the economy and operating flexibility of a reactor. Much effort is required to develop and qualify best estimate methods for licensing applications.

The final Research Co-ordination meeting for a CRP to establish a thermo-physical properties database for light and heavy water reactor materials was convened in Vienna. This CRP has been conducted within the framework of the International Working Group on Advanced Technologies for Water Cooled Reactors. The CRP has collected, critically evaluated and systematised a thermophysical properties database for materials of advanced water cooled reactor sunder normal operating, transient and accident conditions. The materials for which the properties have been collected are fuel cladding, absorbers, steels, concrete, light and heavy water, hydrogen, xenon and mixtures of inert gases. The important thermophysical properties, including thermal conductivity, thermaldiffusivity, specific heat capacity, enthalpy, thermal expansion, oxidation of zirconium based alloys and characteristics of concrete core melt interaction, are presented in the database. A report is currently being prepared for publication.

A CRP on thermohydraulic relationships for advanced water cooled reactors was approved. The main goal of this CRP is to promote the exchange of information in establishing a consistent set of thermohydraulic relationships which are appropriate for use in analysing the behaviour of advanced water cooled reactors. The overall programme will encompass the following main research areas: pressure drop characteristics for single and two phase flow in forced and natural circulation situations; investigations of after heat removal from the reactor; critical heat flux (CHF) and post-CHF heat transfer; quenching/rewetting and boiling instability at the fuel bundle and subchannel levels; and the influence of non-condensable gases on heat transfer.

Liquid metal cooled reactors

At the 27th annual meeting of the International Working Group on Fast Reactors (IWGFR), held in Vienna, reviews were made of the status of national fast reactor development programmes, topics for Technical Committee meetings to be organized in 1995, CRPs currently in progress and preparations for an international topical meeting on fast reactor safety to be held in Obninsk, the Russian Federation.

A Technical Committee meeting on the evaluation of material coolant interaction and material movement and relocation in liquid metal fast reactors (LMFRs) was held at the Oarai Engineering Centre in Japan to review recent progress with regard to in-pile and out-of-pile experimental data (fuel and coolant interaction) and material movement and relocation for the entire spectrum of core disruptive accidents postulated for sodium cooled fast reactors. One key objective of the meeting was to identify common trends in the interpretation of the experiments and the influence on design features. A broad range of technical subjects was discussed, covering all aspects of material motion and interactions relevant to the safety of LMFRs. Recent achievements and the current status of research and development in this area were presented by Member States. The general consensus was that the future direction of safety research should also examine approaches that facilitate harmonization.

A Research Co-ordination meeting for a CRP on intercomparison of LMFR seismic analysis codes was held at the Oarai Engineering Centre in Japan to compare experimental and analytical results obtained by various organizations for the analysis of French Italian tests on Rapsodie, PEC (Prova Elementi di Combustible) and Monju make-ups to validate LMFR structural codes. A wide range of topics dealing with the seismic behaviour of LMFR cores was discussed and it was concluded that more experimental data are needed. At present, it is very difficult to perform an analysis of the whole core, given current limitations on computing power in some countries, but detailed core analyses are very important in ensuring reactor safety in the event of earthquakes.

Another Research Co-ordination meeting for a CRP on acoustic signal processing for the detection of sodium boiling or the sodium/water reaction in LMFRs was held in Kalpakkam, India. The purpose of this meeting was to review the results obtained,finalize the preparation of test data from experiments carried out on prototype fast breeder reactor steam generating units (SGUs) and make recommendations for the future. The possibility of detecting leaks between 0.1 and 1 g/s in a few seconds was demonstrated. The completion of this CRP in 1995 will lead to the development of a highly reliable diagnostic system for the safety surveillance of LMFR SGUs.

A specialists meeting on the correlation between material properties and thermohydraulic conditions in LMFRs, held in Aix-en-Provence, France, focused on the thermo mechanical aspects of temperature fluctuations such as mixing jet phenomena, temperature gradient fluctuations and the transfer of fluctuations from the fluid to the structure materials wall. One key objective of the meeting was to identify common trends in the interpretation of experimental and analytical work and the influence on design codes. It was concluded that with respect to thermo-hydraulics, great advances have been made, but limited available computer capacity prevents the calculation of fluid temperatures at all times at all important locations; however, capacity improvements are planned. With regard to design codes, significant progress has been made, but the codes are still very restrictive in terms of allowable temperature amplitudes. Experimental justification is needed to permit a reduction of the current safety factor of about 2.

At the annual meeting of the IWGFR, it was proposed that the transient characteristics of the BN-800 reactor be evaluated. A joint IAEA/EC benchmark exercise for a severe accident (an unprotected loss of flow (ULOF)) in a BN-800 reactor with a near zero void core was endorsed by all the participants and preparations for the exercise have been initiated. The main objective is twofold: (1) to establish a basis for evaluating the advantages and disadvantages of a BN-800 type reactor with a nearly zero void reactivity core design under hypothetical severe accident conditions, as far as an energetic ULOF is concerned; and (2) to analyse the conditions which help to prevent prompt fuel and steelmelting in the improved fast reactor core under ULOF type and other severe accident conditions. To this end, the Agency made use of the services of consultants to review the general objectives and scope of the comparative calculations, agree upon the input data and establish a work plan for the first year of the exercise. The exercise should be concluded within two years, after which a final report will be prepared.

Gas cooled reactors

The Agency’s CRPs on gas cooled reactor development focus on technical areas which are predicted to provide advanced HTGRs with a high degree of safety, but which must be proven. These technical areas are:

A CRP in the field of HTGR applications is focused on the design and evaluation of heat utilization systems for the Japanese High Temperature Engineering Test Reactor (HTTR), currently under construction at the Oarai Research Establishment of the Japan Atomic Energy Research Institute.

Research Co-ordination meetings were convened for each of these CRPs. Highlights include the progress made by the international team assembled at the PROTEUS critical experiment facility of the Paul Scherrer Institute, Villigen, Switzerland,which has now completed investigations of six core configurations, and the selection of the first priority candidates of steam (and/or CO2) reforming of methane and gas turbine systems for demonstration at the HTTR.

In order to improve the Agency’s capability to perform fuel burn up calculations of graphite moderated, carbon dioxide cooled reactors, the core physics codes VSOP and ORIGEN-JUEL II have been installed on the Agency’s mainframe computer and in the computer of the Agency’s Department of Safeguards, in co-operation with the Nuclear Research Centre in Juelich, Germany. Core burn up analyses for several graphite moderated reactors have been carried out. The computer codes can be utilized to carry out burnup calculations and, after further code improvements have been introduced, in three dimensional geometry to predict the isotopic composition of selected fuel elements. By means of these codes it is possible to describe the buildup and decay of 100 heavy metal isotopes, 250 light elements and more than 800 fission products, including their nuclear properties.


Non-Electrical Applications of Advanced Reactors

Co-generation and heat applications

At the regular session of the General Conference, Resolution GC(XXXVIII)/ RES/7, a Plan for Producing Potable Water Economically, was adopted. This requested the Director General to continue consultations with interested States, the relevant organizations of the United Nations family and other relevant inter-national organizations concerning the main conclusions of the report on the Technical and Economic Evaluation of Potable Water Production Through Desalination of Sea Water by Using Nuclear Energy and Other Means. The Director General was further requested to undertake similar consultations for the implementation of the main recommendations of the Advisory Group on Demonstration Facilities.

To this end, the Agency has initiated an Options Identification Programme to reduce the very broad range of possibilities to a much more limited set of practical demonstration projects. The work will be carried out by a working group which will define and perform the activities necessary to identify and characterize a set of practical demonstration options within a time frame of about two years.

An Advisory Group meeting on technical and economic development in seawater desalination by using nuclear energy was held in Cairo, with the purpose of reviewing current and future options for local participation in the planning, manufacturing, construction, operation and maintenance of nuclear desalination complexes using nuclear energy, both at the level of individual countries and on a regional level.

The accumulated experience in the petrochemical industry, desalination and the nuclear field is considerable and could contribute substantially to the goal of maximum local participation. Potential user countries plan to study this further by identifying the regional capabilities that could be used in the planning, manufacturing, construction, operation and maintenance of a nuclear demonstration facility. It was recommended that a users group be set up to co-ordinate this and other related activities. Depending on the technological lines chosen for the nuclear power source and desalination method, a reasonable level of local participation would be between 35 and 45%.

Transmutation of actinides

A special scientific programme on the use of high energy accelerators for the transmutation of actinides and power production was held in conjunction with the 1994 regular session of the General Conference. The scientific programme was organized to present various technical options for the transmutation of actinides and power production using high energy accelerators, and to discuss their advantages and disadvantages, together with prospects for their technical and economic viability. It was agreed that the possible benefits of this new approach to radioactive waste management warrant further investigation and support.

A Technical Committee meeting on the feasibility of the transmutation of actinides in advanced reactors was held in December as the first step in preparing a status report on actinide transmutation in advanced nuclear reactors in non-OECD/NEA countries. Its objective was to review the status of research and development activities, discuss relevant programmes on transmutation development and provide input for the preparation of the status report. A follow-up meeting will be held in 1995 to finalize the draft of the status report, which is expected to be published by the end of 1995.

Another Technical Committee meeting on unconventional options for plutonium disposition was held in November in Obninsk, the Russian Federation, to review unconventional methods and approaches for the elimination of stockpiles and the disposal of plutonium. It was noted that plutonium can be efficiently and effectively consumed in LMFRs, primarily by removing the uranium blanket. This capability has already been demonstrated. The elimination of plutonium stockpiles and disposal can be achieved in a MOX core by decreasing the fuel volume fraction, increasing core leakage, or adding neutron absorbing materials. In addition, it may be possible to remove the plutonium producing isotope uranium-238 from the fuel, replacing it with inert matrix carriers so that the net plutonium consumption increases significantly. One of the conclusions was that the conventional options (MOX fuel in LWRs, LMFRs and ATRs) that are already used industrially are able to efficiently cope with the disposal of separated plutonium stockpiles, provided that the manufacturing capacity for MOX fuel is increased adequately.


Nuclear Fusion

Fusion research and engineering

A CRP on lifetime predictions for the first wall of fusion machines was completed in 1994. The objective of this CRP was to compare methods used in the various participating laboratories for predicting the lifetime of first wall components and to compare these analytical predictions with the results of experiments at the Ispra Joint Research Centre of the EC. The results of the CRP have shown that the design codes used for predicting the thermal cycling lifetime of stainless steel first wall components are adequate and conservative when compared with experimental results. A technical document reporting on these results will be prepared in 1995.

The 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research was held in Seville, Spain, in September-October. The technical papers presented at this meeting indicated the steady progress made in plasma science and fusion technology in the world, both in magnetic and inertial fusion research.

A CRP on the development of plasma heating and diagnostic systems in institutes in developing countries using middle and small scale plasma devices has the aim of co-ordinating various types of experimental plasma physics and fusion research programmes in developing countries. The CRP includes research using tokamaks and alternative magnetic traps on specific problems which could be resolved using the scientific and technical potential of developing countries.

Nuclear Fusion Journal

Twelve regular issues of Nuclear Fusion were published. Of particular importance were papers on the ITER H mode confinement database and on the behaviour of fast ions in tokamak experiments.