The object of this report is to identify, using material published and reported by the IAEA and others, those problem areas relating to the safe operation of the RBMK reactors and to make recommendations to improve the safety of those reactors. The problem areas discussed in this technical report were not selected in a systematic manner, e.g. according to safety significance, nor do they apply with the same weight to all RBMK reactors. The list of problem areas is not to be regarded as being complete as there are many important issues that have not been discussed or even identified in this technical report. The first objective is to identify the problems and a limited number of physical measures that can be introduced to bring immediate benefit. A second objective is to place both the problems and the measures in the context of the international standards framework provided by the IAEA and the IEC. This type of exercise should be conducted by carrying out a formal safety review to identify problem areas, e.g. along the lines of the MAGNOX long term safety review that was completed in the UK. The recommendations for action then arise naturally from such a safety review. In this case, a number of IAEA reviews of the RBMK have been completed and further international and bi-lateral studies are under way, e.g. the CEC supported project. These are not the formal reviews indicated above. They will, however, bring considerable information to bear on the problem. The exercises have indicated some areas where there is scope for improvement; these are, for example, discussed in IAEA TECDOC 694 and TECDOC 722. The following topics have been identified for consideration and inclusion in this technical report: - the unit computer systems provide a lot of information for plant protection through operator action and plant operation. The systems need to be upgraded to combat obsolescence and improve the quality of information and man-machine interface. Providing safety parameter display systems (SPDS) at RBMKs will address the issue as far as safety parameters are concerned and provide a partial replacement of the unit computer systems. The balance of the function of the unit computer and associate hardware and software should be reviewed to define needed reliability improvements; - the introduction of diverse means of stopping the nuclear reaction and shutting down the reactor; - examination of the problem of channel cooling, its supervision and channel protection and failure prevention in the event of loss of flow. This clause will consider and make reference to critical parameters associated with coolability; - automatic power control, to maintain the reactor at its required power and provide control of the instabilities identified above and defence against equipment failures; - leakage detection from the primary circuit; - the stability of characteristics of the core need to be identified in relation to the different types of power and flow instability. This includes feedback effects due to Xenon, moderator temperature and coolant voiding; - monitoring and protection during reactor startup to improve the equipment practices and procedures and so enhance safety; - hydrogen monitoring. The list above is not a complete list of issues for the RBMK as key topics such as the integrity of and the consequences of failure of circuit components are not considered and other issues such as the heavy dependence on operator action are not fully considered. Other important items such as temperature monitoring and early detection of the failure of the primary pressure boundary in both the core region and around the pressure circuit are not considered along with fire protection or activity and radiation contamination and release monitoring. The work of IEC SC45B Radiation Protection Instrumentation is referred in the context of the latter items. In order to address the topics above and provide solutions, some practical measures will be needed. The proposed measures will for reasons of speed be based upon use of existing sensors and equipment. However in order to fully achieve the ultimate objective of eliminating the safety problems, new equipment and operating procedures will be required. It is intended to identify possible equipment, indicate its function and how it might be installed as part of this process. In considering practical measures, cost must be taken into account thus the scope of the proposals will be consistent with the objective of producing cost effective measures to improve safety. Details of cost and programme information are regarded as being out of the scope of this technical report control, to maintain the reactor at its required power and provide control of the instabilities identified above and defence against equipment failures; - leakage detection from the primary circuit; - the stability of characteristics of the core need to be identified in relation to the different types of power and flow instability. This includes feedback effects due to Xenon, moderator temperature and coolant voiding; - monitoring and protection during reactor startup to improve the equipment practices and procedures and so enhance safety; - hydrogen monitoring. The list above is not a complete list of issues for the RBMK as key topics such as the integrity of and the consequences of failure of circuit components are not considered and other issues such as the heavy dependence on operator action are not fully considered. Other important items such as temperature monitoring and early detection of the failure of the primary pressure boundary in both the core region and around the pressure circuit are not considered along with fire protection or activity and radiation contamination and release monitoring. The work of IEC SC45B Radiation Protection Instrumentation is referred in the context of the latter items. In order to address the topics above and provide solutions, some practical measures will be needed. The proposed measures will for reasons of speed be based upon use of existing sensors and equipment. However in order to fully achieve the ultimate objective of eliminating the safety problems, new equipment and operating procedures will be required. It is intended to identify possible equipment, indicate its function and how it might be installed as part of this process. In considering practical measures, cost must be taken into account thus the scope of the proposals will be consistent with the objective of producing cost effective measures to improve safety. Details of cost and programme information are regarded as being out of the scope of this technical report.