The recommendations provided in this Safety Guide are applicable to any type of research reactor5. However@ the particular characteristics of research reactors necessitate that a graded approach be adopted in implementing the recommendations in this Safety Guide. It is therefore necessary that users of this Safety Guide make a conscious and justified selection of the recommendations provided. In addition@ the extent of detail in the application of the requirements will depend on the potential hazard and on discussions and agreements between the operating organization and the regulatory body@ with the final decision to be made by the regulatory body. This Safety Guide focuses mainly on research reactors of a capacity of up to a few tens of megawatts. The amount of detail required in the safety analysis report for small research reactors (i.e. those with a capacity of less than a few tens of kilowatts) and critical assemblies may be substantially less. Nevertheless@ when using the graded approach@ all items included in this Safety Guide should be assessed. Additional recommendations on the safety analysis@ on preparation of the safety analysis report and on the licensing process for high powered or otherwise advanced or complex research reactors are provided in IAEA Safety Guides for power reactors.6 Use of the Safety Guides for power reactors also necessitates that a graded approach be applied in implementing the recommendations on the basis of the potential hazard associated with the research reactor. Although this Safety Guide mainly concerns newly designed and constructed research reactors@ its content is applicable to any relicensing process or reassessment of a research reactor requested by the regulatory body or decided on by the operating organization. In any case@ the justification for the approach selected on the basis of this Safety Guide should be provided to the regulatory body. Licensing of decommissioning activities7 is not discussed in this Safety Guide. Most research reactors have a small potential for hazard to the public compared with power reactors@ but they may pose a greater potential hazard to operating personnel. The scope@ extent and detail of the safety assessment should be based on the potential hazard associated with the research reactor and its utilization. The requirement for a graded approach should be adopted in applying the recommendations and guidance in this Safety Guide. The interfaces between nuclear safety and nuclear security should be considered in such a way that the impacts of safety on security and the impacts of security on safety are taken into account from the design stage and an appropriate compatibility is achieved. However@ security aspects are subject to confidentiality requirements@ and they are not discussed in this Safety Guide. 5 In this Safety Guide@ the term ??research reactor' includes associated experimental facilities and subcritical and critical assemblies. An experimental facility includes any device installed in or around a reactor to utilize the neutron flux and ionizing radiation from the reactor for research@ development@ isotope production or any other purpose. 6 Further recommendations on preparation of the safety analysis report for a research reactor with greater potential hazard are provided in Refs [7@ 8]. 7 Recommendations on decommissioning activities are provided in Ref. [9].