DS397 Saf Use Mod RRs with NUSSC comments 18-06-2010

educe the power level or to shut down the reactor. The method of effecting this connectionshould receive special attention and should be qualified as a safety related system. Separateannunciators or other devices should be provided in the control room to notify the operatingpersonnel whenever a safety action occurs when a safety system setting of the experiment hasbeen reached. The reactor systems should not be used to control the experiment nor to provideindication of the progress of the experiment.4.14. If a safety device is only used to protect the experiment itself or if the experimentaldevice can fail without creating a hazard to the reactor or to personnel, then the safety devicemay have a lower level of safety categorization. Such safety devices should not be connectedto reactor control and protection systems.4.15. The annunciators provided should operate at an alarm level below the safety limit ofthe experiment. This may enable the reactor operator to take defined action to correct thesituation.Heat generation and cooling4.16. Special consideration should be given to the possibility of an experiment ormodification affecting the capability of heat removal from the reactor core.4.17. A dominant failure potential of many irradiation experiments is related to thepossibility of either excessive heat generation or insufficient cooling. Thus, adequate heatremoval under all design basis conditions for the experiment and the design basis accidentconditions of the reactor itself, should be one of the main aspects to be addressed in any safetyanalysis. In addition, the effect of the presence or absence of an experimental device on thepower distribution in the reactor core should be carefully addressed, as this may influencesafety margins of the reactor. Heat generation due to neutron and gamma deposition needs tobe considered. Adequate cooling should be provided to limit the temperature withinacceptable limits. To avoid excessive high temperatures in all circumstances, means to placethe experiment in a safe configuration should be provided. To reduce the reactor power orshutting down the reactor as discussed in paras 4.11–4.12 or other means, should be analysedand assured.4.18. In addition to the above considerations, irradiation of fissile material warrants specialattention for inadvertent criticality and cooling provisions during and after irradiation toprevent overheating of the target material.18