Upgrade of Tehran research reactor safety with the second shutdown system: Case study of radioactive pollutions release due to occurrence of core meltdown accident

Tehran Research Reactor (TRR) is in a residential area. Some other characteristics such as aged, relatively full time operation and also being the only available reactor for producing some radioisotopes, are the reasons for special attention to this reactor safety. Recently, a Second Shutdown System (SSS) has been designed for this reactor, which is completely independent and diverse from First Shutdown System (FSS) and upgrades this reactor safety. For representing the importance of this system in enhancing the reactor safety, the probable accident of core meltdown which its consequence is release of radioactive pollution in the reactor inside and outside has been investigated. Then, amount of pollution released in environment after happening the accident and malfunction of the shutdown systems has been investigated. In doing this study, the ORIGEN2 code has been used for determining the inventory of one operational core with approximately 28.27% burnup and HotSpot health physics code has been used for simulating the release of radioactive pollution and calculation of Total Effective Dose Equivalent (TEDE). This accident has been analyzed intentionally conservative, for example core inventory supposed after full time operation which the inventory is in maximum or all pollutions released to environment immediately.