BARC/2018/E/005 BARC/2018/E/005 TRANSITION FROM OPERATION TO DECOMMISSIONING OF CIRUS RESEARCH REACTOR by Rakesh Ranjan, S. Bhattacharya, C.G . Karhadkar, Prasit Mandal, M.K. Ojha Reactor Operations Division 2018 BARC/2018/E/005 GOVERNMENT OF INDIA DEPARTMENT OF ATOMIC ENERGY BARC/2018/E/005 TRANSITION FROM OPERATION TO DECOMMISSIONING OF CIRUS RESEARCH REACTOR by Rakesh Ranjan*, S. Bhattacharya, C.G . Karhadkar, Prasit Mandal, M.K. Ojha [email protected]* Reactor Operations Division Reactor Group BHABHA ATOMIC RESEARCH CENTRE MUMBAI, INDIA 2018 BARC/2018/E/005 BIBLIOGRAPHIC DESCRIPTION SHEET FOR TECHNICAL REPORT (as per IS : 9400 - 1980) 01 Security classification : Unclassified 02 Distribution : External 03 Report status : New 04 Series : BARC External 05 Report type : Technical Report 06 Report No. : BARC/2018/E/005 07 Part No. or Volume No. : 08 Contract No. : 10 Title and subtitle : Transition from operation to decommissioning of Cirus research reactor 11 Collation : 82 p., 39 figs., 9 tabs. 13 Project No. : 20 Personal author(s) : Rakesh Ranjan; S. Bhattacharya, C.G. Karhadkar; Prasit Mandal; M.K. Ojha 21 Affiliation of author(s) : Reactor Operations Division, Bhabha Atomic Research Centre, Mumbai 22 Corporate author(s): Bhabha Atomic Research Centre, Mumbai - 400 085 23 Originating unit : Reactor Operations Division, Bhabha Atomic Research Centre, Mumbai 24 Sponsor(s) Name : Department of Atomic Energy Type : Government Contd... BARC/2018/E/005 30 Date of submission : April 2018 31 Publication/Issue date : April 2018 40 Publisher/Distributor : Head, Scientific Information Resource Division, Bhabha Atomic Research Centre, Mumbai 42 Form of distribution : Hard copy 50 Language of text : English 51 Language of summary : English 52 No. of references : 23 refs. 53 Gives data on : Abstract : Cirus, a 40 MW (Thermal), tank type reactor had been in operation since 1960. The 60 reactor was shut down from 1997-2003 for refurbishment based on a comprehensive ageing assessment. It was restarted in year 2003 with significant increase in availability and safety margins and was shut down permanently on 31st December, 2010. Prior to shutting down the reactor, a core management programme was implemented to maximize fuel utilization. After shutting down the reactor, the core was unloaded of all spent fuel assemblies, isotope production assemblies, experimental assemblies and shut off rods. Subsequently the entire spent fuel was sent for reprocessing. Various reactor systems were maintained initially in wet preservation mode and chemistry of process fluids was monitored and maintained. Subsequently the systems were brought to dry preservation mode after draining of process fluids and drying the systems. This state has reduced surveillance requirements as well as cost in maintaining them. Only need based operation of auxiliary systems is being done at present. Radiological and industrial hazards were minimized by taking suitable measures. Suitable modifications in systems were carried out to reduce surveillance. With this, manning of reactor in round-the-clock shifts has been stopped since 10th July 2017 after approval of regulator. Reactor is manned on normal working days in general shift hours. For Cirus reactor, deferred dismantling (decommissioning) strategy is considered as the best option. Near term, mid-term and long-term activities have been identified as a part of deferred decommissioning programme. Detailed radiation mapping to assess radiation field inside core has been carried out. Preliminary waste volume estimation and characterization of radionuclides has been carried out. Detailed radiological characterization has been started. Access control to various areas in and around the reactor building is being maintained in the same manner as it was during the operating days of the reactor. All the areas of potentially high radiation field and contamination are under access control with lock and key. A two-tier set-up of experts having experience in operation and maintenance of reactor, waste management and radiological protection has been made to prepare documents for decommissioning of the reactor. All plans for decommissioning are subjected to regulatory review. Decommissioning Superintendent co-ordinates and executes the plans 70 Keywords/Descriptors : CIRUS REACTOR; REACTOR SHUTDOWN; REACTOR DECOMMISSIONING; MAPPING; RADIOACTIVE WASTE MANAGEMENT; REACTOR SAFETY; RADIOACTIVE WASTE STORAGE 71 INIS Subject Category.: S21 99 Supplementary elements : TRANSITION FROM OPERATION TO DECOMMISSIONING OF CIRUS RESEARCH REACTOR Rakesh Ranjan*, S. Bhattacharya, C.G. Karhadkar, Prasit Mandal, M.K. Ojha Reactor Operations Division, Reactor Group Bhabha Atomic Research Center, Mumbai, India [email protected]* Abstract Cirus, a 40 MW (Thermal), tank type reactor utilizing heavy water as moderator, graphite as reflector, demineralized light water as primary coolant and natural uranium metal as fuel; had been in operation since 1960. After about three decades of operation, the reactor exhibited signs of ageing. The reactor was shut down from 1997-2003 for refurbishment based on a comprehensive ageing assessment. It was restarted in year 2003 with significant increase in availability and safety margins and was shut down permanently on 31st December, 2010. After shutting down Cirus reactor permanently, the core was unloaded of all spent fuel assemblies, isotope production assemblies, experimental assemblies and shut off rods. Subsequently the entire spent fuel was sent for reprocessing. Radio-isotopes were delivered to Radio Pharmaceutical Division for processing and utilization. Irradiation assemblies were sent to Waste Management Division for storage and disposal. At present, Cirus site doesn’t have any irradiated fuel assembly under storage, except a few irradiated test fuel assemblies of Pressurized Water Loop (PWL), stored in water bays of Rod Cutting Building (RCB). Detailed radiation mapping to assess radiation field inside core has been carried out. Preliminary waste volume estimation and characterization of radionuclides has been carried out. Detailed radiological characterization has been started. Various reactor systems were maintained initially in wet preservation mode and chemistry of process fluids was monitored and maintained. Subsequently the systems were brought to dry preservation mode after draining of process fluids and drying the systems. This state has reduced surveillance requirements as well as cost in maintaining them. Only need based operation of auxiliary systems is being done at present. Radiological and industrial hazards were minimized by taking suitable measures. Suitable modifications in systems were carried out to reduce surveillance. With this, manning of Cirus in round-the-clock shifts has been stopped since 10th July 2017 after approval of regulator. Reactor is manned on normal working days in general shift hours. A Supervisor assisted by 2-3 technicians is in charge of the surveillance activities and execution of other planned jobs. A common Radiological Hazard Control (RHC) unit for Dhruva and Cirus facilities provides radiological safety / health physics coverage. A two-tier set-up of experts having experience in operation and maintenance of reactor, waste management and radiological protection has been made to prepare documents for decommissioning of the reactor. The lower tier headed by Decommissioning Superintendent is entrusted with preparation of the documents. The upper tier headed by Director / Associate Director, Reactor Group reviews and approves the documents. All plans for decommissioning are subjected to regulatory review. Decommissioning Superintendent co-ordinates and executes the plans. Access control to various areas in and around the reactor building is being maintained in the same manner as it was during the operating days of the reactor. All the areas of potentially high radiation field and contamination are under access control with lock & key. For Cirus reactor, deferred dismantling (decommissioning) strategy is considered as the best option. Near term, mid-term and long-term activities have been identified as a part of deferred decommissioning programme. Dismantling of reactor structure and core components is envisaged after about 30-35 years when the dominant radionuclide Co-60 will decay significantly for ease of dismantling and handling of radioactive components. Peripheral systems and components will be dismantled and disposed off in the initial years. Ventilation system and other auxiliary systems required for dismantling operations, radiological and industrial safety, security of reactor, etc. has been kept operational. Optimum surveillance is being maintained. Resources available in the nearby Dhruva reactor, which can contribute in long term surveillance requirements, help in deciding deferred decommissioning as a preferred strategy. With implementation of suitable steps, the reactor has been brought to a ‘Safe Storage’ state. Short term activities which are planned to be executed in the next few years have been identified which include isolation and truncation of systems to reduce surveillance requirements, disposal of inactive components, disposal of low contaminated equipment / components to waste management facility, etc. To gain experience with decommissioning, dismantling of some inactive systems and low active systems has been started. The space created from this activity will be used for installation of new experimental facilities. In Cirus reactor hall, several