REACTOR OPERATION & MAINTENANCE GROUP

FAST BREEDER TEST REACTOR (FBTR)

Construction, Commissioning and Operation Summary

Components were manufactured by Indian industries, and were installed in 1984. Commissioning was done in phases. Initially, the primary and secondary sodium systems were commissioned, without the steam generators in place. The reactor was made critical on 18th October 1985 and low power physics experiments were conducted. Steam generator modules were then connected to the secondary sodium circuits.

Reactor was operated up to a maximum power of 1 MW t till 1992 for intermediate power physics and engineering experiments. The steam–water circuit was commissioned, steam generators were put in water service and power was raised to 8 MW t in January 1993. After completing high power physics and engineering experiments, power was raised to 10.2 MW t, generating superheated steam suitable for admission to the turbine-generator. After completing the commissioning activities of TG and auxiliaries, power was raised to 11.5 MW t and the turbine-generator was synchronised to the grid in July 1997.The reactor has operated upto a power level of 17.4 MWt/2.2MWe

Mixed carbide fuel, being a unique fuel of its kind without any irradiation data, it was decided to use the reactor itself as the test bed for this driver fuel. Hence, the core was redesigned as a small carbide core. As against the original design of 65 MOX fuel subassemblies rated for 40 MW t, the small carbide core had 22 fuel subassemblies with 70% PuC and 30% UC composition (designated as Mark-I fuel) during first criticality. This small carbide core was rated for 10.2 MW t, with the peak linear heat rating limited to 250 W/cm. The core has since been progressively enlarged by adding fuel subassemblies to compensate for reactivity loss due to burn-up.

With a view to raise the reactor power to 40 MW t, it was decided, in 1995, to go in for a full carbide core of 78 fuel subassemblies. The fuel composition chosen was 55% PuC + 45% UC (designated as Mark-II fuel). Fuel subassemblies of Mark-II composition were inducted in 1996. A gradual transition to the full carbide core was envisaged. The Mark-I fuel in the centre was retained to continue the irradiation for assessing its ultimate burn-up capability before phasing it out. Mark-II fuel was added at the periphery. The allowable peak linear heat rating of the Mark-I fuel has also been revised up to 400 W/cm based on the fuel performance. The reactor power for the small carbide core has been progressively increased, reaching the highest power of 17.4 MW t in 2002. Table 2 gives the cumulative performance statistics of the reactor as of 30 th September  2005. Thirteen  irradiation campaigns have so far been completed.

Table -2
Summary of performance statistics from 1985 (up to 13th irradiation campaign)