The long-term energy needs of India require utilisation of its large Thorium reserves. Advanced Heavy Water Reactor (AHWR) being developed at BARC envisages large scale utilization of Thorium. A Critical Facility is operational at BARC for validating the reactor physics design and nuclear data for AHWR.
AHWR-CF is a low power research reactor with a nominal power of 100 W. The aluminium reactor tank houses fuel assemblies and moderator. A square box above the reactor tank houses the lattice girders from which the fuel assemblies are suspended. The lattice girders can be moved to vary the pitch. These lattice girders also support the reactor shutdown devices. The top of the square box is closed by a revolving floor, which also permits access to any of the lattice location for handling operations.
Salient features of AHWR-Critical Facility
|Nominal reactor power||100 watts|
|Average Neutron flux||108 n/cm2/sec|
|Lattice pitch||Adjustable (215 mm~300mm)|
|Shut down||Six fast acting Cd shut off rod
|Neutron monitoring||Independent safety and regulating channels to monitor the neutronic power.|
|Reactor trip||Partial moderator dump along with shut off rod drop|
|Power control||By manual control of moderator level.
By Inventory control of Moderator
|Uses||Validation of reactor physics design codes, nuclear data, activation analysis, detector testing|
The major core configurations of AHWR-CF are:
The reference core was initially configured with 55 lattice locations in a lattice pitch of 245 mm, where 49 were occupied by 19 pin natural uranium metal fuel clusters and 6 locations with shut-off rods. Later in 2014, the core was extended to 61 locations with 55 locations for fuel cluster for gaining reactivity in order to perform experiments with thoria based fuel.
AHWR Representative Core
The core for performing detailed experiment with AHWRF will be constituted by replacing the central natural uranium metal fuel clusters with AHWR type of fuel, i.e.54 pin AHWR (Th-Pu Oxide, Th-U233 Oxide) Clusters. Experiments will be performed with AHWR fuel in a typical AHWR neutron spectrum.
AHWR-CF attained its first criticality on 7th April, 2008. The observed critical height for the Reference core configuration was 226.7 cm which agreed well with the estimated value of 226.5 cm.
A large number of reactor physics experiment has been performed in the Reference core of the facility. These experiments ranged from the initial commissioning experiments to various integral and differential measurements. Some of the important experiment carried out at AHWR-CF are as follows:
Differential flux measurement experiments