Characterization of a Neutron Beam Following Reconfi guration of the Neutron Radiography Reactor (NRAD) Core and Addition of New Fuel Elements

The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes,General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. TheEast Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutronradiography, which sits beneath a large hot cell and is primarily used for neutron radiographyof highly radioactive objects. Additional fuel elements were added to the NRAD corein 2013 to increase the excess reactivity of the reactor, and may have changed somecharacteristics of the neutron beamline. This report discusses characterization of theneutron beamline following the addition of fuel to the NRAD. This work includes determinationof the facility category according to the American Society for Testing and Materials(ASTM) standards, and also uses an array of gold foils to determine the neutronbeam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is aCategory I neutron radiography facility, the highest possible quality level according tothe ASTM. Gold foil activation experiments show that the average neutron flux withlength-to-diameter ratio (L/D) = 125 is 5.96 × 106 n/cm2/s with a 2s standard error of 2.90 × 105 n/cm2/s. The neutron beam profile can be considered flat for qualitative neutronradiographic evaluation purposes. However, the neutron beam profile should be taken intoaccount for quantitative evaluation. KCI Citation Count: 3