b'ATR has many irradiation positions including nine flux trap positions with in-pile tubes with customizable coolant conditions. All of theseFigure 2. Booster element in holder.positions are highly scheduled for many years by other testing programs with one exception, the center loop position. The center loop is primarily designated for LWR fuels burnup accumulation. This loop alone cannot support the demand required for LWR because of an overall limitation in specimen capacity, inability to perform flux tailoring, and complication with coolant-voiding conditions (e.g., BWR, dry out). There are several other positions more available within ATRs neck shim housing and inner reflector. While useful for other capsule-based and instrumented-lead type experiments,modifications. Designs in these three these positions dont possess desirableareas are rapidly progressing with no useable diameters to implement LWRmajor obstacles.loops. Only the Large and Medium I-positions, which reside outside ofA standard ATR driver fuel element the reactivity control cylinders in theplaced in ATRs Large-I irradiation outer beryllium reflector, have adequateposition (Figure 1) boosts neutron diameters for LWR loop installationflux outside the cores control because of high availability and acylinders. The standard element was neutron flux similar to the HBWR. chosen over a fuel ring because the Accomplishments: fuel element design is already in-place Enabling an I-Loop for ramp testingand has an established supply chain. as well as filling the Halden voidThis booster fuel element requires requires a boosted reflector flux, aa holder (Figure 2) to position the custom in-pile tube, and reactor vesselelement within the reactor hardware 2019|AFC ACCOMPLISHMENTS 127'