Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112 Page 113 Page 114 Page 115 Page 116 Page 117 Page 118 Page 119 Page 120 Page 121 Page 122 Page 123 Page 124Nuclear Science User Facilities 58 Hydride LWR Fuel Rod Irradiation Donald Olander – University of California, Berkeley – fuelpr@nuc.berkeley.edu The objectives of this experi- mental research are to study the materials issues associated with the use of a hydride fuel for power production in light water reactors (LWRs) and to explore the use of Pb-Bi Eutectic liquid metal (LM) as a replacement for helium in hydride fuel elements. Hydrides provide a number of improvements, including the addi- tion of hydrogen neutron moderation within the fuel, thermally induced hydrogen up-scattering that accompa- nies Doppler Feedback that improves safety, and higher efficiency in elimina- tion of plutonium than achievable with mixed oxide (MOX).The liquid metal bounded fuel-cladding gap assist in lowering the temperature of the fuel. Project Description Feasibility and benefits of incorpora- tion of hydride nuclear fuels into the current fleet of LWRs have been investigated in detail using neutronic and thermal-hydraulic calculations and laboratory-scale materials experiments by the materials group in Nuclear Engi- neering Department at the University of California at Berkeley. Recognizing the necessary shift from laboratory- scale experiments to more relevant environments, an irradiation experi- ment was then conducted to evaluate the feasibility of an LWR hydride fuel. Sealed fuel rodlets were constructed with U0.17ZrH1.6 fuel pellets and conventional Zircaloy-2 cladding with Bi-Pb LM filled-gap, inner and outer surfaces oxidized to nominal 1 micron to prevent hydrogen attack.They were housed inTi capsules surrounded with the same LM used for filling gaps between the fuel and cladding.Three irradiatedTi capsules were then irradi- ated at the Massachusetts Institute of Technology (MIT) research reactor to burnups of 0.19, 0.17, and 0.29 FIMA (%) with up to a maximum 6‑MW thermal power.Along with a fourth unirradiated rodlet for reference use, the capsules were then transferred to PNNL for extensive post-irradiation evaluations. In this fiscal year, novel tools were designed and fabricated to handle and extract the highest-burnup rodlet (0.29% FIMA) from the outerTi capsule. Thin-sliced samples were prepared at two axial locations of the rodlet: close to the axial mid-level of the rod whereTC tips were located, and near to the end of rodlet.The full-round cross-sections were mounted and polished to observe the fuel, gap LM, outer LM, cladding, and their interfaces. Because of radio- activity and pyrophoricity concerns, metallographic samples preparation were performed in hot cells under flowing inert gas. The irradiated samples were evaluated in detail and compared to unirradiated sliced sample from the similar axial location through visual inspection for possible crack development, optical microscopy for detecting dimensional changes in the fuel, cladding, and the gaps and scanning electron microscopy The principal difference between oxide and hydride fuel is the high- thermal conductivity of the latter. This feature greatly decreases the temperature drop over the fuel during operation, thereby reducing the release of fission gases to the fraction due only to recoil. The maximum fuel temperature can be further reduced by filling fuel-cladding gap with low-melting LM instead of He.