Abstract
Long-life fast reactors receive considerable attention for their potential of using uranium efficiently, and because they can operate for extended periods without refueling. However, the main obstacle to achieving maximum operating times and fuel burnup is the neutron radiation damage that accumulates in the cladding and structural materials. Simulations of metal-fueled high-burnup fast reactors showed that the damage in these reactors’ cladding material reached 200 displacements per atom (dpa) long before the maximum burnup was achieved. One possibility for overcoming this problem is spectral softening, which would reduce the kinetic energy imparted to reactor materials when neutrons collide with them. In this work, we compared the peak irradiation damage in metal- and oxide-fueled fast reactors with that in equivalent reactors containing beryllium in the fuel and reflectors. We showed that the peak damage to the cladding in a metal-fueled reactor was reduced from 273 dpa to 230 dpa when beryllium was included in the core. In an oxide-fueled reactor, the peak damage to the cladding was reduced from 225 dpa to 203 dpa. All four reactors were operated with a core-average burnup of 112 MWd/kg of initial heavy metal (IHM), without reshuffling or refueling, and contained the same initial actinide mass profiles.
Highlights
The sustainability of nuclear power depends in large part on its economic competitiveness and its long-term impact on the environment
Long-life fast reactors have been of interest for decades, in part because of their potential to run for extended periods without refueling, and to operate as a “nuclear battery” which could reduce both the cost and the proliferation risks associated with nuclear energy [1]
The biggest obstacle to the practical implementation of a long-life fast reactor is the high degree of irradiation damage to in-core materials
Summary
The sustainability of nuclear power depends in large part on its economic competitiveness and its long-term impact on the environment. Fast-neutron spectrum reactors can achieve high levels of fuel burnup, which increases both the amount of electricity that a unit mass of fuel can produce, and the burnout of transuranic nuclides which give nuclear waste its long-term radioactive signature. High-energy neutrons collide with atoms in these materials, and displace them from their equilibrium lattice positions. Over time, this leads to macroscopic changes in the materials, such as swelling and embrittlement, which can cause the core to deform, and the cladding to rupture. Studies of proposed Generation-IV fast-reactor systems showed that operating these cores produces damage levels ranging from 200 displacements per atom (dpa) to 250 dpa [3] in the cladding. The best candidate material for these applications, HT-9 steel, was demonstrated to have damage levels of only ~200 dpa at temperatures below 873 K [4,5]
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