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RIC panel discusses pathway to fusion commercialization
Fusion leaders at the Nuclear Regulatory Commission’s annual Regulatory Information Conference discussed the path forward for regulating the burgeoning fusion industry. The speakers discussed government and private industry initiatives in the United States and United Kingdom, with a focus on efforts shaping the near-term deployment of commercial fusion machines.
A recurring theme was the need to explain the difference between fission and fusion. Representatives from the Department of Energy and Type One Energy highlighted this as an important distinction for regulators, as it will allow fusion to undergo its own independent maturation process for developing standards and regulations in the same way that fission has. Lea Perlas, Fusion Program director at the Virginia Department of Health, said that confusion between fission and fusion has been a common cause for misplaced concerns among community members surrounding Commonwealth Fusion Systems’ proposed fusion plant site near Richmond, Va.
Jeffrey E. Seifried, Ehud Greenspan
Nuclear Science and Engineering | Volume 181 | Number 1 | September 2015 | Pages 82-95
Technical Paper | doi.org/10.13182/NSE14-104
Articles are hosted by Taylor and Francis Online.
An expression is derived for attributing the reactivity response due to perturbations to spectral, spatial, and isotopic effects. It is shown to be consistent at a global level with similar expressions derived in previous work but can provide more detailed information on the physics phenomena contributing to the reactivity response of the perturbation. Using this expression, the reactivity effect of local coolant density perturbations [local void coefficient of reactivity (VCR)] is studied for two reduced-moderation boiling water reactor (RBWR) core designs—the thorium-fueled RBWR (RBWR-Th) and the uranium-fueled RBWR (RBWR-AC)—as well as for a standard advanced boiling water reactor (ABWR). The RBWR core designs feature large axial variation in their neutron spectra.
The axial distribution of local VCR along the RBWR-Th seed and along the ABWR core were found to have the same general shape: negative throughout but most negative near the bottom and asymptotically approaching zero toward the top. However, the RBWR-Th VCR is roughly four times more negative. The RBWR-AC local VCR axial distribution varies greatly: it is very close to zero in the seed regions and has a significant positive component in the central blanket.
Three effects were identified as contributing to the VCR due to a local water density change in the lower part of the RBWR-Th seed: local spectrum hardening that tends to increase the local reproduction factor (ηr) of each of the fuel isotopes; a redistribution of the local neutron absorption between the fuel isotopes resulting in a shift of absorptions from higher to lower isotopic reproduction factors and, hence, to a reactivity loss; and an axial flux tilt across the core from axial zones of higher ηr to axial zones of lower ηr, which makes another negative contribution to the reactivity worth of the perturbation.
