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Computation of the extend of the disturbed rock zone surrounding long-term excavations in rock salt
Published in N.D. Cristescu, H.R. Hardy, R.O. Simionescu, Basic and Applied Salt Mechanics, 2020
The United States Department of Energy (DOE) is responsible for implementing an effective, environmentally-sound solution to the problem of radioactive waste disposal. A large volume of radioactive waste from US defense programs exists in the form of transuranic (TRU) waste. The solution envisioned by the DOE for disposal of the defense program TRU waste is to emplace it into a deep underground facility expressly engineered for this purposed in bedded rock salt. The DOE project that is now accomplishing this goal is the Waste Isolation Pilot Plan (WIPP) located near Carlsbad, New Mexico.
Initial Neutronics Investigation of a Chlorine Salt-Based Breeder Blanket
Published in Fusion Science and Technology, 2023
Naturally occurring chlorine consists of 35Cl (76 at. %, 75 wt%) and 37Cl (24 at. %, 25 wt%). Chlorine-35 has a substantial absorption cross section, which inhibits neutron multiplication in chloride salts. Further, capture of a neutron by 35Cl leads to 36Cl, which has radioactive waste disposal implications due to its long half-life (301 000 years), high-energy beta emission (0.709 MeV), and being highly soluble in water.23 However, 37Cl has a lower neutron absorption cross section than 35Cl above 0.5 MeV and below 0.002 MeV, as seen in Fig. 1. Additionally, 37Cl has a significant (n,2n) cross section, for which the threshold energy is reachable in D-T fusion reactors. Figure 2 shows the (n,2n) cross section for 35Cl and 37Cl, as well as the commonly proposed Be and Pb multipliers. Thus, enrichment of chlorine in 37Cl provides a potential pathway to the effective use of chloride molten salts by the fusion industry.
Neutronics Calculations for a Hypothetical Plasma-Jet-Driven Magneto-Inertial-Fusion Reactor
Published in Fusion Science and Technology, 2019
Lucas M. Rolison, Michael L. Fensin, Y. C. Francis Thio, Scott C. Hsu, Edward J. Cruz
Each parameter studied for these neutronics calculations is one of many that can be optimized for a PJMIF reactor. Similar studies can be performed on the parameterization of other reactor properties, both geometric and material. Geometric parameterizations would include inner and outer wall thicknesses, inner reactor radius, and different points in plasma compression (changing plasma-liner thicknesses). Material parameterizations would look at different breeder blankets (such as LiPb), different plasma liners other than xenon, and different reactor vessel steels. The addition of shielding materials to help protect plasma guns and increase their lifetimes without reducing fusion gain would be of benefit as well. Future work would also benefit from higher-fidelity models to verify what is calculated in the simpler models used here. In particular, the plasma gun can be modeled and analyzed separately to better understand the radiation damage and heating received to its different components and determine what is most limiting to its performance. In terms of radiation protection, future work could use the nuclide inventories acquired from the outer wall activation analysis as a source term to calculate radiation dose, which would be helpful for determining radioactive waste disposal requirements. Finally, the simple heating studied showed preliminary results for potential thermal-hydraulic requirements of the FLiBe breeding blanket in order to remove heat away from the inner wall as it is bombarded by neutrons. Another potential source of heating that may be necessary to remove from reactor components is decay of radioisotopes that get produced in materials due to constant neutron bombardment. Thermal hydraulics of the breeder blanket is an important future analysis that will be necessary for full engineering development of a PJMIF reactor.