SBIR-STTR Award

Next generation reactor R&D aims to improve overall safety, efficiency, sustainability, and proliferation resistance for economically viable nuclear energy. New reactor design and fuel development rely on novel materials that are resistant to both radiation damage and corrosive environments. However, American nuclear fuel developers face a serious dilemma: there are no existing domestic fast reactors. Thus, the financial cost and time required to test novel fuels and advanced materials overseas prohibits many promising concepts from proceeding beyond early design stages. To overcome this problem, Niowave, Inc. proposes to develop a subcritical testbed that can bombard materials with fast neutrons in a fast reactor like environment, without a nuclear reactor. This would support experimentation and demonstration with novel fuels and materials, without the logistical and regulatory challenges of fast reactors. In this proposed system, a hybrid fast/thermal spectrum subcritical testbed is coupled to a superconducting electron linac through a lead-bismuth eutectic (LBE) neutron converter. This system will create a peak fast- spectrum neutron flux in excess of 1015 n/cm2s in a liquid metal environment for testing and demonstrating novel fuels and materials used in Generation-IV designs, where fast-spectrum reactors are prominent. The proposed subcritical testbed facility is not a reactor, and is simpler to license than a reactor. An initial proof-of-concept fast neutron source, driven by a superconducting linac and LBE neutron converter already exists at Niowave and is designed to produce a fast neutron flux in excess of 1014 n/cm2s. Additionally, Niowave is developing a subcritical LEU target assembly, licensed under 10 CFR 30/70, to provide the US with critical radioisotopes. Our fast neutron source and LEU-based subcritical radioisotope production facility serves as a starting point for the design of a subcritical testbed for fuel characterization. The equipment, experimental data, and expertise Niowave gained will be leveraged and applied to the subcritical testbed to advance novel fuel design and support reactor materials testing. Phase I and II will focus on design and prototype development and demonstration. Ultimately, we intend to build a materials testbed facility for the nuclear energy and reactor community.

Recently, the Generation IV International Forum has established a set of nuclear reactors (advanced nuclear reactors), with main objectives to improve overall reactor safety, efficiency, sustainability, and proliferation resistance for economically viable nuclear energy. These advanced reactor technologies rely on novel fuels and materials that are resistant to radiation damage and corrosive environments, while withstanding significantly higher operating temperatures. However, the lack of data for most of these novel and advanced materials calls for renewed testing efforts performed in an intense fast neutron flux (E >0.1 MeV) while mimicking a fast reactor-like environment. Fast fluxes greater than 1015 n/cm2s provide an accelerated material radiation-damage rates of ~20 dpa/yr. These fluxes are conventionally achieved with fast reactors, which are not currently available in the US, since the shutdown of the Fast Flux Test Facility. Therefore, US researchers are required to ship samples overseas for long-term irradiations or utilize domestic thermal-spectrum test reactors; both of which have their own set of complications and drawbacks. To overcome this problem, Niowave proposed to develop a subcritical testbed that can provide a fast reactor-like environment to support experimentation and demonstration of novel fuels and materials, without the logistical and regulatory challenges and expenses of fast reactors. In this system, an electron linac with a lead-bismuth eutectic neutron converter is coupled to a HYbrid fast/thermal core configuration Subcritical Testbed (called HYST) to provide 1015 n/cm2s fast flux level. The fast core region contains a sufficient volume (?100 cm3) for testing advanced nuclear reactor materials. In Phase I, two candidate core designs were devised by modeling and examining the neutronics performance characteristics of the fast/thermal core and evaluating the linac-based external neutron source. Both core designs, HYST – I and – II, showed the feasibility of the hybrid core configuration concept and a noticeable reduction in the fission power and fissile loading compared to an all fast core design. In Phase II, Niowave proposes to license, construct, and operate a small-scale low-power demonstration system with Niowave’s existing uranium fuel, based on HYST-I concept, and perform detailed core design and tradeoff studies of the targeted goal for HYST while establishing the NRC licensing roadmap. In Phase III, a prototype of HYST design will be licensed, built, and operated at ~200 kW fission power (1/100th of final design level), producing 1013 n/cm2s fast neutron flux level by 2025 with a budget <$10 million. The objective is to establish the prototype HYST facility for US companies and DOE funded researchers at a reduced cost and time. This will provide operational data, characterization, and evaluation of the performance of novel fuels, materials, instrumentations, components, new reactor designs, and safety features. It will also support the regulatory process for licensing novel technologies and the development of high-fidelity reactor codes. This work will be accomplished by leveraging the knowledge, tools, and expertise from Niowave’s existing radioisotope program (thermal subcritical core operating at 210 kW by 2023) and partnering with additional collaborators such as US advanced reactor companies, national laboratories, and DOE. After demonstrating a 200 kW prototype HYST, the final phase will be focused on ultimately building the full scale HYST that offers 1015 n/cm2s fast flux level while supporting US companies with their efforts to license, construct, and build next generation advanced nuclear reactors.