In my previous articles, I proposed the use of AmBe as the neutron source. I would now like to propose an electronic version which provides a much higher neutron flux density. This setup initiates fission—similar to an auto-ignition system—in a much shorter timeframe than other methods.
The setup utilizes a 100 kV neutron generator at its core. The tube features a bottom section that receives a 12V input, with the casing connected to a ground potential. This bottom section includes a glass window for two-way optical communication. Inside the tube, a dedicated electronics suite controls the neutron generator and monitors core fission. To ensure radiation durability, these electronics are fabricated from SiC (Silicon Carbide) with Germanium (Ge) additives. This section is housed in a container filled with low-pressure Xenon (Xe) gas. The Xenon acts as an internal sensor; it absorbs neutrons, and the resulting reaction is measured to determine real-time neutron levels. Above the electronics is a thick EMF insulation section, followed by a high-voltage generator that steps 12V up to 100 kV. Since the 100 kV output is pulsed at only a few milliamps, a 12V supply is sufficient. This power section is also filled with low-pressure Xe for neutron protection.
Unlike traditional metallic-cased designs, this tube utilizes an Aluminum Oxide insulator layer to seal the vacuum. The exterior of this oxide layer is coated with a 2–3 mm thick Thorium (Th) layer. To ensure superior thermal conductivity and adhesion to the Aluminum Oxide, the Thorium is alloyed with Aluminum. The Thorium layer is then encased in a 5–10 mm thick, porous Aluminum-Beryllium (Al-Be) alloy. The porous structure is a critical safety feature, allowing the Helium (He) gas generated by the Beryllium reactions to escape easily without compromising structural integrity. This configuration achieves a neutron multiplication factor of approximately 5.
Operational Physics
The central generator produces ultra-high-energy neutrons (14.1 MeV). The process follows a specific cascade logic:
Fast Fission: The 14.1 MeV neutrons possess sufficient energy to trigger fast fission in the Thorium-232 atoms. Each Thorium atom hit by a neutron fissions, yielding 2.5 to 3 fast neutrons.
Multiplication & Moderation: The outer Beryllium (Be) layer absorbs these secondary neutrons. Through the (n, 2n) reaction, it doubles the neutron count while simultaneously moderating their energy.
Core Ignition: This multiplier effect enhances the generator's performance by both increasing the total neutron count and slowing them to the ideal thermal energy levels required for the Uranium-235 Forest to fission effectively.
By utilizing an electronically controlled high neutron flux, this design ensures the fission process achieves a high k value rapidly. This active control allows for precise management of the reactor's power, providing the thermal kick necessary to initiate the passive capillary siphon within the fuel forest. Because the flux is electronically driven, the reactor can be started and stopped on demand, offering a level of operational flexibility usually absent in traditional designs. A significant breakthrough of this tube is its built-in sensor suite. This marks the first time a nuclear reactor would feature live, integrated sensors at its very core during operation. The SiC-Ge electronics, optical communication and Xenon-gas monitoring chamber allow for immediate data feedback from the highest-flux zone of the system. This generator tube was developed to perfectly integrate with my open-core, closed-cycle, passively cooled, low-pressure water reactor. The synergy between the 100 kV trigger and the vascular fuel forest creates a self-regulating system that is both high-output and inherently safe. I will explain the updated design of the full reactor assembly in my next article.
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