*****refer to Radioactivity_Sim’s first use: Feasibility of a radiation battery with unprocessed waste for feasibility update on this design concept******
Considering the vitrified spent fuel rod concept further, it is found that the primary alpha and beta particles produced by the fuel would certainly be absorbed immediately by the fuel rod encasement. Neutrons and gamma radiation, however, would easily penetrate the case and enter into the surrounding matter. The gamma radiation has the potential to create secondary photons, and the neutrons will with certainty create secondary radiation sources within that surrounding matter with predictable decay mechanisms and half lives. For the production of long term production of visible light in the surrounding matter (as is the goal of the “atomic battery”), it is preferable to have as much secondary radiation sources from free neutrons as possible. Therefore, the vitrification processing of the spent fuel rod for the “atomic battery” should be done as soon as is practical after extraction from the reactor.
Rod Case Irradiation
It is also important to understand and account for the fact that the fuel rod encasement will have been subjected to long term neutron bombardment in the reactor, and will therefore be itself a radiation source.
Mechanisms of Photon generation
- Secondary interactions after electron ejection by gamma absorption or Compton scattering
- Cherenkov and transition radiation from alpha and beta particles emitted by the irradiated fuel rod encasement or from secondary radiation sources created from neutron poisoning in the vitrification matter itself
Mechanisms of Energy loss
- Heat production
- Photon production outside of the optimal absorption ranges.
- Photon resorption prior to encounter with collector cells
Loss mitigation
- Attempt to encourage the production of the desired photon wavelengths by introducing flourescent materials into the glass
Efficiency
Without crunching the numbers, it seems prudent to estimate the efficiency of total nuclear energy conversion to electric energy as quite low. Only a fraction of the nuclear energy will have a mechanism to produce visible light photons and much of it will be lost to heat. After that there will be the conversion efficiency of the photo-voltaic cells. One might consider that the desired affect could still be achieved if the energy efficiency is too low by adding more fuel rods. This could work up to a point, but it will be limited by heat generation. Heat dispersal to the surrounding environment will be low due to the thick containment shell, so adding additional heat sources within the shell will increase the temperatures of the waste material significantly which could cause undesired phase changes leading to containment cracking.
Experimentation and Research Required
I say “without crunching the numbers” above as if that were a realistic feat at this time. This is actually a very complicated system that changes characteristics over time. I don’t think that all of the necessary research and experimentation has been completed at this point for the construction of the theoretical model that would be needed to hypothesize the light energy generated. I can reasonably presume that the heat-generation of fission waste has been studied extensively as that characteristic is key to the design of any containment enclosures, but the other types of energy may not have been as thoroughly studied. I expect that the following matters would need to be either investigated by experimentation or recovered from past research:
- Radiation emissions from fission products over time, all types (likely to have been previously studied)
- The production of radioactive nuclei within radiation and neutron bombarded fuel encasement materials (varies by original chemical composition)
- Radiation emission from encasement materials (previously theorized once the types are radioactive nuclei are known)
- The production of radioactive nuclei within a dielectric material(s) used for vitrification (will be material specific, each material may require study unless predictive models exist)
- Secondary effects of gamma radiation on the dielectric material(s) used for vitrification, specifically looking for photon production and heat production (material specific, needs research)
- Effects of gamma radiation on solar cells: damage, photoelectric (may have been previously researched for satellite solar panels)
- Excitation of fluorescent materials by gamma radiation/beta particles (material specific, likely needs research)
- Physical properties of the dielectric material(s) including heat conduction, phase transitions, mechanical strengths at various temperatures, and mechanical vibration resistance for seismic survivability of any ultimate design. (material specific, some info may exist others will need research)
- Cherenkov and transition radiation produced in the dielectric material(s) (material specific, likely needs research)
- Modeling of total photon energy generated from these several mechanisms as a function of time to predict energy output (needs research)
- Modeling of total heat energy generated from these several mechanisms as a function of time in order to ensure any ultimate design will remain safe. (There is likely to be previous research and design methodology)
- Chemical decomposition over time of the dielectric and other materials caused by gamma ray electron ejections and/or interactions with alpha or beta particles which could reduce transparency or affect the mechanical characteristics (material specific, needs research)
- Many other considerations regarding the fabrication process and integrity and safety of the structure throughout it’s production.
Alternative Configurations
There are many alternative designs which require processing the fission waste in some way. For instance, the waste could be processed into a powder and directly introduced into molten glass. This would increase photon production considerably. Furthermore, the fission waste could be processed with chemical separation techniques to isolate the most active elements. However, any type of fission waste processing is inherently risky because fission waste products are highly biohazardous and will require extraordinary safety and redundancy measures to ensure that nothing can go wrong and to ensure that all failures are safe throughout the entire process.
