Cold Fission — Toward the Low-Heat End of the Design Axis
© 2026 David R. Young — Spectrum Energy Research Foundation · CC BY-NC-SA 4.0
© 2026 David R. Young — Spectrum Energy Research Foundation · CC BY-NC-SA 4.0
Note 028 asked how far toward zero heat a fission system could go, and proposed suspending fuel particles in an electromagnetic field. The concept was sound in principle but unstable in practice — every fission event kicks the floating fuel around, and the chain reaction depends on the fuel staying put. What if the fuel had a base — a lattice to hold it in place — but that base was thin enough and tough enough to let the fission products pass straight through? What material could do that? How would you build it?
Note 028 established that heat is not a product of fission. Heat is what happens when fission products slam into surrounding material and stop. Remove the material and you remove the heat. The logical extreme was fuel suspended in vacuum by electromagnetic fields — no material anywhere near the reaction.
But watch what happens at the atomic level. A neutron strikes a uranium-235 atom and the atom splits. Two fragments fly apart carrying 170 million electronvolts of kinetic energy. If the uranium atom was part of a floating particle, the recoil from that split sends the remaining particle flying. And it is not just fission events that do this — even a neutron that bounces off a uranium nucleus without causing fission transfers a kick. Across billions of events per second, the fuel cloud is being stirred by the very reaction it needs to sustain.
In a solid fuel pellet, the crystal lattice absorbs these recoils. Each atom is locked in place by its neighbors. The lattice is the base — it provides the stability that keeps the fuel arranged for the next neutron to find the next atom. Take away the lattice and you take away the base. The fuel becomes a scattering of billiard balls in three dimensions, rearranging itself with every collision.
A chain reaction requires fuel atoms at a specific density. The reaction itself disrupts that density. This is not an engineering problem to be solved with better fields — it is a consequence of momentum conservation. Every nuclear event moves unsupported fuel. No field can reposition billions of particles per second fast enough to compensate.
The zero-heat target remains the right direction. But the path to it requires something the floating concept abandoned: a base.
The base has one function: hold the uranium atoms in fixed positions so neutrons can find them reliably. But unlike a conventional fuel pellet, this base cannot be a trap. In a conventional reactor, the fuel pellet is roughly a thousand times thicker than the distance a fission fragment can travel. Every fragment stops inside the pellet. All that kinetic energy — 81% of fission output — thermalizes where it lands.
The base for a low-heat design needs to be a scaffold, not a wall. It holds the atoms in place but lets the products pass through. That means two things:
Thin. The uranium layer must be thin enough that fragments escape before stopping. Fission fragments travel about 6 to 10 micrometers in uranium before halting. A layer thinner than that lets them out.
Tough. Every fragment that passes through the base damages the lattice along its path — knocking atoms out of position, creating defect tracks. At reactor power, billions of fragments per second are punching through the same thin membrane. The base material must resist this damage better than anything else available, or the membrane disintegrates.
These two requirements — thin and tough — point in the same direction.
Every material has a displacement energy — the minimum force needed to permanently knock one of its atoms out of the lattice. The higher the displacement energy, the harder it is for a passing particle to damage the structure. Here is where things stand:
Material
Displacement Energy
Relative Toughness
Gallium arsenide
10 electronvolts
1×
Silicon
13–20 electronvolts
1.5×
Silicon carbide
22 electronvolts
2×
Diamond
43 electronvolts
4×
Diamond requires roughly four times the energy to displace an atom compared to gallium arsenide, and twice the energy compared to silicon carbide. Per incoming ion, fewer atoms get knocked out of position. Diamond and silicon carbide detectors have both been tested directly against fission fragments at the Institut Laue-Langevin LOHENGRIN spectrometer — the same facility where cold fission was first observed in 1981. Diamond consistently shows higher radiation hardness.
But radiation hardness is only the first reason. Diamond has two other properties that matter here.
Thermal conductivity. Diamond conducts heat at roughly 2,000 watts per meter-kelvin — five times better than copper, the standard benchmark for heat conduction. Whatever energy a passing fragment does deposit in the diamond moves away from the impact site almost immediately. Hot spots do not accumulate. The membrane stays cool even while absorbing punishment.
Self-annealing. Radiation damage in diamond consists mostly of point defects — individual carbon atoms knocked out of position. At modest temperatures (a few hundred degrees Celsius), these defects migrate back into lattice positions. The diamond repairs itself. This has been observed experimentally and is one reason diamond radiation detectors maintain performance over extended use.
No other known material combines all three: highest displacement energy, highest thermal conductivity, and the ability to heal its own radiation damage. Diamond is not merely a good candidate for this application. It is the only candidate that addresses all three requirements simultaneously.
Start with a single fuel cell. It is a composite membrane with three layers: enriched uranium (5 to 8 micrometers), diamond (10 micrometers), and a thin doped aluminum nitride piezoelectric layer (2 to 3 micrometers). The total thickness is roughly 17 to 21 micrometers. Thinner than a human hair.
Each layer has one function. The uranium is the fuel. The diamond is the base — it holds the uranium atoms in a fixed lattice, provides structural toughness, and conducts heat at 2,000 watts per meter-kelvin. The doped aluminum nitride (aluminum nitride with magnesium and niobium) is a heat recovery layer — it sits at the diamond boundary and converts waste compression energy from the diamond into electrical charge.
Layer order (cross-section of a single fuel cell):
Vacuum ← Uranium (5–8 μm) → Diamond (10 μm) → Doped AlN (2–3 μm) → Vacuum
When a fission event occurs in the uranium layer, two fragments fly in opposite directions. The outward fragment escapes immediately into vacuum for collection by the electrostatic field. The inward fragment enters the diamond.
The fragment passes through the diamond at roughly 500 times the speed of sound in the lattice. It exits the far side before the lattice vibrations from its entry have begun to propagate. Behind it, it leaves a trail of disrupted atoms — a shockwave that expands outward at the speed of sound. When that trailing compression wave reaches the diamond-AlN boundary, it transmits into the doped AlN and generates electrical charge. Energy that would otherwise dissipate as heat in the diamond is recovered as electricity.
The fragment itself also passes through the thin AlN layer, depositing less than 2 MeV in transit — a small fraction of its remaining energy. It exits the membrane with roughly 87 to 88 percent of its original kinetic energy intact, still carrying a high positive charge, and enters vacuum where the electrostatic collector field captures it.
The electrostatic field is the primary converter. A charged particle decelerating against a voltage gradient transfers kinetic energy to electrical potential at high efficiency — potentially 80 to 95 percent. The AlN layer does not compete with the field for fragment energy. Its function is to recover waste heat from the diamond that the field cannot reach. The AlN is deliberately thin — 2 to 3 micrometers — so that the fragment retains maximum energy for the more efficient field collection. Every extra micrometer of AlN would steal energy from the field at a net loss to the system.
Both fragments escape. The membrane is a scaffold and a heat recovery system, not a trap.
Now stack these. An array of composite membranes, each in a rigid frame (tungsten, molybdenum, or silicon carbide), mounted in a rack inside a vacuum chamber. The spacing between membranes — a few centimeters — is the fragment flight space where the collector field operates.
The layer structure of the complete system, from inside out:
Fuel cell array — composite membranes (uranium + diamond + doped AlN), mounted in support frames with electrical connections for piezoelectric output
Vacuum — fragment flight space
Collector field — electrostatic voltage gradient decelerates charged fragments (primary conversion)
Neutralization points — electron injection harvests fragment charge
Xenon gas shell — analog throttle for neutron moderation (from Note 028)
Beryllium shell — neutron reflection and multiplication
Hydrogen shell — emergency shutdown
Converter crystals — scintillators convert gamma to light, photovoltaics convert light to electricity
Shielding and thermal boundary
Each fission product meets its converter in the right order. The charged fragments decelerate against the field — most never touch material at all. The neutrons pass through the field untouched, moderate in the xenon, reflect off the beryllium, and return to the fuel. The gamma passes through everything until it reaches the converters. The removable cartridge concept from Note 028 applies unchanged — neutralized fission products are collected and become Spectrum Energy Cell fuel.
Can an array of thin membranes sustain a chain reaction?
This is the central engineering question, and it must be answered honestly. A conventional fuel pellet is dense — packed solid uranium oxide. The diamond membrane array is mostly vacuum with thin fuel layers separated by centimeters. The average fuel density across the assembly is far lower than a conventional core.
Three factors work in favor of criticality:
Enrichment. The uranium can be enriched to higher U-235 fractions than conventional power reactor fuel (which typically uses 3 to 5 percent). Research reactor fuel routinely uses 20 percent enrichment, and some designs use higher. Higher enrichment means fewer total uranium atoms are needed to sustain a chain reaction.
Beryllium. The beryllium reflector surrounding the assembly returns escaped neutrons and multiplies them. A neutron hitting beryllium-9 above 1.85 million electronvolts can knock out two neutrons. The shell is not just reflecting — it is amplifying.
Moderation. The xenon gas shell moderates fast neutrons to thermal speeds, where U-235's capture cross-section jumps by a factor of 585. From the neutron's perspective, the fuel effectively becomes 585 times larger.
Whether these three factors compensate for the low average fuel density is a neutronics calculation — a problem for computational tools like MCNP (Monte Carlo N-Particle transport code), not for speculation. The answer depends on the number of membranes, their spacing, the enrichment level, and the beryllium geometry. If the calculation shows the configuration cannot reach criticality, then an external neutron source (californium-252 startup capsule or a small accelerator) operates it in subcritical multiplication mode — not self-sustaining, but still converting fission energy directly.
Either path works. Self-sustaining is more elegant. Subcritical is more certain.
Every component in this design uses existing technology. No new materials need to be discovered. No new physics needs to be invented. The manufacturing sequence for the fuel cells themselves:
Step 1 — Grow the diamond. Chemical vapor deposition grows single-crystal diamond on a sacrificial substrate. Methane and hydrogen in a plasma at 700 to 1,000 degrees Celsius. Growth rates of 1 to 100 micrometers per hour are standard. Companies including Element Six and IIa Technologies produce CVD diamond commercially.
Step 2 — Thin the diamond to membrane thickness. Laser slicing separates the diamond from the growth substrate. Mechanical polishing and plasma etching bring it to the target thickness of 15 to 20 micrometers. Single-crystal CVD diamond membranes have been thinned to 3.5 micrometers in published research — our target is thicker than what has already been demonstrated.
Step 3 — Deposit the doped aluminum nitride. Reactive magnetron sputtering deposits the doped AlN heat recovery layer (2 to 3 micrometers) onto the diamond surface. The sputtering targets are aluminum alloyed with magnesium and niobium, deposited in a nitrogen atmosphere. This is standard thin-film processing — doped AlN films are manufactured commercially for sensors and resonators. The layer is deliberately thin: its function is to recover waste compression energy from the diamond, not to intercept fragment energy that the more efficient electrostatic field should capture.
Step 4 — Deposit the uranium. Magnetron sputtering or electron-beam evaporation deposits enriched uranium onto the AlN surface. This is standard physical vapor deposition — the same technique used across the semiconductor industry for depositing metal films of controlled thickness. The uranium target requires a licensed nuclear facility for handling, but the deposition physics is routine. Film thickness is controllable to sub-micrometer precision.
Step 5 — Mount in a support frame. Each membrane sits in a rigid frame — tungsten, molybdenum, or silicon carbide — around its edges. The frame provides structural support, mounting points, and electrical connections to the collector circuit. Like the frame around a drumhead: the membrane is the thin working surface, the frame holds it in place.
Step 6 — Assemble the array. Multiple framed fuel cells mount in a rack inside the vacuum vessel. Spacing is determined by the fragment flight distance needed for electrostatic deceleration. The assembly slides in and out of the vessel as a cartridge, similar to the Warm Fission Reactor's cartridge concept.
The remaining components — vacuum vessel, electrostatic collectors, beryllium reflector, xenon and hydrogen gas systems, scintillator crystals, photovoltaics, shielding — are all described in Note 028 and use commercially available materials and established engineering.
The components exist. The integration does not. These are the experimental questions, in order of importance:
Criticality geometry. Can this membrane array configuration achieve a self-sustaining chain reaction? This is a neutronics modeling question first (MCNP simulation), then a zero-power critical experiment if the model says yes. If the model says no, subcritical operation with an external source is the fallback.
Fragment transmission through diamond. What fraction of a fission fragment's kinetic energy passes through a 15-to-20-micrometer diamond membrane? SRIM (Stopping and Range of Ions in Matter) simulations can predict this. Experimental confirmation with actual fission fragments is available at facilities like the ILL LOHENGRIN spectrometer, where diamond detectors have already been tested.
Diamond survival at reactor duty cycles. Diamond detectors survive counting individual fission events. Can a diamond membrane survive billions of fragment transits per second sustained over months? The question is whether the annealing rate keeps pace with the damage rate at operating temperature. This requires an irradiation endurance test — sustained heavy-ion bombardment of diamond membranes at representative flux levels.
Uranium adhesion to diamond. Metal films on diamond are routine in the semiconductor industry. Uranium-on-diamond specifically has not been tested. Adhesion, interfacial stability, and behavior under thermal cycling and radiation need characterization.
Collector circuit design. How is the electrical energy extracted from the electrostatic collector field as usable current? The electrostatic deceleration principle is established, but the circuit design for continuous power extraction from omnidirectional discrete particle impacts is an open engineering question. The traveling wave direct energy conversion approach studied by EPRI and NASA — which converts fragment kinetic energy to alternating current without requiring million-volt DC electrodes — may offer an alternative path.
The diamond layer absorbs roughly 10 percent of each inward fragment's energy as a compression shockwave in the lattice. In a diamond-only membrane, that energy dissipates as heat — it never reaches the vacuum where the electrostatic field could capture it. The field cannot reach energy trapped inside a solid.
But a piezoelectric material can. A thin piezoelectric layer bonded to the diamond's exit face receives the compression wave as it propagates through the diamond at the speed of sound. The wave crosses the boundary, deforms the piezoelectric lattice, and generates electrical charge. Energy that would have been waste heat becomes electricity.
This is the AlN layer's function: heat recovery, not primary conversion. The electrostatic field in vacuum is the primary converter — it captures the fragment's kinetic energy at potentially 80 to 95 percent efficiency as the charged particle decelerates against the voltage gradient. Piezoelectric conversion operates at roughly 10 to 30 percent efficiency. The AlN should not compete with the field for fragment energy. It should catch what the field cannot reach — the compression energy trapped in the diamond.
This is why the AlN layer is thin — 2 to 3 micrometers. Thick enough to respond to the compression wave from the diamond. Thin enough that the fragment passes through losing less than 2 MeV, retaining roughly 87 to 88 percent of its original energy for the more efficient field collection. Every extra micrometer of AlN would intercept energy the field would have captured more efficiently — a net loss to the system.
Stopping power calculations (ZBL model, same physics as SRIM) confirm this: at fission fragment energies of 70 to 100 million electronvolts, the fragments travel so fast that the charge output and damage ratio in the AlN barely changes across a wide range of diamond thickness. The optimization is not about finding a stopping power sweet spot. It is about energy budget allocation — letting each converter handle the energy it converts most efficiently.
The selected material — aluminum nitride doped with magnesium and niobium
Pure aluminum nitride has been tested inside an operating nuclear reactor core. After exposure to fast neutron fluence of 1.85 × 10^18 neutrons per square centimeter, thermal fluence of 5.8 × 10^18, and 26.8 megagray of gamma dose, its piezoelectric coefficient was unchanged — 5.5 picocoulombs per newton before and after. Its transition temperature is 2,826°C, far above any operating temperature in this design. It can be deposited as a thin film using standard sputtering techniques. Its thermal conductivity is 285 watts per meter-kelvin — not diamond's 2,000, but excellent by any other standard.
Adding magnesium and niobium to the aluminum nitride lattice increases the piezoelectric coefficient to 22 picocoulombs per newton — four times the pure form — without changing the wurtzite crystal structure that provides the radiation hardness. All four constituent elements (aluminum, magnesium, niobium, nitrogen) are abundant. None are neutron absorbers. The doped material is deposited by the same sputtering process as pure AlN, using alloyed targets.
The trade-off is displacement energy. Aluminum nitride's displacement energies are 28 electronvolts on the aluminum sublattice and 19 electronvolts on the nitrogen sublattice — lower than diamond's 43. It takes more damage per fragment transit. The diamond layer in the composite membrane addresses this directly: diamond faces the heavier bombardment, the doped AlN sits behind it and converts the compression pulse that transmits through.
The composite membrane architecture: uranium on the outside (fuel), diamond in the middle (base — structural toughness, thermal conductivity, lattice stability), doped aluminum nitride on the inside face (heat recovery — converts the diamond's waste compression into charge). The diamond takes the fragment impact. The AlN recovers what the diamond would otherwise waste. The fragment exits into vacuum where the field does the heavy conversion.
Nanostructuring may improve the economy further. Cubic boron nitride nanocrystals at 3.4 nanometers produce six times the piezoelectric output of bulk c-BN. If doped AlN shows a similar enhancement at nano scale, the output per fragment impact increases without changing the material. This is an open experimental question.
The geometry search — working backwards to find better candidates
Piezoelectricity is not a material property you can add or adjust. It is a geometric property. A crystal is piezoelectric if and only if its structure lacks a center of symmetry — in crystallography, if it is non-centrosymmetric. Of the 32 possible crystal point groups, exactly 20 are piezoelectric. The other 12 can never be piezoelectric regardless of composition, because their symmetry cancels every compression-generated charge.
Diamond is in the centrosymmetric group (Fd3̄m). No amount of engineering will make diamond piezoelectric. Its geometry forbids it.
But this same geometric rule opens a research question: do any compressed forms of elements or compounds land in one of the 20 piezoelectric groups? If a naturally centrosymmetric element shifts to a non-centrosymmetric structure under compression, it gains a piezoelectric function that the natural form does not have.
This has already been observed in both directions. Quartz (natural silicon dioxide) is piezoelectric — it powers the Kinetic Lattice Battery concept in Note 034. But stishovite (compressed silicon dioxide) has a different geometry and the piezoelectric function is gone. Compression destroyed the function by changing the geometry to a centrosymmetric form. In the opposite direction, hexagonal boron nitride (natural) is layered and centrosymmetric — not piezoelectric. Wurtzite boron nitride (compressed) has the wurtzite structure, which IS non-centrosymmetric. Compression created the geometry needed for piezoelectricity where none existed.
The search method is systematic: for every compressed phase on record, check its space group against the 20 piezoelectric point groups. If it matches, test it. Three candidates already sit in the Spectrum Energy charts, untested:
Material
Form
Structure
Piezoelectric Geometry?
Tested?
Cubic boron nitride (c-BN)
Super compound
Zinc blende (F4̄3m)
Yes — non-centrosymmetric
No
Wurtzite boron nitride (w-BN)
Super compound
Wurtzite (P6
3
mc)
Yes — non-centrosymmetric
No
ST12 germanium (Ge-III)
Primed element
Simple tetragonal (P4
3
2
1
2)
Yes — chiral, no inversion
No
Cubic boron nitride is the most promising for this application. It is the second-hardest material known. Its lattice spacing nearly matches diamond's. It is a super compound — holds its form indefinitely at normal conditions without applied pressure. And its zinc blende structure is the same geometry as gallium arsenide, zinc sulfide, and other established piezoelectric materials. If c-BN's piezoelectric response is confirmed, it could serve as both base and converter in a single layer — harder than nearly everything, permanent, and actively generating charge from every fragment impact.
A broader survey — scanning all characterized compressed phases against the 20 piezoelectric point groups — would map every candidate across the periodic table. The geometry is the filter. The displacement energy, thermal conductivity, and radiation hardness are the selection criteria. The search is well-defined and mappable.
Note 028 defined a design axis from all-heat on the left to zero-heat on the right. Every nuclear energy system sits somewhere on this line. Here is where the diamond membrane fuel cell lands:
Position
Description
Fragment Kinetic Energy Captured Directly
Far left
Conventional reactor — ceramic pellet, water, steam cycle
0%
Left-center
Conventional with waste-stream harvesting
0%
Center
Warm Fission Reactor — selenium-sulfur semiconductor
~81% (all fragment energy, converted in liquid)
Right-center
Diamond Membrane Fuel Cell — fragments pass through base into vacuum
~70–85% (both fragments escape, some energy deposited in diamond)
Far right
Zero-heat target — no material in fission path
~100% (theoretical limit)
The diamond membrane concept does not reach zero heat. It was never going to — zero is the direction, not the destination. What it does is move further right than any other design that keeps the fuel stable. The fragment that flies outward escapes clean. The fragment that flies inward passes through the thinnest, toughest base available and mostly escapes. The diamond conducts away whatever heat it does absorb faster than any other solid. And the base repairs itself.
The name Cold Fission fits this concept. It is real fission, the fuel stays cold, and the fragments escape before the energy they carry becomes heat. It is not zero heat. It is the closest to zero that a stable fuel geometry appears to allow.
This concept builds on and connects to:
Note 028 — The Heat-to-No-Heat Spectrum. The design axis, the energy distribution analysis, the xenon throttle, hydrogen shutdown, beryllium reflector, collector field architecture, and the removable cartridge concept all originated there. This note solves the stability problem that Note 028 left open.
Note 033 — The Geometric Limit. Compressed carbon phases — super-carbon — hold their form indefinitely and have denser, stiffer lattices than standard diamond. If super-carbon's displacement energy exceeds diamond's 43 electronvolts, it could extend the membrane's service life under fission fragment bombardment. An open research question.
Notes 035, 036, 037 — The geometric forms thread. Compressed element properties as control functions. Super-carbon and other compressed phases may have applications as structural or shielding components in this design.
Warm Fission Reactor — Shares the principle of thin fuel for fragment escape but uses a selenium-sulfur semiconductor as the converter medium. The Warm Fission Reactor captures fragment energy in liquid semiconductor immediately adjacent to the fuel. This design lets fragments fly further into vacuum before capturing their energy in a field. Different conversion mechanism, same foundational insight: let the fragments out.
Spectrum Energy Cell — The cascade connection. Fission products collected from this reactor are decay sources — fuel for SE Cells. The reactor feeds the cell. The cell's waste is a stable isotope. Design Principle 4: cascade, don't discard.
Note 034 — The Kinetic Lattice Battery. Piezoelectric conversion of stored mechanical energy to electricity via bismuth titanate. The same principle — mechanical compression generating charge — applied here to fission fragment impacts instead of lattice phase transitions.
External research that supports elements of this design:
Fission fragment direct energy conversion — studied since 1957, with the NERI project at Sandia National Laboratories reviving interest in 2000. Electrostatic deceleration of charged fission fragments is verified physics.
Diamond radiation detectors — tested at ILL LOHENGRIN with fission fragments, confirming diamond's superior radiation hardness. Ongoing development for fast reactor environments.
CVD diamond membranes — single-crystal diamond thinned to 3.5 micrometers demonstrated in published research. The manufacturing process is mature.
Traveling wave direct energy conversion — EPRI/NASA study on converting fragment kinetic energy to alternating current without high-voltage DC electrodes. A potential alternative to electrostatic collection.
Helion Energy — fusion company extracting electricity directly from charged particle deceleration in magnetic fields. Construction began 2025. The engineering of direct charged-particle-to-electricity conversion is advancing rapidly, driven by fusion investment.
US Patent 5,079,469 — Piezonuclear Battery — Los Alamos National Laboratory, Department of Energy. Patent for piezoelectric conversion of fission fragment energy to electrical energy. Validates the active-base concept described in Section 8.
Aluminum nitride in-reactor testing — IEEE publication demonstrating unchanged piezoelectric coefficient after sustained neutron and gamma exposure inside a reactor core. Validates radiation hardness of piezoelectric AlN for nuclear environments.
Can a membrane array achieve criticality, or does it require an external neutron source?
What fraction of fragment kinetic energy transmits through 15 to 20 micrometers of diamond? Can SRIM simulations be validated against experimental data at the ILL?
Does super-carbon (compressed diamond phases from Note 033) offer higher displacement energy than standard diamond? If so, how much, and can it be manufactured as membranes?
What is the maximum sustained fission fragment flux that a diamond membrane can tolerate before damage exceeds self-annealing?
Does uranium metal or uranium nitride adhere better to diamond, and which is more stable under irradiation?
What is the optimal membrane thickness? ZBL stopping power calculations indicate that diamond thickness is a structural survival parameter, not a stopping power optimization — at fission fragment energies, electronic stopping dominates nuclear stopping by a factor of 5,000 or more across the entire practical thickness range. The minimum diamond thickness that provides acceptable service life under sustained bombardment is the optimum. Preliminary calculation suggests 10 micrometers of diamond allows the fragment to exit with 87 to 88 percent of its original energy. These results should be validated with full SRIM Monte Carlo simulation including straggling and channeling effects.
What is the optimal AlN thickness? The AlN layer functions as heat recovery, not primary conversion. The electrostatic field in vacuum converts fragment kinetic energy at 80 to 95 percent efficiency; piezoelectric conversion operates at 10 to 30 percent. Every micrometer of AlN beyond what is needed to capture the diamond compression wave intercepts energy the field would convert more efficiently. Preliminary analysis points to 2 to 3 micrometers. The minimum thickness that fully responds to the acoustic shockwave transmission from the diamond is the optimum.
Can the collector field be designed to accommodate the full range of fission fragment charge-to-mass ratios (light group around mass 95 versus heavy group around mass 137, charge states from +20 to +40)?
What is the startup sequence? How do you bring this system from cold shutdown to sustained operation safely?
Does cubic boron nitride exhibit measurable piezoelectric response? If so, what is the d₃₃ coefficient, and how does it compare to aluminum nitride's 5.5 picocoulombs per newton?
Does ST12 germanium (primed germanium, Prime 1) exhibit piezoelectric response? Its space group (P4₃2₁2) is non-centrosymmetric. If confirmed, it would be a piezoelectric function gained through compression — a new entry on the Geometric Control Functions chart.
How many other compressed element phases across the periodic table have non-centrosymmetric space groups? A systematic survey against the 20 piezoelectric point groups would map the full candidate set.
Can the electromagnetic field concept from the EM Propulsion Vehicle research serve as the collector — a field boundary that decelerates fragments without physical electrodes?
Does this architecture scale down to vehicle power applications, or is there a minimum size set by the neutronics?
US Patent 5,079,469 (Los Alamos, Department of Energy) describes a piezonuclear battery using piezoelectric film to convert fission fragment energy directly to electrical energy. What piezoelectric materials did that work characterize, and what conversion efficiencies were measured?
This note defines a specific architecture — the diamond membrane fuel cell — for moving as far toward zero-heat fission as the physics of stable fuel allows. Every material in the design exists today. Every manufacturing step uses established technology. What remains is integration and the experiments to prove or disprove the critical assumptions. The direction is set. The distance is an experiment.
The following materials were evaluated as candidates for the active piezoelectric base layer. All entries are classified by element form (natural, super, or primed) and filtered against four criteria: piezoelectric output (d₃₃ coefficient), material abundance, radiation hardness, and nuclear compatibility (no significant neutron absorption). Doped AlN was selected as the working material for this design.
Material
Class
d₃₃ (pC/N)
Abundance
Radiation Hardness
Nuclear Compatible?
AlN + Mg + Nb (selected)
Natural compound, doped
22
All elements abundant
Wurtzite structure — proven in reactor
Yes
AlN (pure)
Natural compound
5.5
All elements abundant
Proven in reactor — d₃₃ unchanged
Yes
ZnO
Natural compound
12
Both elements abundant
Moderate — degrades under heavy ions
Yes
c-BN (bulk)
Super compound
~4.3
Boron moderate, nitrogen unlimited
Second-hardest material known
Requires B-11 enrichment — natural boron absorbs neutrons
c-BN nanocrystals (3.4 nm)
Super compound, nanostructured
25.7
Same as bulk c-BN
Untested at nano scale
Requires B-11 enrichment
w-BN
Super compound
Unmeasured
Same as c-BN
Predicted harder than diamond
Requires B-11 enrichment
ST12 germanium
Primed element
Unmeasured
Germanium scarce (1.5 ppm)
Unknown
Yes
Quartz (SiO₂)
Natural compound
2.3
Both elements unlimited
Low — radiation fragile
Yes
Barium titanate (BaTiO₃)
Natural compound
190
Both elements moderate to abundant
Poor — depoles under radiation
Questionable
PZT (lead zirconate titanate)
Natural compound
300–600
Lead moderate
Poor
No — lead absorbs neutrons, toxic
Key findings from the selection process:
Piezoelectric output varies by more than 100× across materials. Formation matters as much as composition — c-BN nanocrystals produce six times the charge of bulk c-BN. Doping AlN with magnesium and niobium produces four times the charge of pure AlN without changing its radiation-hard wurtzite structure.
For pure elements, compressed phases tend to remain centrosymmetric (the geometric opposite of piezoelectric). The charge asymmetry required for piezoelectricity arises most naturally in compounds, where two different atom types create the built-in imbalance. Super-compounds from abundant elements are a more promising search space than super-elements for this application.
The geometry search method remains open: scan all characterized compressed compound phases against the 20 piezoelectric crystal point groups to identify candidates not yet tested. The filter is geometric (non-centrosymmetric space group), the selection criteria are practical (displacement energy, abundance, radiation hardness, d₃₃ economy).
Los Alamos National Laboratory holds US Patent 5,079,469 (Piezonuclear Battery) for piezoelectric conversion of fission fragment energy to electrical energy, validating the active-base principle.
© 2026 David R. Young — Spectrum Energy Research Foundation
Licensed under CC BY-NC-SA 4.0 for research and education. Commercial use requires a separate license from Spectrum Energy Research Foundation. Contact: secharts@proton.me
© 2026 David R. Young — Spectrum Energy Research Foundation
Licensed under CC BY-NC-SA 4.0 for research and education. Commercial use requires a separate license from Spectrum Energy Research Foundation. Contact: secharts@proton.me