# Is LLNL's THUNDER Project the Most Credible Thorium TRISO Program Yet?

Lawrence Livermore National Laboratory has partnered with Ampera — a Palm Beach Gardens, Florida-based startup founded in 2025 — to fabricate TRISO fuel using thorium-232 kernels instead of the conventional uranium oxide core. The program is formally named THUNDER: Thorium Unimodal Droplet Ejection for Reactors. The core manufacturing challenge LLNL and Ampera are tackling is kernel geometry: the two organizations will evaluate and optimize liquid metal–jetting technology to produce highly uniform, spherical Th-232 kernels for subsequent TRISO processing.

This matters because kernel sphericity is a critical quality metric in TRISO fabrication — asymmetric kernels compromise the integrity of the pyrolytic carbon and silicon carbide coating layers that provide the fuel's passive containment function. LLNL's involvement grounds the effort in an existing, demonstrated capability: research engineer Viktor Sukhotskiy led a 2023 internal project called PowderJet that produced a "droplet-on-demand" liquid metal–jetting prototype capable of generating highly spherical, size-controlled metallic particles. THUNDER is the first application of that platform to a nuclear fuel material.

For the broader advanced reactor sector, the partnership signals that thorium TRISO — long a theoretical alternative to uranium TRISO — is entering the laboratory-scale fabrication phase with national laboratory backing.

---

## What Is THUNDER and How Does the Technology Work?

THUNDER stands for Thorium Unimodal Droplet Ejection for Reactors. The manufacturing approach centers on liquid metal–jetting: a process in which molten feedstock is ejected in controlled droplets that solidify into discrete, highly spherical particles. Sukhotskiy's PowderJet prototype, developed at LLNL in 2023, demonstrated this principle with metallic materials. THUNDER extends the technique to thorium-232.

The target output is uniform Th-232 kernels that can then be coated with the standard TRISO layer sequence — typically a porous carbon buffer, inner pyrolytic carbon, silicon carbide, and outer pyrolytic carbon — to produce finished fuel particles. Kernel diameter uniformity and sphericity directly determine coating quality, which in turn governs fission product retention under irradiation. Getting the kernel right is not a secondary concern; it is the critical path.

LLNL describes thorium as offering three specific properties relevant to fuel cycle strategy: abundance, a less persistent waste stream compared to uranium, and proliferation resistance. The proliferation resistance claim rests on Th-232's decay pathway — it is not itself fissile, but absorbs a neutron to breed uranium-233, which is fissile. That breeding mechanism is what enables a thorium fuel cycle, but U-233 also carries its own nonproliferation considerations that any eventual regulatory submission will need to address.

---

## Ampera's Broader Strategy: Vertical Integration and Subcritical Systems

Ampera CEO Brian Matthews has been explicit about the company's commercial rationale. In the ANS-reported statement, Matthews described the LLNL collaboration as part of a strategy to "vertically integrate our fuel supply, reduce cost and supply-chain risk, and support the deployment of our compact subcritical nuclear energy systems."

That language — subcritical nuclear energy systems — is unusual and worth noting. Ampera is not, based on publicly available information, developing a conventional critical reactor. The subcritical framing suggests an accelerator-driven or otherwise externally-sourced neutron configuration, though the source material does not elaborate on the reactor architecture beyond a description of a 3D-printed core model.

What the source does confirm is a rapid series of milestones over the summer of 2026:

- **June 2026:** Ampera established an Australian subsidiary to secure a thorium supply chain.
- **July 2026:** Ampera produced a full-scale, additively manufactured model of its nuclear core architecture — a spherical, monolithic gyroid structure 3D printed in silicon carbide.
- **August 2026:** The LLNL partnership and THUNDER project announced.

The pace is notable for a company founded in 2025. However, Ampera has not yet disclosed funding amounts, regulatory engagements with the NRC, or a timeline to irradiation testing. For investors and program managers evaluating this effort, the absence of those data points is the relevant gap.

---

## TRISO Fabrication Competition Is Intensifying

Ampera and LLNL are entering a TRISO development landscape that has become considerably more active. [X-energy](https://smrintel.com/companies/x-energy)'s TRISO-X subsidiary recently received an $11 million economic development grant from Tennessee's Nuclear Energy Supply Chain Investment Fund to continue construction of its fuel fabrication facilities. Standard Nuclear has separately disclosed construction and regulatory approval milestones for two TRISO production facilities targeting 2026 operations.

Both of those programs use conventional uranium-based TRISO kernels, which have an established irradiation database and a defined regulatory path. Thorium TRISO has neither. LLNL's involvement addresses the manufacturing science question, but Ampera will eventually need irradiation data — ideally in a test reactor — to demonstrate fission product retention performance equivalent to or better than uranium TRISO before any NRC licensing pathway becomes viable.

The [breeding ratio](https://smrintel.com/glossary/breeding-ratio) dynamics of a thorium cycle also introduce fuel management complexity that uranium-fueled [high temperature gas-cooled reactor](https://smrintel.com/glossary/htgr) developers have not had to address. U-233 buildup during operation affects reactivity control and, depending on irradiation time and neutron flux, the isotopic purity of the bred fissile material.

---

## What LLNL's Involvement Actually Signals

National laboratory partnerships carry real weight in advanced nuclear development, but they are not equivalent to demonstrated commercial readiness. LLNL brings the PowderJet manufacturing platform, Sukhotskiy's materials science expertise, and institutional credibility. What the partnership does not bring — at least at this stage — is an irradiation campaign, a fuel qualification program, or a defined path to commercial-scale throughput.

The honest read: LLNL and Ampera are solving a real manufacturing problem (uniform thorium kernel production) with a plausibly differentiated technology (liquid metal–jetting). If PowderJet-derived droplet ejection can produce Th-232 kernels with the dimensional tolerances TRISO coating requires, that is a genuine technical contribution. The distance from that milestone to qualified fuel in an operating reactor is, however, measured in years and hundreds of millions of dollars of capital — neither of which Ampera has disclosed.

---

## Key Takeaways

- LLNL and Ampera have launched **THUNDER**, a project to fabricate TRISO fuel using thorium-232 kernels produced via liquid metal–jetting technology.
- The manufacturing approach builds on LLNL research engineer Viktor Sukhotskiy's 2023 **PowderJet** prototype, which demonstrated droplet-on-demand spherical particle production.
- LLNL cites thorium's abundance, less persistent waste stream, and proliferation resistance as advantages over uranium in fuel applications.
- Ampera — founded in **2025**, based in Palm Beach Gardens, Florida — is pursuing vertical integration of its thorium fuel supply, including an Australian subsidiary for thorium sourcing established in June 2026.
- In July 2026, Ampera 3D-printed a full-scale silicon carbide model of its spherical gyroid core architecture.
- Ampera has not publicly disclosed funding amounts, NRC engagement timelines, or irradiation testing schedules — the gaps that will determine whether THUNDER moves from laboratory to fuel qualification.
- Uranium-based TRISO programs at X-energy and Standard Nuclear are already in the facility construction phase, giving thorium TRISO a significant regulatory and irradiation-database deficit to close.

---

## Frequently Asked Questions

**What is the THUNDER project?**
THUNDER stands for Thorium Unimodal Droplet Ejection for Reactors. It is a joint program between Lawrence Livermore National Laboratory and Ampera to fabricate TRISO fuel particles using thorium-232 kernels rather than conventional uranium. The manufacturing approach uses liquid metal–jetting technology developed at LLNL to produce highly uniform, spherical Th-232 kernels.

**Why use thorium instead of uranium in TRISO fuel?**
LLNL identifies three potential advantages: thorium is more abundant than uranium, produces a less persistent waste stream, and is harder to weaponize due to its proliferation-resistant properties. Th-232 breeds fissile uranium-233 when it absorbs a neutron, generating its own fuel during reactor operation. However, thorium TRISO lacks the irradiation database and regulatory precedent that uranium TRISO has accumulated.

**Who is Ampera and what kind of reactor does it plan to use this fuel in?**
Ampera is a nuclear startup founded in 2025 and headquartered in Palm Beach Gardens, Florida. The company describes its target systems as "compact subcritical nuclear energy systems," suggesting a non-conventional reactor configuration. Ampera has established an Australian subsidiary for thorium supply and produced a 3D-printed silicon carbide model of its spherical gyroid core architecture.

**How does liquid metal–jetting produce TRISO kernels?**
Liquid metal–jetting ejects molten feedstock as controlled droplets that solidify into discrete spherical particles. LLNL's PowderJet prototype, developed in 2023, demonstrated this capability with metallic materials. THUNDER applies the same platform to thorium-232, aiming to produce kernels with the dimensional uniformity required for consistent TRISO coating quality.

**How does thorium TRISO compare to uranium TRISO programs already underway?**
Uranium-based TRISO development is well ahead. X-energy's TRISO-X facilities are under construction with state grant funding, and Standard Nuclear is targeting 2026 milestones for two production facilities. Thorium TRISO has no commercial-scale irradiation data and no established NRC regulatory pathway — making THUNDER fundamentally a materials and manufacturing science program at this stage, not a near-term fuel supply solution.