There’s a genuinely exciting story coming out of Oak Ridge right now. Isotek Systems — the contractor operating at Building 3019 and Building 2026 at Oak Ridge National Laboratory — has extracted more than 17 grams of thorium-229 (Th-229) from the uranium-233 (U-233) inventory stored there. That represents a 1,700% increase in the world’s supply of Th-229 — a number that would have been unimaginable just a few years ago, when only 1 gram was available worldwide outside of Oak Ridge.

That Th-229 is going to TerraPower, which uses it to produce actinium-225 (Ac-225), the active ingredient in targeted alpha therapy — a cancer treatment showing remarkable results in clinical trials for leukemia, glioblastoma, and prostate cancer. Material sourced from ORNL has already made it into clinical trials. These are real patients. This is real medicine. The people at Isotek who are doing this work should feel proud of it.

I mean that. This is genuinely good news, and I don’t want to minimize it for a moment.

But I need to explain what is being left out of every press release, every news article, and every celebration surrounding this achievement. Because buried inside this good-news story is one of the most consequential scientific policy errors I have ever witnessed. And once you understand it, the celebration becomes very complicated.

What Thorium-229 Actually Is

Let’s start with the physics, because it’s essential.

U-233 is a mildly radioactive isotope with a half-life of about 160,000 years. As it sits in storage, it slowly decays. One of the products of that decay chain is thorium-229, with a half-life of about 7,340 years. Over time, Th-229 builds up inside any batch of U-233 — reaching an equilibrium concentration that grows predictably with the age of the material. Once you chemically separate the Th-229 from the U-233, the Th-229 starts building toward its own equilibrium with its decay daughters — including radium-225, which decays to Ac-225, the cancer-killing isotope.

Here is the crucial point that every DOE press release carefully omits: you do not have to destroy U-233 to get Th-229 from it.

You extract the Th-229. You put the U-233 back in storage. The U-233 continues to decay. More Th-229 grows back in. In roughly 7,000 years, the Th-229 has grown back to half its previous concentration — but in practical terms, meaningful quantities of new Th-229 are available for harvest in just years or decades, not millennia. The U-233 is a perpetual Th-229 generator. It is a cow that can be milked indefinitely.

What Isotek is doing is milking the cow once — and then slaughtering it.

What 40 Grams Actually Means

Once all Th-229 has been extracted over the next four years — an estimated 40 grams — 100 times more doses of next generation cancer treatments will be available annually than are currently available worldwide.

That number — 100 times more doses — sounds extraordinary. And it is. But think carefully about what it means for the long term.

Today, the world has roughly 1 gram of Th-229 available outside Oak Ridge. After Isotek finishes, the world will have about 40 grams total — held by TerraPower. As Sarah Schaefer, Isotek’s president, has acknowledged publicly: “Most of the world’s supply of U-233 is stored at ORNL, so once this material is dispositioned, no more Th-229 will be available.”

She said it herself. Once the U-233 is gone, no more Th-229. Ever.

The 40 grams will produce Ac-225 for a long time — Th-229’s 7,340-year half-life means it will decay slowly and keep producing daughters for generations. But the quantity of Th-229 is fixed the moment the last canister of U-233 is downblended. It will never increase. It will only decrease, slowly, over millennia.

Now consider: global demand for Ac-225 is exploding. TerraPower has announced it has enough Th-229 to produce Ac-225 at a commercial scale, and global demand is expected to increase as more treatments are developed and approved.

Demand is increasing. Supply is fixed. That is not a sustainable situation. That is a policy failure in slow motion.

The Alternative Nobody Is Talking About

If the U-233 were preserved instead of destroyed, the situation looks completely different.

Preserved U-233 is a perpetual Th-229 factory. You extract the Th-229 — just as Isotek is doing now — but instead of then downblending the U-233 into useless waste, you put it back in storage. Th-229 grows back in. You extract again in a few years. The supply grows over time rather than being fixed at 40 grams forever.

In fact, the supply grows faster than most people realize. Each time you extract Th-229, you’re not just getting the Th-229 that was present — you’re resetting the clock. The freshly extracted U-233 begins immediately producing new Th-229. Multiple extraction cycles from the same inventory compound the total yield enormously over the course of decades.

A preserved U-233 inventory is not a 40-gram one-time harvest. It is a supply infrastructure that grows with global medical demand, for as long as humanity needs it.

DOE knows this. ORNL’s own researchers have published that U-233 is the only viable source for high-purity Th-229. The decision to extract once and then destroy the source is not a scientific decision. It is a bureaucratic one — driven by the institutional momentum of a cleanup program that classified U-233 as waste in 2006 and has never reconsidered that classification.

The Numbers Don’t Add Up

Let’s be specific about what is being sacrificed.

The roughly 250 kilograms of U-233 that remains in the active campaign contains, at any given moment, a certain equilibrium quantity of Th-229. Isotek extracts it. The U-233 is then downblended — diluted with depleted uranium to below 1% enrichment, solidified in cement, and shipped to Nevada for permanent burial.

The downblended material still contains the U-233 atoms. It still has a 160,000-year half-life. It will still produce radiation for hundreds of thousands of years — which is precisely why Nevada objects to receiving it. But downblending destroys exactly one thing: the chemical separability of U-233 from uranium-238. Once mixed to below the enrichment threshold, it can never be separated again. The Th-229 that would have grown back into that U-233 over the next 50, 100, 500 years — years during which targeted alpha therapy may become one of the most important cancer treatments in human history — is gone. Not because the atoms decayed. Not because the physics changed. Because someone decided to mix the U-233 with depleted uranium.

That decision was made in a 2001 memo by an Under Secretary of the Clinton administration who had concluded there was no future in nuclear energy.

What Should Be Done

The answer is simple to state, if not simple to execute.

Stop downblending the U-233. Transfer it to secure storage — the Highly Enriched Uranium Materials Facility (HEUMF) at Y-12, just miles away on non-public roads, or Idaho National Laboratory, which has stored U-233 before. Continue extracting Th-229 on a regular schedule. Allow the supply to grow with demand rather than be frozen at 40 grams. And preserve the option for future generations to use this material as the seed fuel for a thorium molten-salt reactor — the same technology that ORNL proved out in the Molten Salt Reactor Experiment more than 50 years ago, and that China has now deployed in an operational reactor.

President Trump’s May 2025 executive orders directed DOE to halt dilute-and-dispose programs for fissile materials with fuel value, to identify all uranium suitable for reactor use, and to evaluate nuclear materials for isotope value before disposal. Every one of those directives applies directly to U-233. The executive orders are there. The policy authority is there. The technical plan for transfer exists. The receiving sites have been identified.

What is missing is a Secretarial decision to stop.

A Word to the People at Isotek

Sarah Schaefer and the team at Isotek are doing extraordinary work under genuinely difficult conditions. The extraction of 17+ grams of Th-229 is a real achievement. The cancer patients in those clinical trials are real people whose lives may be extended by this material. None of that is in dispute.

But Isotek is also the instrument of a policy that is permanently destroying something irreplaceable. That is not Isotek’s fault. They are executing the contract they were given. The policy failure belongs to the officials who wrote the 2001 memo, the officials who have renewed the cleanup budget year after year without reconsidering it, and the officials who have not yet connected the President’s May 2025 executive orders to the ongoing destruction in Building 2026.

The people of Oak Ridge should be proud of the Th-229 they’ve produced. They should also ask: why are we destroying the source after one harvest, when we could be doing this forever?

That question deserves an answer from Secretary Wright.