# Is Onkalo Now Actively Drilling Permanent Nuclear Waste Disposal Holes?

Yes. As of last week, Finland's Posiva has drilled its first deposition hole intended for actual spent nuclear fuel disposal at the Onkalo deep geological repository — a milestone that separates the world's only operational deep geological repository from years of preparatory test drilling. The hole measures 8.4 meters deep and 1.75 meters in diameter, bored into bedrock that is 1.9 billion years old, and took approximately 10 hours to complete using a German-made Deposition Hole Boring Machine (DHBM) built by Herrenknecht. The work comes weeks after Finland's Radiation and Nuclear Safety Authority issued a favorable safety assessment for the repository in August 2026.

Onkalo sits near the Olkiluoto nuclear power plant in western Finland and is jointly owned by Finnish nuclear utilities Fortum and Teollisuuden Voima Oyj (TVO). At full operational tempo, Posiva targets approximately two finished deposition holes per week. The repository is designed for a 100-year operational life, with an estimated 100 tunnels totaling 35 kilometers of combined length planned for excavation at a depth of around 450 meters.

This is the first deposition hole with real operational status. Test holes have been drilled at the site since 2022, but this marks the transition from engineering validation to the actual disposal process.

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## What Makes This Hole Different from Previous Test Drilling

Posiva has been drilling test holes at Onkalo since 2022, but those were validation exercises. The hole drilled last week is the first intended to become part of the final disposal process — meaning an iron-copper canister containing spent nuclear fuel will ultimately be emplaced in it.

The distinction matters for repository licensing and operational sequencing. The favorable safety assessment issued by Finland's Radiation and Nuclear Safety Authority (STUK) earlier in August 2026 cleared a critical regulatory gate that allowed this transition from test to operational drilling.

Posiva construction manager Kimmo Lehtola described the moment plainly: "We have already practiced with a couple of holes and preparations for the drilling of the actual deposition holes have been ongoing for quite some time; this day has been much anticipated by our team. It is great to have the opportunity to drill for the first time a hole which will actually become part of the final disposal process."

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## The DHBM: Engineering Tolerances at the Extremes

The Herrenknecht-manufactured DHBM is not a standard piece of mining equipment. The machine is approximately nine meters long, more than three meters wide, and nearly four meters tall, weighing 78 metric tons. It operates alongside a 22-metric-ton energy unit supplying electricity and an 18.5-metric-ton separator that removes loosened rock fragments from the drilling water.

The tolerance specifications are exceptionally tight. According to Posiva, the center point of each deposition hole cannot deviate from the vertical centerline by more than 25 millimeters along the full length of the hole. The DHBM monitors its own position continuously during drilling and corrects deviations using control cylinders.

To verify these standards are being met before committing to a full drilling program, the first three holes drilled will undergo careful post-drilling measurements. Any hole showing geometric deviation or quality deficiencies will be rejected. Only once the process is validated and routine does Posiva intend to reach its target cadence of approximately two finished holes per week.

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## Repository Scale and Operational Timeline

The numbers behind Onkalo's full build-out are substantial. A single 330-meter-long final disposal tunnel — already excavated at a depth of approximately 450 meters — will contain around 30 deposition holes. At full scale, Posiva plans approximately 100 such tunnels, totaling 35 kilometers of combined tunnel length, over the repository's 100-year operational life.

Each deposition hole will receive an iron-copper canister containing spent nuclear fuel. The copper exterior provides corrosion resistance in the groundwater environment; the iron insert provides structural integrity. The multi-barrier concept — copper canister, bentonite clay buffer, and 1.9-billion-year-old crystalline bedrock — is the technical foundation of the safety case that STUK assessed favorably this August.

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## Industry Significance: What Onkalo Proves and What It Doesn't

For the global nuclear industry, Onkalo's operational drilling phase is significant for one reason above all: it demonstrates that a deep geological repository for spent nuclear fuel can actually be built and operated, not just licensed and studied. Every other country with a significant nuclear program — the United States, France, Sweden, Canada, the United Kingdom — is still in licensing, site characterization, or political negotiation phases.

For advanced reactor developers and SMR vendors, this matters indirectly but concretely. One of the persistent credibility challenges for expanding nuclear capacity is the unresolved back-end question: what happens to the fuel? Onkalo's operational status provides a working answer, even if the specific geology, fuel type, and regulatory framework are Finnish and not universally transferable.

The [dry cask storage](https://smrintel.com/glossary/dry-cask-storage) interim solutions used in most other countries remain the dominant paradigm globally, but Onkalo now represents the proof-of-concept for the permanent alternative.

It is worth being precise about what Onkalo does not yet prove. The first iron-copper canister has not been emplaced. Posiva must perfect the drilling process across three validation holes before scaling. The full 100-tunnel, 35-kilometer build-out spans a century. Repository programs have a long history of timeline slippage. The transition from drilling validation to routine two-holes-per-week production will be the next meaningful operational milestone to watch.

For [Westinghouse Electric Company](https://smrintel.com/companies/westinghouse) and other vendors pursuing reactor opportunities in Nordic countries, Finland's demonstrated competence across the full nuclear fuel cycle — from Olkiluoto's operating reactors to Onkalo's repository — reinforces the country's position as a reference market for nuclear development.

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## Key Takeaways

- Posiva drilled its first actual disposal hole at Onkalo on or around August 25, 2026 — 8.4 meters deep, 1.75 meters in diameter, taking approximately 10 hours.
- The Herrenknecht DHBM weighs 78 metric tons and must maintain vertical alignment within 25 millimeters across the full hole length.
- The first three holes will be measured carefully before full-scale drilling begins; target cadence is approximately two finished holes per week.
- A single 330-meter disposal tunnel holds approximately 30 deposition holes; the full repository plan encompasses around 100 tunnels totaling 35 kilometers over 100 years.
- Finland's nuclear safety authority STUK issued a favorable safety assessment for Onkalo in August 2026, enabling the operational drilling transition.
- Posiva is jointly owned by Finnish utilities Fortum and Teollisuuden Voima Oyj.
- Onkalo remains the only facility in the world at this stage of operational spent fuel disposal.

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## Frequently Asked Questions

**What is Onkalo and where is it located?**
Onkalo is a deep geological repository for spent nuclear fuel located near the Olkiluoto nuclear power plant in western Finland. It is owned and operated by Posiva, a company jointly held by Finnish nuclear utilities Fortum and Teollisuuden Voima Oyj. The repository is excavated into bedrock approximately 450 meters underground.

**What was drilled at Onkalo in August 2026?**
Posiva drilled the first deposition hole intended for actual spent fuel disposal — as opposed to prior test holes drilled since 2022. The hole is 8.4 meters deep and 1.75 meters in diameter, bored using a 78-metric-ton Herrenknecht Deposition Hole Boring Machine.

**How precise does the drilling have to be?**
The center point of each deposition hole cannot deviate from the vertical centerline by more than 25 millimeters along the full length of the hole. The DHBM monitors its own position and corrects deviations in real time using control cylinders.

**How many disposal holes and tunnels does Onkalo need?**
A single 330-meter tunnel contains approximately 30 deposition holes. Posiva estimates the full repository will require approximately 100 tunnels with a combined length of around 35 kilometers, built over the repository's 100-year operational life.

**Why does Onkalo matter for the broader nuclear industry?**
Onkalo is the world's only facility actively drilling operational disposal holes for spent nuclear fuel. It demonstrates that permanent geological disposal is technically achievable, addressing one of the most persistent back-end challenges cited by critics of nuclear expansion. Other major nuclear nations remain years or decades behind in their own repository programs.