What nuclear waste actually is
The three categories — from contaminated gloves to spent fuel rods
Nuclear waste is not a single substance — it ranges from mildly contaminated paper towels to intensely radioactive spent fuel assemblies. The critical distinction is how long the material remains hazardous and how much heat it generates — these two factors determine the required disposal method.
~370,000 t
Global spent fuel inventory (IAEA 2023)
~100,000 yr
Required isolation period for HLW spent fuel
1
Approved permanent repository — Onkalo Finland
£121 B
UK Sellafield lifetime cleanup cost (NDA)
High-Level Waste (HLW) — the hard problem:
Spent nuclear fuel contains uranium (still ~96% by mass), plutonium (~1%), and highly radioactive fission products (~3%) — including caesium-137 (half-life 30 years), strontium-90 (half-life 29 years), iodine-129 (half-life 15.7 million years), and plutonium-239 (half-life 24,100 years). Freshly removed from a reactor, a spent fuel assembly is lethal at close range within seconds and hot enough to boil water from decay heat alone. It must spend 5–10 years in a spent fuel pool at the reactor site, cooled by circulated water (as Fukushima demonstrated — when pool cooling fails, catastrophe can follow). After cooling, it can be transferred to dry cask storage (sealed welded stainless steel containers, passive air cooling) — the current "interim" solution used worldwide. The challenge: "interim" storage at reactor sites was meant to last decades while permanent repositories were built. Permanent repositories are still not operating (Onkalo being the first). Many reactor sites have fuel stored since the 1970s — 50+ years of "interim." Source: IAEA Nuclear Technology Review 2024 · NEA OECD Uranium 2024.
Spent nuclear fuel contains uranium (still ~96% by mass), plutonium (~1%), and highly radioactive fission products (~3%) — including caesium-137 (half-life 30 years), strontium-90 (half-life 29 years), iodine-129 (half-life 15.7 million years), and plutonium-239 (half-life 24,100 years). Freshly removed from a reactor, a spent fuel assembly is lethal at close range within seconds and hot enough to boil water from decay heat alone. It must spend 5–10 years in a spent fuel pool at the reactor site, cooled by circulated water (as Fukushima demonstrated — when pool cooling fails, catastrophe can follow). After cooling, it can be transferred to dry cask storage (sealed welded stainless steel containers, passive air cooling) — the current "interim" solution used worldwide. The challenge: "interim" storage at reactor sites was meant to last decades while permanent repositories were built. Permanent repositories are still not operating (Onkalo being the first). Many reactor sites have fuel stored since the 1970s — 50+ years of "interim." Source: IAEA Nuclear Technology Review 2024 · NEA OECD Uranium 2024.
ILW and LLW — the bulk of the volume:
Intermediate-Level Waste (ILW) includes reactor components (irradiated steel pressure vessels, control rods, internal hardware), ion exchange resins, sludges from reprocessing — typically requires around 10,000 years of isolation. In volume, ILW is the dominant waste stream from decommissioning. Most countries dispose of ILW in near-surface or intermediate-depth engineered structures. Low-Level Waste (LLW) includes contaminated clothing, tools, wiping materials, and some structural materials — typically requires ~300 years. LLW is disposed of in specially engineered near-surface facilities. UK's Drigg LLW repository (54.39°N 3.47°W, Low Level Waste Repository Ltd, opened 1959, capacity 4.4 million m³) is Europe's largest. USA's Envirocare/Energy Solutions near Salt Lake City (40.72°N 112.34°W). India disposes LLW at near-surface facilities adjacent to reactor and research sites. Source: IAEA Safety Standards · NEA OECD disposal concepts.
Intermediate-Level Waste (ILW) includes reactor components (irradiated steel pressure vessels, control rods, internal hardware), ion exchange resins, sludges from reprocessing — typically requires around 10,000 years of isolation. In volume, ILW is the dominant waste stream from decommissioning. Most countries dispose of ILW in near-surface or intermediate-depth engineered structures. Low-Level Waste (LLW) includes contaminated clothing, tools, wiping materials, and some structural materials — typically requires ~300 years. LLW is disposed of in specially engineered near-surface facilities. UK's Drigg LLW repository (54.39°N 3.47°W, Low Level Waste Repository Ltd, opened 1959, capacity 4.4 million m³) is Europe's largest. USA's Envirocare/Energy Solutions near Salt Lake City (40.72°N 112.34°W). India disposes LLW at near-surface facilities adjacent to reactor and research sites. Source: IAEA Safety Standards · NEA OECD disposal concepts.
Onkalo — the world's first deep geological repository
How Finland solved the nuclear waste problem
Onkalo (61.24°N 21.44°E), Eurajoki, southwest Finland:
Onkalo means "cave" or "hollow" in Finnish. The facility is being built by Posiva Oy (owned by Fortum and TVO — Finland's two nuclear utilities) in the Olkiluoto bedrock, adjacent to the Olkiluoto nuclear power station (61.24°N 21.44°E — Europe's newest nuclear reactor, Olkiluoto-3, is also here). Depth: 400–450 metres into stable 1.9-billion-year-old Olkiluoto granite. Method: KBS-3 (Kärnbränslesäkerhet-3), developed by Sweden's SKB — spent fuel assemblies placed in copper canisters (5 cm thick copper shell over cast iron insert), surrounded by bentonite clay (swells when wet to form a tight seal), and placed in tunnels bored into the rock. The triple barrier: copper canister + bentonite buffer + granite host rock. If any one barrier fails, the others contain the radioactivity. Design life: 100,000 years. Construction: tunnels and shafts being dug now, first fuel emplacement planned for 2025. Capacity: ~6,500 tonnes of heavy metal (Finland's total expected spent fuel from its 5 reactors). Scientific validation: groundwater in the Olkiluoto bedrock is extremely slow-moving (~1 metre per 1,000 years) — meaning even if a canister eventually fails, radionuclides would take millions of years to reach the surface. The IAEA, OECD NEA, and multiple international peer reviews have validated the safety case. Why Finland succeeded when no other country has: (1) Small country — decisions can be made nationally; (2) Local community in Eurajoki voted to accept the facility in exchange for economic benefits (2001 municipal vote); (3) Strong nuclear regulatory culture; (4) Political will maintained across multiple governments over 40 years of site selection. Source: Posiva Oy Construction and Operation Documents · IAEA Onkalo safety review.
Onkalo means "cave" or "hollow" in Finnish. The facility is being built by Posiva Oy (owned by Fortum and TVO — Finland's two nuclear utilities) in the Olkiluoto bedrock, adjacent to the Olkiluoto nuclear power station (61.24°N 21.44°E — Europe's newest nuclear reactor, Olkiluoto-3, is also here). Depth: 400–450 metres into stable 1.9-billion-year-old Olkiluoto granite. Method: KBS-3 (Kärnbränslesäkerhet-3), developed by Sweden's SKB — spent fuel assemblies placed in copper canisters (5 cm thick copper shell over cast iron insert), surrounded by bentonite clay (swells when wet to form a tight seal), and placed in tunnels bored into the rock. The triple barrier: copper canister + bentonite buffer + granite host rock. If any one barrier fails, the others contain the radioactivity. Design life: 100,000 years. Construction: tunnels and shafts being dug now, first fuel emplacement planned for 2025. Capacity: ~6,500 tonnes of heavy metal (Finland's total expected spent fuel from its 5 reactors). Scientific validation: groundwater in the Olkiluoto bedrock is extremely slow-moving (~1 metre per 1,000 years) — meaning even if a canister eventually fails, radionuclides would take millions of years to reach the surface. The IAEA, OECD NEA, and multiple international peer reviews have validated the safety case. Why Finland succeeded when no other country has: (1) Small country — decisions can be made nationally; (2) Local community in Eurajoki voted to accept the facility in exchange for economic benefits (2001 municipal vote); (3) Strong nuclear regulatory culture; (4) Political will maintained across multiple governments over 40 years of site selection. Source: Posiva Oy Construction and Operation Documents · IAEA Onkalo safety review.
Sellafield — the world's largest nuclear cleanup
Sellafield UK (54.42°N 3.47°W) — £121 billion, 70 years of cleanup
What Sellafield is:
Sellafield in Cumbria, northwest England (54.42°N 3.47°W) is the world's most complex nuclear decommissioning project — and arguably the most challenging industrial cleanup in history. The site contains: (1) Britain's early Magnox reactors (Calder Hall, world's first commercial nuclear power station, 1956 — now being decommissioned); (2) THORP (Thermal Oxide Reprocessing Plant, reprocessed spent fuel from UK and Japan until 2018); (3) B30 Pond — an outdoor pond containing spent fuel and radioactive sludge from the 1950s, described as "the most hazardous building in Western Europe"; (4) Highly Active Liquor evaporators containing concentrated liquid HLW — if they fail, a release could make large areas uninhabitable; (5) Decades of intermediate and low-level waste. The NDA (Nuclear Decommissioning Authority) estimates the lifetime cost of cleaning up Sellafield at approximately £121 billion over 70 years. Work has been ongoing since 1981 and will continue until approximately 2120. Source: NDA Annual Report 2024 · NAO (National Audit Office) Sellafield review 2024.
Sellafield in Cumbria, northwest England (54.42°N 3.47°W) is the world's most complex nuclear decommissioning project — and arguably the most challenging industrial cleanup in history. The site contains: (1) Britain's early Magnox reactors (Calder Hall, world's first commercial nuclear power station, 1956 — now being decommissioned); (2) THORP (Thermal Oxide Reprocessing Plant, reprocessed spent fuel from UK and Japan until 2018); (3) B30 Pond — an outdoor pond containing spent fuel and radioactive sludge from the 1950s, described as "the most hazardous building in Western Europe"; (4) Highly Active Liquor evaporators containing concentrated liquid HLW — if they fail, a release could make large areas uninhabitable; (5) Decades of intermediate and low-level waste. The NDA (Nuclear Decommissioning Authority) estimates the lifetime cost of cleaning up Sellafield at approximately £121 billion over 70 years. Work has been ongoing since 1981 and will continue until approximately 2120. Source: NDA Annual Report 2024 · NAO (National Audit Office) Sellafield review 2024.
Why it costs so much and takes so long:
Sellafield's complexity has three root causes: (1) Legacy of the nuclear weapons era: Early decisions (1940s–1970s) prioritised plutonium production speed over waste management. Waste was stored in whatever was available — many legacy ponds and silos were never designed for the waste they received. (2) Reprocessing legacy: Reprocessing separates plutonium from spent fuel — generating large volumes of liquid High-Level Waste (HLW) that must be vitrified (mixed with molten glass and solidified) before being stored. The Sellafield vitrification plant (WVP) has processed liquid HLW into glass blocks that are now stored in purpose-built vaults. (3) Technical difficulty: Some buildings contain radioactive sludge and plutonium contamination from 70 years of operations — remotely operated equipment must handle material that would be lethal to any human in proximity. New technologies (remotely operated arms, improved sensors) are being developed specifically for Sellafield cleanup. Source: NDA AR 2024 · Sellafield Ltd operational reports.
Sellafield's complexity has three root causes: (1) Legacy of the nuclear weapons era: Early decisions (1940s–1970s) prioritised plutonium production speed over waste management. Waste was stored in whatever was available — many legacy ponds and silos were never designed for the waste they received. (2) Reprocessing legacy: Reprocessing separates plutonium from spent fuel — generating large volumes of liquid High-Level Waste (HLW) that must be vitrified (mixed with molten glass and solidified) before being stored. The Sellafield vitrification plant (WVP) has processed liquid HLW into glass blocks that are now stored in purpose-built vaults. (3) Technical difficulty: Some buildings contain radioactive sludge and plutonium contamination from 70 years of operations — remotely operated equipment must handle material that would be lethal to any human in proximity. New technologies (remotely operated arms, improved sensors) are being developed specifically for Sellafield cleanup. Source: NDA AR 2024 · Sellafield Ltd operational reports.
Questions
Questions about nuclear waste
Is nuclear waste a bigger problem than other industrial waste streams?
Nuclear waste is frequently cited as nuclear power's insurmountable problem — but the comparison to other energy waste streams is almost never made in public discourse. The scale argument for nuclear: The entire global nuclear industry over 60 years of operation has produced approximately 370,000 tonnes of spent nuclear fuel — all of which would fit within a single large warehouse (approximately 9 metres deep to 9 metres high, 90 metres × 90 metres footprint). By volume, nuclear waste is extraordinarily compact compared to its energy output: a single nuclear fuel pellet (1 cm diameter, 1 cm tall) produces as much energy as 800 kg of coal, 480 m³ of natural gas, or 564 litres of oil. The "waste" from coal, gas, and oil — CO₂ — is 50 million times larger by mass than nuclear waste from equivalent energy production, and is distributed into the atmosphere where it causes long-term climate damage with no engineered containment. The counter-argument: CO₂ distributes globally and dilutes — it does not concentrate in one location with lethal properties. Nuclear waste is extremely hazardous in concentrated form for tens of thousands of years — requiring engineered systems to remain functional longer than any human civilisation has ever lasted. Whether future generations will maintain Onkalo's containment markers and institutional knowledge for 100,000 years is genuinely uncertain. The IAEA is developing communication strategies for future civilisations who may have no memory of our nuclear era. Balance: Nuclear waste is a real and serious problem that has been solved technically (Onkalo demonstrates this) but not yet at sufficient scale globally. It is not, however, larger in mass or environmental impact than the waste streams from coal combustion — it is simply more concentrated and long-lasting. Source: IAEA Nuclear Power and Sustainable Development · OECD NEA nuclear waste comparison studies.
Why don't more countries have a Sellafield or Onkalo — why has nuclear waste been so neglected?
Most nuclear countries have failed to build permanent repositories for three decades, despite knowing the need since the 1960s. The reasons are structural: (1) NIMBY (Not In My Back Yard): No community willingly hosts nuclear waste. Every site selection process faces intense local opposition. In democratic countries, local opposition (backed by national NGOs and politicians) has blocked or indefinitely delayed repository programmes in Sweden (Forsmark site finally approved 2022), Germany (Gorleben abandoned 2020 after 40 years of controversy), USA (Yucca Mountain programme suspended 2010 after Nevada's intense opposition despite billions in investment), Japan (Rokkasho reprocessing alone repeatedly delayed). (2) Political timescales: Politicians elected on 4–5 year cycles face short-term opposition to repository siting with benefits (safe disposal, energy security) that materialise over decades. The rational political calculation is often delay. (3) Technical confidence gap: Until Onkalo proved geological disposal works in practice, opponents could always raise genuine technical uncertainties. Finland succeeded partly because its geological conditions (stable granite, very slow groundwater) were exceptionally good and its safety case was completed to IAEA satisfaction. (4) "Future generations" argument: Some waste management experts and nuclear critics argue we should not seal waste permanently, but keep it retrievable in case future technologies can treat it more effectively. This argument — while philosophically interesting — has been used to delay permanent disposal indefinitely. The consensus of international nuclear safety experts (IAEA, OECD NEA) is that permanent geological disposal is the safest option and delay increases risk. Source: IAEA Joint Convention Safety Review · OECD NEA progress on geological repositories · Posiva Oy Onkalo safety case.
Provenance
Attribution and citation
- Sources
- IAEA Nuclear Technology Review 2024 · Posiva Oy Onkalo Safety Case · NDA UK Annual Report 2024 · OECD NEA Uranium 2024 · IAEA Joint Convention on the Safety of Spent Fuel Management
- Cite as
- "Nuclear Waste and Decommissioning — The Energy Codex", The Energy Codex, https://thecodex.expert/energy/nuclear/waste/, last updated .