This section summarises the changes in the 2025 Inventory compared with the previous 2022 Inventory.
Information about radioactive wastes may change from one inventory to the next due to a range of technical, commercial or policy reasons:
- Understanding of the waste streams has improved. Some radioactive waste streams generated many years ago lack detailed contemporary records. As these waste streams (often referred to as legacy wastes) are characterised a better understanding of amounts and compositions are gained.
- The waste stream category has changed. Opportunities may arise to optimise the waste lifecycle where waste streams are close to the boundary between categories. For example, decay storage or decontamination of ILW to LLW or of LLW to VLLW.
- The strategy for managing wastes has been updated. This may be due to more sustainable and cost-effective techniques being used such as new treatment, packaging and disposal options.
- Operational activities have affected the volume of waste. Volumes of waste recorded may change as waste continues to be generated, treated, conditioned and packaged.
- Forecasts of future volumes have been updated. Waste arisings are projected over many decades. Because of this, there will be inevitable changes in future estimates and updated assumptions underpinning the forecasts and plant operating lifetimes.
Key facts
A number of waste streams show changes in volume as inventories have been updated.
Package numbers in stock have increased as progress continues in conditioning HLW and ILW for long-term management.
Reported volumes
Stocks
Table 1 gives the changes in the reported volumes of waste stocks compared with the 2022 Inventory.
| Waste category | Reported volume (m3) Change 2022 Inventory | Reported volume (m3) Change 2025 Inventory | Change (m3) | (%) |
| HLW | 1,990 | 1,960 | -29.1 | -1.5 |
| ILW | 102,000 | 100,000 | -1,490 | -1.5 |
| LLW | 32,100 | 69,900 | +37,800 | +118 |
| VLLW | 1,490 | 1,610 | +120 | +8.0 |
| TOTAL | 137,000 | 174,000 | +36,400 | +26.5 |
The principal reasons for changes are:
For HLW, decreases in liquid waste from fuel reprocessing and a reassessment of the volume of conditioned waste from vitrification.
For ILW, a decrease due to the reassessment of the volume of aluminium ferric floc from effluent treatment at Sellafield.
For LLW, an increase at Springfields as disposal of waste in the year of generation has not been assumed as for previous Inventories.
For VLLW, the increase is from building decommissioning and land remediation at Harwell.
Total
Table 2 gives the changes in total projected reported volumes compared with the 2022 Inventory.
| Waste category | Reported volume (m3) Change 2022 Inventory | Reported volume (m3) Change 2025 Inventory | Change (m3) | (%) |
| HLW | 1,670 | 1,150 | -528 | -31.5 |
| ILW | 249,000 | 315,000 | +65,800 | +26.4 |
| LLW | 1,580,000 | 1,470,000 | -114,000 | -7.2 |
| VLLW | 2,750,000 | 2,690,000 | -62,800 | -2.3 |
| TOTAL | 4,580,000 | 4,470,000 | -111,000 | -24 |
The principal reasons for changes are:
For HLW, revised estimates of arisings from reprocessing operations and transfers to the Waste Vitrification Plant for final vitrification.
For ILW, increase due to the inclusion of future arisings of floc storage tank decommissioning wastes at Sellafield for the first time and revision of future arisings for wastes generated (PCM drums) from routine plant operations and current decommissioning projects at Sellafield.
For LLW, a decrease due to a revised forecast for waste generated from authorised site aerial discharges at Sellafield.
For VLLW, a decrease due to the reassignment of waste from VLLW to LLW for excavated spoil from construction at Sellafield and reduced future arisings of contaminated land wastes from Capenhurst.
Packaged volumes and package numbers
Most wastes in stock at 1st April 2025 are in an untreated or partly treated state. However, increasing amounts of legacy wastes are being retrieved from stores and packaged for long-term management. Progress in the packaging of wastes is indicated by the accumulation in the number of waste packages over time, illustrated in Table 3.
| Date | HLW | ILW | LLW (2) | Total |
| At 1.4.2001 | 2,281 | 21,654 | 23 | 23,958 |
| At 1.4.2004 | 3,037 | 31,557 | 123 | 34,717 |
| At 1.4.2007 | 4,319 | 40,797 | 8,527 | 53,643 |
| At 1.4.2010 | 5,108 | 47,662 | 1,288 | 54,058 |
| At 1.4.2013 | 5,626 | 55,326 | 2,549 | 63,501 |
| At 1.4.2016 | 5,781 | 60,407 | 648 | 66,836 |
| At 1.4.2019 | 6,101 | 67,307 | 1,324 | 75,694 |
| At 1.4.2022 | 6,191 | 69,894 | 1,260 | 77,345 |
| At 1.4.2025(3) | 6,114 | 71,958 | 56 | 78,128 |
(1) The table gives the numbers of packages accumulated at various Inventory reference dates. As VLLW can be disposed to appropriately permitted landfill sites, no package numbers are collated for this waste category in the inventory.
(2) LLW package numbers exclude those in short-term storage before consignment for disposal. Packages at 1.4.2007, 1.4.2010, and 1.4.2013 include those held in vaults at the LLWR and which were not classed as disposed under existing environmental permits. Most of the packages reported at 1.4.2007 were subsequently classed as disposed.
(3) At 1.4.2025 HLW packages were at Sellafield, ILW packages were at Sellafield, Dounreay, Harwell, Berkeley, Bradwell, Chapelcross, Dungeness A, Oldbury, Trawsfynydd, Wylfa, Sizewell B, and Hunterston A, and LLW packages were mostly at Dounreay.
Table 4 gives the changes in total projected packaged volumes compared with the 2022 Inventory.
| Waste category | Reported volume (m3) Change 2022 Inventory | Reported volume (m3) Change 2025 Inventory | Change (m3) | (%) |
| HLW | 1,470 | 1,340 | -134 | -9.1 |
| ILW | 496,000 | 618,000 | +122,000 | +25.0 |
| LLW | 1,340,000 | 1,280,000 | -67,200 | -5.0 |
| VLLW | 2,610,000 | 2,550,000 | -66,000 | -2.5 |
| TOTAL | 4,450,000 | 4,440,000 | -10,800 | -0.2 |
The principal reasons for changes are:
For HLW, there has been a decrease in the volume of liquid waste (2D02 High Level Liquid Waste) because it has been transferred to Waste Vitrification Plants for vitrification.
For ILW, an increase at Sellafield is due to updated packaging data for a number of waste streams.
For LLW, a decrease due to the reassessment of waste generated as a result of authorised site aerial discharges at Sellafield.
For VLLW, a decrease due to reassignment of the waste category for excavated spoil from construction from VLLW to LLW and contaminated land wastes at Capenhurst no longer included in the UK Inventory.
Table 5 gives the changes in the total projected numbers of packages compared with the 2022 Inventory.
| Waste category | Number of packages 2022 Inventory | Number of packages 2025 Inventory | Change (number) | (%) |
| HLW | 7,520 | 6,830 | -685 | -9.1 |
| ILW | 282,000 | 341,000 | +58,900 | +21.0 |
| LLW | 19,900 | 80,800 | +60,800 | +305 |
| VLLW (1) | – | – | – | – |
| TOTAL | 310,000 | 429,000 | +119,000 | +38.0 |
(1) As VLLW can be disposed to appropriately permitted landfill sites, no package numbers are collated for this waste category in the inventory.
For LLW, the increase in package numbers as opposed to the decrease in packaged volume is due to the inclusion of additional LLW package types. For example, 1 tonne flexible intermediate bulk container bags for demolition wastes at Dounreay (~ 45,800 packages) are included within the total.
Radioactivities
Table 6 gives the changes in total radioactivities at 1st April 2025 compared with the 2022 Inventory.
| Waste category | Total radioactivity at 2200 (TBq) 2022 Inventory | Total radioactivity at 2200 (TBq) 2025 Inventory | Change (TBq) | (%) |
| HLW | 1,900,000 | 1,100,000 | -840,000 | -44.3 |
| ILW | 430,000 | 470,000 | +39,000 | +9.0 |
| LLW | 81 | 110 | +28 | +34.2 |
| VLLW | 14 | 13 | -1.1 | -8.2 |
| TOTAL | 2,300,000 | 1,500,000 | -800,000 | -34.5 |
The principal reasons for changes are:
For HLW, the decrease in radioactivity due to revised estimates of arisings from reprocessing operations and a reassessment of specific activities.
For ILW and LLW, the change in radioactivities is largely the result of a reassessment of specific activities.
Why does data change?
Information about waste and material streams may have changed since the last Inventory.
These changes can be due to a range of technical, commercial or policy reasons.
Data in the Inventory may change because:
- Understanding of the waste streams has increased. Some radioactive wastes generated a long time ago lack detailed records, but as these waste streams are characterised, a better understanding is gained. Find out more about how we characterise waste.
- The national strategy for managing radioactive waste materials has been updated. This may be due to more sustainable or cost-effective waste management techniques becoming available, such as new packaging, treatment or disposal options. These can affect the assumptions used when forecasting future waste arisings.
- Operational activities have affected the amount of waste in stock. The quantities of waste or materials recorded may change as waste continues to be generated, treated, conditioned and packaged.
- Baseline scenario assumptions for forecasts have been updated. Given the long period over which arisings are forecast, there are inevitably changes to future estimates, and assumptions about future forecasts and plant operating lifetimes are updated.