MOX in UK: High Costs and Cut Corners

Neal Mann

This report is the first comprehensive history of the development, production, and use of mixed oxide (MOX) plutonium-uranium fuel in the UK. Field interviews were conducted in the UK in 2018 with current and former employees of the government (including British Nuclear Fuels Ltd, and the Nuclear Decommissioning Authority), industry officials, and independent experts. The two commercial fabrication plants – the MOX Demonstration Facility (MDF) and the larger Sellafield MOX Plant (SMP) – are analyzed in detail, covering engineering design, production, economics, security, safety, and environmental impacts. In addition, all UK power reactor types are evaluated for their technical and economic suitability for MOX fuel.  Production in the UK had mixed success. Some innovative processes were demonstrated, including a dry pelletizing process, but quality control data problems and design flaws hampered output, especially for the SMP that achieved only one percent of its intended capacity. Despite producing MOX fuel for foreign customers, the UK never used MOX fuel in its own reactors on a commercial basis. This resulted primarily from the higher cost of MOX fuel but also the prospective expenses of retrofitting reactors and safety licensing. Due to reprocessing its spent nuclear fuel but not utilizing MOX, the UK has accumulated an enormous stockpile of 110 tons of separated civilian plutonium (excluding foreign-flagged plutonium).  The nominal UK policy is eventually to recycle this plutonium in MOX.  However, this would be expensive, requiring a new MOX fabrication plant and subsidies to reactor operators to use MOX fuel rather than economical low-enriched uranium (LEU) fuel.