The United Kingdom released a report "Sellafield MOX Plant - Lessons Learned Review" (PDF) issued in July 2012. The release was made in response to a Freedom of Information Act request filed by Dr David Lowry, an independent environmental policy and research consultant.

According to the review, "the actual performance of the plant was very poor." With the "projected annual throughput of 120te HM ... SMP actually manufactured 13.8te HM of MOX fuel during its operating life."

Also, the review noted that "SMP had very significant gaps both in its design and operating capability. This meant that the plant as built was not fit for purpose and struggled from the start with a wide range of operational problems." In addition, "the SMP culture (as part of the Sellafield site) was not well suited to a precision manufacturing production facility and for much of its operating life there was an unwillingness to face up to the scale of the
problems facing the plant."

The report estimated "aggregate net total loss for the full plant lifecycle of around £2.2BN."