Safety in the UK nuclear industry is regulated by the Nuclear Installations Inspectorate (NII).
The NII claims to provide independent evaluation of the reactor safety. However, the information upon which they base their evaluations is provided solely by the operators of the reactor, BNFL.
Even possible accident scenarios are provided by the industry. If BNFL doesn't consider an accident to be credible, it doesn't provide information on it to the NII.
This system ensures that information on nuclear safety is effectively dictated by the industry itself, rather than the regulator.
As the reactors age, their materials and components become increasingly worn out and degraded. The extent of this age related deterioration is, however, often impossible to verify, as the reactors were not designed to allow access for inspections. The industry and therefore the NII base their assessments of the state of the reactors on extrapolation from small scale tests rather than from detailed analysis of the components actually affected.
This problem is exacerbated by the endemic secrecy in the nuclear industry. Information on the actual state of the reactors, and the NII's evaluation of them, are classed as 'commercially confidential'. Even if you wanted to know about the exact state of a reactor near you, neither BNFL nor the NII would allow you to find out.
