The CEGB evidence to the Sizewell В Public Enquiry included an assessment of safety aspects of the trans­port of irradiated PWR fuel [31]. The following notes are based on that assessment.

Consideration of the reactor refuelling pattern and of the capacity of the transport flasks, shows that the frequency of fuel movements from a PWR power station would be small, e. g., six to ten per year, compared say to the 50 or so journeys per year from a magnox station. There is considerable on-site fuel storage capacity, which gives operational flexibility, and it is a requirement that fuel for reprocessing should have a decay period of at least five years.

In view of the above, and of the design flexibility in the arrangements for flask handling at a PWR plant, the choice of flask design would not need to be made at an early stage.

There is a considerable amount of experience of transporting PWR and BWR fuel in the UK, mainly by BNFL and associated companies. There are many different flask designs, including ‘dry’ flasks in which inert gas rather than water is used as a heat transfer medium. PWR flasks are cylindrical rather than cu­boid in shape, the lid and base sections being pro­tected by shock absorbers. Like their magnox and AGR counterparts, they are massive and relatively simple structures with valves for venting and filling. The lids are secured by numerous large diameter high tensile bolts, and sealed by elastomeric О-rings. Flasks are subject to a regular programme of maintenance.

Current practice for flask loading and pre-despatch procedures is similar in principle to those for magnox and AGR fuel transport. However, in the case of some wet flasks the PWR fuel is transported in a multi­element bottle (MEB) rather than as individual elements. In the case of dry flasks, the flask is filled with water before fuel loading and after fuel load­ing the water is removed from the flask by vacuum pumping.

From present experience it can be said that fuel transport from a PWR power station would fully meet the requirements of the IAEA Regulations, in par­ticular those in respect of nuclear criticality, heat dispersion, containment and radiation shielding.

In respect of the last mentioned, estimates have been made of the annual radiation doses to transport workers and to members of the public as a result of routine fuel transport from a PWR power station. It is estimated that a dose to an individual member of the public living close to a rail marshalling yard would be about 0.75 Sv/year (0.075 mrem/year). For transport workers the maximum individual dose would be about 20 Sv/year (2.1 mrem/year). These dose rates are negligible compared, for example, to the average natural background radiation level in the UK of 1870 Sv/year (187 mrem/year). The corre­sponding collective radiation doses to members of the public living close to marshalling yards, and to marshalling yard workers are estimated as about 1.4 x 104 man-Sv/year (0.0144 mrem/year) and 1.2 x 10~6 man Sv/year (1.2 x 10 ~4 mrem/year) respec­tively. In addition, the collective dose to members of the public living close to the transport route would be about 1.1 x 10 4 man Sv/year (0.0105 mrem/ year).