Mechanized welding machines and other equipment for component replacements

The authors' experience shows that it is possible to plan the replacement of a piping system in a nuclear power plant with a high degree of accuracy. The planned sequence of work shows good agreement with the actual sequence (dark bars). Deviations from the schedule seen here must be effectively compensated for by a professional site management staff. In the case of the Muhleberg recirculation loop replacement, it was actually possible to complete work 22 days ahead of schedule. Adjustments of this magnitude are not the result of faulty planning: the high fabrication accuracy and reliability made it unnecessary to use the time allotted for making repair welds. The need for and expediency of meticulous planning and preparation are thus confirmed by this field experience. A significant reduction of personnel radiation exposure was achieved by implementing high-efficiency decontamination techniques and shielding measures not previously mentioned in this presentation. Appropriate measures taken as a result of the initially high radiation actually led to a reduction of the manrem dose rates, in spite of increases in personnel numbers and hours worked. Substantial reductions in the personnel residence time in the radiation area can be achieved by the implementation of sophisticated pipe installation and welding systems. A very high level of quality is also attained at the same time. Factors which cannot be quantitatively predicted, such as impermissible edge offset or pipe ovality, can be dealt with