The foreign materials which enter plant systems and components predominantly comprise grinding dust, metal chips, cable ties, welding beads and blasting abrasives for surface cleaning, but also include parts of tools, auxiliary materials and other loose parts which are discarded or forgotten during work.

As experience shows, these foreign materials can cause damage or disruption to plant components, such as

• damage to fuel cladding tubes by fretting (friction corrosion),
• disturbance of measurement and control equipment,
• impaired function of valves (e. g. pilot valves), pumps and electrical components,
• reduction of thermal conductivity,
• increased radiation levels as a result of stray materials, and
• unpredictable system disturbances/failures.

This VGB-Standard lists measures which are conducive to maintaining cleanliness in the plant (in mechanical, electrical and chemical regards) during maintenance and modification work.

This VGB-Standard is not intended to be exhaustive. Its purpose is above all to provide guidelines to the persons performing work at site and as a means of creating consciousness and promoting prevention of the ingress of foreign materials into systems and components.

This VGB-Standard applies to all inspection measures, maintenance work, projects/modifications and repairs, especially on opened systems and/or components in nuclear facilities, involving

• decontamination measures,
• sampling,
• radiation protection measures,
• specific quality expectations in processes along the delivery chain, and further measures.

The VGB-Standard can be used as a training document during in-house instruction of employees and contractors’ personnel.