Remote replacement of first core vessel insert at SNS

During SNS construction, four of the eighteen instrument beam lines received water-cooled Core Vessel Insert plugs in lieu of functional Core Vessel Inserts. Replacement of these Core Vessel Insert plugs is required prior to instrument operation to enable proper neutronics performance. Access to the Core Vessel Inserts for replacement is difficult due to their installed configuration within the Core Vessel in conjunction with the high radiation environment due to their close proximity to the neutron moderators. Due to the hazardous nature of the operation along with the complexity of the installation, replacement of a Core Vessel Insert is considered one of the most difficult remote handling operations required at the SNS facility. Replacement of the Beam Line 16 Core Vessel Insert was completed during the January 2011 planned maintenance outage utilizing an array of specially-designed, complex tooling. The details of this replacement operation will be discussed along with the specialized tooling developed to facilitate remote handling. Details of activities prior to replacement along with subsequent testing will be discussed. Dose rates and contamination levels encountered during the replacement activities will be outlined along with lessons learned from the operation.