Drywell Moisture Barrier Recoating

Drywell Moisture Barrier DADO Coatings Replacement

Champion was contracted by Detroit Edison (DTE) to remove and replace existing DADO coatings and a moisture barrier seal in the boiling water reactor (BWR) drywell basement of the Enrico Fermi Nuclear Generating Station.

The seal had deteriorated to the point of adherence failure in multiple locations, while the DADO coatings had deteriorated to the point of spot delamination, potentially affecting Torus strainer loading during a safe shutdown event.

By replacing both components, Champion helped bring Fermi into compliance with operating system procedures.

Sequence of Work

Champion crews partnered with client teams throughout pre-outage planning and outage execution to ensure efficiency within the constraints of the environment’s radiological conditions.

Prior to project implementation, “Hot Spot” shielding was installed to protect crews from elevated radioactive doses, and Foreign Material Exclusion (FME) barriers were installed to prevent foreign material intrusion into safety-related components. The entire moisture seal and DADO regions were then decontaminated. Additionally, workers wore double-protective contamination prevention clothing.

The Abrasive Blast Recovery System used to remove the existing DADO coatings was so successful that respirators were not required by the Fermi Radiation Protection Department. In fact, while the original dose estimate was assessed at 26 REMS, the actual dose received was 16.7.

Additionally, though access was limited by drywell coolers, piping and other system components, the moisture barrier seal was replaced successfully in a single outage, a first-time evolution for the nuclear industry.

The project was completed with zero personal external or internal contamination events and successfully adhered to both the budget and the schedule.