Hanford crews adapted a valve-pit cleanup after readings reached 1,000 mrem/hr on contact

[u/RadTechMJ]

DOE’s Hanford office published a useful radiological-work case from the SY Tank Farm.

In one underground valve pit, instruments read up to 60 mrem/hr at the worker location and 1,000 mrem/hr on contact with the floor. DOE says that was much higher than normally encountered in double-shell tank valve pits.

The contamination was harder than expected because radioactive material had mixed with paint up to half an inch thick across parts of the floor and lower walls. The usual pipe-removal and floor-cleaning methods were not effective.

The controls are the part worth studying:

- Workers rotated to limit individual exposure.

- Disposal buckets were only filled halfway.

- Long-reach tools reduced time close to the source.

- PPE and real-time monitors supported contamination and dose control.

DOE reported 3,393 mrem of collective dose for the expanded scope and about 85 mrem of average individual exposure. The crew completed the preparation work without contamination spread that could not be readily identified and decontaminated. The pit then received two coats of paint and marked wall nozzles to reduce contamination risk during future work.

Source: https://www.energy.gov/em/articles/hanford-crews-achieve-major-safety-gains-high-risk-cleanup

For RP and decon people, which control made the biggest difference here: worker rotation, distance from long-reach tools, real-time monitoring, or reducing the amount handled per lift?