the container surrounding and protecting the core of a nuclear reactor.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use reactor vessel in a sentence
Steel pipes and the reactor vessel grew increasingly radioactive over time, as did traces of sodium in the snow.The US military’s first experiment with portable nuclear reactors was short and tragic | Purbita Saha | July 22, 2021 | Popular-Science
Fukushima hasn't yet melted through the reactor vessel, thanks to engineers pumping seawater into the cooling systems.