Ultra-clean underground counting facility for low-level environmental samples

An underground counting facility with cleanroom conditions has been designed and constructed to improve detection of low-level radioisotopes in the environment. The 3.0m × 4.3m × 2.4m counting chamber is placed 14.3m below ground, has 10.2cm thick walls of pre-WWII naval armour plate, and is further shielded by a minimum of 1.2m of specular hematite. The total overburden of shielding is equivalent to 31.7m of water. Careful selection of building materials and a special air filtering system maintain a cleanroom environment with minimum contamination potential.