Engineering and economic variables of long duration frozen barriers

Long-term ground freezing designs have been used since the beginning of the 20^th century with supplemental ground freezing provided by single phase and 2-phase passive systems since the early 1950’s. Mechanical refrigeration systems for ground freezing have generally been considered temporary. Long-term freezing was introduced at Oak Ridge National Laboratory in 1997 and has been functioning since. The engineering and economic variables are discussed along with the life expectancy of such installations.