Like mimivirus, mamavirus was isolated from an amoeba in a cooling tower. This compound is used as cooling tower biocide. The neighboring Salem units utilize once-through cooling with no cooling tower. In 1990, construction of a cooling tower for K Reactor began. The cooling tower at Callaway is tall. The plant has a 520-foot natural draft cooling tower. A smokestack was constructed to complement the cooling tower. In 2006, a cooling tower was installed. This unique type of cooling tower causes the unique shape seen in pictures. The cooling tower set point used depends upon the refrigerant being used. Petroleum refineries also have very large cooling tower systems. They also require a cooling tower to conserve water. The heat can also be dissipated via a cooling tower into the atmosphere. This cooling tower serves only Hope Creek's single reactor. However, in some cases, evaporative cooling is used via a cooling tower.