Page:Operation Crossroads 1946.pdf/142

 :1. For shielded systems -- 0.01 R/24 hours (gamma)


 * 2. For unshielded systems -- 0.05 R/24 hours (gamma plus beta)


 * 3. For underwater body -- 0.05 R/24 hours (gamma plus beta)

During the development of clearance standards, work had continued at the San Francisco Naval Shipyard on removing radioactivity from condensers and satisfactory methods had been worked out.

Clearance Standards Adopted

On 22 November, BuMed, and BuShips jointly issued a letter giving agreed upon decontamination methods and clearance standards (Reference C.9.187, pp. 30 through 51), which superseded all previous directives (Reference C.9.185, pp. 57 and 58).

The criteria for clearance are:

(1) The existence of any areas of radioactivity with readings in excess of 0.1r (gamma) or 0.5r (beta) combined will be considered as above safety tolerance for external radiation and will be immediately decontaminated or disposed of, and there will be taken such other precautions as are required to insure safety of personnel. Serious radioactive hazard, not involving external radiation, will exist in enclosed salt water systems which give a reading of 0.1r (gamma) through the metal of the system. All areas of contamination within closed saltwater systems with readings between 0.1 and 0.01 gamma on external reading will be decontaminated immediately.

(2) Operational Clearance MAY be granted for urgent reasons when readings are:


 * (a) Maximum, shielded, between 0.1 and 0.001r gamma


 * (b) Maximum, unshielded, between 0.5 and 0.005r beta gamma combined except underwater bodies with surface readings having statistical averages between 0.5 and 0.02 beta gamma combined.

Operational Clearance WILL be granted when readings are:


 * (a) Maximum, shielded, between 0.01 and 0.001r gamma


 * (b) Maximum, unshielded, between 0.05 and 0.005r gamma beta combined except hulls of external surface readings having statistical averages between 0.05 and 0.02 R beta gamma combined.

(3) Final Clearance will be granted when readings are:


 * (a) Maximum, shielded, not above 0.001r gamma


 * (b) Maximum, unshielded, not above 0.005r gamma beta combined.

137