Abstract: Two nuclear accidents involving a plutonium sphere just subcritical in size occurred at the Los Alamos Laboratory, LA-1 in 1945 and LA-2 in 1946. Because remote control devices were deemed unreliable at the time, the tamper material (tungsten carbide bricks in LA-1 and beryllium hemispheres in LA-2) was added by hand with the operator standing next to the assembly. In each case the critical size of the assembly was accidentally exceeded and the resultant exponentially increasing chain reaction emitted a burst of neutrons and gamma rays. Ten persons were exposed to the radiation bursts which were largely composed of neutrons. The doses ranged from fatal in the case of the two operators, to small in the case of some survivors. The two operators died within weeks as a result of acute radiation injury. Only six of the eight survivors were available for follow-up study ten or more years after the accident. Four of these six survivors are now dead, but the two living survivors are in excellent health with no clinical or laboratory evidence of late radiation injury. Two of the deceased died of acute myelogenous leukemia, another died at age 83 of refractory anemia, and the fourth of …

Preface: This report contains data and information on the resurvey effort and the effect of residual contamination as a result of nuclear weapons development programs conducted in this area.

This report documents the CY 1975 environmental monitoring program of the Los Alamos Scientific Laboratory (LASL). Data are presented for concentrations of radioactivity measured in air, ground and surface waters, sediments, soils, and foodstuffs, and are compared with relevant U.S. Energy Research and Development Administration guides and/or data from other reporting periods. Levels of external penetrating radiation measured in the LASL environs are given. The average whole-body radiation dose to residents of Los Alamos County resulting from LASL operations is calculated. Chemical qualities of surface and ground waters in the LASL environs have been determined and compared to applicable standards. Results of related environmental studies are summarized.

Notes Based on a set of five lectures given by R. Serber during the first two weeks of April 1943, as an "indoctrination course" in connection with the starting of the Los Alamos project.