The radioactive lanthanum (RaLa) process was designed to extract Ba-140 (half-life of 12.9 days), which decays to La-140 (40.2 hours), from irradiated reactor fuel. The latter isotope, an intense source of high-energy gamma rays, was used to evaluate the implosion process of a nuclear weapon. The short half-life of Ba-140 required the design of a process in which fuel elements irradiated in a nuclear reactor were dissolved shortly after irradiation.

The RaLa process at the Idaho Chemical Processing Plant used fuel elements irradiated in the Material Testing Reactor (MTR) located on-site at INEL. A total of 36 RaLa runs took place at the ICPP between February 1957 and December 1959. Additional releases of radionuclides occurred as a result of a nuclear criticality accident on October 16, 1959.

Essentially all releases from the ICPP during the years 1957-1959 were due to RaLa process operations. Radionuclide emissions through the ICPP stack were monitored continuously during 1957-1959 by sampling of air that went out the stack. Information obtained from stack monitoring datasheets provided the basis for estimated releases of iodine and other radionuclides. Additional sources of information include official RaLa project reports, progress reports, operational logs, calculation sheets, and contemporary project letters.

Estimated releases of isotopes of iodine, bromine, krypton, and xenon are described in the following report:

Gaseous Releases from ICPP

Atmospheric releases of 115 radionuclides attached to aerosols have been treated separately as described in the following report:

Aerosol Releases from ICPP

Principal authors:
Robert P. Wichner, SENES Oak Ridge, Inc.
John-Paul Renier, SENES Oak Ridge, Inc.
A. Iulian Apostoaei, SENES Oak Ridge, Inc.
Lynn Anspaugh, SENES Oak Ridge, Inc.