Staple-bound NASA Technical Memorandum (TM X-52820), entitled "Evaluation of Critical Mass for Open-Cycle, Gas-Core Rocket Reactors," 8 x 10.5, 14 pages, presented at the annual meeting of the American Nuclear Society at Los Angeles, June 28-July 2, 1970. The abstract reads: "A nuclear analysis using transport theory was made of an open-cycle gas-core reactor for assumed operating conditions. Calculations were made for cavity diameters from 8 to 16 feet, for hydrogen (cavity) bypass variation from 0 to 99 percent, for reflector thickness from 2 to 3.5 feet, and for both isotopes 235U and 233U as fuel. For these configurations the results indicated that 233U and some bypass hydrogen may be necessary to keep critical mass levels low enough to give system pressures of less than 1000 atmospheres." In fine condition, with several stamps and annotations to the front cover.
