High temperature pile irradiation of the n‐heptane‐hydrogen system

Abstract

A pilot unit for the high-temperature irradiation of flowing reactants was designed for the beam port of a nuclear reactor. Radiation-thermal cracking of the n-heptane-hydrogen system was studied with molal HJG ratios from 0 to 5 a t 250 Ib./sq. in., 600' to 75OoF., 2 to 8 min. residence time, and up to 3,600 rep./min. Although conversions were law, the decomposition rate was significantly increased by radiation giving G values > 103. Product distributions were not significantly altered by radiation. These results, while different from low-temperature data, appear consistent with other published high-temperature results. Radiation yields were found to be reasonably linear with total dose from 0 to 14 krep., but a twofold increase was observed in passing from a molal HJC, ratio of 0 to 0.5.Although the radiation decomposition of organic compounds has been studied extensively, a majority of these studies have been concerned with room-temperature effects and have utilized cobalt-60 or machine radiation sources (1, 2 ) . The possibility of using a full scale nuclear reactor to produce process steam and simultaneously irradiate chemicaIs has led to experiments with reactor radiation and elevated temperatures ( 3 to 8 ) . Lucchesi e t al. (7) reported a study of the high temperature radio-cracking (radiation decomposition) of several organic systems with G values far larger than those reported for low-temperature irradiations. The present work was designed to extend these studies to the n-heptane-hydrogen system. APPARATUSIrradiations were carried out in the University of Michigan's Ford Nuclear Reactor, a 1-mw. swimming pool type (9, 10, 11). Two beam ports, designated G and J, were utilized. Experiments in J port used a fission plate (an encased uranium slab placed against the end of the port to increase the fast neutron flux).A flow-system pilot unit was designed to handle multistream, liquid-gas, chemical reactions at high temperature and pressure (Figure 1). External equipment such as the feed pumping and product separation section are fairly conventional and are described elsewhere ( 9 ) . The irradiation vessel involved unique problems (Figure 2 ) . The unusual shape is a result of space limitations imposed by the beam port. Reactants enter the lower section and flow under the horizontal baffle plate to the end of the vessel nearest the nuclear reactor core before exiting. A calrod heater was immersed in the lower half of the vessel, and the vessel and inlet lines were wrapped with heating tape and asbestos insulation. Thermocouples were located on George H. Miley is with the University of Illinois, Urbana, Illinois. Vol. 7 , No. 4the vessel shell, on inlet and outlet lines, and at 3-in. intervals in the thermowell. A cooling coil provided an additional means of temperature regulation. Type 304 stainless steel was used throughout. Because induced radioactivity made direct maintenance impossible after initial exposure, special precautions were taken to prevent plugging. A strainer was placed at the vessel outlet,...

Nuclear radiation‐induced cracking of n‐hexadecane

“…Radiation-induced cracking in the vapor phase was emphasized at elevated temperatures, since it was anticipated that the radiation might effectively be utilized by initiating free-radical chain types of reactions. High radiation yields were reported at intermediate (6) and high temperatures (8). Although these high yields have been reported, thermal cracking tended to mask radiation effects at high temperatures, while at intermediate temperatures and short residence times conversions were low.…”