NOTATION c = specific heat of new phase A T I 8'(~) = S/~~~dirnensionless melt (or frost) thickness k L = h/cTs p = p = d2i2/d7 t = time T T w = wall temperature T , = fusion temperature = thermal conductivity of new phase = absolute temperature of new phase U = T / T s U w = T J T s x = distance from plate Greek Letters a = thermal diffusivity, k / p c S ( t ) = distance from plate to phase boundary C F , v'g r)=-, dimensionless thermal boundary layer A ~~ thickness 1 A p 7 = at = x/S, dimensionless distance coordinate = latent heat of fusion = density of material in contact with plate LITERATURE CITED 1. Carslaw, H.A representative paraffin hydrocarbon in the gas oil range, n-hexadecane, has been irradiated in the Industrial Reactor Laboratories' 5 mw. nuclear research reactor. In the vapor phase radiation-induced cracking proceeded efficiently, and G values* for radiation conversion of nhexadecane were 200 to 1.200 a t temperatures near 7 5 0 O F . Total conversions of n-hexadecane were less than 3 wt. % and were due only in part to the radiation effect. The distributions o f products which were obtained were similar to those which result from thermal cracking of nhexadecane. There were however significant increases in the yields of hydrogen, reductions in the yields of very light hydrocarbons and small yields of high molecular weight products. A t temperatures above 8 5 O O F . extensive thermal cracking obscured the effects of radiation.In liquid phase radiation-induced cracking a t 7 5 O O F . conversions of n-hexadecane up to 15 wt. % have been obtained a t liquid spaces velocities near 4 v./hr./v. In many exposures nearly one-half of this conversion was attributed to the direct utilization o f radiation. The corresponding G values were 30 t o 60. The products obtained have been accounted for by adding together the products which would be expected from a radiation-induced reaction producing primarily dimer, from radiation-initiated chain propagated cracking, and thermally initiated chain cracking. The product distribution from these reactions can be changed by variation o f the cracking temperature and/or radiation dose.Nuclear reactors built to produce electric power are now competitive in high fuel-cost areas of the United States. Nuclear reactor technology, under continuing development, may in the near future be applied to the design of reactors which will be used for chemical or petroleum processing. In addition kilocurie sources of CO-60 and Cs-137 are available, and techniques for their application are being developed.Radiation processing will become of commercial interest when nuclear radiation energy can be employed more economically than other energy forms to sustain established processes. In addition radiation processing may be of commercial interest if unique and valuable products can be produ 2ed. Growth in nuclear radiation processing 0 Molecules n hexadecane converted per 100 ev. of energy absorbed.thus depends strongly upon the basic information obtained in research in radiation chemistry an...