The segregation of alloying elements in steels even as small as undetectable in X-ray miroanalysers seems to affect physical properties for instance, the ridging phenomenon in a 17 Cr stainless steel sheet due to fine winkles of the surface by drawing, the mechanism of which is not yet clear. Study was made of a method for detecting small segregations by autoradiography using51Cr for the 17 Cr stainless steel. In results, (1) in the steel containing a 0.025% carbon or no carbon content, a small variation in photographic density relating to the concentration of chromium was found. (2) In the case of the steel with a 0.05% carbon content, similar one to commercial steel, a clear photographic density variation was observed which was considered to be a cause of the ridging. (3) The autoradiography is suitable to investigation of the small segregation undetected by an X-ray microanalyses.
Since the initial findings that67Ga has a preferential affinity for soft tissue tumors, in humans numerous suggestions have been advanced for the basic mechanism involved. The effects produced by whole-body X-irradiation on the excretion and tissue distribution of67Ga have been reported by Swartzendruber and others. Bradley and coworkers have shown that these irradiation effects were associated with an increase in serum iron. The present investigation was undertaken in order to study the relationships between the change in the serum iron concentration and67Ga accumulation in the tumor and soft tissues in mice bearing Ehrlich's ascites tumor. The following results were obtained. (1) The serum iron concentration was significantly decreased between 3 and 6 hours after 10 Gy (1, 000 rad) dose of whole-body60Co-irradiation. Subsequently, the serum iron levels were slowly elevated. (2) The uptake of67Ga in the tumor and soft tissues was increased if the serum iron concentration was decreased by whole-body60Co-irradiation during the early phase. On the contrary, if the serum iron concentration was high, the uptake of67Ga in the tumor was decreased. (3) The excretion of67Ga from the body was delayed if the serum iron concentration was decreased by whole-body60Co-irradiation. However, if the serum iron concentration was high, the excretion of67Ga from the body significantly increased.
A grain irradiator was deviced for the radiation disinfestation of rice. In this irradiator, dose of rice was varried through regulation of rice velocity in irradiation region. The velocity was regulated by variation of opening area and time of an annular gate valve setted at the bottom of the region. For the irradiator design, experiments of rice flow in the region were conducted by a pilot plant of the irradiator. The main results are as follows: (1) Flow rate of rice from slits of the valve independed on curvature of arrangement of the slits, (2) The flow rate was controlled within 2.7 %, (3) Standard diviation of the velocity of a rice grain in an irradiation region was 1.8%, (4) Distribution of the velocity was uniform within 1% with no inclination of shutter of the valve to the slit, (5) Rice were not damaged by mechanical action of the irradiator.
The dosimetry was performed in order to evalute accuracy of an approximation formula of dose rate in multi-layer of rice separated with thin iron cylinders. Main results are; (1) Energy absorption build-up factor of multi-layer of rice was independent of radius of the multi-layer, radius and thickness of the iron cylinder and an incident angle of gamma-ray to the multi-layer. (2) Approximation formula of the build-up factor of the multi-layer was consisted with Broder's approximation formula of the build-up factor in multi-layer and previously introduced formula of the build-up factor in infinite medium. (3) Derived value of the build-up factor from dosimetry agreed with approximated values within ±3%. Standard deviation of the derive values was 7%. (4) In the irradiation regions of a pilot scale irradiator, approximated values of dose rate agreed with the measured values within ±8.5%. (5) Approximated values of dose of rice passed through the region agreed with the measured values within ±5.7%.