Ultrasonic NDE in a reactor core
We have irradiated bulk single crystal piezoelectric AlN operating as an ultrasonic transducer up to a fast and thermal neutron fluence of 1.85×1018 n/cm2 and 5.8×1018 n/cm2 respectively along with a gamma dose of 26.8 MGy. Our primary interest was in the radiation effects on the piezoelectric performance of the AlN crystal. Ideally standard procedures for extracting material properties from the impedance spectra would have been applied. However, this procedure was anticipated to be very error prone due the effects of radiation on passive components, such as electrodes and cabling. As a result the transducer was coupled to an aluminum cylinder and operated in pulse echo mode throughout the irradiation. In addition to the pulse echo testing impedance data were obtained. Although, material parameters such as d33 could not be measured in-situ during irradiation with our procedure, our work is the only publication, to the author's knowledge, showing the operation of an ultrasonic transducer in a reactor core. Further, the piezoelectric coefficient was measured prior to irradiation and found to be 5.5 pC/N which is unchanged from as-grown samples, and in fact higher than the measured d33 for many as-grown samples. Further proof of the viability of utilizing ultrasonic transducers in a reactor core is provided by means of successful time of flight (TOF) measurements throughout the irradiation. The TOF data was used to measure the gamma heating of an aluminum cylinder. The heating due to short lived isotopes in the Al was also detected via TOF.
Neutron irradiation effects on isotope tailored aluminum nitride ceramics by a fast reactor up to 2 × l026 n/m2
Abstract Physical property changes of AlN ceramics prepared with 14N and 15N by fast neutron irradiation were investigated. Sintered specimens were concurrently fast-neutron irradiated in JOYO fast reactor up to a fluence of 1.94 × l026 n/m2 at 530 °C. After irradiation and post-irradiation annealing up to 1500 °C, changes in macroscopic length, thermal diffusivity and microstructure were observed to examine the isotope effects. Swelling of Al15N was slightly larger than that of Al14N. Degree of recovery in length of Al15N after annealing was less than that of Al14N. Degradation of thermal diffusivity in both specimens was almost the same, but recovery in Al15N was more restricted. He release profiles up to 1500 °C was qualitatively similar, although the evolution amount was larger in Al14N. No clear isotope effect on microstructure change was observed. One of the possible reasons for the difference in property change due to the irradiation and recovery behaviour in Al14N and Al15N ceramics is the difference in diffusion rate of 14N and 15N, but further confirmation should be necessary.
Complex thoracic vascular injury repair using deep hypothermia and circulatory arrest.
A 61-year-old man with a penetrating injury to the innominate artery, left common carotid artery, and left subclavian artery at their origins from the aortic arch with associated injuries to both innominate veins and an innominate artery to vein fistula after a single stab wound is described. The patient was managed successfully using cardiopulmonary bypass together with deep hypothermia and circulatory arrest. Presentation and management are discussed.