The design and thermo-structural analysis of target assembly for high intensity neutron source

The engineering design of an integrated target assembly of IFMIF lithium target was performed in IFMIF/EVEDA project for a high intensity neutron source. In the evaluation of the design, a thermos-structural analysis of was evaluated by ABAQUS code, and the modeling region was a part of the target assembly which was from the inlet nozzle to the outlet pipe. The material of the target assembly including the back plate was F82H steel. In the thermal-structural analysis, the normal operations and start/stop or abnormal operations were evaluated at 250 or 300 °C operation of Li flow in inlet pipe. The result showed that the temperature of the target assembly was evaluated to be still lower than the Li boiling point of 344 °C under a vacuum pressure of 10−3 Pa. In a temperature constant operation, the calculated stresses and displacements were small enough for thermal soundness of the target assembly in steady states. In a transient cooling process from 300 °C to 20 °C through 250 °C, the maximum Mises stress was found to be 372 MPa, which was lower than the yield stress at 300 °C. Keywords: High intensity neutron source, Target assembly, Thermo-structural analysis, Li target, IFMIF, F82

Analysis of radioactivity releases in the MEGAPIE reference accident

A computer model for the MEGAwatt Pilot Target Experiment (MEGAPIE) was developed, verified and applied to the analysis of the reference accident, resulting from the hypothetical loss of a Pb–Bi inventory and subsequent cooling down of the target with free convection of the atmospheric air. The radioactivity releases caused by evaporation of activation products from the lead–bismuth films on the surfaces of the target inner structures are estimated. The maximum radioactivity releases were found to be from evaporation of the mercury and polonium estimated as 7.0e11 and 6.2e8 Bq, respectively. Thermal conductivity and radiation heat transfer through the gas gaps were found to be more important mechanism of the target cooling down than the atmospheric air convection. The final conclusion made on the basis of the work is that MEGAPIE in the reference accident meets the 1 mSv criterion

Reproducibility assessment of rapid strains in cardiac MRI: Insights and recommendations for clinical application

PURPOSE: Studies have shown the incremental value of strain imaging in various cardiac diseases. However, reproducibility and generalizability has remained an issue of concern. To overcome this, simplified algorithms such as rapid atrioventricular strains have been proposed. This multicenter study aimed to assess the reproducibility of rapid strains in a real-world setting and identify potential predictors for higher interobserver variation. METHODS: A total of 4 sites retrospectively identified 80 patients and 80 healthy controls who had undergone cardiac magnetic resonance imaging (CMR) at their respective centers using locally available scanners with respective field strengths and imaging protocols. Strain and volumetric parameters were measured at each site and then independently re-evaluated by a blinded core lab. Intraclass correlation coefficients (ICC) and Bland-Altman plots were used to assess inter-observer agreement. In addition, backward multiple linear regression analysis was performed to identify predictors for higher inter-observer variation. RESULTS: There was excellent agreement between sites in feature-tracking and rapid strain values (ICC = 0.96). Bland-Altman plots showed no significant bias. Bi-atrial feature-tracking and rapid strains showed equally excellent agreement (ICC = 0.96) but broader limits of agreement (=18.0 % vs. =3.5 %). Regression analysis showed that higher field strength and lower temporal resolution (>30 ms) independently predicted reduced interobserver agreement for bi-atrial strain parameters (ß = 0.38, p = 0.02 for field strength and ß = 0.34, p = 0.02 for temporal resolution). CONCLUSION: Simplified rapid left ventricular and bi-atrial strain parameters can be reliably applied in a real-world multicenter setting. Due to the results of the regression analysis, a minimum temporal resolution of 30 ms is recommended when assessing atrial deformation