[en] In order to verify the program system used for the study of Accelerator-Driven Radioactivity Clean Nuclear System (ADRCNS), neutronics calculation is done for the IAEA benchmark problem of Accelerator Driven System (ADS) (Stage 1). The calculation of the spallation neutron source was done using the code LAHET. The transport of the neutrons with energies lower than 20 MeV is simulated using code MCNP. The code ORIGEN2 is used for burnup calculation. The results showed good agreement with those calculated by Russia and Sweden who are the members of Accelerator Driven System Coordinated Program

[en] The 10 MW high temperature gas cooled reactor (HTR-10) was built at Institute of Nuclear Energy Technology, Tsinghua University, and the first criticality was attained in Dec. 2000. The high temperature gas cooled reactor physics simulation code VSOP was used for the prediction of the fuel loading for HTR-10 first criticality. The number of fuel element and graphite element was predicted to provide reference for the first criticality experiment. The prediction calculations toke into account the factors including the double heterogeneity of the fuel element, buckling feedback for the spectrum calculation, the effect of the mixture of the graphite and the fuel element, and the correction of the diffusion coefficients near the upper cavity based on the transport theory. The effects of impurities in the fuel and the graphite element in the core and those in the reflector graphite on the reactivity of the reactor were considered in detail. The first criticality experiment showed that the predicted values and the experiment results were in good agreement with little relative error less than 1%, which means the prediction was successful

[en] The modular high temperature gas cooled reactor (MHTGR) can be used to burn plutonium in a thorium-based fuel cycle to reduce high-level radioactive wastes. The author studies the physics of a thorium-based plutonium-burning modular high temperature gas cooled reactor (PBMHTGR). The initial composition of the plutonium isotopes in the fresh fuel element was the same as that in the spent fuel from the energy-producing modular high temperature gas cooled reactor (EPMHTGR) with ²³³U used as fuel to supply reactivity. The physics of the two reactors was analyzed using the VSOP code. The results show that one PBMHTGR can burn the plutonium produced by more than 6 EPMHTGRs and suggest plutonium can be burned in the MHTGR using a thorium-based fuel cycle

[en] The modular high temperature gas cooled reactor (MHTGR) has good safety characteristics because of the use of coated particles in the fuel element. After the particles cool outside of the reactor for some time, the spent fuel can be re-utilized. The author describes a physics feasibility study for the burning of spent fuel from a 350 MW ring-shaped modular high temperature gas cooled reactor in an accelerator-driven sub-critical reactor. A conceptual design is given for the 30 MW accelerator-driven sub-critical reactor. The neutron transport in the sub-critical reactor was simulated using the MCNP code, and the burnup was calculated using the ORIGEN2 code. The results show that the accelerator-driven sub-critical gas-cooled reactor has reliable sub-criticality and low power density and that the spent fuel from a 350 MW ring-shaped modular high temperature gas cooled reactor can be burned to provide 20% more energy

[en] Accelerator-Driven Sub-critical Fast Reactor (ADSFR) is chosen for transmutation of minor actinides from the spent fuel of PWR(U). In the core, the fuel type is (PuNpAmCm)Ox. Liquid sodium is chosen as coolant the neutronics calculation and analysis of the selected scheme have been done by using the following codes: LAHET, for the simulation of the interaction between the protons and the nuclei of the target; MCNP4A, for the simulation of interaction between neutrons with energy below 20 MeV and the nuclei of materials in the sub-critical blanket; ORIGEN2, for the multi-region burnup calculation of the blanket by using the one-group effective cross-section provided in the output of MCNP4A. The neutronics calculation and analysis show that the proposed scheme is feasible for transmutation of minor actinides, considering the factors such as the criticality safety, power density, burnup, etc

[en] Objective: To explore the feasibility of 256-slice whole-brain CT perfusion (CTP) in evaluate graft reperfusion after surgical revascularization and hemodynamic alterations before and after surgery in Moyamoya disease. Methods: Twenty-five cases with Moyamoya disease were scanned on a 256-slice CT. CTP was performed pre- and post- surgical revascularization. The volumetric CT angiographic (CTA) images were generated from volumetric data acquired at the arterial phase of CTP. CBF, CBV, TTP and MTT were measured in functional maps at the operated side within middle cerebral artery perfusion areas and contralateral mirroring areas. Relative CBF(rCBF), relative CBV (rCBV), relative TTP (rTTP), relative MTT (rMTT) were also obtained. Differences in perfusion CT values pre- and post operation were assessed with the paired t test or matched-pairs signed-ranks test. Data with normal distribution was present as x±s, while those with the non-normal distribution were present as M (P₂₅-P₇₅). Results: All the direct graft patencies were displayed on volumetric CTA, No significant differences were found between volumetric CTA and conventional CTA. Postoperative CBF, rCBF and rCBV values of the operated side [72.86 (55.54- 112.19) ml · 100 g^-1 · min^-1, 1.31 (1.05-1.73), 1.45±0.62] were significantly higher than those before operation [46.72 (28.57-57.67) ml · 100 g^-1 · min^-1, 0.53 (0.33-0.82), 1.01±0.36] (Z= -2.72, -2.98, t=-2.85, P<0.05). Postoperative MTT, TTP and rTTP values of the operated side [(3.98±2.36) s, (17.56±4.38) s, 1.01±0.09] were significantly lower than those before operation [(5.43±2.07) s, (19.40±3.87) s, 1.14±0.28] (t=2.41, 2.17, 2.17, respectively, P<0.05 ). However, no significant differences were detected for changes of CBV and rMTT after revascularization (P>0.05). Conclusion: 256-slice CT has the potential value for the non-invasive assessment of both the graft patency and cerebral hemodynamics changes in Moyamoya disease after surgery with administration of one contrast medium bolus in a single examination. (authors)