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The D-T neutron induced fission fragments from 238U, i.e., 134Te, 134 mI and 134 gI, were measured by low-background HPGe-γ detector. The fission cross-sections of the 238U(n, f) 134Te, 238U(n, f))134 mI and 238U(n, f)134 gI reactions induced by D-T neutrons, i.e., 14.7 ± 0.3, 14.5 ± 0.3 and 14.1 ± 0.3 MeV, were measured precisely with the neutron activation technique, where the neutron flux was monitored by accompanying α-particle and the neutron energy was determined by the cross-section ratio of 90Zr(n, 2 n)89Zr to 93Nb(n, 2 n)92 mNb reaction. The fission cross-sections of the 238U(n, f)134Te reaction are 54.3 ± 3.5 mb, 52.6 ± 3.4 mb and 50.0 ± 3.2 mb, corresponding to the above energy points. However, the cross-sections of 238U(n, f)134 gI reactions were estimated to be below a value about 8.2 × 10−3 mb, since almost all the 134 gI nuclide, of which characteristic γ-rays were detected in the spectrum, originated from the 134Te decay. Meanwhile, the characteristic γ-rays of 134 mI were not found on any spectrum, and beyond the lower limit of measurement.

The transient analysis software, HTR-GTsim, is developed to simulate transient characteristics of a high temperature gas-cooled reactor helium turbine power system (HTR-10GT) of INET in Tsinghua University, which is the secondary engineering project of HTR-10. The analysis models include point reactor neutron kinetics model, one-dimensional thermodynamic reactor model, rotor dynamic blower model, counter-current heat exchanger model, quasi-static helium turbine and pressure compressor model, and so on. HTR-GTsim is verified by 3 tests of a 10 MW high temperature gas-cooled reactor (HTR-10), which are reactivity insertion test, helium flow change test and water flow change test. The simulation results of reactivity insertion test show that there is a strong self-adjusting ability for HTR-10 reactor power due to negative temperature feedback. The simulation results of helium flow change test are compared with those of the water flow change test. It is found that the disturbance induced in the latter test is significantly weaker than that in the former due to the huge heat capacity of the graphite in the core. The calculation results of HTR-GTsim are compared with the test data and simulation results of THERMIX program. Good agreement is obtained. Because of the limitation of validation, more work need to be done to verify the accuracy of HTR-GTsim to simulate a gas turbine device.

In scientific applications, there often are several competing models that could be fit to the observed data, so quantification of the model uncertainty is of fundamental importance. In this paper, we develop an inferential model (IM) approach for simultaneously valid probabilistic inference over a collection of assertions of interest without requiring any prior input. Our construction guarantees that the approach is optimal in the sense that it is the most efficient among those which are valid. Connections between the IM's simultaneous validity and post-selection inference are also made. We apply the general results to obtain valid uncertainty quantification about the set of predictor variables to be included in a linear regression model., 24 pages, 4 figures, 2 pages of supplementary material

This paper presents investigations on the possible combination of modular high-temperature gas-cooled reactor (MHTGR) technology with the supercritical (SC) steam turbine technology and the prospective deployments of the MHTGR SC power plant. Energy conversion efficiency of steam turbine cycle can be improved by increasing the main steam pressure and temperature. Investigations on SC water reactor (SCWR) reveal that the development of SCWR power plants still needs further research and development. The MHTGR SC plant coupling the existing technologies of current MHTGR module design with operation experiences of SC FPP will achieve high cycle efficiency in addition to its inherent safety. The standard once-reheat SC steam turbine cycle and the once-reheat steam cycle with life-steam have been studied and corresponding parameters were computed. Efficiencies of thermodynamic processes of MHTGR SC plants were analyzed, while comparisons were made between an MHTGR SC plant and a designed advanced passive PWR - AP1000. It was shown that the net plant efficiency of an MHTGR SC plant can reach 45% or above, 30% higher than that of AP1000 (35% net efficiency). Furthermore, an MHTGR SC plant has higher environmental competitiveness without emission of greenhouse gases and other pollutants.