We have measured the absolute intensity, and the energy spectrum, and the pulse shapes as function of neutron energy for the IPNS liquid CH4 "F" moderator, at 108 K. We have fitted the spectrum, corrected for attenuation by aluminum in the beam, using a new cutoff function and fitted the pulse shapes to a new function which is the sum of two decaying exponentials, convoluted with a gaussian, and determined the wavelength variation of the parameters. We present here the results of a preliminary analysis.

When ISIS was first constructed the target and moderators were optimised to exploit the large epithermal fluxes of neutrons that are inherent to pulsed neutron sources. Since then, experience has shown that pulsed sources can effectively compete with reactors for certain applications even in the thermal and cold neutron regions. The plan to build a second target station at ISIS, that is specifically designed to use these low energy neutrons, has prompted this design study.The second target station will use one pulse in five from an upgraded 300 mA synchrotron giving a total power of 48 kW. This low power makes it possible to use highly efficient target designs such that, for some instruments, there will be substantial gains in flux compared to similar instruments on the existing ISIS target. In this preliminary report we present our current thoughts on the design of the second target station and the results of Monte-Carlo calculations of flux and pulse shape.

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This paper describes the development of a three-dimensional methodology for the assessment of neutron damage and nuclear energy deposition (or nuclear heating) throughout the graphite cores of the UK’s Advanced Gas-cooled Reactors. Advances in the development of the Monte Carlo radiation transport code MCBEND have enabled the efficient production of detailed fully three-dimensional models that utilise three-dimensional source distributions obtained from Core Follow data supplied by the reactor physics code PANTHER. The calculational approach can be simplified to reduce both the requisite number of intensive radiation transport calculations, as well as the quantity of data output. These simplifications have been qualified by comparison with explicit calculations and they have been shown not to introduce significant systematic uncertainties. Simple calculational approaches are described that allow users of the data to address the effects on neutron damage and nuclear energy deposition predictions of the feedback resulting from the mutual dependencies of graphite weight loss and nuclear energy deposition.

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