No abstract available

No abstract available

No abstract available

[en] This paper briefly reviews some of the recent work at AEE Winfrith to establish the validity of the RELAP-UK code by comparison with blowdown experiments. Five sources of experimental data have been used which include two of the Edwards' simple pipe blowdown experiments, the LOFT semi-scale Benchmark Problem No. 2, and the Italian and Japanese blowdown rig results. Various difficulties in the comparison between theory and measurements are highlighted and the steps proposed to resolve the problems are indicated. (author)

[en] This report gives details of changes in model which have been, or are about to be, implemented in the UK version of RELAP III. The changes embrace features representing steam slip ratio, momentum flux terms including change of area, frictional pressure drop interaction with discharge conditions, options for discharge models, the Smith slip ratio and two-phase multiplier, modifications to dryout and rewetting criteria, bubble rise in a horizontal steam drum, pipework heat and radiation cooling, spray cooling under stagnant conditions, determination of steady state conditions, and inclusion of a slave pin calculation. Most of these features are already programmed, those on which work is continuing being indicated in the test. (author)

No abstract available

[en] Measurements of worths of banks control rods by either the rod drop or the pulsed neutron methods can be seriously affected by the presence of spatial harmonics. In the work described in this paper, the method of modal analysis for determining transient behaviour is described and the results obtained by the method are illustrated in terms of experimental rod drop and pulsed source measurements. The experimental results were obtained in a heterogeneous core at the startup of the Prototype SGHWR at Winfrith and include an asymmetric rod pattern under both hot and cold conditions. It is shown that reasonable accuracy in the predicted flux transients and assessed reactivities can be obtained by computing the fundamental mode and its first seven harmonics in the horizontal plane for these experiments. Some comparisons are also made between the results of the modal method and those obtained from a more conventional finite difference solution has the attraction of providing a deeper insight into the basic characteristics of the transient behaviour, which can be useful in planning the experimental procedure. On the other hand the conventional finite difference method is probably more directly suitable for use in safety studies once the fit to experimental rod worths has been completed. (author)

[en] TUTANK is a two-dimensional neutron kinetics code which treats two neutron energy groups and up to six groups of delayed neutron precursors. A 'theta differencing' method is used to integrate the time dependence of the equations. A position dependent exponential transformation on the time variable is available as an option, which in many circumstances can remove much of the time dependence, and thereby allow longer time steps to be taken. A further manipulation is made to separate the solutions of the neutron fluxes and the precursor concentrations. The spatial equations are based on standard diffusion theory, and their solution is obtained from alternating direction sweeps with a transverse buckling - the so-called ADI-B² method. Other features of the code include an elementary temperature feedback and heat removal treatment, automatic time step adjustment, a flexible method of specifying cross-section and heat transfer coefficient variations during a transient, and a restart facility which requires a minimal data specification. Full details of the code input are given. An example of the solution of a NEACRP benchmark for an LWR control rod withdrawal is given. (author)

No abstract available

No abstract available