^{Simulation 238 U Integral Experiments And Sample Pre-collimator System Design}

Benchmark experiment is an important means to inspect the reliability andaccuracy of the evaluated nuclear data. Has a very important role in the application ofnuclear technology, the design of nuclear engineering as well as the development ofthe nuclear device. The²³⁸U is a very important nuclide in the application of nucleartechnology. Benchmark experiment for²³⁸U not only be able to obtain the data of the²³⁸U, but also be able to test the sectional data of the²³⁸U in CENDL. The CIAEEstablished an experimental system for the benchmark experiment in the EleventhFive-Year period, also complete the benchmark experiment of the plate-like²³⁸Usample.This simulation is based on the benchmark experiments of the²³⁸U in theEleventh Five-Year period. Use the TARGET code to simulate the data of neutronenergy spectrum and angular distribution; use the NEFF code to simulate theefficiency of detector. Use the MCNP4C to simulate the leakage neutron spectra withthe data of CENDL3.1、ENDF/B-VII、JENDL4.0. Process the data of the experiment,and transform the time-of-flight spectrum into the energy spectrum, conducted apreliminary analysis of the data of the difference.The effect/background ratios are the important parameters to weight the qualityof experimental data. Through this experiment found at the high energy region, thebackground is high to result the effect/background ratio is low. The the background ismainly due to the collimator hole scattering, designed a pre-collimator system toincrease the effect/background ratio of the elastic scattering neutron energy region.The materials used in pre-collimator system were analyzed to select the most suitablematerial to pre-collimator system.Use the MCNP4C to simulate the leakage neutronspectra of the sample²³⁸U and9Be with the pre-collimator system. After a preliminaryanalysis on simulated data find that except the elastic energy region is less than10, at other energy region all can improve the effect/background ratio well. Thereforeconsider this pre-collimator system is quite reliable.