A crystal detector system, composed of a small LiI(Eu) crystal, highly enriched in 6Li, and a flexible light pipe, has been used to determine the fast- and thermal-neutron distributions resulting from a Pu-Be neutron source. The thermal-neutron flux is determined by the cadmium difference technique. It is found that the thermal flux thus determined agrees well with the two-group diffusion solution and with absolute foil measurement, but gamma-ray backgrounds cause serious problems in the fast flux determination by crystal. It is also found that the non-rigid light pipe offers a great deal of flexibility in the measuring process. The high efficiency in thermal-neutron measurement obtained (41%) implies that smaller crystals or longer light pipes can be used, thereby improving the accessibility of the detector. The crystal detector used is also sufficiently sensitive to follow the small change in flux magnitude with increasing temperature.