  In order to measure the total cross section for thermal neutrons, a
photoneutron source (PNS, phase 1) has been developed for the acquisition of
nuclear data for the Thorium Molten Salt Reactor (TMSR) at the Shanghai
Institute of Applied Physics (SINAP). PNS is an electron LINAC pulsed neutron
facility that uses the time-of-flight (TOF) technique. It records the neutron
TOF and identifies neutrons and $\gamma$-rays by using a digital signal
processing technique. The background is obtained by using a combination of
employing 12.8 cm boron-loaded polyethylene(PEB) (5$\%$ w.t.) to block the
flight path and Monte Carlo methods. The neutron total cross sections of
natural beryllium are measured in the neutron energy region from 0.007 to 0.1
eV. The present measurement result is compared with the fold Harvey data with
the response function of PNS.
