在

232

Th快中子俘获截面测定工作中，由于

233

Th的

β

射线能量大、半衰期短，比起

233

Pa来，具有更强的放射性。这样通过测定

233

Th的

β

放射性，可以求得

232

Th的中子俘获截面。同时由于大量

232

Th存在，可作为载体，便于进行放化分离。

After irradiation

the thorium is rapidly extracted by TBP (15% in CC1

4

) in NH

4

SCN solution (1.0

M

pH=2.5) . The beta ray of

233

Th was counted by liquid GM counter

without the α particles of

232

Th and

228

Th being detected. The whole process was finished in 15~20 min. Half-life of

233

Th was determined as 22.1 min. The recovery of thorium was about 80%.

This method was successfully used for the measurement of fast neutron capture cross-section of

232

Th.