137Cs activities in purple surface soil on grass land have a good relationship with the medium grain size(d50)by sieving method,but do not have a defined relationship with the medium grain size(d50)by normal method.

such as Oxidationreduction environment of agaifersystem,degree of rock retarding (adsorbing)radionuclides ingroundwater etc according to natural radionuclides activity ratio relative to ￣(222)Rn, retardationfactor,dlstrobution coefficlent and radionuclide concentration in the groundwater.

The paper introduces the method of dating the zero time by utilizing the activity ratio of two fission products in no-isobaric or parent-daughter fission products in isobaric.

Computerized γ-spectrometric specific activity-meter Model H-90B;

It can be used both to automatically calculate contents of 40 K ,U and Th, and to fast measure the specific activity of natural radioactive nuclides 226 Ra, 232 Th and 40 K in stones and architecture.

By determining specific activity of nuclein Cs-137 in s oil pellet samples with different size, the logarithm relation between specific activity of Cs-137 in soil and surface area of soil pel lets is obtained.

The a-specific activity of 234U is about three orders higher than that of 235U.

Microcomputer γ spectrum ratio activity meter;