Method of determining radioactive nuclides

Abstract

A method of simply and quickly determining α-ray releasing nuclides having long half-life without carrying out a chemical separation is provided. By inputting a data of pulses incident to an α-ray detector in a computer, obtaining time distribution of the incident pulses by using a very short time measuring timer and plotting, and fitting the linear originated in a random event corresponding to the background and the non-linear originated in the correlated events of parent nuclides-progenies by using the least squares method, the whole generating probability P(t) from the parent nuclide to the progeny thereof is obtained. By subtracting the random events portion from the P(t), the correlated events portion is extracted. The radioactivity per unit can be obtained by dividing the extracted correlated events portion by the measured time, the amount of the supplied sample and the counting efficiency. Also, by determining nuclides unnecessary for the measurement by this method and removing the determined nuclides from the energy spectra of objective nuclides to thereby lower the background, the objective nuclides can be determined by using pulse-height discrimination.

What is claimed is:  
     
         1 . A method of determining radioactive nuclides comprising: 
 inputting a data of pulses incident to an α-ray detector in a computer;    obtaining and plotting a time distribution of the incident pulses by using a very short time measuring timer;    obtaining from the plotted time distribution of the incident pulses, the following whole generating probability P(t) from a parent nuclide to a disintegrated product thereof by fitting the linear originated in a random event corresponding to the background and the non-linear originated in a correlated event of the parent nuclide-disintegrated product by using least squares method     P ( t )={α t ·exp(−λ t )·λ+ C}dt     wherein, 
 P(t): the probability of starting from an optional pulse and expiring at the event within a very short time dt after t milliseconds,  
 λdt: the probability of generating the correlated events within a very short time dt after t milliseconds,  
 C dt: the probability of generating the random events within a very short time dt after t milliseconds,  
 α t : the probability that the events are caused by the correlated events;  
   subtracting the random events portion from the P(t) to thereby extract the correlated events portion; and    dividing the extracted correlated events portion by the measured time, the amount of supplied sample and the counting efficiency to thereby obtain the radioactivity per unit.    
     
     
         2 . A method of determining radioactive nuclides comprising: 
 determining nuclides, which are unnecessary for the measurement by the method described in  claim 1 , on the basis of the half-life thereof and the time intervals of the incident pulses;    removing the thus determined nuclides from the energy spectra of objective nuclides to thereby lower the background and reduce the detection limit value of the objective nuclides; and    detecting the objective nuclides by using pulse-height discrimination.