Introduction:
In recent years, the use of neutrons has increased in various fields such as medicine and industry. One of the important applications of neutrons is in medical research. Neutrons have greater linear energy transfer than gamma rays and are considered more dangerous radiation. Hence, the detection and determination of neutron dose is a very important and vital issue. For determination of neutron dose, measurement of its intensity or flux is essential. One of the ways of neutron flux determination is using of gold foil activation method. In this method, the activity of the irradiated foil is proportional to the neutron flux. The gold foil is activated by reaction 197Au (n,γ) 198Au because of the thermal neutron capture,. In the decay of activated gold, a gamma radiation of 411.8 keV is released with a probability of more than 95%, that By measuring the area below the peak associated with this energy, by the NaI(Tl) detector, the activity of gold and then the neutron flux is determined.
 
Materials and Methods:
In this paper, an 18 carat gold foil was used to measure the flux of a neutron radioisotope source Ra-Be in the nuclear laboratory of the Faculty of Science of Guilan University.
 
Results:
After irradiation, the gold foil was counted by NaI(Tl) detector and its flux was determined
 
Conclusion:
Finally, by comparing the measured flux and the flux in the Ra-Be neutron source catalogue, it is resulted that the mentioned method has a good accuracy in determination of the flux of the neutron source.