Gold foil was used to help scientists determine if the Idaho National Laboratory’s (INL) NRAD neutron beam still meets national standards after its nuclear reactor received upgrades, Joe Campbell of INL reports.
“We wanted to make sure we still met ASTM’s Category I standard after the core upgrade, but we realized that other researchers wishing to conduct examinations here would find a precise map of the beam’s intensity very useful. Testing with an array of gold foil targets was the best way to do that,” said INL postdoc researcher Aaron Craft.
Gold is the best material for the job because of its short half-life and “how it reacts to exposure to the neutron flux in a reactor.”
“Gold as it is found in nature—gold-197—contains no traces of its radioactive isotopes. But, when exposed to a neutron beam, a small percentage of a given sample of gold will turn to gold-198, which has a half-life of 2.7 days.”
“The percentage of gold-198 created is directly proportional to the intensity of the neutron beam that hits each sample in the array. Using the half-life of 2.7 days for gold-198, and the data from the sample counts done in MFC’s Analytical Lab, I then have everything I need to create a precise map of NRAD’s beam intensity,” Craft explained. “Such a map can help attract other researchers who need to examine or test samples after exposure to a neutron flux that matches NRAD’s profile.”