Located in the ATR canal, the Gamma Facility is an aluminum dry tube projecting from the spent fuel rack to the top of the ATR canal. The tube contains a removable shielded plug at the top to block shine and is sealed at the bottom and weighted with lead. Spent fuel can be placed in the fuel grid around the gamma facility to generate high gamma fields. The gamma facility has historically been used to determine material degradation in a high gamma field. For example it has been used to determine effects on electronics, wire insulation, and even oil. Test samples must fit inside an aluminum dry tube sealed at the bottom and weighted with lead to prevent floating. The 21-foot tube has a useable inner diameter of 12.7 cm (5 inches) [or 8.9-cm (3.5-in)] and a useable length of 6 m (19 feet - 8 inches) from the top to the lead. The mid-plane of the gamma field is approximately 5.54 m (18 feet - 2 inches) from the top of the tube. During the test, the dry tube is inserted vertically into one of the gamma grid positions. Test samples are lowered through the open end of the dry tube to the gamma field. A shield plug caps the open end of the dry tube and shields the gamma beam emitted from the fuel elements near the lower end of the dry tube. Radiological control surveillance is required whenever the shield plug is removed for sample handling.
Unique Functions
The ATR Gamma Facility, formerly designated the ATR Small Gamma Facility, is located toward the east end and on the south side of the ATR storage canal. This is not the original EG&G "Large" Gamma Irradiation Facility, that has been decommissioned. The gamma field is produced by placing irradiated fuel elements in grid locations around the position where the test is inserted. The dose rate of the field produced is approximately 1E+6 R/hr., but can be varied (5E+6 R/hr. maximum) by varying the distance of fuel elements from the test or by selecting fuel of different gamma strengths. That intensity will fall off at the rate of approximately 5% per day as the fission products in the fuel elements decay away. The peak field at the center of the tube was recently measured to be approximately 2.5E+6 rad/hr. The dose rates are normally measured by using high range ionization chambers and instrumentation. These can be lowered into the dry tube for actual counting before installing the test sample hardware. Fuel elements can be moved from one location to another with the dry tube in place.
Hotwork Facilities
Located in Building TRA-670 in the ATR canal.
Support Equipment
Located in Building TRA-670 in the ATR canal. Returned to service in 2016 following inactivation in 2004.
