When did UFTR first go critical?

When did UFTR first go critical?

• A. April 1958
• B. May 1959
• C. June 1958
• D. May 1960

Answer: (B)

Going critical means the reactor has achieved a self-sustaining neutron chain reaction, with the reactivity adjusted so that neutron production balances losses and the power can be raised from zero. For the UFTR, historical records show this milestone was reached in May 1959, after the initial subcritical commissioning and configuration checks. That timing aligns with the UFTR’s documented startup sequence, making May 1959 the date that first criticality occurred. The other dates fall outside the established startup timeline—either before the reactor was ready or later than the initial criticality—so they don’t match the recorded history.

Going critical means the reactor has achieved a self-sustaining neutron chain reaction, with the reactivity adjusted so that neutron production balances losses and the power can be raised from zero. For the UFTR, historical records show this milestone was reached in May 1959, after the initial subcritical commissioning and configuration checks. That timing aligns with the UFTR’s documented startup sequence, making May 1959 the date that first criticality occurred. The other dates fall outside the established startup timeline—either before the reactor was ready or later than the initial criticality—so they don’t match the recorded history.