System including a bypass pipe that routes some sodium coolant from a primary pump discharge upward to sodium measuring instruments located near a nuclear reactor head

A system for measuring sodium in a sodium fast reactor, comprising:

• a primary sodium pump configured to circulate primary sodium coolant within a reactor vessel, the primary sodium pump having a discharge;
• a bypass pipe fluidly coupled to the discharge at a first bypass end and having a second bypass end;
• an instrument tank coupled to a reactor head at a first instrument tank end and having a second instrument tank end open to a pool of sodium within the reactor vessel;
• and
• an instrument module insertable through an aperture in the reactor head into the instrument tank and selectively coupled to the second bypass end at a coupling, the instrument module comprising one or more instruments configured to measure a characteristic of sodium within the bypass pipe, wherein the coupling is a slip-on coupling with the instrument module fitting over the second bypass end.