[en] In the Chatillon reactor the temperature is measured (1) in the interior of one of the vertical A1 cylinders filled with UO₂ (temperature interval 20 to 70 deg. C), and (2) in the center of the tank containing D₂O (20 to 50 deg. C). The instruments used are silver-constantan thermocouples; the wires are insulated by SiO₂ sheaths, those immersed in D₂O being placed within Al cases 10 mm diameter. In the Saclay reactor the temperature is taken (1) in the interior of 4 U rods (20 to 300 deg. C), (2) at 2 points of the D₂O mass (20 to 60 deg. C), (3) at one point in graphite (20 to 100 deg. C), and (4) at 5 points in the catalytic setup (200 deg. C). Copper-constantan couples are used (Ag-constantan is not suitable above 150 deg. C); the wires are enclosed in a sheath of glass fabric. In both reactors the accuracy of the temperature measurements is 0.5 deg. C. (author)