A temperature measurement sensor for use in a nuclear reactor, the temperature measurement sensor comprising: a first neutron detector member; and a second neutron detector member; each of the first and second neutron detector members (12, 42) being comprised of an inner electron emitter (14, 44), a first layer of insulation (16, 46) surrounding the emitter (16, 46), a charge collector (18, 48) surrounding the first layer of insulation (16, 46), a negative charge output pin (26, 36) extending outwardly from the charge collector (18, 48), and a positive charge output pin (28, 38) extending outwardly from the emitter (16, 46); the first neutron detector member further comprising a second layer of insulation surrounding the charge collector of the first neutron detector member, an electron absorbing layer surrounding the second layer of insulation, and an outer shield for capturing neutrons surrounding the electron absorbing layer; wherein in use, the first neutron detector member outputs a first current signal and the second neutron detector member outputs a second current signal; the temperature measurement sensor further comprising an electrical connection between the first neutron detector member and the second neutron detector member, the electrical connection being configured to produce the difference in current between the first and second signals, wherein the difference in current is proportional to changes in temperature; wherein each of the emitters (14, 44) is made of an emitter material; characterized in that the outer shield is made of a material having a Doppler temperature neutron capture cross section larger than the corresponding cross section of the emitter material. a first neutron detector member; and a second neutron detector member; each of the first and second neutron detector members (12, 42) being comprised of an inner electron emitter (14, 44), a first layer of insulation (16, 46) surrounding the emitter (16, 46), a charge collector (18, 48) surrounding the first layer of insulation (16, 46), a negative charge output pin (26, 36) extending outwardly from the charge collector (18, 48), and a positive charge output pin (28, 38) extending outwardly from the emitter (16, 46); the first neutron detector member further comprising a second layer of insulation surrounding the charge collector of the first neutron detector member, an electron absorbing layer surrounding the second layer of insulation, and an outer shield for capturing neutrons surrounding the electron absorbing layer; wherein in use, the first neutron detector member outputs a first current signal and the second neutron detector member outputs a second current signal; the temperature measurement sensor further comprising an electrical connection between the first neutron detector member and the second neutron detector member, the electrical connection being configured to produce the difference in current between the first and second signals, wherein the difference in current is proportional to changes in temperature; wherein each of the emitters (14, 44) is made of an emitter material; characterized in that the outer shield is made of a material having a Doppler temperature neutron capture cross section larger than the corresponding cross section of the emitter material.