Neutron continued lifetime

The incorporation of associated alpha particle detection in a sealed tube neutron generator (STNG) appears to severely aggravate the concerns over the limited neutron flux and tube lifetime previously detailed for STNG FNA approaches. A mean time to failure of some APSTNGs at a neutron flux of lO n/s is about 200 h [24]. Work is continuing to improve this mean time to failure. 

The electrons lose energy by radiating and so have a limited lifetime. Tired electrons must somehow be replaced. The continuous source of relativistic electrons is in fact the central pulsar. Indeed, at the centre of the expanding nebula is enthroned a rapidly spinning neutron star (turning at some 33 revolutions per second), as witnessed by the punctuated message we receive on Earth. This star is clearly an excellent electron accelerator. 

The time between neutron generations is the time between a neutron being produced and the time it is absorbed, into either a fissile or non-fissile nucleus. In reality this time interval will vary between individual neutrons, but we will make the simplifying assumption that the lifetime of all neutrons may be characterized by the average neutron lifetime, /, which is typically 1 millisecond in a commercial thermal reactor. Neutrons are being bom continuously in a reactor, and we may assume that at any instant of time the neutrons have a uniform spread of all ages between 0 and I seconds. Let us divide the neutron lifetime. /, into a large number, M, of time intervals. Si, where... 

Carbon-14 is continually being produced in the atmosphere from nitrogen, by the action of cosmic rays. These rays generate neutrons, which themselves have a lifetime of only about 12 minutes. However, during their lifetnne, the neutrons generate carbon-14 by the reaction... 

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