Xenon

Xenon that we are going to discuss here is not the xenon flash in mobile camera or xenon gas which is one of the member in inert gas family. It is Xenon-135 that we are talking about. Being one of the fission products in reactors, and with its significant neutron absorption cross sections, Xenon-135 is not very "welcomed" or "liked" by nuclear reactor operators or designers. It removes neutrons from the reactor, affecting the thermal utilization factor and thus keff and reactivity. It will builds up to an equilibrium level and absorbs neutrons up to an extend that, even when the reactor is shut down, it goes through a peaking transient that can affect the ability to restart the reactor.


Xenon-135 is produced in 2 ways. It is produced as a daughter in a radioactive decay chain (from Iodine-135) and also as a direct yield from fission. By all means, it can be "eliminated" or "wasted" by radioactivedecay and also by absorption of a neutron to become Xenon-136 which is a weaker absorber. Such "elimination" process is also knowned as poison removal from the reactor, as Xenon-135 is considered as poison and undesirable in the reactor.

Now, let us see the effect of xenon on reactivity. When a new reactor was started up, it was xenon-free; as the reactor goes critical at low power (low flux) xenon starts to be produced but in a negligible amount. However, when the reactor is brought up to high power, the xenon will builds up to an extend that the operators have to withdraw control rods in order for the reactor to maintain the critical state as if the control rods remain, the reactor will face deficit in neutrons.

Hope this post will provide you readers with better understanding of xenon in nuclear field. Thank you for viewing and again do not hesitate to LIKE and COMMENT! =)