What is xenon?

During class, Mr.Syamsul's lecture was very much about control rods...Then, he introduced a chapter on Xenon Transients Effect. Although this chapter was not fully covered, I still feel that this particular chapter is very important..

So what is Xenon?
The discovery of  Xenon can be considered as an 'accidental discovery'.It all happened in Hanford,US(1944) by Enrico Fermi as he fired up the first nuclear reactor. By the way, Enrico Fermi was a well known Italian-American physicist who has also won a nobel prize. Shortly after the reactor went critical, power stalled and the reactor shut down. A few hours later, the reactor unexpectedly started up again all by itself. This was the result of poisoning brought on by Xenon-135 (Xe). The word 'poison' is used because during that time, physicists and scientists sees xenon as a very dangerous component in a nuclear reactor. Later on, 'poison' is used to describe a substance that has a strong ability to absorb neutrons. In a way, control rods is also a 'poison'(non-burnable).

Xenon-135 is one of the most common and troublesome poisons found in nuclear reactors. It is a radioactive isotope of Xenon which is predominately formed by the beta-decay of Iodine-135. The iodine is a common byproduct of the fission of Uranium-235. When the Uranium splits, it releases several neutrons and also two smaller daughter elements; among them Iodine-135

So, if xenon is dangerous.....what shall be done?

One is by neutron absorption..The other way is by beta-decay..

When Xe-135 captures a neutron, it becomes Xe-136, a stable isotope which does not absorb neutrons. This process is referred to as the burn up or burn out of Xenon, where the poisonous Xenon is removed.
I will explain in a Malay "kedai kopi" way, Xenon ni bagaikan hidup segan, mati tak mahu... Xenon wujud dalam reactor tapi kerja dia ialah untuk makan neutron jee.....Bile dia dah makan, dia mati....Kiranya, dah puas hidup laa...Jadik, kita tak boleh anggap xenon tu 100% bahaya sebab xenon boleh mengurangkan populasi neutron dalam sesebuah reactor...Kawalan populasi penting sebab kalau overpopulation, reactor boleh menjana kuasa yang terlebih dan menyebabkan reactor meltdown.....Hopefully, writing in dual languanges can increase one's understanding.

The other way is by beta-decay.Xe-135 has a half life of about 9 hours. I-135 has a half life of about 6.5 hours. This time differential is one of the factors that makes Xenon such a problem for nuclear reactors. Since Xenon takes longer to decay than the Iodine takes to build in the Xenon, then there is a natural tendency for Xenon levels to increase in a reactor when not at equilibrium... Malay i go again....jadi, kalau xenon dah terlampau banyak, ini yang akan mendatangkan bahaya terutamanya selepas reactor ditutup atas sebab-sebab tertentu seperti power yang dijana menjadi terlampau tinggi.....Xenon yang terlampau banyak akan menyebabkan apabila operasi reactor dimulakan semula, power akan menjadi lebih tinggi dari semasa reactor ditutup......Apabila power jadik terlampau tinggi secara tiba-tiba, keselamatan akan sukar dikawal dan faham-fahamlah sendiri apa yang akan jadik selepas tu.....Chernobyl? remember?It all happened because operators tried to restart the reactor too soon after a shutdown.

There is a lot of articles/blogs which say that when a reactor reaches super criticallity, control rods will do all the work in keeping the reactor safe.... Control rods cannot do all that by itself. That is why i think that xenon plays an important part in keeping any reactor safe......

ONE NUCLEAR FOR ONE MALAYSIA