Xenon Balance in the Reactor

Xenon balance in the reactor is illustrated in Figure 8.1. Since iodine-135 decays to become xenon-135, its balance in the reactor must also be considered, Iodine-135 is formed by decay of tellurium-135 and as a fission product and, in turn, decays to become xenon 135. The half life of tellurium-135 is 19 seconds in comparison to 6.7 hours for iodine-135, For all practical purposes it can be assumed that all iodine-135 is formed directly by fission, For this reason a fission product yield fraction for iodine-135, Vt, is given in Table 8,2 when tellurium-135 is, in fact, the fission product. Tables 6.2 and 8.3 provide fission product yields, half-lives, and decay constants for those isotopes involved with fission product poisoning. 

---