A Green Road Blog 

Radioactive xenon-135 is produced from iodine-135 as a result of nuclear fission, and it acts as the most significant neutron absorber in nuclear reactors.[11]

129Xe is produced by beta decay of129I, which has a half-life of 16 million years, while 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu,[60] and therefore used as indicators of nuclear explosions.

Some radioactive isotopes of xenon, for example, 133Xe and 135Xe, are produced by neutron irradiation of fissionable material within nuclear reactors.[7] 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.6×106 barns,[11] so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation.

This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel).[69] 135Xe reactor poisoning played a major role in the Chernobyl disaster.[70]

A shutdown or decrease of power of a reactor can result in buildup of 135Xe and getting the reactor into the iodine pit. Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may be found emanating from nuclear reactors due to the release of fission products from cracked fuel rods,[71] or fissioning of uranium in cooling water.[72]

In nuclear energy applications, xenon is used in bubble chambers,[144] probes, and in other areas where a high molecular weight and inert nature is desirable. A by-product of nuclear weapon testing is the release of radioactive xenon-133 and xenon-135. The detection of these isotopes is used to monitor compliance with nuclear test ban treaties,[145] as well as to confirm nuclear test explosions by states such as North Korea.[146]

http://en.wikipedia.org/wiki/Xenon

One of the common fission products is tellurium-135, which undergoes beta decay with half-life of 19 seconds to iodine-135. Iodine-135 itself is a weak neutron absorber. It builds up in the reactor in the rate proportional to the rate of fission, which is proportional to the reactor thermal power. Iodine-135 undergoes beta decay with half-life of 6.57 hours to xenon-135. The yield of 135Xe for uranium fission is 6.3%; about 95% of xenon-135 originates from decay of iodine-135.

Xenon-135 is the most powerful known neutron absorber. Its buildup in the fuel rods significantly lowers reactivity of the reactor core. By a neutron capture, Xe-135 is transformed ("burned") to xenon-136, which is stable and does not significantly absorb neutrons. The burn rate is proportional to the neutron flux, which is proportional to the reactor power; a reactor running on twice the power will have twice the xenon burn rate.

Xenon-135 beta-decays with half-life of 9.2 hours to caesium-135; a poisoned core will spontaneously recover after several half-lives. For some reactors, the 135Xe concentration will be equal to its equilibrium concentration at full power. After about 3 days of shutdown, the core can be assumed to be free of 135Xe, without it introducing errors into the reactivity calculations.[4] http://en.wikipedia.org/wiki/Iodine_pit

129Xe is produced by beta decay of 129I (half-life: 16 million years); 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, and therefore used as indicators of nuclear explosions.

The artificial isotope 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.65×106barns, so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation.

This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. Fortunately the designers had made provisions in the design to increase the reactor'sreactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel). Relatively high concentrations of radioactive xenon isotopes are also found emanating from nuclear reactors due to the release of this fission gas from cracked fuel rods or fissioning of uranium in cooling water.

http://en.wikipedia.org/wiki/Isotopes_of_xenon

133Xe, 137Xe, and 135Xe that has not captured a neutron all beta decay to isotopes of caesium. Fission produces 133Xe, 137Xe, and 135Xe in roughly equal amounts, but after neutron capture, fission caesium will contain more stable 133Cs (which however can become 134Cs on further neutron activation) and highly

radioactive137Cs than 135Cs.

135Xe that does not capture a neutron decays to Cs-135, one of the 7 long-lived fission products,(SEE BELOW) while 135Xe that does capture a neutron becomes stable 136Xe. Estimates of the proportion of 135Xe during steady-state reactor operation that captures a neutron include 90%,[6] 39%–91%[7] and "essentially all".[8]136Xe from neutron capture ends up as part of the eventual stable fission xenon which also includes 136Xe, 134Xe, 132Xe, and 131Xe produced by fission and beta decay rather than neutron capture.

133Xe, 137Xe, and 135Xe that has not captured a neutron all beta decay to isotopes of caesium. Fission produces 133Xe, 137Xe, and 135Xe in roughly equal amounts, but after neutron capture, fission caesium will contain more stable 133Cs (which however can become 134Cs on further neutron activation) and highly radioactive137Cs than 135Cs.

http://en.wikipedia.org/wiki/Xenon-135#Decay_and_capture_products

Very little has changed since Chernobyl blew up and radiated everyone, except that many more nuclear accidents, meltdowns, melt throughs and ‘accidental’ radiation releases happened, plus way more radioactive substances are now in the air, on the ground and in the ocean as well as inside all of us.

How many radioactive elements and isotopes are released from something like Fukushima, some of which eventually end up inside all of us?

According to Asahi: about 1,000 kinds of radioactive materials have been released from  Fukushima reactors. http://enenews.com/asahi-sources-reveal-about-1000-kinds-of-radioactive-materials-released-from-fukushima/comment-page-1#comment-195658

Let’s focus on just 93 out of the 1,000 total, shall we? There are 93 different long lived radioactive elements that hang around and pollute both the environment and us for at least 17,000 years and up to BILLIONS of years in total decay life. Want to see the list of all 93?

http://www.care2.com/c2c/share/detail/3069680

Long half life radioactive elements

Part I http://www.care2.com/c2c/share/detail/3047473  Elements 1-9

Part II http://www.care2.com/c2c/share/detail/3048444  Elements 10-13

Radioactive xenon-135 is produced from iodine-135 as a result of nuclear fission.[11] Radioactive xenon known as 129Xe is produced by beta decay of Radioactive Iodine, known as I29I, which has a half-life of 16 million years, while 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu,[60] and therefore used as indicators of nuclear explosions.

Some radioactive isotopes of xenon, for example, 133Xe and 135Xe, are produced by neutron irradiation of fissionable material within nuclear reactors.[7] 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.6×106 barns,[11] so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation.

This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel).[69] 135Xe reactor poisoning played a major role in the Chernobyl disaster.[70]

A shutdown or decrease of power of a reactor can result in buildup of 135Xe and getting the reactor into the iodine pit. Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may be found emanating from nuclear reactors due to the release of fission products from cracked fuel rods,[71] or fissioning of uranium in cooling water.[72] (This is what happened at Chernobyl and Fukushima for example.)

In nuclear energy applications, xenon is used in bubble chambers,[144] probes, and in other areas where a high molecular weight and inert nature is desirable. A by-product of nuclear weapon testing is the release of radioactive xenon-133 and xenon-135. The detection of these isotopes is used to monitor compliance with nuclear test ban treaties,[145] as well as to confirm nuclear test explosions by states such as North Korea.[146] http://en.wikipedia.org/wiki/Xenon

One of the common fission products is tellurium-135, which undergoes beta decay with half-life of 19 seconds to iodine-135. Iodine-135 itself is a weak neutron absorber. It builds up in the reactor in the rate proportional to the rate of fission, which is proportional to the reactor thermal power. Iodine-135 undergoes beta decay with half-life of 6.57 hours to xenon-135. The yield of 135Xe for uranium fission is 6.3%; about 95% of xenon-135 originates from decay of iodine-135.

129Xe is produced by beta decay of radioactive Iodine - 129I (half-life: 16 million years); 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, and therefore used as indicators of nuclear explosions.

The artificial isotope 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.65×106barns, so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation.

This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. Fortunately the designers had made provisions in the design to increase the reactor'sreactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel). Relatively high concentrations of radioactive xenon isotopes are also found emanating from nuclear reactors due to the release of this fission gas from cracked fuel rods or fissioning of uranium in cooling water.http://en.wikipedia.org/wiki/Isotopes_of_xenon

133Xe, 137Xe, and 135Xe that has not captured a neutron all beta decay to isotopes of caesium. Fission produces 133Xe, 137Xe, and 135Xe in roughly equal amounts, but after neutron capture, fission caesium will contain more stable 133Cs (which however can become 134Cs on further neutron activation) and highly radioactive137Cs than 135Cs.

135Xe that does not capture a neutron decays to Cs-135, one of the 7 long-lived fission products,(SEE BELOW) while 135Xe that does capture a neutron becomes stable 136Xe. Estimates of the proportion of 135Xe during steady-state reactor operation that captures a neutron include 90%,[6] 39%–91%[7] and "essentially all".[8]136Xe from neutron capture ends up as part of the eventual stable fission xenon which also includes 136Xe, 134Xe, 132Xe, and 131Xe produced by fission and beta decay rather than neutron capture.133Xe, 137Xe, and 135Xe that has not captured a neutron all beta decay to isotopes of caesium. Fission produces 133Xe, 137Xe, and 135Xe in roughly equal amounts, but after neutron capture, fission caesium will contain more stable 133Cs (which however can become 134Cs on further neutron activation) and highly radioactive137Cs than 135Cs. http://en.wikipedia.org/wiki/Xenon-135#Decay_and_capture_products

Long half life radioactive elements

Part I http://www.care2.com/c2c/share/detail/3047473  Elements 1-9

Part II http://www.care2.com/c2c/share/detail/3048444  Elements 10-13