Editing Europium (section)

====Europium as a nuclear fission product====
{{Medium-lived fission products}}
Europium is produced by nuclear fission; 
[[Europium-155|<sup>155</sup>Eu]] (half-life 4.7612 years) has a fission yield of 330 parts per million (ppm) for [[uranium-235]] and [[thermal neutron]]s.<ref>{{cite journal |last1=Aarkrog |first1=A. |last2=Lippert |first2=J. |title=Europium-155 in Debris from Nuclear Weapons |journal=Science |date=28 July 1967 |volume=157 |issue=3787 |pages=425–427 |doi=10.1126/science.157.3787.425 |pmid=6028023 |bibcode=1967Sci...157..425A }}</ref>
The [[fission product yield]]s of europium isotopes are low near the top of the mass range for [[fission products]].

As with other lanthanides, many isotopes of europium, especially those that have odd mass numbers or are neutron-poor like <sup>152</sup>Eu, have high [[Neutron cross-section|cross section]]s for [[neutron capture]], often high enough to be [[neutron poison]]s.
<div style="float:left; margin:0.25em">
{| class="wikitable" align="right" style="margin:1em"
|+ Thermal neutron capture cross sections
!Isotope
|<sup>151</sup>Eu||<sup>152</sup>Eu||<sup>153</sup>Eu||<sup>154</sup>Eu||<sup>155</sup>Eu
|-
!Yield
|~10||low||1580||>2.5||330
|-
!Barns
|5900||12800||312||1340||3950
|}
</div>
<sup>151</sup>Eu is the [[beta decay]] product of [[samarium-151]], but since this has a long decay half-life and short mean time to neutron absorption, most <sup>151</sup>Sm instead ends up as <sup>152</sup>Sm.

<sup>152</sup>Eu (half-life 13.516 years) and <sup>154</sup>Eu (half-life 8.593 years) cannot be beta decay products because <sup>152</sup>Sm and <sup>154</sup>Sm are non-radioactive, but <sup>154</sup>Eu is the only long-lived "shielded" [[nuclide]], other than [[Caesium-134|<sup>134</sup>Cs]], to have a fission yield of more than 2.5 [[parts per million]] fissions.<ref>[http://wwwndc.jaea.go.jp/NuC/index.html Tables of Nuclear Data], Japan Atomic Energy Agency {{webarchive |url=https://web.archive.org/web/20150610213313/http://wwwndc.jaea.go.jp/NuC/index.html |date=June 10, 2015 }}</ref> A larger amount of <sup>154</sup>Eu is produced by [[neutron activation]] of a significant portion of the non-radioactive <sup>153</sup>Eu; however, much of this is further converted to <sup>155</sup>Eu.