https://phys.org/news/2019-01-zirconium-isotope-master-neutron-capture.html

Zirconium-88 is a particular type, or isotope, of zirconium, distinguished by the number of neutrons it contains. Typical zirconium contains about 50 neutrons, but ⁸⁸Zr, which is radioactive and not found naturally on Earth, has fewer than normal, with 48 neutrons.

While neutron absorption (known as a neutron-capture cross section) has been studied in detail for many stable isotopes, not much is known about this property for radioactive isotopes. The newly discovered ⁸⁸Zr thermal neutron-capture cross section is larger than that of any stable isotope. This means that when the ⁸⁸Zr nucleus encounters a thermal neutron, it is very likely to capture it and incorporate it as part of the nucleus. Thermal neutrons are found in nuclear reactors, and any other neutron (from a nuclear reaction or nuclear decay) that starts out at high energy, will bounce around until it reaches room temperature.