Details

Autor(en) / Beteiligte

• Shusterman, Jennifer A.
• Scielzo, Nicholas D.
• Thomas, Keenan J.
• Norman, Eric B.
• Lapi, Suzanne E.
• Loveless, C. Shaun
• Peters, Nickie J.
• Robertson, J. David
• Shaughnessy, Dawn A.
• Tonchev, Anton P.

Titel

The surprisingly large neutron capture cross-section of 88Zr

Ist Teil von

• Nature (London), 2019-01, Vol.565 (7739), p.328-330

Ort / Verlag

United States: Nature Publishing Group

Erscheinungsjahr

2019

Beschreibungen/Notizen

• The probability that a nucleus will absorb a neutron, described in units of area as the neutron-capture cross section, is important to many areas of nuclear science including stellar nucleosynthesis, reactor performance, nuclear medicine, and defense applications. Although neutron-capture cross-sections have been directly measured for most stable nuclei, fewer results exist for radioactive isotopes and predictions typically have large uncertainties. There are almost no nuclear data for neutron-induced reactions on the radioactive nucleus 88Zr, despite its significance for nuclear-security missions. By exposing 88Zr to the intense neutron flux of a nuclear reactor, it was determined that 88Zr has a thermal neutron capture cross section of (861,000 ± 69,000) b, which is the second-largest ever measured, despite being predicted to be only 10 b. The only other nuclei known to have thermal neutron capture cross sections greater than 1x105 b are 135Xe and 157Gd (2.6x106 b and 2.5x105 b, respectively) and no other cross section of comparable size has been discovered in the past 70 years (Fig. 1). The measurement of the 135Xe cross section followed the determination that a fission product was poisoning the early reactors.7 The applications for 157Gd were not immediately appreciated, but now the isotope has been developed into a detector material, burnable reactor poison, and potential medical neutron capture therapy (NCT) agent. In the case of 88Zr, a unique aspect of the neutron-capture reaction is that both the target and the product 89Zr nuclei are radioactive and give intense γ-ray emissions upon decay. This result suggests that as additional measurements with radioactive isotopes become feasible in the near future via access to new facilities for sample production and measurement, other cross-section surprises may be uncovered.