The surprisingly large neutron capture cross-section of ⁸⁸Zr

Journal Article · Mon Jan 07 00:00:00 EST 2019 · Nature (London)

DOI:https://doi.org/10.1038/s41586-018-0838-z· OSTI ID:1512575

Shusterman, Jennifer A. ^[1]; Scielzo, Nicholas D. ^[2]; Thomas, Keenan J. ^[2]; Norman, Eric B. ^[3]; Lapi, Suzanne E. ^[4]; Loveless, C. Shaun ^[4]; Peters, Nickie J. ^[5]; Robertson, J. David ^[5]; Shaughnessy, Dawn A. ^[2]; Tonchev, Anton P. ^[2]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); City Univ. (CUNY), NY (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering
4. Univ. of Alabama, Birmingham, AL (United States)
5. Univ. of Missouri, Columbia, MO (United States)

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.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1512575
• Report Number(s): LLNL-JRNL-744886; 899468
• Journal Information: Nature (London), Vol. 565, Issue 7739; ISSN 0028-0836
• Publisher: Nature Publishing Group
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY