NSUF 24-4941: Measurement of Fission Product production yields

Hundreds of nuclides can be produced in the fission of actinides. An accurate inventory of their amount, referred to as the product's Fission Yield (FY), is essential for numerous applications like reactor physics, nuclear forensics, and nuclear waste disposal, as well as for a basic understanding of the fission process.

In recent years, a renewed interest has been placed on updating the FY included in the evaluated nuclear data libraries with new measurements complemented by improved theoretical models. We propose a FY measurement campaign that uses the X-ray fluorescence capabilities at NSLS-II for high-precision determinations of charge fission yields of long-lived nuclei. The XRF technique would improve on and complement the information on long-lived FYs that come from a measurement performed using Isotope Dilution Mass Spectrometry (IDMS) in the 1970s at Idaho National Laboratory (INL), still the most precise determination of FYs to date.

Thanks to their low uncertainty, the results from INL constitute the foundation of the current recommended FY distributions published in the US nuclear data library (ENDF/B). However, these values were never published in a peer-reviewed journal and were never replicated, raising doubts on the uncertainties reported by the authors. In addition, while yields as low as 0.1% were measured, some refractory elements could not be detected with the IDMS technique and their FYs had to be interpolated.

We will take advantage of the bright X-ray beams and state-of-the-art detectors available at NSLS-II to measure high-precision charge yields of long-lived fission products from neutron-induced fission of actinides using synchrotron-based X-ray Fluorescence (s-XRF). After careful calibration with standard samples, s-XRF is expected to provide the same level of uncertainty as IDMS, and being able to measure concentrations at the ppm level would allow us to reach yields as low as 10-5, or 2 orders of magnitude lower than those measured in the 1970s, potentially making this dataset the new gold-standard for FY evaluations worldwide.

The first phase of the program, which we intend to explore in this RTE, will allow us to develop the workflow and confirm the sensitivity of the method measuring a series of irradiated foils from the NSUF Material Library. We have selected samples that have been exposed to various, and known, integrated neutron fluences. The samples contain four elements in the transition metals region of the periodic table – i.e., where the majority of the fission products are produced. The fraction of the elements transmuted via neutron capture will be assessed using s-XRF as a surrogate for fission.

A valuable scientific result obtained in this phase is the determination of the neutron capture cross-section of some of the low-abundance isotopes contained in the irradiated samples, which were selected based on their importance for intentional forensics applications.

A successful RTE will: (1) assess the viability of the method and estimate the sensitivity limits for s-XRF applied to FY measurements; (2) determine the uncertainties associated with this application, to verify its competitiveness against other techniques; (3) help identify and solve difficulties in the workflow associated with the identification of fission products with s-XRF. If shown to be successful, this project will also enable accurate measurement of elemental composition of nuclear materials in addition to X-ray diffraction (XRD) data collected at XPD beamline of NSLS-II – an NSUF partner facility serving multiple users from nuclear materials science community every year.

추가 정보

필드	값
Award Announced Date	2024-05-28T16:56:44.393
Awarded Institution	Brookhaven National Laboratory
Facility Tech Lead	Alina Montrose, Simerjeet Gill
Irradiation Facility
PI	Andrea Mattera
PI Email	[email protected]
Project Type	RTE
RTE Number	None