IAEA CRP on a Reference Database for Beta-Delayed Neutron Emission

Code F41028; Duration 2013-2018

CRP completed - final database and publications

Tables of compiled and evaluated half-lives and beta-delayed neutron emission probabilities for individual precursors:

The final CRP technical report on compiled, evaluated and validated microscopic and macroscopic delayed-neutron data:

The database containing all the microscopic and macroscopic delayed-neutron data:

Consultant's Meeting on Benchmarking the New Evaluated beta-delayed neutron data

Participants of the CRP who are involved in measurements, compilations and calculations of macroscopic delayed neutron data such as total delayed neutron yields, average half-lives and delayed-neutron spectra, attended a Consultant' Meeting from 13 to 15 December 2017 at the IAEA, to discuss the impact of the newly evaluated beta-delayed neutron emission probabilities produced by the CRP evaluators on these macrosocpic data, the new systematics of measured macrosocpic data and the contents of the final CRP document.

More information about the meeting is available here.

IAEA TM on Fission Product Yields: status and perspectives

The yields of fission products produced after the fission process and subsequent decay of fission fragments are important data for calculating the total yields and other aggregate properties of delayed neutrons such as decay rates, decay constants and delayed neutron spectra, using the summation method.

A meeting was held at the IAEA, Vienna, from 23 to 26 May 2016, to assess the current status of fission product yields in terms of a) measurements, b) modelling and evaluation, and c) evaluation of covariances. The presentations, participants list and summary report are available here.

Theoretical calculations of β-decay properties

β-decay half-lives and β-delayed neutron emission probabilities, including first-forbidden transitions, have been calculated within a fully self-consistent microscopic theoretical framework. The results were used in an r-process nucleosynthesis calculation to assess the sensitivity of heavy element nucleosynthesis to weak interaction reaction rates. By Marketin et al., in Phys. Rev. C 93, 025805 (2016). A supplemental table with all the calculated properties is also available here.

Evaluation of beta-delayed neutron emission probabilities Pn and T1/2 for Z = 2-28

The compilation and evaluation of beta-delayed neutron emission probabilities and half-lives for nuclides in the Z = 2-28 region performed within the CRP has been published by Birch et al., in Nuclear Data Sheets 128, 131 (2015). The article includes tables of compiled and evaluated data, as well as systematics.

Systematics of beta-delayed neutron emission probabilities

A phenomenological model of the beta-delayed neutron-emission probability, based on a level density function, was developed. The effective level density systematics, empirically determined from the experimental data, have been modeled and used to determine beta-delayed neutron-emission probabilities. The work was performed by K. Miernik and is now published in PRC 88, 041301(R) (2013) [PDF]. Files containing the calculated data and graphical presentations can be downloaded from this [link].

The CRP on beta-delayed neutron emission data

CRP Objective

The overall CRP Objective is to enhance Member States' (MS) knowledge and calculational capabilities in the fields of nuclear energy, safeguards, used fuel and waste management and nuclear sciences by creating a Reference Database for Beta-Delayed Neutron Emission that contains both a compilation of existing data, evaluated data and recommended data, which will be made readily available to the user community. The project starts in 2013 and will have a duration of 4 years.

Specific Research Objectives

Expected Research Outputs

Useful material

Delayed Neutron Energy Spectra
Integral Delayed Neutron Data
Summation Method
Experimental Aggregate Delayed Neutron Spectra