Why is it in the news?

• Researchers have recently published a distinctive analysis of the neutron energy generated by Pu-240 fission, as India’s nuclear power initiative shifts its focus to

Background

• India reached a significant milestone on March 4 this year when engineers initiated the core-loading process of the prototype fast breeder reactor (PFBR) at the Madras Atomic Power Station in Kalpakkam.
• This event marks the transition to the second stage of India’s nuclear power programme. The first stage primarily utilized uranium isotopes in pressurized heavy-water reactors to generate plutonium-239 (Pu-239) and energy. In contrast, the focus of the second stage revolves around plutonium fission.

Significance of Pu-240 and Reactor Operations

• Within nuclear reactors, the transformation of a Pu-239 nucleus to Pu-240 after capturing a Neutron result in a significant fraction becoming Pu-240 instead of undergoing fission immediately. This process is pivotal in both nuclear reactors and the aftermath of nuclear weapon tests.
• Following this, when Pu-240 captures a neutron, it frequently transitions into Pu-241. Despite this, the uncertainty remains regarding the energy dissipated by the fission products of Pu-240, requiring researchers to rely on complex theoretical models for estimating the outcomes.
• Pu-239, a product of neutron bombardment of U-238 in reactors, gradually accumulates as Pu-240 due to fixed conversion rates. The challenging task of separating these isotopes prompts the removal of spent fuel as Pu-240 increases.
• Despite its propensity for spontaneous fission and alpha particle emission, Pu-240 is typically categorized as a contaminant in weapons-grade plutonium, where its composition must remain below 7%.

About the Study

• The study conducted in the U.S. marked only the second-ever attempt to measure the PFNS of induced fission in Pu-240, employing neutrons of energy exceeding 0.85 mega-electron-volt (MeV).

• Notably, this study highlighted significant disparities between the projected and observed PFNS following induced fission, providing essential insights for a range of professionals, from reactor designers to nuclear medicine practitioners.
• Further, researchers at the Los Alamos Neutron Science Centre in the U.S. performed crucial tests using proton-pulsed tungsten discs to generate neutrons encompassing a diverse energy range.
• By directing these neutrons towards pure Pu-240 samples, the team meticulously tracked the emitted particles using liquid scintillators.
• Through strategic data analysis, the scientists unveiled unique insights into the PFNS using incident neutrons within the 1-20 MeV energy range.
• Beyond uncovering disparities between predicted PFNS and empirical observations, the study highlighted unexpected trends such as second-chance fission occurrences in Pu-240.
• These findings accentuate the importance of comprehensive nuclear data libraries, crucial for enhancing models related to nuclear reactions and facilitating advancements in various fields, including nuclear energy research and radiation shielding design.