Academic Lecture: Nuclear reactor antineutrinos, hard to detect, but with a traceable lineage


Speaker: Alejandro Sonzogni (Brookhaven National Laboratory) 
Moderator: Prof. Cao Jun
Time: 15:00, May 24
Place: Room C305 IHEP Main Building
Nuclear reactors are prolific sources of electron antineutrinos, producing about 10^{21} antineutrinos per second for a typical power reactor. These electron antineutrinos are produced by the beta-minus decay of the more than 800 neutron-rich fission fragments, which are the debris from the main source of energy generation in a reactor, the neutron induced fission of actinide nuclides.  These antineutrinos are also the only radiation escaping from a safely operating reactor.Nuclear reactors have been an essential tool to study the weak interaction. Their large antineutrino flux was capitalized by Cowan and Reines to discover antineutrinos in 1956, more than 25 years after they were first hypothesized by Pauli in 1930 to explain the continuum electron spectra observed following beta-minus decay.    

In the last few years, the transformation of electron antineutrinos into the other flavors was beautifully measured by three large-scale experimental efforts, Daya Bay, Double Chooz and RENO. These experiments also confirmed a deficit of antineutrinos of about 5% at short distances that had been revealed in a 2011 re-analysis of the conversion procedure to obtain antineutrino spectra from the measured electron spectra. The antineutrino spectrum produced in a nuclear reactor is calculated as the sum of the spectra produced by each of the nuclear fuels, 235,238U and 239,241Pu, weighted by the respective fission fractions. Nuclear data activities started in Brookhaven National Laboratory in 1952, in a group that would eventually become the National Nuclear Data Center (NNDC) in 1977. Using the databases that the NNDC manages, the antineutrino spectra for each nuclear fuel can be calculated in what is commonly known as the ‘summation method’.   

In this talk, we will present what we have learned using the summation method, such as antineutrino yield systematics, main contributors and their signature in both electron and antineutrino spectra, as well as sensitivity studies to identify nuclides with deficient knowledge for future experiments. We would also highlight the need and efforts in properly curating nuclear data for future use.    

About the speaker:     

MS from the University of Buenos Aires, PhD from the University of Washington, Post-doc at Argonne National Laboratory, staff member in Brookhaven National Laboratory since 1999. Currently head of the National Nuclear Data Center, Chair of the US Nuclear Data Program and the Cross Section Evaluation Working Group.