Beta-delayed fission in the lead region

Lead Research Organisation: University of the West of Scotland
Department Name: School of Science

Abstract

Recently, in the year 2008, the 70th anniversary of nuclear fission, which was discovered in 1938 by Otto Hahn and Fritz Strassmann, was celebrated. In the next 15 years since the discovery a few landmark developments in nuclear fission and its application have followed, including among others, the creation of the first man-made nuclear reactor in 1942, the first atomic bomb explosion (1945) and the first generation of electricity by a nuclear reactor in 1951. The world's first commercial nuclear power station, Calder Hall in Sellafield, UK was opened in 1956. Since then, the nuclear fission and its applications became omnipresent both in science and in our day-by-day life. According to the World Nuclear Association, globally during the 1980s one new nuclear reactor started up every 17 days on average. In the year 2007, 14% of the world's electricity came from nuclear power. As of September 2009 in 31 countries 436 nuclear power plant units with an electric net capacity of about 370 GW are in operation and 53 plants with an installed capacity of 47 GW are in 15 countries under construction. In the UK, in 2009, nearly one fifth of the electricity was generated by the existing 19 nuclear power reactors. Following the UK Government's January 2008 decision to support the building of new nuclear power stations, plans have been announced to open four new plants in the UK by 2017. The programme described in this Standard Grant application covers research into nuclear fission and has both scientific and society- oriented impact and outreach. In fundamental research, one of the main goals of our research programme is to achieve a better understanding of the fission process and fission properties of very exotic nuclei. The specific type of the nuclear fission studied in this project - exotic beta-delayed fission - is believed to occur in the astrophysical r-process, which is responsible for production of the heaviest elements in Universe. In particular, theorists suggest that beta-delayed fission, together with the spontaneous and neutron-induced fission, is responsible for the so-called fission recylcing and the r-process termination by fission, the latter establishing the limit for the heaviest elements production in Nature. To achieve our goals, we will exploit a combination of charged-particle, fission and gamma-ray spectroscopy by using three complementary techniques: the mass separator ISOLDE (CERN, Geneva, Switzerland), the velocity filter SHIP (GSI, Darmstadt, Germany) and the fission spectrometer of the Japan Atomic Energy Agency (JAEA, Tokai, Japan). Society-wise, in view of the new initiatives on nuclear power development by the UK government, many new specialists in nuclear industry will be required in the coming years. Our project, apart of pure fundamental nuclear fission research, will also provide the much needed specialized training of the young post-graduate students and post-doctoral researchers in the radiation and nuclear fission applications, detectors and techniques, including the nuclear waste management. .

Publications

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Kalaninová Z (2013) a decay of the very neutron-deficient isotopes 197 - 199 Fr in Physical Review C

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Seliverstov M (2013) Charge radii of odd-A 191-211Po isotopes in Physics Letters B

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Andreyev A (2013) Colloquium : Beta-delayed fission of atomic nuclei in Reviews of Modern Physics

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Kalaninová Z (2014) Decay of 201 - 203 Ra and 200 - 202 Fr in Physical Review C

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Venhart M (2012) Determination of a-decay branching ratios for 178, 179Hg in The European Physical Journal A

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Cocolios T (2012) Early onset of deformation in the neutron-deficient polonium isotopes in Journal of Physics: Conference Series

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Sagaidak R (2014) Effects of beam energy distribution on fusion-evaporation excitation functions in International Journal of Modern Physics E

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Seliverstov M (2014) Electromagnetic moments of odd- A Po 193 - 203 , 211 isotopes in Physical Review C

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Veselský M (2012) Fission-barrier heights of neutron-deficient mercury nuclei in Physical Review C

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Page R (2011) In-beam conversion-electron spectroscopy of 180 Hg in Physical Review C

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Andreyev AN (2013) Signatures of the Z = 82 shell closure in a-decay process. in Physical review letters

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De Witte H (2013) ß - decay of the neutron-rich isotope 215 Pb in Physical Review C

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Liberati V (2013) ß -delayed fission and a decay of 178 Tl in Physical Review C

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Truesdale V (2016) ß -delayed fission and a decay of At 196 in Physical Review C

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Elseviers J (2013) ß -delayed fission of 180 Tl in Physical Review C

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Lane J (2013) ß -delayed fission of 186 , 188 Bi isotopes in Physical Review C

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Andreyev A (2013) ß -delayed fission of 192 , 194 At in Physical Review C

Related Projects

Project Reference Relationship Related To Start End Award Value
ST/H008691/1 25/04/2011 31/08/2012 £230,714
ST/H008691/2 Transfer ST/H008691/1 01/09/2012 30/04/2014 £82,138
 
Description We studied exotic process of beta-delayed fission in several isotopes in the lead region.
Exploitation Route Traditional models of nuclear fission predict that heavy nuclei break into unequally sized (asymmetric) parts, which is consistent with the findings of most experiments in low-energy fission. This is naturally explained by the fact that one of the fragments tends to be in the vicinity of doubly magic tin-132132, which is highly stable.

The vast majority of fission experiments, however, have focused on heavy nuclides ranging from thorium to fermium. Now, new experiments performed at the ISOLDE facility in CERN and presented in Physical Review Letters (Andrei Andreyev et al.), probe a different corner of the nuclear chart. The team studies mercury-180180 (with 8080 protons and 100100 neutrons) and finds that the fission products are also asymmetric. However, in this particular case, the outcome is counterintuitive, since a symmetric decay of the nucleus into two copies of zirconium-9090 (with 4040 protons and 5050 neutrons) would have produced exceptionally stable nuclei.

The ISOLDE team's puzzling result hints that a very subtle interplay between macroscopic and microscopic interactions plays a deeper role in the fission process than expected and is likely to inspire detailed theoretical studies and further experiment. - Abhishek Agarwal
Sectors Energy

URL http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.105.252502
 
Description Collaboration with the Japanese Atomic Energy Agency (JAEA) 
Organisation Japan Atomic Energy Agency (JAEA)
Country Japan 
Sector Public 
PI Contribution I have performed a very successful experiment at JAEA in Feb.2010. The JAEA partners provided their detection setup.
Collaborator Contribution JAEA provides their detectors to my experiments JAEA pays for the beam time provided to my experiments
Impact data analysis from '2010 experiment is underway, a paper will be prepared soon
Start Year 2010
 
Description ISOLDE(CERN) 
Organisation European Organization for Nuclear Research (CERN)
Department ISOLDE Radioactive Ion Beam Facility
Country Switzerland 
Sector Public 
PI Contribution ISOLDE pays for beam time
Collaborator Contribution ISOLDE pays for the beam time provided to my experiments
Impact a paper in under preparation
Start Year 2010