1 / 19

Measurement of the 240 Pu( n,f ) reaction cross-section at the CERN n_TOF facility EAR-2

Measurement of the 240 Pu( n,f ) reaction cross-section at the CERN n_TOF facility EAR-2.

lazaro
Download Presentation

Measurement of the 240 Pu( n,f ) reaction cross-section at the CERN n_TOF facility EAR-2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement of the 240Pu(n,f) reaction cross-section at the CERN n_TOF facility EAR-2 • A. Tsinganis1, N. Colonna2, R. Vlastou1, P. Schillebeeckx3, A. Plompen3, J. Heyse3, M. Kokkoris1, M. Barbagallo2, E. Berthoumieux5, M. Calviani4, E. Chiaveri4,A. Stamatopoulos1 • and the n_TOF Collaboration • 1) National Technical University of Athens (NTUA), Greece • 2) IstitutoNazionalediFisicaNucleare, Bari, Italy • 3) European Commission JRC, Institute for Reference Materials and Measurements, Geel, Belgium • 4) European Organisation for Nuclear Research (CERN), Geneva, Switzerland • 5) Commissariat a l‘ EnergieAtomique (CEA) Saclay - Irfu, Gif-sur-Yvette, France • Spokespersons: A. Tsinganis, M. Kokkoris (NTUA) • Technical Coordinator: O. Aberle (CERN) 47th Meeting of the INTC CERN, June 25, 2014

  2. Outline • Introduction and motivation • The 2010 240,242Pu(n,f) proposal • The 240Pu(n,f) measurement in EAR-1 • Sample-induced damage to detectors • Advantages of EAR-2 • Neutron fluence gain • Background suppression • Experimental • Samples, detectors etc. • Analysis • Software, simulations etc. • Beam request • Summary 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  3. The measurement in EAR-1: motivation • Proposal CERN-INTC-2010-042 / INTC-P-280 (21/05/2010) • An (n,f) measurement on 240,242Pu • Both included in the NEA Nuclear Data High Priority Request List • Pu isotopes and minor actinides represent the main long-term contribution to waste radiotoxicity, persisting for ~105 y • 240Pu is produced in significant quantities in conventional reactors • Fission cross-sections of these isotopes are of great significance in the context of nuclear waste management and advanced nuclear systems, especially fast reactors (Generation IV, ADS) • Discrepancies ~10% exist above the fission threshold in 240Pu data • Physics motivation has already been endorsed by the INTC • In addition, recent attempts at n_TOF and elsewhere within the ANDES project were not successful for different reasons ANDES: Accurate Nuclear Data for Nuclear Energy Sustainability,www.andes-nd.eu Fission cross section measurements for 240Pu, 242Pu. Deliverable 1.5 of the ANDES project, DOI: 10.2787/81004 A. Plompen, “Minor Actinides, Major Challenges, the Needs for and Benefits of International Collaboration”, Nucl. Data Sheets (2014), Under publication 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  4. The measurement in EAR-1: detector degradation • An unexpected alteration of some detectors was observed after removal from the chamber • A distinct discoloration of the micromesh is visible in the 4 detectors used with the 240Pu samples • Physical damage to the micromesh is visible under inspection with a microscope • A unique – if inadvertent – ageing test 3cm Courtesy A. Teixeira (CERN) 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  5. The measurement in EAR-1: detector degradation • This leads to a deterioration of the electrical field • Separation of α-particles and fission fragments becomes impossible • A significant part of the data had to be discarded • Even under normal operation, the analysis would be challenging due to the long α-pile-up tail 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  6. The measurement in EAR-1: detector degradation • This leads to a deterioration of the electrical field • Separation of α-particles and fission fragments becomes impossible • A significant part of the data had to be discarded • Even under normal operation, the analysis would be challenging due to the long α-pile-up tail By comparison, 242Pu… 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  7. Two experimental issues identified • Gradual deterioration of detector performance due to high current / high α-activity • Shorter measurement due to higher flux • High α-activity of the 240Pu samples (>6MBq/sample) • Improved signal-to-background due to shorter acquisition window •  Both issues can be addressed in EAR-2 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  8. Neutron fluence gain • Comparing EAR-2 (3cm diameter) with conditions of previous measurement in EAR-1 x7-10 x100-1000 x40-55 x30-45 x10-15 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  9. Samples • Four 240Pu samples manufactured at IRMM • 3 cm diameter PuO2 deposit • 0.25 mm aluminium backing (5cm diameter) • The same samples used in the previous measurement • Reference samples (to be manufactured) • 235U (≈ 70 μg/cm2) • 238U (≈ 340 μg/cm2) • Preferably of 3cm diameter to match the Pu samples • Could add 237Np (≈ 60 μg/cm2) as additional reference 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  10. Sample impurities • Measurement unaffected by impurities above ~1keV and at selected resonances NEA request range 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  11. Sample holders • Samples adapted to internal frame of the chamber • Samples kept in place by mechanical pressure only, “sandwiched” between to thin aluminium rings kept together by two-sided adhesive tape and two thick aluminium rings compatible with the chamber support frame. • Already designed & sample safety file in place 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  12. Experimental setup • Chamber support for EAR-2 • Micromegas detectors • Detector chamber • Preamplifier module • FINAL SETUP (picture from EAR-1) 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  13. Analysis software, simulations • Already developed for previous measurement • Peak-search routine, routine for high-energy data analysis etc.... • Simulations of detector response: • Simulated amplitude spectrum compared with experimental spectrum  240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  14. Beam request • 2x1018 protons on target • 3-5 weeks, depending on beam delivery rate • 240Pu (435 μg/cm2, 4 samples) • Statistical uncertainty • <3% above 10keV • <1% above 300keV • Expected systematic uncertainties ~3-4% • Detector efficiency • Amplitude threshold correction • Selected resonances will also be studied with good statistics 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  15. Summary • An important measurement • …especially in the light of recent not-so-successful attempts within ANDES • 2x1018 protons requested • Statistical uncertainty < 3% above 10keV, <1% above 300 keV • Improved conditions in EAR-2: • Shorter experiment (3-5 weeks) due to higher flux • Avoiding detector degradation • Shorter acquisition window • Stronger background suppression • Cross-check with different reference reactions • 235U(n,f), 238U(n,f), 237Np(n,f) • A useful study also for future measurements • Hardware already available • Procedures for Pu samples already in place • Analysis software already developed • Improvements, adjustments… • Could be ready to go on day 1 • Only foreseeable delay could be sample manufacturing and transport • One PhD student (NTU Athens) starting in September 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  16. Thank you for your attention… 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  17. Extra slides

  18. Beam request • 2x1018 protons on target • Reference sample masses chosen to keep countrate <1 count/μs • 235U (70 μg/cm2) 238U (340 μg/cm2) • 237Np (60 μg/cm2) 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

  19. Beam request • 2x1018 protons on target • 237Np (60 μg/cm2) 240Pu(n,f) measurement @ n_TOF EAR-2 47th INTC Meeting, CERN, June 25, 2014

More Related