1. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 G. Parzych (UwB), A.N. Lihachev (JINR), V.R. Andrianov (JINR), P. Sibczynski (US), J. Žemlička (CTU), Z. Mrázová (CTU), O.Šimek (CTU), J. Sieracki (UZG)

2. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 Scheme of pulse reactor IBR-2

3. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 The mechanism of delayed neutron generation

4. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 Motivations of the measurements of the yields of the delayed neutrons for transuranium elements Well known the fundamental role of delayed neutrons in the safety operation and time-dependant behavior of nuclear reactors. The delayed neutron data such as the absolute yield of DN, relative abundances of DN, half-lives of their precursors, and energy spectra of DN are important for kinetics and safety operations of nuclear reactors. In spite of great efforts in investigation of delayed neutron physics the fundamental delayed neutron characteristics for most common fissionable reactor isotopes are little-studied.

5. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 The experimental installation “Isomer-M” Fig. 1. The scheme of the “Isomer-M” installation: 1 – IBR-2 reactor core and the moderator of neutrons, 2, 3 – collimators, 4 – bent mirror guide, 5 – Cd-Ping-Pong, 6 – chopper, 7 – neutron detector assembly and combined shield, 8 – 3 He-counters, 9 – Cd-shield, 10 – sample.

6. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 The method of experiment and measurement The number of fission events, which happened in a sample for all time of measurement The number of prompt neutrons registered by the detector The number of delayed neutrons registered by the detector

7. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 Calibration measurement of 235 U sample Fig. 2. The time-of-flight spectrum of 235 U measured at the “Isomer-M” installation: а – effect + background ( 235 U), b – background ( 235 U+Cd-shield).

8. Fig. 3. The time-of-flight spectrum of 237 Np measured at the “Isomer-M” installation: а – effect + background ( 237 Np), b – background ( 237 Np+Cd-shield). Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Calibration measurement of 237 Np sample Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

9. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 Detector Count components Count numbers without Cd filterwith Cd filter Thermal peak region (210 - 730 channels) N s + N bgr N α n N f n N p exp 0.965 ± 0.001 0.0410 ± 0.0001 0.0058 ± 0.0005 4.67 ± 0.003 0.0542 ± 0.0002 0.410 ± 0.0001 0.0058 ± 0.0005 0.1010 ± 0.0005 Delayed-neutron region (1200 - 4096 channels) N sc + N bgr N α n N f n N d exp 0.2220 ± 0.0004 0.2960 ± 0.0006 0.028 ± 0.002 0.556 ± 0.001 0.2183 ± 0.0004 0.2960 ± 0.0006 0.028 ± 0.002 0.542 ± 0.001

10. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007 From calibration measurements with 237 Np, mean value of is The final result is ν d = 0.0110 ± 0.0009 Known constant ν p is And so, from

11. Special thanks for our supervisors, whose patiently answered for all kinds of our questions. For Mr. Zawodny and Mr. Chmielowski for help to survive in this beautiful country. And, of course, for direction of all JINR sections for possibility to see one of the biggest laboratories in the world. Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

12. Thank You for attention Grzegorz Parzych, Jaroslaw Sieracki, Pawel Sibczynski