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Measurement of Delayed-Neutron Yield from 237 Np Fission Induced by Thermal Neutrons

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Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

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)

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

Scheme of pulse reactor IBR-2

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

The mechanism of delayed neutron generation

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

Motivations of the measurements of the yields ofthe 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.

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

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 – 3He-counters, 9 – Cd-shield, 10 – sample.

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

The method of experiment and measurementThe 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

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

Calibration measurement of235U sampleFig. 2 . The time-of-flight spectrum of 235U measured at the “Isomer-M” installation: а – effect + background (235U), b – background (235U+Cd-shield).

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

Calibration measurement of237Np sampleFig. 3 . The time-of-flight spectrum of 237Np measured at the “Isomer-M” installation: а – effect + background (237Np), b – background (237Np+Cd-shield).

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

From calibration measurements with 237Np,mean value of isKnown constant νp is

And so, from

The final result is

νd = 0.0110 ±0.0009

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Measurement of Delayed-Neutron Yieldfrom 237Np Fission Induced by Thermal Neutrons

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.

Frank Laboratory of Neutron Physics - Dubna 24.06.2007-7.07.2007

Grzegorz Parzych, Jaroslaw Sieracki, Pawel Sibczynski

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