Nuclear safety of the fast reactor with <sup>208</sup>Pb-reflector at neutron flash above effective fraction of delayed neutrons

Kulikov, G. G.; Шмелев, А. Н.; Kulikov, E. G.; Апсэ, В. А.

doi:10.1088/1742-6596/1133/1/012037

Cited by 1 publication

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“…It is shown in (Shmelev et al 2011, 2013, Kulikov et al 2014, 2017a, b, c, d, Kulikov 2017) that the use in a fast reactor of a physically thick reflector about 4 m thick made of lead-208 instead of a reflector made of natural lead 0.5 m thick makes it possible to radically slow down the development of a fission chain reaction. This is due to the long return of neutrons to the core from a reflector made of lead-208 due to its heavy atomic weight and low neutron absorption.…”

Section: Introductionmentioning

confidence: 99%

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

Kulikov¹,

Шмелев²,

Апсэ³

et al. 2020

NUCET

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The kinetics of nuclear reactors is determined by the average neutron lifetime. When the inserted reactivity is more than the effective delayed neutron fraction, the reactor kinetics becomes very rapid. It is possible to slow down the fast reactor kinetics by increasing the neutron lifetime. The authors consider the possibility of using the lead isotope, 208Pb, as a neutron reflector with specific properties in a lead-cooled fast reactor. To analyze the emerging effects in a reactor of this type, a point kinetics model was selected, which takes into account neutrons returning from the 208Pb reflector to the reactor core. Such specific properties of 208Pb as the high atomic weight and weak neutron absorption allow neutrons from the reactor core to penetrate deeply into the 208Pb reflector, slow down in it, and have a noticeable probability to return to the reactor core and affect the chain fission reaction. The neutrons coming back from the 208Pb reflector have a long ‘dead-time’, i.e., the sum of times when neutrons leave the reactor core, entering the 208Pb reflector, and then diffuse back into the reactor core. During the ‘dead-time’, these neutrons cannot affect the chain fission reaction. In terms of the delay time, the neutrons returning from the deep layers of the 208Pb reflector are close to the delayed neutrons. Moreover, the number of the neutrons coming back from the 208Pb reflector considerably exceeds the number of the delayed neutrons. As a result, the neutron lifetime formed by the prompt neutron lifetime and the ‘dead-time’ of the neutrons from the 208Pb reflector can be substantially increased. This will lead to a longer reactor acceleration period, which will mitigate the effects of prompt supercriticality. Thus, the use of 208Pb as a neutron reflector can significantly improve the fast reactor nuclear safety.

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Section: Introductionmentioning

confidence: 99%

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

Kulikov¹,

Шмелев²,

Апсэ³

et al. 2020

NUCET

View full text Add to dashboard Cite

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Nuclear safety of the fast reactor with ²⁰⁸Pb-reflector at neutron flash above effective fraction of delayed neutrons

Cited by 1 publication

References 6 publications

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

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Nuclear safety of the fast reactor with 208Pb-reflector at neutron flash above effective fraction of delayed neutrons

Cited by 1 publication

References 6 publications

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

On a significant slowing-down of the kinetics of fast transient processes in a fast reactor

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Nuclear safety of the fast reactor with ²⁰⁸Pb-reflector at neutron flash above effective fraction of delayed neutrons