Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

External Moderation of Reactor Core Neutrons for Optimized Production of Ultra-Cold Neutrons

Graham Medlin
,
Ekaterina Korobkina
* ,
Cole Gresham Teander
ORCID logo ,
Bernard Wehring
,
Eduard Sharapov
,
Ayman I. Hawari
,
Paul Huffman
,
Albert R. Young
ORCID logo ,
Grant Palmquist
,
Matthew Morano
,
Clark Hickman
,
Thomas Rao
ORCID logo ,
Robert Golub
Version 1 : Received: 21 August 2024 / Approved: 22 August 2024 / Online: 22 August 2024 (12:18:23 CEST)

How to cite: Medlin, G.; Korobkina, E.; Teander, C. G.; Wehring, B.; Sharapov, E.; Hawari, A. I.; Huffman, P.; Young, A. R.; Palmquist, G.; Morano, M.; Hickman, C.; Rao, T.; Golub, R. External Moderation of Reactor Core Neutrons for Optimized Production of Ultra-Cold Neutrons. Preprints 2024, 2024081602. https://doi.org/10.20944/preprints202408.1602.v1 Medlin, G.; Korobkina, E.; Teander, C. G.; Wehring, B.; Sharapov, E.; Hawari, A. I.; Huffman, P.; Young, A. R.; Palmquist, G.; Morano, M.; Hickman, C.; Rao, T.; Golub, R. External Moderation of Reactor Core Neutrons for Optimized Production of Ultra-Cold Neutrons. Preprints 2024, 2024081602. https://doi.org/10.20944/preprints202408.1602.v1

Abstract

The Ultra-Cold Neutron (UCN) source being commissioned at North Carolina State Universityâs PULSTAR reactor is uniquely optimized for UCN production in the former graphite-filled thermal column outside of the reactor pool. The source utilizes a remote moderation design which is particularly well suited to the PULSTAR reactor on account of its large thermal and epithermal neutron leakage from the core face. This large non-equilibrium flux from the core is efficiently transported to the UCN source through the specially designed beam port in order to optimize UCN production at any given reactor power. The increased distance to the source from the core also greatly limits the heat load on the cryogenic system. A MCNP model of this system was developed and is in good agreement with gold foil activation measurements using a mock-up setup as well as with the real UCN source heavy water moderator. These results established a firm baseline for estimates of the cold neutron flux available for UCN production and prove that remote moderation in a thermal column port is a valuable option for future designs of cryogenic UCN sources.

Keywords

neutron moderation; ultra-cold neutrons; PULSTAR reactor; neutron activation; epithermal flux; thermal column; MCNP6

Subject

Physical Sciences, Nuclear and High Energy Physics

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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