Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

Makoto Fukuda; N. A.P. Kiran Kumar; Takaaki Koyanagi; Lauren M. Garrison; Lance L. Snead; Yutai Katoh; Akira Hasegawa

doi:10.1016/j.jnucmat.2016.06.051

Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

Makoto Fukuda, N. A.P. Kiran Kumar, Takaaki Koyanagi, Lauren M. Garrison, Lance L. Snead, Yutai Katoh, Akira Hasegawa

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Abstract

Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 10²⁵ n/m² (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10²⁵ n/m² (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10²⁵ n/m² (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.

Original language	English
Pages (from-to)	249-254
Number of pages	6
Journal	Journal of Nuclear Materials
Volume	479
DOIs	https://doi.org/10.1016/j.jnucmat.2016.06.051
State	Published - Oct 1 2016

Funding

This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). This research was supported in part by the Japan/U.S. Cooperation (PHENIX) in Fusion Research and Development , the High Flux Isotope Reactor , which is sponsored by the Office of Basic Energy Sciences , U.S. Department of Energy , and the JSPS KAKENHI Grant Number 15H06030 . Contribution from ORNL was supported by the U.S. Department of Energy, Office of Fusion Energy Sciences , under Contract DE-AC05-00OR22725 with UT-Battelle, LLC. This research was carried out in part at the International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University.

Funders	Funder number
U.S. Department of Energy
Basic Energy Sciences
Fusion Energy Sciences	DE-AC05-00OR22725
Oak Ridge National Laboratory
Japan Society for the Promotion of Science	24246151, 15H06030

Keywords

HFIR
Irradiation hardening
JMTR
Joyo
Microstructure
Neutron irradiation
Neutron spectrum effect
Tungsten

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title = "Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten",

abstract = "Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.",

keywords = "HFIR, Irradiation hardening, JMTR, Joyo, Microstructure, Neutron irradiation, Neutron spectrum effect, Tungsten",

author = "Makoto Fukuda and {Kiran Kumar}, {N. A.P.} and Takaaki Koyanagi and Garrison, {Lauren M.} and Snead, {Lance L.} and Yutai Katoh and Akira Hasegawa",

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AU - Fukuda, Makoto

AU - Kiran Kumar, N. A.P.

AU - Koyanagi, Takaaki

AU - Garrison, Lauren M.

AU - Snead, Lance L.

AU - Katoh, Yutai

AU - Hasegawa, Akira

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N2 - Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.

AB - Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.

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Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

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