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Technical Paper

Decay Radioactivity Induced in Plasma-Facing Materials by Deuterium-Tritium Neutrons

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Pages 99-155 | Published online: 09 May 2017
 

Abstract

Deuterium-tritium (D-T) neutron-induced radioactivity constitutes one of the foremost issues infusion reactor design. Designers have been using radioactivity codes and associated nuclear data libraries for nucleonic designs of fusion reactors. However, in the past, there was hardly any experimental validation of these codes/libraries. An elaborate, experimental program was initiated in 1988 under a U.S. Department of Energy/Japan Atomic Energy Research Institute collaborative program to validate the radioactivity codes/libraries. Measurements of decay gamma spectra from irradiated, high-purity samples of Al, Si, Ti, V, Cr, Mn-Cu alloy, Fe, Co, Ni, Cu, SS316/AISI316, Zn, Zr, Nb, Mo, In, Sn, Ta, W, and Pb, among others, have been carried out under D-T neutron fluences ranging from 1.6 × 1010 to 6.1 × 1013 n/cm2 and cooling times ranging from ∼10 min to ∼3 weeks. As many as 14 neutron energy spectra were covered for a number of materials. The analyses of the isotopic activities of the irradiated materials using the activation cross-section libraries of four leading radioactivity codes, i.e., ACT4/THIDA-2, REAC-3, DKR-ICF, and RACC, have shown large discrepancies among the calculations on one hand and between the calculations and the measurements, on the other. Vanadium, Co, Ni, Zn, Zr, Mo, In, Sn, and W each count the largest number of discrepant isotopic activities. It is strongly recommended to continue additional radioactivity experiments under additional neutron energy spectra and large neutron fluence on one hand and to improve activation cross sections related to the problematic isotopic activities on the other. A unique activation cross-section library and associated radioactivity code are also recommended for the best results. In addition to providing detailed results of the status of predictability of individual isotopic activities using the ACT4, REAC-3, DKR-ICF, and RACC activation cross-section libraries, safety factors cum quality factors characterizing each library are presented and discussed. The related issues of confidence level and associated uncertainty are also highlighted. These considerations are of direct practical importance to reactor designers.

Additional information

Notes on contributors

A. Kumar

Anil Kumar (PhD, University of Bombay, India, 1981) is senior development engineer at the University of California, Los Angeles (UCLA). His current research interests include fusion reactor nucleonics experiments and analysis, technique development for nuclear heating, decay heat measurements, biological dose, fusion diagnostics, safety factor methodology for fusion reactor design parameters, low-activation materials, inertial confinement fusion, and sequential reactions. He has conducted experiments at leading facilities such as the Fusion Neutronics Source (FNS) facility in Japan, the Tokamak Fusion Test Reactor (TFTR) at Princeton University, and LOTUS in Switzerland.

Y. Ikeda

Yujiro Ikeda (PhD, nuclear engineering, Nagoya University, Japan, 1981) is head of the Fusion Neutronics Laboratory in the Department of Reactor Engineering at the Japan Atomic Energy Research Institute (JAERI). He has worked in the areas of fusion neutronics experiments, induced radioactivity experiment and analysis, direct nuclear heating measurements, activation crosssection measurements, and fusion dosimetry.

M. A. Abdou

Mohamed A. Abdou is a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at UCLA and also is the director of fusion technology at UCLA. His research interests include neutronics, thermomechanics, fusion technology, and reactor design and analysis. He served as the U.S. leader of the JAERI/U.S. Department of Energy (U.S. DOE) collaboration on fusion blanket neutronics.

M. Z. Youssef

Mahmoud Z. Youssef (PhD, nuclear engineering, University of Wisconsin, 1980) is a senior research engineer in the Department of Mechanical, Aerospace, and Nuclear Engineering at UCLA. He participated in several conceptual magnetic fusion energy and inertial fusion energy reactor design studies with emphasis on nuclear analysis and blanket/shield design. His research interests are in the areas of blanket/shield design optimization, nuclear data, sensitivity/uncertainty studies, neutronics methods and code development, tritium fuel cycle, radioactivity and safety aspects of fusion, integral experiments, neutronics testing, and research and development for fusion reactors, particularly the International Thermonuclear Experimental Reactor (ITER).

C. Konno

Chikara Konno (MS, physics, Kyoto University, Japan, 1985) is a research scientist in the Department of Reactor Engineering at JAERI. He has worked in the areas of fusion neutronics experiments, cross-section measurements, and neutron spectrum measurements using a proton-recoil counter.

K. Kosako

Kazuaki Kosako (BE, atomic engineering, Tokai University, Japan, 1984) has worked at Sumitomo Atomic Energy Industries since 1994. He worked in the Department of Reactor Engineering at JAERI from 1984 to 1992 where he was involved mainly in fusion neutronics. He is currently interested in the area of radiation damage of materials.

Y. Oyama

Yukio Oyama (BS, physics, 1975; MS, nuclear physics, 1977; and Dr. Eng., 1989, Osaka University, Japan) is a principal scientist at JAERI. He has worked in the area of fusion neutronics experiments since 1978. He is currently involved in intense and high-energy neutron source projects.

T. Nakamura

Tomoo Nakamura (BS, physics, Kyoto University, Japan, 1957) is currently director of the Public Acceptance Database Center, Research Organization for Information Science and Technology. His research background includes experimental reactor physics on fast breeder reactors and nuclear technology on fusion reactor blankets. He served as the former Japanese leader of the JAERI/U.S. DOE collaboration on fusion blanket neutronics.

H. Maekawa

Hiroshi Maekawa (BE, 1965; MS, 1967; and Dr. Eng., 1970, nuclear engineering, Tokyo Institute of Technology, Japan) is the deputy director of the Department of Reactor Engineering and the head of the Intense Neutron Source Laboratory at JAERI. He has worked on fusion neutronics for more than 20 years, and he planned and constructed the FNS facility. He served as the Japanese leader of the JAERI/U.S. DOE collaboration on fusion blanket neutronics. His recent research has focused on International Fusion Materials Irradiation Facility conceptual design activities.

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