Scoping corrosion tests on candidate waste package basket materials for the Yucca Mountain Project

Abstract

S.E. Summers March 1998This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. DISCLAIMERThis document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.This report has been reproduced directly from the best available copy. i Abstract A scoping corrosion test was performed on candidate waste package basket materials. The corrosion medium was a pH-buffered solution of chemical species expected to be produced by radiolysis. The test was conducted at 90°C for 96 hours. Samples included aluminum-, copper-, stainless steel-and zirconium-based metallic materials and several ceramics, incorporating neutron-absorbing elements. Sample weight losses and solution chemical changes were measured. Both corrosion of the host materials and dissolution of the neutron-absorbing elements were studied. The ceramics and the zirconium-based materials underwent only minor corrosion. The stainless steel-based materials performed well except for a welded sample. The aluminum-and copper-based materials exhibited the highest corrosion rates. Boron dissolution depends on its chemical form. Boron oxide and many metal borides dissolve readily in acidic solutions while high-chromium borides and boron carbide, though thermodynamically unstable, exhibit little dissolution in short times. The results of solution chemical analyses were consistent with this. Gadolinium did not dissolve significantly from monazite, and hafnium showed little dissolution from a variety of host materials, in keeping with its low solubility.

Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

“…It is possible that the corrosion rate of the secondary phase has a different corrosion rate dependence on environment than the base material. The corrosion rates obtained by LPR for Alloy 22 are about two orders of magnitude higher than the rates (slightly different environments) obtained by exposure testing for Alloy 22 (see Reference 19,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. One explanation for the discrepancies between the two measurement methods might be the higher rates for a material immediately following immersion.…”

“…Initial corrosion testing performed by Lawrence Livermore National Laboratory on a borated stainless steel gave favorable results. 9 However, the corrosion rates measured on the Neutronit material at the Long-term Corrosion Test Facility located at Lawrence Livermore National Laboratory were higher than expected. 10,11 The BSC materials staff then decided that the Ni-Cr-Mo-Gd alloy under development at INL was a promising replacement.…”

Microstructure and Fracture Property of 1A Grade Duplex Stainless Steel with the Addition of Gadolinium

“…Gd의 중 성자 흡수 단면적은 255,500 barn (barn = 10 −24 cm 2 )으로서 B의 중성자 흡수단면적 3,840 barn에 비해 월등히 높다 [3][4][5][6][7][8][9][10][11]. 두 번째, B는 기존의 중성자 차폐 재료 주요합금원소인 크롬(Chromium, Cr)과 반응하여 크롬붕화물(Chromium borides)이란 화합물을 만들게 되며, 이는 핵연료 저장수조에서 내부식성과 열간 가공성 특성을 크게 떨어뜨리지만, Gd는…”

“…Fe나 Cr에 합금원소로 첨가되면 열간 가공성 및 열간 산화 저항성을 증가시키는 것으로 보고되고 있다 [11]. 세 번째, B 는 Gd로 유지할 수 있기 때문에 중성자 차 폐 재료로서 신뢰성이 B보다 뛰어나다 [3].…”

“…세 번째, B 는 Gd로 유지할 수 있기 때문에 중성자 차 폐 재료로서 신뢰성이 B보다 뛰어나다 [3]. 이러한 희토류 원소 Gd의 장점으로부터 최근에는 중성자 차폐 재료로서, Gd를 첨가한 합금에 대한 관심도가 증가하고 있으며 최근에는 우수한 내부식성을 가지는 스테인리스 강종 과 Gd의 연구가 진행되고 있지만, 아직까지 스테인레스 강의 주요원소와 Gd의 반응, 미세조직, 기계적 특성 등에 대한 연 구가 부족한 실정이다 [9][10][11][12]. 본 연구에서는 우수한 기계적 특성과 내 부식성을 바탕으 로 원자력설비에 각광받고 있는 듀플렉스 스테인리스 강 (Duplex Stainless Steel, DSS)에 Gd를 합금화하여 중성자 차폐 재료로서의 가능성을 연구하였다.…”