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Research Papers

Combined Effect of Irradiation, Temperature, and Water Coolant Flow on Corrosion of Zr-, Ni–Cr-, and Fe–Cr-Based Alloys

[+] Author and Article Information
O. S. Bakai

NSC KIPT of NAS of Ukraine,
Kharkiv 61108, Ukraine
e-mail: bakai@kipt.kharkov.ua

V. M. Boriskin

NSC KIPT of NAS of Ukraine,
Kharkiv 61108, Ukraine
e-mail: boriskin@kipt.kharkov.ua

A. M. Dovbnya

NSC KIPT of NAS of Ukraine,
Kharkiv 61108, Ukraine
e-mail: dovbnya@kipt.kharkov.ua

S. V. Dyuldya

NSC KIPT of NAS of Ukraine,
Kharkiv 61108, Ukraine
e-mail: sdul@kipt.kharkov.ua

D. A. Guzonas

CNL, Chalk River Laboratories,
Chalk River, ON K0J 1J0, Canada
e-mail: david.guzonas@cnl.ca

1Corresponding author.

Manuscript received May 8, 2015; final manuscript received July 16, 2015; published online February 29, 2016. Assoc. Editor: Thomas Schulenberg.

ASME J of Nuclear Rad Sci 2(2), 021007 (Feb 29, 2016) (11 pages) Paper No: NERS-15-1077; doi: 10.1115/1.4031126 History: Received May 08, 2015; Accepted July 23, 2015

Investigation of the role of irradiation on the corrosion resistance of structural alloys is of vital importance for selection of supercritical water-cooled reactor (SCWR) materials. Gamma heating under SCWR conditions, which induces enhancement of radiolysis and corrosion kinetics at interfaces, can be efficiently simulated by electron beam irradiation over a wide range of deposited dose and temperature. The NSC KIPT-sited Canada–Ukraine Electron Irradiation Test Facility (CU-EITF) still remains the only operating facility capable of in situ irradiation of specimens in a supercritical water (SCW) natural circulation loop. This paper reports the results of postirradiation studies of Zr–1%Nb and Ni–Cr Inconel 690/52MSS alloys after a ~500-h-long exposure in the CU-EITF in the near-critical (23.5 MPa/360–385°C) regime. Results of scanning electron microscopy (SEM) studies of the sample microstructure are presented along with those of the electron-irradiated loop piping, SS X18H10T. The results of corrosion tests under electron-irradiation are correlated to the calculated three-dimensional (3D) fields of absorbed dose and temperature and to the reference data obtained in-pile for topical materials. The paper also discusses the prospects for the use of the CU-EITF facility within a cooperative SCWR program and presents an outlook of the facility development.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

CU-EITF circulation loop mounted on the NSC KIPT LPE-10 electron linac shelter (a) general (b) and top/front (c/d) sectional views of the coupons holding four-pipe IC before (b) and after (e) the irradiation session. Scanning electron-beam glass plate monitor images behind IC (f) and in front of it (g) outline the electron fluence spatial distribution over the irradiated samples, as shown in (g) for the IC tube #I internal cassette filled with Inconel coupons (h).

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Fig. 2

Specific weight gains δm/S of as-irradiated Zr–1%Nb (a) and Ni–Cr Alloy 690/In52MSS (b) coupons. Right axes indicate tentative estimates [4] of the corrosion layer thickness H using δm/S-to-H scaling factors of [5] (Zr–1%Nb, a) and [6] (Alloy 690, b).

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Fig. 3

Photo of the as-irradiated Alloy 690/In52MSS coupon N5-2 (a) and the MC/FEM calculated spatial maps of the specific electron-beam deposited energy Edep (b) and temperature T (c) of this coupon.

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Fig. 4

Scheme of the Ni–Cr Inconel coupon N5-2 cutting for the postirradiation microstructure analysis of the base Alloy 690 weld joint with In52MSS.

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Fig. 5

Optical metallographic (a) and backscattered electron (b) images and chemistry (c) of the Inconel base-to-weld sectional area of the specimen N5-2/I-2.

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Fig. 6

Optical (a, d) and SEM (b, c, e, f) micrographs of the cross section (a, b, d, e) and surface (c, f) of the Inconel specimens N5-2/I-1 (top row) and N5-2/I-2 (bottom row) after 500-h-long exposure to 23.5  MPa/375°C water under electron-irradiation to 11-keV/atom energy deposition.

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Fig. 7

Light microscopy images of the N5-2/I-1 Alloy 690 specimen (top row) and the specimen N5-2/I-2 in the area of welded alloy In52MSS (bottom row) at different magnifications.

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Fig. 8

SEM images of the surfaces of oxidized Alloy 690 (a) and In52MSS (b) and the oxide film chemistry obtained by EDS (c) in the indicated areas, which were selected to be free of large-scale particles.

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Fig. 9

SEM micrographs and the spot EDS-derived chemistry of the oxide particles on the corrosion surface in the areas of base Alloy 690 (a, b) and the weld joint with In52MSS (c, d).

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Fig. 10

Cross section SEM images of the oxide film morphology (top) and the location-resolved EDS chemistry (bottom) in the base (a) and weld (b, c) areas of the specimen N5-2/I-2.

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Fig. 11

STEM EDS line scans and cross section composition profiles of the slices scanned from the front (a) and rear (b) to electron-irradiation surfaces of the Alloy 690 specimen N5-2/I-1. Higher spatial resolution data are shown in (c) for the same material.

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Fig. 12

SEM micrographs before (a) and after (b) 60 min of 100  nm/minAr+ ion gun sputter etching of the Alloy 690/In52MSS weld area of the specimen N5-2/I-2. The correspondent AES microprobe composition profile is shown in (d). The chemistry of the indicated area of the source (a) and sputter-etched (b) material is shown in (e) together with that of the low-sputtered grain (c) of the surface agglomerate of oxide particles.

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Fig. 13

Drawing and photos of the SS 12X18H10T samples cut out from the IC tube #II.

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Fig. 14

MC-/FEM-calculated distribution diagram of the electron-beam specific energy deposition and temperature in the 100-μm-thick interface layer of the bottom sample IIB/1/0 with coolant.

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Fig. 15

Light microscopy images of the SS 12X18H10T IIB/1/0 highly irradiated sample metallographic section. The electron-irradiation direction is indicated with arrows.

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Fig. 16

Azimuthal distribution diagrams of the microhardness of unirradiated IIB/4 (a) and electron-irradiated IIB/1/0 (b) samples of SS 12X18H10T after 500-h-long 23.5  MPa/370°C (a) and 400–455°C (b) exposure to water flow under electron-irradiation.

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Fig. 17

TEM image with cross section line scans indicated and the EDS atomic composition profiles of the closely coupled sectors of the SS 12X18H10T sample IIB/I/0 internal surface.

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Fig. 18

Top-view planar (top row) and cross section (bottom row) SEM images of the SS 12X18H10T specimen corrosion surface (a–c) and layer (d, e) at different magnifications. The EDS X-ray spectra measured at locations A (oxides) and B (bulk) are shown in (e).

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Fig. 19

FIB/SEM images and the EDS-derived chemistry of the corrosion surface (a) and cross section (b) in the vicinity of the FIB-produced template for STEM.

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Fig. 20

STEM EDS maps of the FIB-prepared specimen (shown, in secondary electrons, in the top-left image; see also Fig. 19) of the austenitic SS 12X18H10T after the ≈500-h-long exposure to 23.5  MPa/≈430°C SCW (see Fig. 14) under electron-irradiation.

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Fig. 21

Exposure time dependence of the Cr content in the circulation loop water coolant under electron-irradiation.

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