ML23214A034

RIC 2023 Regulatory Information Conference (RIC) Project Advanced Characterization of ATF Cladding for Understanding Their Degradation Under Short-time Temperature Excursions and Implications in Dry Storage

ML23214A034
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Issue date:	08/02/2023
From:	-Neednewvalue, Rojas J Office of Nuclear Regulatory Research
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U.S. Nuclear Regulatory Commissions 35th Annual Regulatory Information Conference Project:

Advanced characterization of ATF cladding for understanding their degradation under short-time temperature excursions and implications in dry storage PI: Jessika Rojas, Associate Professor Co-PI: Carlos E. Castano (Assistant professor)

Braden Goddard (Assistant Professor)

Virginia Commonwealth University Reza Mohammadi (Associate Professor)

Acknowledgements TEAM MEMBERS This work is being supported by NRC University Dr. Reza Dr. Carlos E.

Nuclear Leadership Program Mohammadi Castano MNE MNE Industry and University collaborators:

Nanomaterials Characterization Core Facility at VCU Dr. Braden Dr. Jessika Goddard Rojas Ge Global Research (Andrew Hoffman), MNE MNE Rajnikant Umretiya Victoria Davis Caleb King Tristan Norrgard Christian England James Cahill Ph.D student, MNE UG. Res. Asst. MNE UG. Res. Asst. MNE UG. Res. Asst. MNE Ph.D. student MNE 2

Moving on to the topic of todays talk o Fukushima nuclear disaster radioactive release Earthquake Tsunami https://world-nuclear.org/

Zr + 2 H2O ZrO2 + 2 H2 Hydrogen explosion Exothermic reaction and release of hydrogen Zircaloy How to improve the safety and reconstruct the publics confidence in nuclear power?

3 The Fukushima Daiichi Accident Report by the Director General (2015)

Accident Tolerant Fuel Technologies ATF Claddings Improved Fuel Properties Improved Clad Reaction Kinetics with Steam o Lower operating temperatures Surface modification Replacement o Clad internal oxidation o Heat of Oxidation o Fuel relocation o Oxidation rate o Fuel melting Concept 1 Concept 2 o Hydrogen bubble and Zr alloys explosion o Hydrogen embrittlement of the Surface Alloys coating clad Enhanced Retention of Fission Products Improved Cladding FeCrAl APMT Properties o Gaseous fission products o Solid/liquid fission products Cr C26M o Clad fracture o Geometric stability Mo 310SS o Thermal shock resistance o Melting of the cladding SiC Arevas Enhanced Accident Tolerant Fuel Program (2017) 4

How do these cladding concepts evolve at high temperatures?

The following reactor parameters affect safety margins:

Cladding

• Reactor power

• Reactor coolant flow rate Fuel

• Reactor coolant inlet temperature Pellet

• Reactor coolant pressure How does the material evolves at high Heat temperatures and how quick?

Coolant: flux water After CHF Zr-4 PVD Cold Spray Surface characterization before and after CHF testing 5

Umretiya, R.V., Elward, B., Lee, D., Anderson, M., Rebak, R.B. and Rojas, J.V., 2020. J. Nuc. Mat., 541, p.152420.

Project Goals The main goal of this project is to investigate the oxidation and degradation of accident-tolerant fuel (ATF) claddings, both Cr-coated Zircaloy and FeCrAl alloys, under short time temperature excursions and quenching performance that will reveal their behavior and evolution during accident scenarios.

This project also investigates the mechanical properties of these materials relevant to dry storage conditions.

Implementing (ATF) cladding in light water reactors (LWRs) and advanced reactor designs aims to improve fuel reliability and safety during design-basis and beyond-design-basis accident scenarios.

Implementation of non-destructive examination techniques for quality control of coated Zircaloy.

Zr-4 subjected to rapid heating and cooled in air or water 6

Research Objectives Aim 1: ATF cladding selection, sample manufacturing, and characterization:

- Use various advanced materials characterization techniques to study surface characteristics microstructure, materials surface chemistry, mechanical properties Aim 2: Short-time temperature excursions and quenching:

- We will investigate cylindrical specimens of both pristine and aged specimens

- The aging process: samples exposed to BWR and PWR using a hydrothermal autoclave

- The specimens will be subjected to high temperature heating profiles to peak temperatures ~1400 C Aim 3: Simulated dry-storage conditions and ductility studies:

- The simulated dry storage conditions for the specimens: Interim Staff Guidance 11, Rev. Spent Fuel Project Office Aim 4-5: Development of X-ray fluorescence spectroscopy ATF cladding non-destructive examination:

- Design and construction of XRF setup for continuous analysis of cylindrical specimens The versatility of X-ray fluorescence spectroscopy will allow for simultaneous elemental composition and coating thickness analysis 7

Materials Selection and characterization Sample mounted on a powder specimen holder filled with Phenom ProX SEM polyvinylpyrrolidone

• Scanning Electron Microscope (SEM) used to image sample surfaces (PVP) powder for

• Equipped with energy dispersive XRD analysis spectroscopy (EDS)

PANalytical XPert Pro Diffractometer To obtain crystalline structure of materials PHI VersaProbe III X-ray Photoelectron Spectrometer To study chemistry of sample surface Figure 1. ATF cladding samples selected for materials characterization. In the photograph, A)

FeCrAl alloy C26M, B) Zircaloy-4, C) Cr-coated Zr-4 prepared by PVD, D) Cr-coated Zr-4 prepared by JEOL JEM-F200 TEM

• Transmission electron microscope for 8 Cold-spray nanoscale analysis

Coating deposition: Cr-Zr4 a) b)

Cr-coating Cr-coating (211)

Zircaloy-4 Zircaloy-4 (110)

(200) (220)

(101)

Cross sectional SEM view for Cr-coated Ziraloy-4: a) AR-Zr4-Cr- (103)

CS and b) AR-Zr4-Cr-PVD (112)

(002) (211) (114)

(102) (110) (004) o The XRD patterns of the substrate Zr-4 and Cr-coated Zr-4 (PVD and (202)

Cold spray) confirm the hexagonal closed packed crystal structure of substrate and the presence of Cr layer with cubic crystal structure.

o SEM micrographs evidence a Cr coating thickness of AR-Zr4-Cr-CS and AR-Zr4-Cr-PVD of 29.0+/-2.0 µm and 6.48+/-1.41 µm, respectively.

X-ray diffraction patterns of Zircaloy-4 (AR-Zr4), AR-Zr4-Cr-PVD and AR-Zr4-Cr-CS.

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FeCrAl Alloys: another alternative SEM micrograph of etched FeCrAl APMT SEM micrograph of etched FeCrAl C26M Average grain size 8.35 +/- 2.03 µm Average grain size 46.04 +/- 19.50 µm

%wt. Cr Al Mo Y Si Fe C26M 11.894 5.263 1.978 0.027 0.279 Balance APMT 21.146 2.701 3.059 0.127 0.886 Balance 10

Design of Temperature Excursions and Quenching device Pyrometer with data acquisition Induction coil software for where samples measuring are centered temperature for testing during testing Flowmeter for a 7.5 kW high- measuring frequency (100- argon input 400 kHz) flow SolidWorks model showing the inputs for steam, induction Submersible water, and argon into the system.

furnace Pump for Water, Impact- Stainless steel Resistant/Open- rod Stainless steel Air, 120V AC Bubbler system Set screws as steam Water container for generator quenching process Drill bushing Temperature excursion and quenching setup. Sample rod 11

Example of heat excursion and water quenching Video of thermal shock event Date acquisition software Photograph of thermal Shock at 30% recording temperature of the at 30% power of the induction power of the induction furnace sample from the pyrometer furnace 12

Preliminary results with Zr-4 and Zr-702 Temperature profiles of Zr-4 in dry air 1% 5% 10% 16%

5% 10% 15% 20%

• The system can achieve a maximum The top images show sample rods heated and cooled in air. The heating rate of 100 ºC/s bottom images show sample rods heated with quenching.

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Preliminary results with Zr-4 and Zr-702 ZrO2 ZrO2 ZrO2

-Zr(O)

-Zr(O) ZrN Prior Prior -Zr(O)

Prior SEM micrographs of Zr-702 after rapid to various temperatures and water quenching a) 800 ºC b) 865 ºC c) 1200 ºC.

Average thickness of the oxide layer is 3.4 +/- 0.4 µm, 8.8 +/- 1.1 µm, 21.9 +/- 8.3 µm, respectively 14

Progress on X-ray fluorescence spectroscopy for ATF Quality control IXRi IXRs layer IXRs subs X-ray beam spot Fig. 1. Diagram of X-ray tube from C.

size 3 mm Turner, et al., Mobile Miniature X-ray Source X-ray fluorescence working principle for elemental analysis Thickness measurements down to nanometer scale; ability to evidence thickness variations and lack of coating. 15

MCNP simulation of the X-ray source for benchmarking with the experimental results Effect of W collimator and 1 µm graphene window on the Transmission spectra produced by the Ag target anode with spectrum generated by an 8 and 15 keV electron beam an incident electron beam energy of 8, 15, 20, and 50 keV

• The future work include validating the X-ray simulated beam with the emission spectra from several substrates.

• Defects will be manufactured on the surface of the Cr-coated Zr-4 specimens and XRF spectra at 16 various length steps will be collected to determine the resolution of the device for quality control

Concluding remarks:

Accident tolerant fuel cladding materials have been acquired and characterized. FeCrAl alloys and Cr-coated Zircaloy-4, produced by PVD and cold spray, are the focus of our work.

A system for heat excursion and quenching procedures has been designed and built. The system relies the induction mechanism to heat the metallic samples at a high rate. The device includes several components that includes gas, steam, and water inlets.

Preliminary tests have been conducted with Zr-4 and Zr-702 to optimize the device. The results obtained for these specimens aligned with those reported in the literature on high temperature oxidation of Zircaloys in various environments.

Monte Carlo N-Particle simulations have been completed to generate an X-ray spectrum of our handheld device. The results of the modeling implemented to achieve the output spectrum of the XRF device are supported by the presence of predicted characteristic X-rays and X-ray attenuation.

Future work:

Design of experiments for FeCrAl and Cr-coated Zr cladding for high temperature excursions and quenching.

The output spectra obtained for the XRF device will be used as the source definition for future models. The spectra will be used to produce fluorescence in various material specimens.

Dry storage simulated environments, temperature profiles and hoop stresses, are being determined. A loading mechanism has been designed and is being manufactured.

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Thank You!!

Questions??

Contact Information:

Jessika Rojas, Associate Professor Virginia Commonwealth University jvrojas@vcu.edu 18