Abstract
In situ neutron radiography experiments can provide information about diffusive processes and the kinetics of chemical reactions. The paper discusses requirements for such investigations. As examples of the zirconium alloy Zircaloy-4, the hydrogen diffusion, the hydrogen uptake during high-temperature oxidation in steam, and the reaction in nitrogen/steam and air/steam atmospheres, results of in situ neutron radiography investigations are reviewed, and their benefit is discussed.
Highlights
Hydrogen in metals is an evergreen in material research
In situ neutron radiography investigations of hydrogen-related processes occurring at temperatures between 250 and 1400 ◦C combine the requirements of laboratory reaction furnaces:
In situ measurements of the hydrogen diffusion into a solid cylinder made of the zirconium alloy Zircaloy-4 (Zry-4) were described, followed by investigations of the hydrogen uptake of cladding tube segments made of Zry-4 during steam oxidation and during oxidation in various nitrogen-containing atmospheres
Summary
Hydrogen in metals is an evergreen in material research. Even small amounts of hydrogen absorbed in a material can degrade the mechanical properties significantly. Hydrogen pickup degrades the mechanical properties of zirconium alloys used for nuclear fuel claddings too. Hydrogen is absorbed by water corrosion during operation or by high-temperature steam oxidation under accident conditions. The hydrogen concentration in spent fuel claddings has values between 50 and 80 wt.ppm depending on the chemical composition and the production paths of the tubes [1]. The solubility of hydrogen in Zircaloy-4 (Zr 1.3% Sn) at a reactor operation temperature of 300 ◦C is about 70 wt.ppm [2]. Most of the hydrides become dissolved again (hydrogen solubility at 400 ◦C is about 200 wt.ppm). The decrease in decay heat results in a very slow cool-down of the spent fuel rods, and with it to a reprecipitation of the hydrides. Diffusion, and redistribution in nuclear fuel claddings made of zirconium alloys Hydrogen distribution in the cladding around the burst opening of rod #04 of the QUENNNeCeuHutrt-orLon3ntiemismta(gathigneignpgiossiasitipaoonpwsocewornfeutralfiutnolinotgol foholyrfdtorhroegthiennevaienrsevtimegsaattriikgoeandtioowfnihthoyfdbrhluoyegdecronologinre)nz. irincozniirucmonium aalllooyyssbbeeccaauuseseththe emmacarcorsocsocpoipc itcotaoltanlenuetruotnrocnrocsrsossesctsieocntioofnhoyfdhriyddersidcaens bcaenubpetoup25t0o0%2500% ccoommppNaarereeuddtrwowintihtihmoonanegeionofgftthihseeattypypopiwcicaael lrzfziurilrccotoonnoiuilumfmoraaltllholoeyysisnavapeppspltilieigdeadtaisaosnclcaoldaf ddhdiynidgnrgmomgaetanetreiranila.zlS.ireScveo-vneiuraml eagrlralool uygpsrosbuewpcosaruwlsdoewrtlhiddewemiadpaecparlpoiespdcloienpdeiucntterouottnarloinmeiaumgtiarnoggninfcgorrofossrsuscsuehcihtnioivnnevsoetfisgthiagytadiotrinoidsnesdsudcruairnnignbgethtuhepelatlasots2ty5e0a0r%s yc[e4oa–mr1sp4[]a4.r–He1d4o]w.wHeitvohewroe,nvoeenrol,yof ntfhelywefteiywnpviiecnsavtleigzstaiirtgciaootnniosiunwsmweraeelrlepoypersefroafoprmrpmleiededdiinansssiicttluua..dOOdffittneegnn,,mssuauctchehriinianls.istSuiteuveinra-l igvnrevoseutsitpgigasatwitoioonnrslsdaarwreeivdveeerrayyphhpeelllippedffuunll tetoouuturnnoddneerirmssttaaangndidntghthefeodrdysynunacmahmiciincovfoepfshptiyhgsyaictsoiiocconhcsehmdeiumcraiilncpagrlotphcreeosclsaeessst.seyse.ars [4–14T]h.iHs poawpeevr edri,scounslsyesfethwe irneqvueisrteigmaetniotsnfsowr ienresitpuenrfeourtmroendraindiosigtrua.pOhyfteinnv, essuticghatiinonssitu inavnedstsighaotwiosntshaerbeevneerfiytshoelfpsfuuclhtoinuvnedsteigrsattaionndstihneedxyamnapmleisc ooff tphheyhsyicdorcohgeemn iacbasloprrpoticoens,ses. diffusion, and redistribution in nuclear fuel claddings made of zirconium alloys
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