Autoclave Corrosion of Zircaloy-4 Cladding Samples in LiOH Solutions

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Armin Hermann

former member of Laboratory for Materials Behavior, retired

Autoclave Corrosion of Zircaloy-4 Cladding Samples in LiOH Solutions

Nuclear Energy and Safety Research Department

Laboratory of Nuclear Materials

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Autoclave Corrosion of Zircaloy-4 Cladding Samples in LiOH Solutions

Paul Scherrer Institut 5232 Villigen PSI Switzerland

Tel. +41 (0)56 310 21 11 Fax +41 (0)56 310 21 99 www.psi.ch

Nuclear Energy and Safety Research Department Laboratory of Nuclear Materials

Armin Hermann

former member of Laboratory for Materials Behavior, retired

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ABSTRACT

In reactor operation pH of the cooling water is adjusted by addition of alkaline hydroxides, and LiOH has been found to be the most suitable one. The addition of LiOH above a certain concentration level (depending on temperature) increases the corrosion rate of zirconium and its alloys. Hydrogen pick-up by the metal is also increased, and this effect is used to produce hydrided specimens for different investigations using the corrosion reaction. At the Paul Scherrer Institute several projects were accomplished to investigate the influence of hydrogen in Zircaloy cladding on its mechanical properties. In order to produce hydrided specimens for comparison and for adjusting new equipment, Zircaloy tubing samples were hydrogen charged by autoclave corrosion in lithiated water. Results of the corrosion experiments are outlined in this publication. Because of the great variety of possible experimental parameters these results are still of interest for the scientific community.

Autoclave corrosion was accomplished in 0.2 M or 0.5 M LiOH solution at a constant temperature of 340 ° C and a pressure of 160 bar. The corrosion rate increases from 84 mg/(dm²·d) in 0.2 M LiOH to 153 mg/(dm²·d) in 0.5 M LiOH. The hydrogen pick-up fraction in 0.5 M LiOH amounts to 80%. In 0.5 M LiOH Zircaloy tubing samples can be charged with ~ 500 ppm hydrogen in about 40 hours.

In the corrosion experiments described in this report a homogeneous distribution of hydrides should be expected (except very high hydride concentrations) because no temperature gradient exists through the tubing wall. Hydrogen stringers are homogeneously distributed with circumferential orientation (stress-relieved tubing samples).

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Im Reaktorbetrieb wird der pH des Kühlwassers durch Zusatz von Alkalihydroxiden eingestellt, und LiOH wurde als am meisten geeignet befunden. Der Zusatz von LiOH über ein bestimmtes Konzentrationsniveau (abhängig von der Temperatur) hinaus erhöht allerdings die Korrosionsrate von Zirconium und dessen Legierungen. Die Wasserstoffaufnahme durch das Metall wird ebenfalls erhöht, und dieser Effekt wird genutzt, um hydrierte Proben für verschiedene Untersuchungen mit Hilfe der Korrosionsreaktion herzustellen. Am Paul Scherrer Institut wurden und werden verschiedene Forschungsprojekte durchgeführt mit dem Ziel, den Einfluss von Wasserstoff in Zircaloy-Hüllrohren auf deren mechanische Eigenschaften zu untersuchen. Zircaloy-Hüllrohrproben wurden durch Korrosion im Autoklaven in mit LiOH versetztem Wasser mit Wasserstoff beladen, um hydrierte Proben für Vergleichszwecke und für Tests an Versuchsapparaturen herzustellen. Die Ergebnisse der Korrosionsexperimente werden in dieser Publikation dargestellt.

Wegen der Vielfalt möglicher experimenteller Parameter sind diese Ergebnisse immer noch von Interesse für die Gemeinschaft der Wissenschaftler.

Die Korrosion im Autoklaven wurde in 0.2 m oder in 0.5 m LiOH bei konstanter Temperatur von 340 ° C und einem Druck von 160 bar durchgeführt. Die Korrosionsgeschwindigkeit erhöht sich von 84 mg/(dm²·d) in 0.2 m LiOH auf 153 mg/(dm²·d) in 0.5 m LiOH. Der Aufnahmeanteil des bei der Korrosion in 0.5 m LiOH freigesetzten Wasserstoffs beträgt 80%. In 0.5 m LiOH können Zircaloy- Hüllrohrproben in ca. 40 Stunden mit ~ 500 ppm Wasserstoff beladen werden.

Bei den Korrosionsexperimenten, die in diesem Bericht beschrieben werden, kann eine homogene Hydridverteilung erwartet werden (ausgenommen sehr hohe Hydridkonzentrationen), denn es gibt keinen Temperaturgradienten durch das Hüllrohr. Die fadenförmigen Hydridphasen sind homogen verteilt und in Umfangrichtung orientiert (spannungsarm geglühte Hüllrohrproben).

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RÉSUMÉ

Dans les réacteurs nucléaires, le pH de l’eau de refroidissement est réglé par l’addition des hydroxydes, LiOH étant le plus convenable. La concentration optimale doit être bien respectée, car au dessus d’une certaine concentration de LiOH (en fonction de la température) la vitesse de corrosion du zirconium et ses alliages augmente. L‘absorption d’hydrogène par le métal est aussi influencé.

Par conséquent, cette méthode est utilisée dans le laboratoire pour créer des échantillons dopés à l’hydrogène afin d’étudier les phénomènes liés à la corrosion.

A l’Institut Paul Scherrer, plusieurs projets ont été menés afin d’étudier le rôle d’hydrogène dans les alliages à base de Zircaloy, sur leurs propriétés mécaniques.

Afin de préparer les échantillons pour la comparaison et le réglage des nouveaux équipements, les sections de gaines de combustible à base de Zircaloy ont été dopés à l’hydrogène dans un autoclave en présence de l’eau avec une faible concentration de lithium. Les résultats des expériences sont décrits dans cette publication. En raison de grande variété de paramètres expérimentaux, ces résultats présentent un intérêt pour la communauté scientifique.

Les essais de corrosion dans l’autoclave étaient menés avec les concentrations de 0.2 M et 0.5 M de LiOH en solution, à une température de 340° C et 160 bar. La vitesse de corrosion s’élève à 84 mg/(dm².d) pour une concentration de 0.2 M de LiOH et à 153 mg/(dm².d) dans le cas de 0.5 M LiOH. La fraction d’hydrogène absorbée dans le cas de cette concentration plus riche est de l’ordre de 80%. Les tubes de Zircaloy ont été chargés dans cette condition de 500 ppm de l’hydrogène après 40 hrs.

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TABLE OF CONTENTS Page

ABSTRACT II ZUSAMMENFASSUNG III RÉSUMÉ IV

TABLE OF CONTENTS V

LIST OF TABLES VI

LIST OF FIGURES VI

1 INTRODUCTION 1

2 ZIRCALOY CORROSION IN SOLUTIONS OF LiOH 2

3 EXPERIMENTAL 3

3.1 Equipment and Materials 3

3.2 Corrosion Experiments 4

4 RESULTS 6

4.1 Corrosion of Zircaloy-4 Tubing Specimens in LiOH

Solutions 6 4.2 Hydrogen Uptake of Zircaloy-4 Tubing Specimens in

LiOH Solutions 7

4.3 Hydrogen Distribution in LiOH-Corroded Zircaloy-4

Tubing Specimens 9

5 DISCUSSION 13

ACKNOWLEDGEMENTS AND REMARK 14

REFERENCES 15

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Page LIST OF TABLES

Table 3.1 Materials Specification of Zircaloy-4 Tubing from Nuklearrohrgesellschaft

3

LIST OF FIGURES

Figure 3.1 Schematic of the autoclave with auxiliary equipment

3 Figure 3.2 Corrosion Rate of Zircaloy-4 in >0.1 M LiOH 4 Figure 4.1 Corrosion of Zircaloy-4 in LiOH 6 Figure 4.2 Hydrogen Uptake of Zircaloy-4 in 0.5 M LiOH 7 Figure 4.3 Zircaloy-4 Hydrogen Uptake vs. Weight Gain in

0.5 M LiOH

8 Figure 4.4 Hydride Distribution in Zircaloy-4 corroded in

0.2 M LiOH ( 48 h; 340 ° C; 160 bar )

0.2 M LiOH ( 124 h; 340 ° C; 160 bar )

0.5 M LiOH ( 16 h; 340 ° C; 160 bar;  400 ppm H )

0.5 M LiOH ( 77 h; 340 ° C; 160 bar;  1500 ppm H )

12 Figure 5.1 Comparison of Different Results of Hydrogen

Ingress During Zircaloy Corrosion in LiOH

13

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1 INTRODUCTION

In reactor operation pH of the cooling water is adjusted by addition of alkaline hydroxides, and LiOH has been found to be the most suitable one [1, 5, 9]. The addition of LiOH above a certain concentration level (depending on temperature) increases the corrosion rate of zirconium and its alloys (e. g. [2]). Hydrogen pick-up by the metal is also increased, and this effect is used to produce hydrided specimens for different investigations using the corrosion reaction [6]. Corrosion in water can also be used in the gas phase with water vapour at elevated temperatures (e. g. [30, 39, 40]). In both cases a corrosion oxide layer is also produced, and if it disturbs it has to be removed.

There are other methods of charging Zircaloy specimens with hydrogen:

Good results (homogeneous hydride distribution) have been achieved by hydriding in a gas phase at temperatures above 300 ° C [26-28, 31, 36, 38, 41]. Temperature cycling is necessary to achieve homogeneously distributed higher hydride concentrations [28, 29, 31, 34, 35]. A problem in the gaseous methods is to avoid traces of oxygen leading to an oxide scale on the surface. Therefore in some procedures the specimen surface is first electrolytically coated with copper which has to be removed after hydrogen charging [7, 27].

Another method is cathodic hydriding (e. g. [32, 33]). This method uses the electrochemical decomposition of water to produce a high concentration of hydrogen on the specimen surface. Hydrogen penetrates into the metal and precipitates as a hydride rim.

At the Paul Scherrer Institute several projects were accomplished to investigate the influence of hydrogen in Zircaloy cladding on its mechanical properties [7, 8]. In order to produce specimens for comparison and for adjusting new equipment, Zircaloy tubing samples were hydrogen charged by autoclave corrosion in lithiated water [37]. Results of the corrosion experiments are outlined in the following chapters. Because of the great variety of possible experimental parameters these results are still of interest for the scientific community.

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2 ZIRCALOY CORROSION IN SOLUTIONS OF LiOH

LiOH is added to the cooling water in PWRs to adjust an alkaline pH for inhibiting deposition of corrosion products on the fuel cladding and for reducing corrosion rates of structural materials. Because of its technological relevance the influence of LiOH on the corrosion of zirconium and its alloys has been investigated by several authors [1,2,5,6,9-25]. The influence of other alkaline additions (NaOH, KOH, RbOH, CsOH, Ca(OH)₂) as well as of other lithium salts has also been tested [5,9,13]. It was found that LiOH has the most detrimental effect on Zircaloy corrosion compared to the other alkaline additions, but nevertheless it is preferred because it has no long-lived high radioactive activation products. The used concentration in the cooling water is in the range of 1.5 – 3 ppm Li, but the threshold for accelerating corrosion of Zircaloy is about 30 ppm [11,13].

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3 EXPERIMENTAL

3.1 Equipment and Materials

The corrosion experiments were performed in an arrangement schematically demonstrated in Fig. 3.1.

Eight samples consisting of 150 mm long segments from Zircaloy-4 cladding tubes were arranged in a manner that only two point areas each at one open end of the tubing were connected to the sample holder.

The materials characteristics of the Zircaloy-4 tubing used can be found in Table 3.1.

Tab.3.1: Materials Specification of Zircaloy-4 Tubing from Nuklearrohrgesellschaft

Chemical Composition, wt.-% or (ppm) Heat Treatment

Dimensions, mm

Sn Fe Cr O C Si N H Zr Stress relief

annealed

OD: 10.75

1.49 0.22 0.11 0.11 (131) (<30) (24) (7) balance as-received ID: 9.30

a b

c

d

e

f g

autoclave

i h

Fig. 3.1: Schematic of the autoclave with auxiliary equipment

a: heating; b: preheating; c:

cooling by air; d: relief valve 160 bar; e: solution reservoir; f: high pressure pump; g: pressure gauge; h: non-return valve; i:

relief valve 180 bar

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3.2 Corrosion Experiments

Corrosion was accomplished in 0.5 M or 0.2 M LiOH solution at 340 ° C and 160 bar.

The following measurements were performed in all tests and on all samples:

- before the corrosion experiment:

 sample weight;

 sample dimensions;

 concentration of Li-ions by ion chromatography;

- after the corrosion experiment:

 sample weight ( weight gain )

 concentration of Li-ions by ion chromatography

Because sometimes a change in the concentration of Li was determined in the solutions before and after the test the weight gain of all test series was corrected to the same concentration of Li ( mean before and after testing at room temperature) using the relation demonstrated in Fig. 3.2.

0,20 0,25 0,30 0,35 0,40 0,45 0,50

80 90 100 110 120 130 140 150 160

340 °C 160 bar

[ mg dm^-2 d^-1 ] = 38,7 + 229 M_LiOH

Corrosion Rate [ mg dm-2 d-1 ]

LiOH Molarity

Fig. 3.2: Corrosion Rate of Zircaloy-4 in >0.1 M LiOH

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Some samples differing in corrosion time and corrosion medium were investigated for hydrogen content, oxide thickness and distribution of hydrides.

The hydrogen concentration was determined by hot extraction using a LECO-404 analyser. Metallography images revealed oxide thickness and hydride distribution.

After grinding and polishing hydride contrast was produced by etching in a mixture of 9 parts nitric and 1 part hydrofluoric acids.

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4 RESULTS

4.1 Corrosion of Zircaloy-4 Tubing Specimens in LiOH Solutions

Most of the corrosion experiments were performed in 0.5 M LiOH. The mean corrosion rate in 0.5 M LiOH at 340 ° C and a pressure of 160 bar was determined to be 153 mg dm^-2 d^-1.

Some samples were corroded in 0.2 M LiOH at 340 ° C and 160 bar where the mean corrosion rate amounts to 84 mg dm^-2 d^-1.

The dependence of weight gain from corrosion time is demonstrated in Fig. 4.1.

0 50 100 150 200 250 300

0 200 400 600 800 1000 1200 1400

Samples: 150 mm long open tubing 340 °C

160 bar

WG_0.5M = 28,878+5,081T-0,00245T² WG_0.2M = 3,537T

0.5M LiOH 0.2M LiOH

Weight Gain [ mg/dm2 ]

Time [h]

Fig. 4.1: Corrosion of Zircaloy-4 in LiOH

At short corrosion times up to 100 hours the dependence of the weight gain of Zircaloy-4 tubing samples from time could be well fitted by a linear equation. If the longer corrosion experiments in 0.5 M LiOH are included a second order polynomial fit better represents all the results ( see Fig. 4.1 ).

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value determined under the optical microscope.

4.2 Hydrogen Uptake of Zircaloy-4 Tubing Specimens in LiOH Solutions The corrosion of zirconium ( and the Zircaloys ) in water can be described by the general equation:

Zr + 2 H₂O  ZrO2 + 4 H

It is well known that the increase of the thickness of the corrosion layer is accompanied by an ingress into the metal of a certain part of the hydrogen evolved according to equation (4.1). As the corrosion itself also the hydrogen uptake by Zircaloy is accelerated by lithium ions. The increase in hydrogen content of Zircaloy-4 tubing samples with increasing corrosion time in 0.5 M LiOH is plotted in Fig. 4.2.

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000

Samples: open tubing 150 mm long 340 °C

160 bar

[H]=27,6 T

Hydrogen Concentration [ppm]

Time [h]

Fig. 4.2 Hydrogen Uptake of Zircaloy-4 in 0.5 M LiOH

(4.1)

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From Fig. 4.2 it follows that the ingress of hydrogen into Zircaloy-4 at 340 ° C and 160 bar in 0.5 M LiOH can be described by a linear equation up to a corrosion time of about 150 hours. The result at a corrosion time of 300 hours has not been taken into account because of the great uncertainty of the hydrogen content at that high ppm level. Indeed standards for the calibration of the LECO hydrogen analyser are available only up to about 200 ppm H. The hydrogen content of 5500 ppm after 300 hours of corrosion can be qualified only as a rough estimate.

The pick-up fraction of hydrogen in Zircaloy-4 is quite higher during corrosion in 0.5 M LiOH compared to PWR conditions. Whereas the Zry-4 cladding in a PWR picks up 16-18 % of the corrosion hydrogen [3] the pick-up fraction amounts to 80 % during corrosion in 0.5 M LiOH at 340 ° C and 160 bar calculated from the data of Fig. 4.3.

0 200 400 600 800 1000

0 500 1000 1500 2000 2500 3000 3500 4000

samples: 150 mm long open cladding 340 °C

160 bar

[H] = 4,23 * WG

Hydrogen Concentration [ ppm ]

Weight Gain [ mg/dm² ]

Fig. 4.3 Zircaloy-4 Hydrogen Uptake vs. Weight Gain in 0.5 M LiOH

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It is well known that the solubility of hydrogen in zirconium ( and Zircaloy-4 ) is very low, about 100 ppm at 340 ° C and about 10 ppm at room temperature (see e. g.

[4] ). At hydrogen levels above the so called terminal solid solubility (TSS) hydrides are precipitated in the Zr/Zircaloy matrix that appear as separate phases. The distribution of the hydrides ( homogeneous or locally accumulated ) is of great importance and determines e. g. the mechanical behavior of the hydrogen charged Zircaloy.

In the corrosion experiments described in this report a homogeneous distribution of hydrides should be expected because no temperature gradient exists through the tubing wall.

In Fig. 4.4 a metallography image is demonstrated showing a hydride distribution that could be characterized as homogeneous. In this case the corrosion was performed in 0.2 M LiOH at 340 ° C and 160 bar during a moderate time period of 48 hours.

Fig. 4.4 Hydride Distribution in Zircaloy-4 corroded in 0.2 M LiOH ( 48 h; 340 ° C; 160 bar )

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Fig. 4.5 Hydride Distribution in Zircaloy-4 corroded in 0.2 M LiOH ( 124 h; 340 ° C; 160 bar )

With longer corrosion the hydride distribution becomes more and more non- homogeneous as can be concluded from Fig. 4.5 revealing the hydride distribution after 124 hours corrosion in 0.2 M LiOH at 340 ° C and 160 bar. Some broad hydride stringers and a hydride rim are apparent in Fig. 4.5

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Fig. 4.6 Hydride Distribution in Zircaloy-4 corroded in 0.5 M LiOH ( 16 h; 340 ° C; 160 bar;  400 ppm H )

A short corrosion treatment of Zircaloy-4 tubing specimens in 0.5 M LiOH results in about the same hydride distribution as that achieved in 0.2 M LiOH at some longer time. The metallography images of Fig. 4.4 and Fig. 4.6 are comparable and characterise a 48 h corrosion in 0.2 M LiOH and a 16 h corrosion in 0.5 M LiOH at the same temperature and pressure conditions respectively.

With more prolonged corrosion in 0.5 M LiOH at 340 ° C and 160 bar broad hydride stringers appear in the cladding and an accumulation of hydrides in both rim regions can be observed ( see Fig. 4.7 )

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Fig. 4.7 Hydride Distribution in Zircaloy-4 Corroded in 0.5 M LiOH ( 77 h; 340 ° C; 160 bar;  1500 ppm H )

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5 DISCUSSION

The results outlined in this publication complete and are some proof of previously published data on Zircaloy corrosion in lithiated water.

The publication of McDonald, Sabol and Sheppard [11] allows some comparison of data in spite of differences in LiOH concentration and pressure of the experiments (atmospheric pressure against 160 bar in our case). A weight gain of 942 mg/dm² measured after 21 days corrosion in 0.1 molal LiOH at 344 ° C in [11] corresponds to our 415 mg/dm² after 4.5 days in 0.2 M LiOH at 340 ° C (see Fig. 4.1).

Another comparison: The ~ 390 mg/dm² at 360 ° C after two days in ([5], Zry-2) are comparable to the ~ 300 mg/dm² at 340 ° C after two days in this investigation (both in 0.5 molar LiOH).

A comparison of our results on Zircaloy-4 with data from Murgatroyd and Winton (Zircaloy-2, [6]) and from Domizzi, Lanzani, Coronel and Bruzzoni (Zircaloy-4, [27]) is plotted in Fig. 5.1. Besides the LiOH concentration the enormous influence of the corrosion temperature becomes evident from Fig. 5.1.

0 50 100 150 200 250

0 1000 2000 3000 4000 5000

Hydrogen Concentration (ppm)

Time (hour)

0.5 M LiOH, 340°C this work 1 M LiOH, 343°C [27]

3 M LiOH, 300°C [6]

2.1 M LiOH, 300°C [6]

Fig. 5.1 Comparison of Different Results of Hydrogen Ingress During Zircaloy Corrosion in LiOH

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As already mentioned in chapter 4.2 the hydrogen pick-up is considerably increased in concentrated LiOH compared to corrosion in water or diluted LiOH solutions (< 0.001 M [11]). At lower temperatures (e. g. 316 ° C) the hydrogen pick- up fraction of Zircaloy-4 increases with increasing LiOH concentration [10].

The hydrogen pick-up fraction in 0.5 M LiOH at 340 ° C and 160 bar was found in this investigation to amount to 80 % in agreement with the same value found in 0.7 M LiOH at 316 ° C published in [10].

In general the hydride distribution resulting from hydriding under conditions published in this report is homogeneous (see Figures 4.4 and 4.6). With longer corrosion periods and higher LiOH concentrations the hydride distribution becomes more and more non-homogeneous (see Figures 4.5 and 4.7). It can be assumed that in the latter cases the hydride distribution can be made more homogeneous by long-term isothermal holding of the specimens at a temperature > 300 ° C [29].

ACKNOWLEDGEMENTS

The experimental assistance of R. Knecht (autoclave corrosion), R. Keil (Li concentration analyses), M. Steinemann (LECO hydrogen analyses) and M.

Geringer (metallography) is kindly acknowledged.

REMARK

The author of this report, Armin Hermann, was the project manager of the work performed at the former Laboratory for Materials Behavior and is meanwhile retired.

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[1] H. Coriou, L. Grall, J. Meunier, M. Pelras, H. Willermoz,

"Corrosion du Zircaloy dans Divers Milieux Alcalins a Haute Temperature", Journal of Nuclear Materials 7 (1962) 320

[2] F. Garzarolli, R. Holzer,

"Waterside Corrosion Performance of Light Water Power Reactor Fuel", Nuclear Energy 31 (1992) 65

[3] G. Bart, H. Blank, F. Garzarolli, O. Gebhardt, A. Hermann, I.L.F. Ray,

"Gösgen Project - Post-Irradiation Characterization", EPRI TR-105060 (1996), Electric Power Research Institute, Palo Alto, CA, USA

[4] J. J Kearns,

"Terminal Solubility and Partitioning of Hydrogen in the Alpha Phase of Zirconium, Zircaloy-2 and Zircaloy-4",

Journal of Nuclear Materials 22 (1967) 292 [5] E. Hillner, J.N. Chirigos,

"The Effect of Lithium Hydroxide and Related Solutions on the Corrosion Rate of Zircaloy in 680 F Water",

WAPD-TM-307 (1962), Bettis Atomic Power Laboratory, Pittsburgh, PA, USA

[6] R.A. Murgatroyd, J. Winton,

"Hydriding Zircaloy-2 in Lithium Hydroxide Solutions", Journal of Nuclear Materials 23 (1967) 249

[7] S.K. Yagnik, A. Hermann, R-C. Kuo,

"Ductility of Zircaloy-4 Fuel Cladding and Guide Tubes at High Fluences", Zirconium in the Nuclear Industry: Fourteenth International Symposium, ASTM STP 1467, ASTM 2006, pp. 604-631, Journal of ASTM International 2, (2005) 604

[8] A. Hermann, S.K. Yagnik, D. Gavillet,

"Effect of Local Hydride Accumulations on Zircaloy Cladding Mechanical Properties", Zirconium in the Nuclear Industry: Fifteenth International Symposium, ASTM STP 1505, Journal of ASTM International 4, (2007) No.

10

[9] Y.H. Jeong, J.H. Baek, S.J. Kim, H.G. Kim, H. Ruhmann,

"Corrosion Characteristics and Oxide Microstructures of Zircaloy-4 in Aqueous Alkali Hydroxide Solutions",

Journal of Nuclear Materials 270 (1999) 322

(24)

[10] S. Kass,

"Corrosion and Hydrogen Pickup of Zircaloy in Concentrated Lithium Hydroxide Solutions",

WAPD-TM-656 (1967), Bettis Atomic Power Laboratory, Pittsburgh, PA, USA

[11] S.G. McDonald, G.P. Sabol, K.D. Sheppard,

"Effect of Lithium Hydroxide on the Corrosion Behavior of Zircaloy-4", Zirconium in the Nuclear Industry: Sixth International Symposium, ASTM STP 824, ASTM 1984, pp. 519-530

[12] N. Ramasubramanian, N. Precoanin, V.C. Ling,

"Lithium Uptake and the Accelerated Corrosion of Zirconium Alloys", Zirconium in the Nuclear Industry: Eighth International Symposium, ASTM STP 1023, ASTM 1989, pp. 187-201

[13] F. Garzarolli, J. Pohlmeyer, S. Trapp-Pritsching, H.G. Weidinger,

"Influence of Various Additions to Water on Zircaloy-4 Corrosion in Autoclave Tests at 350 ° C",

IWGFPT-34 (1990) pp. 65-72, IAEA, Vienna [14] R.A. Perkins, R.A. Busch,

"Corrosion of Zircaloy in the Presence of LiOH",

Zirconium in the Nuclear Industry: Ninth International Symposium, ASTM STP 1132, ASTM 1991, pp. 595-612

[15] N. Ramasubramanian,

"Lithium Uptake and the Corrosion of Zirconium Alloys in Aqueous Lithium Hydroxide Solutions",

[16] I.L. Bramwell, P.D. Parsons, D.R. Tice,

"Corrosion of Zircaloy-4 PWR Fuel Cladding in Lithiated and Borated Water Environments",

[17] B. Cox, Y-M. Wong,

"Effects of LiOH on Pretransition Zirconium Oxide Films",

[18] B. Cox, C. Wu,

"Dissolution of Zirconium Oxide Films in 300° C LiOH", Journal of Nuclear Materials 199 (1993) 272

(25)

[19] Y. Ding, D.O. Northwood,

"Effects of LiOH on the Microstructure of the Oxide Formed During the Aqueous Corrosion of a Zr-2.5 wt% Nb Alloy",

[20] S.-J. Kim, K.H.Kim, J.H. Baek, B.K. Choi, Y.H. Jeong, Y.H. Jung

"The Effect of Hydride on the Corrosion of Zircaloy-4 in Aqueous LiOH Solution",

[21] Y.-M. Wong, B. Cox, N. Ramasubramanian, V.C. Ling,

"Synergistic Effects of LiOH and F^- in Accelerating the Corrosion of Zircaloy-4",

[22] T. Kido, S. Wada, T. Takahashi, H. Uchida, I. Komine, Y. Inoue,

"Behavior of Lithium and Boron in Irradiated and Unirradiated Oxides Formed on Zircaloy-4 Claddings",

Zirconium in the Nuclear Industry: Twelfth International Symposium, ASTM STP 1354, ASTM 2000, pp. 773-792

[23] M. Oskarsson, E. Ahlberg, K. Pettersson,

"Oxidation of Zircaloy-2 and Zircaloy-4 in Water and Lithiated Water at 360°

C",

Journal of Nuclear Materials 295 (2001) 97 [24] M. Oskarsson, E. Ahlberg, K. Pettersson,

"Phase Transformation of Stabilised Zirconia in Water and 1.0 M LiOH", Journal of Nuclear Materials 295 (2001) 126

[25] J.H. Lee, S.K. Hwang,

"Effect of Mo Addition on the Corrosion Resistance of Zr-based Alloy in Water Containing LiOH",

Journal of Nuclear Materials 321 (2003) 238 [26] J.-H. Huang, S.-P. Huang,

”Hydriding of Zirconium Alloys in Hydrogen Gas".

Materials Science and Engineering, A161 (1993) 247 [27] G. Domizzi, L. Lanzani, P. Coronel, P. Bruzzoni,

"Supercharging of Zircaloy-4",

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[28] D.G. Westlake, S.T. Ockers,

"Hydrogen Supercharging during Thermal Cycling of Zirconium", Journal of Nuclear Materials 37 (1970) 236

[29] R. Westerman,

"Charging Zircaloy-2 with Hydrogen beyond the Solubility Limit", Journal of Nuclear Materials 18 (1966) 31

[30] K. Une, S. Ishimoto,

"Dissolution and Precipitation Behavior of Hydrides in Zircaloy-2 and High Fe Zircaloy",

Journal of Nuclear Materials 322 (2003) 66 [31] H.C. Chu, S.K. Wu, K.F. Chien, R.C. Kuo,

"Effect of Radial Hydrides on the Axial and Hoop Mechanical Properties of Zircaloy-4 ",

Journal of Nuclear Materials 362 (2007) 93 [32] M.E. Habermann,

"Elektrolytisches Hydrierungsverhalten und Wasserstoffversprödung der IVa-Metalle Titan, Zirconium und Hafnium",

PhD Thesis, Universität Erlangen, Germany, 1995 [33] Y. Choi, J.W. Lee, Y.W. Lee, S.I. Hong,

"Hydride Formation by High Temperature Cathodic Hydrogen Charging Method and its Effect on the Corrosion Behavior of Zircaloy-4 Tubes in Acid Solution ",

Journal of Nuclear Materials 256 (1998) 124 [34] E. Hillner, J.N. Kass, J.J. Kearns,

"Hydrogen Supercharging During Corrosion of Zircaloy ", Journal of Nuclear Materials 45 (1972) 175

[35] M.P. Puls,

"On the Consequences of Hydrogen Supersaturation Effects in Zr Alloys to Hydrogen Ingress and Delayed Hydride Cracking ",

Journal of Nuclear Materials 165 (1989) 128 [36] S. Kass, W.W. Kirk,

"Corrosion and Hydrogen Absorption Properties of Nickel-Free Zircaloy-2 and Zircalloy-4 ",

Transactions of the ASM 55 (1962) 77 [37] O. Gebhardt, A. Hermann,

"Microscopic and Electrochemical Impedance Spectroscopy Analyses of Zircaloy Oxide Films Formed in Highly Concentrated LiOH Solution ", Electrochimica Acta, 41 (1996) 1181

(27)

1959",

Atomic Energy of Canada Limited, Report AECL-919 (1959) [39] W.E. Berry, D.A. Vaughan, E.L. White,

"Hydrogen Pickup During Aqueous Corrosion of Zirconium Alloys", Corrosion 17 (1961) 109t

[40] B. Cox,

"Hydrogen Absorption by Zircaloy-2 and Some Other Alloys During Corrosion in Steam",

Journal of the Electrochemical Society 109 (1962) 6

[41] T. Arima, K. Moriyama, N. Gaja, H. Furuya, K. Idemitsu, Y. Inagaki

"Oxidation Kinetics of Zircaloy-2 Between 450° C and 600° C in Oxidizing Atmosphere ",

(28)

(29)