Improvements in zirconium alloy corrosion resistance

266 Pages·2009·7.94 MB·English

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" / \ v International Atomic Energy Agencv
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V ^ V y^ JM INTERNATIONAL WORKING GROUP
^ S^ ^ ON W* ATER REACTOR FUEL PERFORMANCE AND TECHNOLOGY
FUNDAMENTAL ASPECTS OF CORROSION
ON ZIRCONIUM BASE ALLOYS
IN WATER REACTOR ENVIRONMENTS
PROCEEDINGS OF A TECHNICAL COMMITTEE MEETING
ORGANIZED BY THE
INTERNATIONAL ATOMIC ENERGY AGENCY
AND HELD IN PORTLAND, OREGON, USA,
11-15 SEPTEMBER 1989
INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1990
FUNDAMENTAL ASPECTS OF CORROSION
ON ZIRCONIUM BASE ALLOYS
IN WATER REACTOR ENVIRONMENTS
PROCEEDINGS OF A TECHNICAL COMMITTEE MEETING
ORGANIZED BY THE
INTERNATIONAL ATOMIC ENERGY AGENCY
AND HELD IN PORTLAND. OREGON. USA.
11-15 SEPTEMBER 1989
INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1990
FUNDAMENTAL ASPECTS OF CORROSION ON ZIRCONIUM BASE ALLOYS
IN WATER REACTOR ENVIRONMENTS
IAEA. VIENNA. 1990
IWGFPT/34
ISSN 1011-2766
Printed by the IAEA in Austria
September 1990
FOREWORD
The present meeting was scheduled by the International Atomic
Energy Agency, upon proposal of the Members of the International Working
Group on Water Reactor Fuel Performance and Technology (IWGFPT).
At the invitation of the United States Department of Energy the
meeting was hosted by Teledyne Wah Chang Albany (TWCA) and held in
Portland, Oregon, USA, from 11 to 15 September 1989.
The purpose of this meeting was to understand the status of
knowledge of zirconium alloys corrosion mechanisms and to identify areas
where further work would be valuable.
Forty-five participants from 13 countries attended the meeting and
25 papers were presented and discussed. The papers were presented in 7
sub-sessions and following the meeting working groups composed of the
session co-chairmen and paper authors prepared a summary of each session,
with the objective of reaching conclusions from each session and
recommendations for future work.
The meeting was a success and covered the most important aspects
of zirconium alloy technology. Significant progress is being made in
understanding the effect of zirconium alloy composition and fabrication
on the performance of zirconium alloy claddings under reactor conditions.
EDITORIAL NOTE
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CONTENTS
Su.nmary of the Technical Committee Meeting 7
ELECTROCHEMISTRY (Session I A)
Nodular corrosion mechanisms and their applications to alloy development 27
D.F. Taylor, B. Cheng, R.B. Adamson
Nodule nucleation at and away from intermetallics 36
R. Ramasubramanian
Localized corrosion of zirconium alloys 45
G.C. Palir, H.S. Gadixar
COOLANT CHEMISTRY (Session I B)
Thermal gradient effects on the oxidation of Zircaloy fuel cladding 61
A.C. Klein, J.N. Reyes, Jr., M.A. Maguire
Influence of various additions to water on Zircaloy 4 corrosion in autoclave tests at 35C°C ... 65
F. Garzarolli, J. Pohlmeyer, S. Trapp-Pritsching, H.G. Weidinger
IRRADIATION EFFECTS (Session II)
Fuel channel oxide thickness measurements at the Oyster Creek
Nuclear Generating Station 75
T.G. Piascik, P.M. Kasik
Effect of irradiation on the microstructure of Zircaioy 4: Amorphous transformation
and alloying element resolution — Impact upon corrosion 80
F. Lefebvre, C. Lemaignan
Relationship of precipitates, their composition, heat treatment and irradiation
to corrosion resistance of Zircaloys 88
A.A. Strasser. M.G Andrews
CHARACTERISTICS OF ZIRCONIUM OXIDE (Session III)
Characterization of Zircaloy corrosion films by analytical transmission
electron microsccoy 101
E.R. Bradley, R.A. Perkins
Thick-film effects in the oxidation and hybriding of zirconium alloys 107
A.B. Johnson, Jr.
Effect of oxide structure on nodular corrosion susceptibility 120
R.A. Perkins, R.A. Busch, E.R. Bradley
Electron microscopical analyses of oxides in Zr-2.5 Wt% Nb 124
B.D. Warr, EM. Rasile, A.M. Brennenstuhl
Thermoluminescence of oxidized Zr and Zr alloys 134
A.J. Bychov, A'.G. Petrik. A.B. Alexandrov. 4.F. Nechaev
EFFECTS OF ALLOYING ON CORROSION (Session IV A)
Improvements in zirconium alloy corrosion resistance 145
G.R. Kilp. DR. Thornburg, R.J. Comstock
Corrosion behaviour of Zr-Nb-Sn-Fe alloy 158
AG. Glazkov, V.M. Grigor'ev, V.F. Kon'kov, A.S. Moinov, A.V. Nikulina, V.I. Sidorenko
CORROSION MODELLING (Session IV B)
What is wrong with current models for in-reactor corrosion 167
B. Cox
Mechanistic understanding of Zircaloy corrosion in PWRs through a corrosion model 173
P. Billot, J.C. Robin
Evaluation of the EPRI/Garzarolli Zircaloy corrosion model for US reactors 180
K.P. Sheppard, A.A. Strasser
A model for uniform Zircaloy clad corrosion in pressurized water reactors 187
K. Forsberg, A.R. Massih
EFFECT OF Zr BASE METAL PROPERTIES ON CORROSION (Session V)
Correlation of waterside corrosion and cladding microstructure in high-burnup fuel
and gadolinia rods 201
H.M. Chung
Precipitate growth kinetics in Zircaloy 4 211
J. P. Gros, J.F. Wadier
Recent activities to elucidate the nodular corrosion phenomenon 226
K. Ogata, T. Kubo, Y. Etoh, N. Fujii
Influence of microstructure on 400 and 500CC steam corrosion behaviour of Zircaloy 2
and Zircaloy 4 tubing 237
T. Andersson, T. Thorvaldsson
Corrosion behaviour and oxide characterization of surface treated Zr-1% Nb
fuel cladding tubes 249
T. Planman, M Vaittinen, J. Moisio
Fragema zirconium alloy corrosion behaviour and development 255
J. Thomazet, J. P. Mardon, D. Charquet, J. Senevat, P. Billot
Effect of microstructure on the corrosion of Zr-2.5 Nb alley 262
V.F. Urbanic, R. W. Gilbert
Organizing Committee 273
List of Participants 273
SUMMARY OF THE TECHNICAL COMMITTEE MEETING
The purpose of this meeting was to discuss the state of knowledge
of zirconium alloy corrosion mechanisms. Forty-five participants
from 16 countries attended the meeting, and 25 papers were
presented and discussed. One additional paper was provided only
in written form.
The papers were presented in seven sub-sessions under the
following headings:
Session IA Electrochemistry
Session IB Coolant Chemistry Effects
Session II Irradiation Effects
Session III Characteristics of Zirconium Oxide
Session IVA Effects of Alloying on Corrosion
Session IVB Corrosion Modeling
Session V Effect of Zirconium Base Metal Properties on
Corrosion
Many of the papers covered aspects of several of these topics.
The program included time for discussion of each papsr and the
discussions were generally lengthy and extremely valuable.
Following the meeting, a working group composed of the Session
Co-chairmen and paper authors prepared a summary of each session
with the objectives of reaching conclusions from each session and
making recommendations for future work. These reports are
attached.
General Conclusion
It is clear that mechanistic understanding of zirconium alloy
corrosion is still some way off, although a significant amount of
progress has been made toward experimental determination of the
micro-scale phenomena. The papers presented a status report of
our knowledge of these corrosion mechanisms, but they also served
to illustrate the fact that much of the work done to date has
been phenomenological rather than mechanistic. The perceived
value of gaining a mechanistic understanding of the zirconium
corrosion process has not yet been realized.
The summaries of individual sessions detail the specific
conclusions and recommendations made at the meeting.
7
SESSION I A
Elec trocheeistry
and
SESSION I B
Coolant Chemistry
Chairman: J.F. Wadier
The individual papers can be summarized as follows
A. D. Taylor et al., "Nodular Corosion Mechanisms and
Their Applications to Alloy Development"
1. Local solute depletion in the matrix causes
nodular corrosion.
2. Experience with binary alloys shows that only
solute elements with oxidation states other than
+4, can protect zirconium:
- Sn, Si, Hf have no influence
- Only Fe, Cr, Nb, Ni and multivalent elements can
protect Zr.
3. In the oxide, only these elements with a valence
difference of 4 and which can oxidize, can dope
Zr0 either electronically or ionically. Large
2
particles which do not oxidaze do not play any
role in oxide resistance.
4. The concentration of multivalent oxidized elements
in the oxide may not have to be very high to be
effective.
B. Ramasubramanian, "Nodule Nucleation at and Away From
Intermetallics"
1. The presence of subsurface precipitates are the
cause of nodule nucleation.
2. The concentration of vacancies generated by the
solute in the oxide is a small fraction of those
which are thermally generated.
3. Proton entry into the corrosion film generates
hydrogen at the subsurface intennetallic because
of the relatively high cathodic potential of the
partial oxidized nature of the precipitates.
C. Klein - Maguire, "Thermal Gradient Effects on the
Oxidation of Zircaloy Fuel Cladding"
1. Thermal gradient caused by heat flux is important
in the uniform corrosion oxidation.
2. A laboratory facility has been btilt to measure
the effect and simulate PWR conditions.
3. Two test programs are currently being performed.
They will compare the oxide film developed in air
plus steam and those performed in current rate
solution in LiOH.
Gadiyar et al., "Localized Corrosion of Zirconium
Alloys"
1. Pit nucleation potential in chlorine containing
solution have been measured.
a. Pit nucleation occurs at 10"* molar for
normal chlorine.
b. Pit nucleation potentials (PNP) are more
active for Zr2 than for pure Zr.
c. Metastable pitting has been observed for Zr
but not for Zr2.
d. The kinetics for Zr and Zr2 appear to be
similar
e. High pH near the pit site, hydrogen
evolution, low activation energy and low IR
drop are rate controlling diffusion or salt
film diffusion.
f. The cracks are initiated in trans-granular
attack.
H. Weidinger et al., "Influence of Various Additions to
Water and Zircaloy Corrosion in Autoclave Tests at
350*C"
The effect of different impurities or chemical
compounds intentionally added into PWR primary water on
the corrosion behavior of Zircaloy-4 was studied by
autoclave tests in water at 350'C lasting up to 250
days. Significantly increased corrosion was only seen
at high fluoride or LiOH-concentrations. A moderate
increase was caused by high concentrations of chloride,
chromate, cation resin, oxygen and a mixture of LiOH,
KOH and boric acid. Hydrogen decreased the corrosion
somewhat. Nitrides, sulfates, anion resin, hydracin?
and Fe0» had no noticeable effect. The metal oxides
3
Cr0,, NiO, NiFe0 and Si0 caused a reduction of the
2 2 3 2
time to transition but had no effect on the post-
transition corrosion rate. The results indicate that
the effect of alkalizing additions may be more the
result of an increased pH value than from Li
concentration in the oxide. The morphology of the
oxide formed by corrosion plays an important role to
understand the mechanisms of these effects.
Possibly the enhancing of corrosion by fluorides as
well as by LiOH can be explained by the mineralization
effect of the compounds or the recrystallization of the
primarily bulk Zr0.
2
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