U.S. patent application number 11/333643 was filed with the patent office on 2006-10-12 for zirconium alloy and components for the core of light water-cooled nuclear reactors.
This patent application is currently assigned to Framatome ANP GmbH. Invention is credited to Friedrich Garzarolli, Heinrich Ruhmann, Angelika Seibold.
Application Number | 20060225815 11/333643 |
Document ID | / |
Family ID | 34071702 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060225815 |
Kind Code |
A1 |
Garzarolli; Friedrich ; et
al. |
October 12, 2006 |
Zirconium alloy and components for the core of light water-cooled
nuclear reactors
Abstract
A zirconium alloy has the following composition in percent by
mass: Sn: 0.2-0.5%; Nb: 0.2-0.8%; Fe: 0.05-0.40%; V: 0-0.20%;
0:0.12-0.20%; Si: 80-120 ppm; C:=120 ppm; and a remainder of
reactor-pure zirconium and acceptable impurities. The alloy is
particularly suitable for components for the core of light water
reactors, in particular, for pressurized water reactors.
Inventors: |
Garzarolli; Friedrich;
(Hochstadt/Aisch, DE) ; Seibold; Angelika; (Furth,
DE) ; Ruhmann; Heinrich; (Erlangen, DE) |
Correspondence
Address: |
LERNER GREENBERG STEMER LLP
P O BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Assignee: |
Framatome ANP GmbH
|
Family ID: |
34071702 |
Appl. No.: |
11/333643 |
Filed: |
January 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP04/07822 |
Jul 15, 2004 |
|
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11333643 |
Jan 17, 2006 |
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Current U.S.
Class: |
148/421 ;
420/422 |
Current CPC
Class: |
C22C 16/00 20130101 |
Class at
Publication: |
148/421 ;
420/422 |
International
Class: |
C22C 16/00 20060101
C22C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2003 |
DE |
DE 103 32 239.6 |
Claims
1. A zirconium alloy, comprising, in percent by mass: Sn: 0.2-0.5%
Nb: 0.2-0.5% Fe: 0.05-0.40% V: 0-0.20% O: 0.12-0.20% Si: 80-120 ppm
C: .ltoreq.120 ppm and a remainder of reactor-pure zirconium
together with standard impurities.
2. The alloy according to claim 1, wherein a content of vanadium is
at least 0.07%.
3. The alloy according to claim 1, wherein a sum of Sn, Nb, Fe, and
V contents is at most 1.3%.
4. A component for the core of a light water reactor, comprising
the alloy according to claim 1.
5. The component according to claim 4 configured for use in a
pressurized-water reactor.
6. The component according to claim 4, produced maintaining a
cumulative annealing parameter of (10-40) E-18 h.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuing application, under 35 U.S.C. .sctn.
120, of copending international application PCT/EP2004/007822,
filed Jul. 15, 2004, which designated the United States; this
application also claims the priority, under 35 U.S.C. .sctn. 119,
of German patent application No. 103 32 239.6, filed Jul. 16, 2003;
the prior applications are herewith incorporated by reference in
their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention lies in the nuclear reactor technology field.
More specifically, the invention relates to a zirconium alloy, or
zirconium-based alloy, and to structural parts made from an alloy
of this type for the core of light-water-cooled nuclear reactors,
in particular of pressurized-water reactors. Structural parts of
this type are in particular fuel cladding tubes, spacers and
control rod guide tubes.
[0003] For physical reasons, zirconium, which has a low neutron
absorption, is used as base metal for the structural parts in
reactor cores. On account of the separation of the neutron absorber
hafnium, it is customary to use reactor-pure zirconium sponge, the
composition of which is governed by standards.
[0004] Zircaloy-2 (for boiling-water reactors) and Zircaloy-4 (for
pressurized-water reactors) or other zirconium-based alloys, for
example those known from U.S. Pat. Nos. 5,940,464 and 4,938,920
(corresp. German published patent application DE 38 05 124 A1);
U.S. Pat. Nos. 5,230,758 and 5,112,573 (cf. German DE 690 10 115
T2), and from international PCT publication WO 01/24193 A1, are
nowadays generally used for the above-mentioned purpose. Binary
Zr--Nb alloys are also used to a lesser extent.
[0005] The following table gives the compositions of zirconium
sponge and the standardized alloys which have hitherto been
customary in Western engineering. In this context, it should be
mentioned that nowadays some of the permitted impurities can be set
in a particularly controlled way or even, by using suitable
additions, set to specific values. By way of example, on account of
its hardening action on zirconium, oxygen was originally controlled
only to levels corresponding to manufacturing requirements, but
nowadays it is actually used deliberately as a hardening
addition.
Table
[0006] Reactor-pure zirconium (maximum contents in ppm):
TABLE-US-00001 Al B Cd C Cl H Hf Fe O Si 75 0.5 0.5 250 1300 25 100
1500 1600 20
[0007] Composition of Zircaloy and ZrNb alloys (in % by mass):
TABLE-US-00002 Other Sn Fe Cr Ni stipulations Zircaloy-2: 1.2-1.7
0.07-0.20 0.05-0.15 0.03-0.08 0.18-0.36 FeCrNi Zircaloy-4: 1.2-1.7
0.18-0.24 0.07-0.13 .ltoreq.0.007 0.28-0.37 FeCr Zr-2, .ltoreq.0.05
.ltoreq.0.150 .ltoreq.0.02 .ltoreq.0.007 2.40-2.80% 5% Nb: Nb
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
zirconium alloy, which is further improved relative to the
above-mentioned materials and structural parts of the general type
and which, in particular, provides for further improved zircaloy
structural parts for light water reactor cores.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a zirconium alloy,
comprising, in percent by mass: [0010] Sn: 0.2-0.5% [0011] Nb:
0.2-0.5% [0012] Fe: 0.05-0.40% [0013] V: 0-0.20% [0014] O:
0.12-0.20% [0015] Si: 80-120 ppm [0016] C: .ltoreq.120 ppm and a
remainder of reactor-pure zirconium together with standard
impurities.
[0017] In accordance with an added feature of the invention, there
is provided an amount of vanadium with a content of at least
0.07%.
[0018] In accordance with an additional feature of the invention, a
sum of the contents of Sn, Nb, Fe, and V is at most 1.3%.
[0019] In other words, the novel alloy is composed of a matrix of
reactor-pure zirconium together with 0.2 to 0.5% of Sn, 0.2 to 0.5%
of Nb, 0.05 to 0.40% of Fe and 0 to 0.20% of V, with the carbon
content being restricted to at most 120 ppm, and a range of from 80
to 120 ppm for Si and from 0.12 to 0.20% for O being maintained. It
has been found that alloys of this type can be used to produce
components, such as cladding tubes, spacers, guide tubes and
further structural elements of a fuel assembly, for the core of
light water reactors, in particular of pressurized water reactors.
The components have an improved resistance to corrosion compared to
components made from Zircaloy-4, while maintaining substantially
the same production and the same heat treatment. This property is
particularly pronounced if the sum of the alloying constituents Sn,
Nb, Fe and V must drop if the total amount of Sn and Nb
increases.
[0020] Values higher than 0.5% of Sn, for example up to 0.75%, have
an adverse effect on the corrosion resistance, increase the
radiation-induced growth, while the mechanical properties are
significantly improved, which means that the proposed value of at
most 0.5% represents a good compromise. The minimum Sn content at
which components with good mechanical properties can still be
produced is 0.2%.
[0021] Vanadium is an addition which is not absolutely imperative
with a view to improving the corrosion properties. For example, it
is possible to increase the corrosion resistance with a high
burn-up using Sn contents of 0.4% to 0.5%. However, if some of the
iron is replaced by V or if V is added to the alloy in small
quantities (0.02 to 0.20%), the hydrogen pickup factor (HPUF) and
therefore the formation of hydrides, which in addition to
embrittling the material also cause material growth, is
reduced.
[0022] To achieve an optimum creep rupture strength and at the same
time a yield strength with a high value, it is possible to add Nb
to the alloy in an amount of up to 0.8%, preferably up to its
solubility limit, i.e. up to 0.5%. If this limit is not
significantly exceeded, there is no risk of uncontrolled phase
transitions, which result at relatively high temperatures, e.g.
when welding spacers or cladding tubes to their end stoppers, on
account of the complicated phase diagrams of ZrNb. Consequently, it
should not be necessary for the alloy according to the invention to
be subjected to a further heat treatment following welding.
[0023] Furthermore, the alloys are relatively insensitive to the
effects of high heating surface stresses and local boiling
processes at the interface with water. In this context, in
particular a low uptake of lithium and a low level of nodular
corrosion--as is found with cladding tubes made from Zircaloy-4
under standard pressurized-water conditions--are observed.
Moreover, they have a low radiation-induced growth.
[0024] With the above and other objects in view there is also
provided, in accordance with the invention, a component for the
core of a light water reactor, in particular, a pressurized-water
reactor, the is formed of the above-outlined zirconium-based
alloy.
[0025] In a preferred embodiment of the invention, the component is
produced while maintaining a cumulative annealing parameter of
(10-40) E-18 h.
[0026] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0027] Although the invention is illustrated and described herein
as embodied in a zirconium alloy and components for the core of
light-water-cooled nuclear reactors, it is nevertheless not
intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
[0028] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0029] The sole FIGURE of the drawing is a chart in which the
thickness of a resultant oxide layer is plotted over burn-up.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The following table illustrates four exemplary embodiments
of the invention: TABLE-US-00003 Sn(%) Nb(%) Fe(%) V(%) O(%)
Si(ppm) C(ppm) A 0.30 0.25 0.35 0.16 0.14 110 100 B 0.30 0.45 0.15
0.10 0.14 110 100 C 0.40 0.45 0.10 0.07 0.14 110 100 D 0.30 0.75
0.13 0.07 0.14 110 100
[0031] Remainder: reactor-pure unalloyed zirconium in each, with
permitted foreign substances or impurities.
[0032] To produce cladding tubes, ingots of the alloys A to D are
melted in vacuo in a number of melting steps and then forged in the
.beta.-range of the alloys below the melting point. The forgings
are heated again to a temperature in the .beta.-range and then
quenched in a water bath with a cooling rate of at least 30 K/s.
The forgings are then forged to form rods.
[0033] The forged rods are machined and cut into pieces which are
used to extrude tubes. To obtain a fully recrystalized
microstructure, an anneal is carried out after the extrusion. The
tubes treated in this way are pilgered in a number of steps by
cold-forming to form cladding tubes. Prior to each deformation
operation, an intermediate anneal is carried out in vacuo at
temperatures of approximately 700.degree. C., which brings about
recovery and recrystalization. The final deformation, which leads
to the definitive cross section of the cladding tube, is followed
by a final anneal at approximately 600.degree. C. In this way, a
low creep deformation with a high yield strength is set for the
intended reactor use. A cumulative annealing parameter in the range
A=10-40 E-18 h is maintained during production. It is in addition
optionally possible to carry out an anneal in the alpha range
following production of the forged rods.
[0034] The cladding tubes which have been produced in the manner
outlined are finally filled with fuel pellets and welded to end
stoppers in a gastight manner at both ends. This concludes the
production of the fuel rods. Control rod guide tubes are also
produced by the same process.
[0035] In another exemplary embodiment, following corresponding
heating and quenching of an ingot of the same composition, the
forging is hot-rolled (once or in a number of steps with anneals
between them) to form plates. For the hot-forming and intermediate
annealing steps, the temperatures are selected in such a way that
they are in the .alpha.-range of the alloys. Then, the plate is
cold-rolled in a number of steps to form a metal sheet of the
desired thickness. Between the deformation steps and following the
final deformation, a vacuum anneal is carried out, which can also
take place as a continuous process and brings about complete
recrystalization. These metal sheets are processed further to form
spacers.
[0036] If spacers, guide tubes and fuel rods produced in this way
are used in a pressurized-water reactor, these components have
better corrosion properties, in particular after a prolonged
operating period, compared to components made from conventional
Zircaloy-4 with a low tin content (low tin Zirc-4), as can be
established from empirical calculations. The results of these
calculations are disclosed in the diagram of the FIGURE. The
burn-up is plotted on the abscissa and the oxide layer thickness on
the ordinate. It can be seen that the alloys according to the
invention can remain in the reactor for approximately twice as long
(6 cycles) as the conventional alloys (3 cycles) before they have
to be replaced for corrosion reasons. As noted above, all
percentages cited herein are in percent by mass.
* * * * *