Note: Descriptions are shown in the official language in which they were submitted.
WO 2020/233814
PCT/EP2019/063328
1
System and Method for Removing Irradiation Targets from a Nuclear
Reactor and Radionuclide Generation System
FIELD OF THE INVENTION
The present invention is directed to a system and a method for removing
irradiation targets from a commercial nuclear reactor and a radionuclide
generation
system.
TECHNICAL BACKGROUND OF THE INVENTION
Radionuclides are used in various fields of technology and science, as well as
for medical purposes. Usually, radionuclides are produced in research reactors
or
cyclotrons. However, since the number of facilities for commercial production
of
radionuclides is limited already and expected to decrease, it is desired to
provide
alternative production sites.
The neutron flux density in the core of a commercial nuclear reactor is
measured, inter alia, by introducing solid spherical probes into
instrumentation
tubes passing through the reactor core. It was therefore suggested that
instrumentation tubes of commercial nuclear reactors shall be used for
producing
radionuclides.
EP 2 093 773 A2 suggests that existing instrumentation tube systems
conventionally used for housing neutron detectors may be used to generate
radionuclides during normal operation of a commercial nuclear reactor. In
particular, spherical irradiation targets are linearly pushed into and removed
from
instrumentation fingers extending into the reactor core. Based on the axial
neutron
flux profile of the reactor core, the optimum position and exposure time of
the
targets in the reactor core are determined. A driving gear system is used for
moving
and holding the irradiation targets in the instrumentation tube system.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 2 -
Due to the high activity of the activated irradiation targets retrieved from
the
instrumentation tube system, and since space within the reactor containment is
limited, the activated targets are difficult to handle. In particular, the
activated
targets including the radionuclides must be filled into and stored in
containers
provided with heavy radiation shielding. The chambers for a Traversing Incore
Probe (TIP) system and/or an Aero-ball Measuring System (AMS) do not have any
structures for packaging and transporting those heavy containers. Provision of
additional water locks in the reactor containment for handling of the
activated
targets and shielded containers would also be too expensive.
WO 2016/173664 Al describes an irradiation target processing system for
insertion and retrieving irradiation targets into and from an instrumentation
tube in
a nuclear reactor core. The target processing system comprises a target
retrieving
system, a target insertion system and a transport gas supply, which are
mounted
on a movable support. The target retrieving system comprises a discharge tube
having a lock element for blocking movement of the irradiation targets into an
exit
port. The discharge tube is formed as inverse U, forming an apex and a first
section
and a second section of the discharge tube. The lock element blocks the
movement
of the activated irradiation targets in the first discharge tube section. The
exit port
comprises a gas inlet port coupled to a first gas supply tubing and a ball
valve,
which connects the exit port with a storage container and an external exhaust
system. The target processing system comprises at least one movable magnet,
which can differentiate between irradiation targets and positioning targets in
case
the two types of targets differ in their magnetic properties.
WO 2017/012655 Al describes a method of producing radionuclides from
irradiation targets in a nuclear reactor using at least one instrumentation
tube
system of a commercial nuclear reactor. Irradiation targets and dummy targets
are
inserted into an instrumentation finger and the irradiation targets are
activated by
exposing them to neutron flux in the nuclear reactor core to form a desired
radionuclide_ The dummy targets are used to hold the irradiation targets at a
predetermined axial position in the reactor core corresponding to a pre-
calculated
neutron flux density sufficient for converting the irradiation targets to the
radionuclide. The dummy targets are separated from the activated irradiation
targets by exposing the dummy targets and/or the activated irradiation targets
to a
magnetic field to retain either the dummy targets or the activated irradiation
targets
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 3 -
in the instrumentation tube system and release the other one of the activated
irradiation target or the dummy target from the instrumentation tube system.
For
this purpose, the dummy targets and the activated irradiation targets have
different
magnetic properties.
WO 2017/012655 Al describes a method for harvesting activated irradiation
targets from an instrumentation tube system of a nuclear reactor. For this
purpose,
the instrumentation tube system is coupled to a discharge tube having an apex,
an
exit port and a lock element between the apex and the exit port. The activated
irradiation targets are passed from the instrumentation tube system into the
discharge tube and their movement is blocked by means of the lock element. Due
to the apex, the activated irradiated targets can be separated into two
quantities of
targets. By releasing the lock element, the irradiation targets between the
lock
element and the apex can be passed under action of gravity into a storage
container coupled to the exit port, retaining the other quantity of the
targets in the
discharge tube by means of the apex.
However, the quantity of activated irradiation targets in the discharge tube
between the lock element and the apex is fixed by the given geometry of the
harvesting system comprising the discharge tube and the apex. However, it has
been shown that the size of the available and needed storage containers is
often
not big enough to incorporate the given quantity of activated irradiation
targets.
At the same time, the use of dummy targets, which can be magnetically
separated from the irradiation targets, is unfavorable, as the number of
targets
within the nuclear core is limited and the irradiation times can be very long,
in some
cases up to 2 weeks. Therefore, it is desirable to use the positions needed
for the
dummy targets for irradiation targets, too.
It is therefore an object of the invention to provide an irradiation target
removal
system, which allows the use of a higher amount of irradiation targets for the
production of radioisotopes in a commercial nuclear reactor and provides an
improved possibility of portioning activated irradiation targets. Furthermore,
it is an
object of the invention to provide a radionuclide generation system comprising
such an irradiation target removal system. In addition, it is an object of the
invention
to provide a method for removing activated irradiation targets in such
systems.
CA 03136561 2021- 11- 3
- 4 -
SUMMARY OF THE INVENTION
The above objects are solved by an irradiation target removal system as
described
herein, a radionuclide generation system as described herein, a discharge tube
as
described herein, and a method for removing activated irradiation targets as
described
herein.
According to a first aspect, the invention provides an irradiation target
removal
system comprising at least one storage container for receiving activated
irradiation
targets from an instrumentation tube system of a nuclear reactor; and
a discharge tube comprising a first discharge tube section, a second discharge
tube section and a conjunction of the first and second discharge tube section;
and
a supply of pressurized gas connected to the first discharge tube section for
pressurizing the discharge tube;
wherein the second discharge tube section is coupled to the instrumentation
tube
system, and wherein the first discharge tube section comprises an exit port
assigned
to the storage container, a first lock element for blocking movement of the
activated
irradiation targets to the storage container, wherein the first lock element
is located
between the exit port and the conjunction; and at least one opening located
between
the first lock element and the conjunction, wherein the supply of pressurized
gas is
connected to the at least one opening.
In some implementations, there is provided an irradiation target removal
system
comprising: at least one storage container for receiving activated irradiation
targets
from an instrumentation tube system of a nuclear reactor; a discharge tube
comprising
a first discharge tube section, a second discharge tube section and a
conjunction of
the first and second discharge tube sections; and a supply of pressurized gas
connected to the first discharge tube section for pressurizing the discharge
tube;
wherein the second discharge tube section is coupled to the instrumentation
tube
system, and wherein the first discharge tube section comprises:
Date recue / Date received 2021-11-24
- 4a -
- an exit port assigned to the storage container;
- a first lock element for blocking movement of the activated
irradiation targets
to the storage container, wherein the first lock element is located between
the exit port
and the conjunction; and
- at least one opening located between the first lock element and the
conjunction, wherein the supply of pressurized gas is connected to the at
least one
opening; and
wherein the exit port comprises a stop valve for pressure-tightly sealing the
exit
port.
The irradiation target removal system comprises several possibilities for
separating
the activated irradiation targets into smaller quantities. A first separation
can be done
by means of the shape of the discharge tube. Due to the first lock element, a
predefined amount of irradiation targets can be kept between the first lock
element
and the conjunction in the first discharge tube section (from here on defined
as "full
quantity").
When the first lock element is released, all irradiation targets in the first
discharge
tube section are removed from the discharge tube, for instance due to gravity,
and can
be collected by the storage container. This corresponds to methods for
harvesting
activated irradiation targets from an instrumentation tube system of a nuclear
reactor
as known in the art. However, in this case storage _____________
Date recue / Date received 2021-11-24
WO 2020/233814
PCT/EP2019/063328
- 5 -
containers are needed, which are big enough to incorporate the "full quantity"
of
activated irradiation targets.
In contrast, by providing at least one opening located between the first lock
element and the conjunction, it is possible to further divide the "full
quantity" of
irradiation targets into smaller predefined quantities. The size of these
predefined
quantities is defined by the location of the at least one opening within the
first
discharge tube section. In fact, the at least one opening is located at a side
area of
the first discharge tube section, namely the lateral side.
Providing openings is an easy way to realize the supply of pressurized gas
into
the discharge tube. Also, this is an easy solution to incorporate the
irradiation target
removal system of the present invention into existing systems.
For instance, the at least one opening relates to a borehole that is drilled
into
the first discharge tube section_ Hence, already existing discharge tubes can
be
used.
By applying a stream of pressurized gas through the at least one opening, all
irradiation targets above the level of the at least one borehole can be
transferred
back into the second discharge tube section and even back to instrumentation
fingers of the nuclear reactor. Alternatively or additionally, further holding
or rather
stopping positions may be defined that are located closer to the nuclear
reactor
with respect to the at least one opening_ For instance, these holding or
rather
stopping positions are defined by other openings in the discharge tube, which
may
interact with other lock elements.
In any case, only a predefined quantity of activated irradiation targets is
retained in the first discharge tube section due to the pressurized gas, which
corresponds to the distance between the first lock element and the position of
the
at least one opening.
The predefined quantity of activated irradiation targets can be adjusted to
the
size of the available storage containers, in which the activated irradiation
targets
are typically stored.
The separation of the different quantities of targets in the first discharge
tube
section is based only on the location at which gas is supplied into the
discharge
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 6 -
tube. Therefore, there is no need to implement means to differentiate between
different types of targets, for example by their magnetic properties. In this
way,
there is no need to use dummy targets in the inventive irradiation target
removal
system for realizing smaller predefined quantities of activated irradiation
targets
compared to the "full quantity" defined by the geometry of the discharge tube.
Therefore, all possible positions within the instrumentation fingers of the
nuclear
core of the nuclear reactor can be used for production of irradiation targets.
This
increases the efficiency of the generation of radionuclides compared to
previous
radionuclide generation systems. Simultaneously, the portioning is simplified
since
no magnetic systems are required for selecting the activated irradiation
targets.
However, it is still possible to use dummy targets if wished. This can be
necessary if it is known that there are positions in the instrumentation
fingers of the
nuclear core that do not exhibit sufficiently high neutron flux density to
obtain the
desired radionuclides in sufficiently high amounts for their intended
applications.
Preferably, the dummy targets are magnetic, which allows for using a selector
mechanism to easily distinguish between and separate activated irradiation
targets
from the dummy targets_
Furthermore, the inventive irradiation target removal system can easily be
applied to existing facilities by providing the at least one opening to,
particularly
drilling the at least one borehole into, the first discharge tube section and
connecting this at least one opening, particularly borehole, to a supply of
pressurized gas.
An apex may be formed at the conjunction of the first and second discharge
tube sections, wherein the first and second discharge tube sections are
directed
downwardly from the apex. The first lock element is located between the exit
port
and the apex. The at least one opening is located between the first lock
element
and the apex. As mentioned above, the irradiation target removal system
comprises the first separation that is done by means of the shape of the
discharge
tube, namely the apex. Due to the first lock element, a predefined amount of
irradiation targets can be kept between the first lock element and the apex in
the
first discharge tube section (from here on defined as "full quantity"). The
apex and
both tube sections directed downwardly from the apex ensure that gravity can
be
used for the first separation.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 7 -
In one embodiment, the at least one opening can comprise a set of openings
provided at the first discharge tube section circumferentially at the same
height. In
this way, the pressurized gas can be supplied evenly into the first discharge
tube,
especially when the individual openings are provided symmetrically around the
circumference of the first discharge tube section. This leads to a better
control of
the system when separating the irradiation targets. Particularly, a set of
boreholes
is drilled into the first discharged tube section circumferentially at the
same height.
In a preferred embodiment, the pressurized gas supply comprises a control
valve, preferably a 2/2 control valve. This provides an easy and secure way to
control the gas flow coming from the gas supply.
To avoid that the gas coming from the gas supply leaks out around the
discharge tube, the at least one opening can be housed in a pressure-tight
encapsulation. This also increases the stability and control of the applied
pressurized gas. Furthermore, the pressure-tight encapsulation may have
radiation
shielding properties.
In another embodiment, a second lock element can be located in a pathway
originating from the instrumentation tube system. For instance, the second
lock
element is located in a pathway connecting the second discharge tube section
and
the instrumentation tube system.
In this way, the already activated irradiation targets, which are removed from
the first discharge tube section, particularly the entire discharge tube, by
the
pressurized gas, can be blocked in the pathway before they are charged back
into
the instrumentation tube system. Therefore, it can be prevented that the
irradiation
targets again enter the nuclear core and are exposed to additional irradiation
without the need to precisely adjust and control the gas flow into the first
discharge
tube section.
This system can be used for moving the irradiation targets several times
between the pathway and the first discharge tube section, particularly the
discharge tube section, e.g. when several times predefined quantities of
activated
irradiation targets are to be collected from the total amount present in the
radionuclide generation system and filled in individual storage containers.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 8 -
The possibilities of an operator to collect a certain quantity of activated
irradiation targets can be further increased by providing, particularly
drilling, two or
more sets of openings, for instance boreholes, at different heights of the
first
discharge tube section, wherein each set of openings, particularly boreholes,
is
connected to the pressurized gas supply.
The different sets of openings can be connected to the same or to different
supplies of pressurized gas, which can have coupled or uncoupled valves for
controlling the gas flow.
The distance between the first lock element and a first set of openings can be
different to the distance between the first and a second set of openings.
By choosing different height differences between the first lock element and
the
different sets of openings, it becomes possible to choose between several
different
predefined quantities of irradiation targets retained in the first discharge
tube
section, dependent on through which set of openings pressurized gas is
supplied,
for instance.
The exit port can be positioned above the assigned storage container so that
the predefined quantity of activated irradiation targets can be transferred to
an filled
in the storage container, for example by the action of gravity. The distance
between
the exit port and a corresponding opening in the storage container is adapted
such
that the irradiaton targets cannot miss the opening.
Preferably, the exit port is configured to be coupled to the assigned storage
container. Providing a removable connection between the exit port and the
storage
container allows for operating in a closed system and minimizing the risk for
an
operator of being exposed to radiation.
In a preferred embodiment, the exit port comprises a stop valve for pressure-
tightly sealing the exit port. Such an exit port prevents the pressurized gas
supplied
through the at least one opening to leak out of the exit port and therefore
ensures
that the pressure in the first discharge tube section increases and lifts the
irradiation targets above the at least one opening beyond the conjunction,
particularly over the apex, of the discharge tube.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 9 -
In a further preferred embodiment, at least one cartridge is provided that is
assigned to the irradiation targets, the cartridge containing a radionuclide
precursor
material. Preferably, the cartridge comprises a housing containing one or more
irradiation targets. In this way, the radionuclide precursor material does not
need
to be capable of forming spherical irradiation targets, which are stable
enough to
withstand the conditions in the radionuclide generation system. Especially in
a
pneumatically driven system, the forces acting on the targets might be large
and
not every desired precursor material is capable of forming sufficiently stable
spheroids, which do not break or shatter when exposed to these forces. By
using
at least one cartridge, only the cartridge has to withstand the mechanical
forces
encountered. Therefore, radionuclides can be generated which would otherwise
be not obtainable.
In another aspect, the invention provides a radionuclide generation system
comprising an irradiation target removal system as described above.
According to a further aspect, the invention provides a discharge tube for an
irradiation target removal system, particularly an irradiation target removal
system
as described above, the discharge tube comprising at least a first discharge
tube
section that comprises:
-
an exit port assigned to a storage container of the irradiation target
removal
system;
-
a first lock element for blocking movement of activated irradiation
targets
to the storage container, wherein the first lock element is located between
the exit
port and a connecting port to an instrumentation tube system of the
irradiation
target removal system; and
- at least one
opening located between the first lock element and the
connecting port, wherein the at least one opening is configured to provide an
interface for a supply of pressurized gas.
In fact, the discharge tube according to the invention relates to the lower
part
of the irradiation target removal system described above.
CA 03136561 2021- 11- 3
- 10 -
In yet another aspect, the invention provides a discharge tube for an
irradiation
target removal system, the discharge tube comprising at least a first
discharge tube
section that comprises:
- an exit port assigned to a storage container of the irradiation
target removal
system;
- a first lock element for blocking movement of activated
irradiation targets to
the storage container, wherein the first lock element is located between the
exit port
and a connecting port to an instrumentation tube system of the irradiation
target
removal system; and
- at least one opening located between the first lock element and the
connecting
port, wherein the at least one opening is configured to provide an interface
for a supply
of pressurized gas; and
wherein the exit port comprises a stop valve for pressure-tightly sealing the
exit
port.
In fact, the discharge tube according to the invention relates to the lower
part of
the irradiation target removal system described above.
In yet another aspect, the invention provides a method for removing activated
irradiation targets from an instrumentation tube system of a nuclear reactor,
wherein
the method comprises the steps of:
a) Coupling at least one instrumentation finger of an instrumentation tube
system
to the irradiation target removal system as described above;
b) Passing the activated irradiation targets from the instrumentation finger
into
the discharge tube and blocking movement of the activated irradiation targets
out of
the discharge tube by means of the first lock element;
Date recue / Date received 2021-11-24
- 10a -
c) Separating a predefined quantity of the activated irradiation targets from
another quantity of the activated irradiation targets in the discharge tube;
and
d) Assigning the exit port to a storage container and releasing the first lock
element to pass the predefined quantity of activated irradiation targets in
the discharge
tube into the storage container;
wherein said separating step comprises supplying pressurized gas into the
first
discharge tube section through the at least one opening, thereby driving the
another
quantity of activated irradiation targets above the at least one opening from
the first
discharge tube section beyond the conjunction into the second discharge tube
section,
and keeping the predefined quantity of activated irradiation targets in the
first
discharge tube section.
Besides the pressurized gas used for portioning or rather separating the
activated
irradiation targets, a pneumatically operated drive system may be provided
that is
configured to insert the irradiation targets, for instance so-called aero-
balls, into an
instrumentation finger and to remove the irradiation targets, for instance the
aero-balls,
from the respective instrumentation finger after their activation.
BRIEF DESCRIPTION OF THE DRAWINGS
Further aspects and advantages of the invention will become more apparent from
the following description of preferred embodiments and from the accompanying
drawings wherein like elements are represented by like numerals. The preferred
embodiments are given by way of illustration only and are not
Date recue / Date received 2021-11-24
WO 2020/233814
PCT/EP2019/063328
-11 -
intended to limit the scope of the invention, which is apparent from the
attached
claims.
In the drawings:
- Figure 1 shows a schematic sketch of a radionuclide generation system
setup according to the invention;
- Figure 2 shows a schematic sketch of an irradiation target removal system
of the present invention;
- Figure 3 shows a close-up view of the first discharge tube section of an
irradiation target removal system;
- Figure 4 shows the first discharge tube section of Figure 3 during
separation
of the irradiation targets;
- Figure 5 shows the first discharge tube section of Figure 3 after the
separation of the irradiation targets while releasing the predefined quantity
of
activated irradiation targets;
- Figure 6 is a schematic sequence of the method according to the invention;
- Figure 7 shows another schematic sketch of a radionuclide generation
system setup according to the invention; and
- Figure 8 shows a close-up view of the first discharge tube section of
another
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention contemplates that a commercial nuclear reactor can be used for
producing radionuclides. In particular, conventional aero-ball measuring
systems
or other instrumentation tube systems of the commercial reactor can be
modified
and/or supplemented to enable an effective and efficient production of
radionuclides.
Some of the instrumentation tubes for example of a commercial Aero-ball
Measuring System (AMS) or Traversing Incore Probe (TIP) system are used to
guide the irradiation targets into the reactor core and to lead the activated
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 12 -
irradiation targets out of the reactor core. The activation of the targets is
optimized
by positioning the irradiation targets in predetermined areas of the reactor
core
having a neutron flux sufficient for converting the parent material in the
irradiation
targets completely into the desired radionuclide(s).
The proper positioning of the irradiation targets may be achieved by means of
dummy targets made of an inert material, preferably a magnetic material, and
sequencing the dummy targets and the irradiation targets in the
instrumentation
tube system so as to form a column of the targets within the instrumentation
finger.
In fact, the irradiation targets are at pre-calculated optimum axial positions
in the
reactor core and the other positions are occupied by the inert dummy targets
or
remain empty. However, it is preferred to use as many positions within the
instrumentation fingers for irradiation targets instead of dummy targets to
produce
as much radionuclides as possible.
Figure 1 illustrates the basic setup of a radionuclide generation system 6
within
a commercial nuclear power plant 8. As opposed to a research reactor, the
purpose
of a commercial nuclear reactor is the production of electrical power.
Commercial
nuclear reactors typically have a power rating of 100+ Megawatt electric.
The basis of the radionuclide generation system 6 described in the example
embodiments is derived from a conventional Aero-ball Measuring System (AMS)
used to measure the neutron flux density in the core of the nuclear reactor,
namely
the reactor core 10.
A plurality of aero-balls are arranged in a linear order thereby forming an
aero-
ball column. The aero-balls are substantially spherical or round probes but
can
have other forms such as ellipsoids or cylinders, as long as they are capable
of
moving through the conduits of the instrumentation tube system.
The aero-ball measuring system includes a pneumatically operated drive
system configured to insert the aero-balls into an instrumentation finger and
to
remove the aero-balls from the respective instrumentation finger after
activation.
Typically, the instrumentation fingers extend into and pass the core 10
through
its entire axial length.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 13 -
Referring to Figure 1, a commercial nuclear reactor comprises an
instrumentation tube system 12 including at least one instrumentation finger
14
passing through the reactor core 10 of the nuclear reactor. The
instrumentation
tube system 12 is configured to permit insertion and removal of irradiation
targets
16 and optionally magnetic or non-magnetic dummy targets 18 (cf. Fig. 2) into
the
instrumentation fingers 14.
The aero-ball measuring system of the commercial nuclear reactor is adapted
to handle irradiation targets 16 having a round, cylindrical, elliptical or
spherical
shape and having a diameter corresponding to the clearance of the
instrumentation
finger 14 of the aero-ball measuring system. Preferably, the diameter of the
targets
16, 18 is in the range of between 1 to 3 mm, preferably about 1.7 mm.
Conduits of the instrumentation tube system 12 penetrate an access barrier 11
of the reactor and are coupled to one or more instrumentation fingers 14.
Preferably, the instrumentation fingers 14 penetrate the pressure vessel cover
of
the nuclear reactor, with the instrumentation fingers 14 extending from the
top to
the bottom over substantially the entire axial length of the reactor core 10.
A
respective end of the instrumentation fingers 14 at the bottom of the reactor
core
10 is closed and/or provided with a stop so that the irradiation targets 16
inserted
into the instrumentation finger 14 form a column wherein each target 16 is at
a
predefined axial position.
According to a preferred embodiment, the commercial nuclear reactor is a
pressurized water reactor. More preferably, the instrumentation tube system 12
is
derived from a conventional aero-ball measuring system of a pressurized water
reactor (PWR) such as an EPRTM or SiemensTM PWR nuclear reactor.
The person skilled in the art will however recognize that the invention is not
limited to use of an aero-ball measuring system of a PWR reactor. Rather, it
is also
possible to use the instrumentation tubes of the Traversing Incore Probe (TIP)
system of a boiling water reactor (BWR), the view ports of a CANDU reactor and
temperature measurement and/or neutron flux channels in a heavy water reactor.
As shown in Figure 1, the instrumentation tube system 12 is connected to a
target drive system 20 configured to insert the irradiation targets 16 and
optionally
dummy targets 18 into the instrumentation fingers 14 in a predetermined linear
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 14 -
order and to force the irradiation targets 16 and dummy targets 18 out of the
instrumentation finger 14 thereby retaining the linear order of the targets
16, 18.
Preferably, the dummy targets are magnetic.
Preferably, the target drive system 20 is pneumatically operated allowing for
a
fast processing of the irradiation targets 16 and optionally the dummy targets
18
using pressurized gas such as nitrogen or air.
The target drive system 20 cooperates with an irradiation target removal
system 22 configured to receive activated irradiation targets 16 and
optionally
dummy targets 18 from the instrumentation tube system 12 and pass a predefined
quantity 16 of the activated irradiation targets 16 into a shielded storage
container
34 (c.f. Figure 2). The irradiation target removal system 22 will be described
in
greater detail below, with reference to Figure 2.
With further reference to Figure 1, an instrumentation and control unit (ICU)
24
is connected to the target drive system 20 and the irradiation target removal
system 22 as well as an online core monitoring system 26 for controlling
activation
of the irradiation targets 16. Preferably, the ICU 24 is also connected to a
fault
monitoring system 28 of the aero-ball measuring system for reporting any
errors.
The fault monitoring system 28 may also be designed without connection to the
existing aero-ball measuring system, but be connected directly to a main
control
room.
According to an embodiment, the core monitoring system 26 and the
instrumentation and control unit 24 are configured such that the activation
process
for converting the irradiation targets 16 to the desired radionuclide is
optimized by
considering the actual state of the reactor, especially the current neutron
flux, fuel
burn-up, reactor power and/or loading. Thus, an optimum axial irradiation
position
and irradiation time can be calculated for optimum results. It is however not
important whether the actual calculation is performed in the ICU 24 or by the
core
monitoring system 26 of the aero-ball measuring system.
The irradiation targets 16 are made of non-fissile material and comprise a
suitable precursor material for generating radionuclides, which are to be used
for
medical and/or other purposes. More preferably, the irradiation targets 16
consist
of the precursor material, which converts to a desired radionuclide upon
activating
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 15 -
by exposure to neutron flux present in the reactor core 10 of an operating
commercial nuclear reactor. Useful precursor materials are Mo-98, Yb-176 and
Lu-
176, which are converted to Mo-99 and Lu-177, respectively. It is understood,
however, that the invention is not limited to the use of a specific precursor
material.
The optional dummy targets 18 are made of an inert material, which is not
substantially activated under the conditions in the reactor core 10 of an
operating
nuclear reactor. Preferably, the dummy targets 18 can be made of inexpensive
inert materials and can be re-used after a short decay time so that the amount
of
radioactive waste is further reduced. More preferably, the dummy targets are
magnetic.
For use in a conventional aero-ball measuring system, the irradiation targets
16 and the dummy targets 18 have a round shape, preferably a spherical or
cylindrical shape, so that the targets 16, 18 may slide smoothly through and
can
be easily guided in the instrumentation tube system 12 of the aero-ball
measuring
system by pressurized gas, such as air or nitrogen, and/or under the action of
gravity.
The irradiation target removal system 22 of the present invention is
schematically shown in more detail in Figure 2.
A discharge tube 30 is connected to the instrumentation finger 14 through aero-
ball conduits of the instrumentation tube system 12. The discharge tube 30 is
configured to receive the irradiation targets 16 driven out of the
instrumentation
finger 14 after activation is completed. The linear order of the irradiation
targets 16
and/or the dummy targets 18 is retained in the discharge tube 30. Preferably,
the
discharge tube 30 is located outside the reactor core 10, but within
accessible
areas inside the reactor containment.
The discharge tube 30 has an exit port 32, which is assigned to at least one
storage container 34, 34' for receiving the activated irradiation targets 16
from the
instrumentation finger 14. The exit port 32 can be positioned above the
assigned
storage container 34 to be filled, or can be coupled and/or removably
connected to
the assigned storage container 34. The at least one storage container 34, 34'
preferably has a shielding to minimize an operator's exposure to radiation
from the
activated irradiation targets 16.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 16 -
A first lock element 36 is provided in the discharge tube 30 for blocking
movement of the activated irradiation targets 16 to the storage container 34,
34'.
The first lock element 36 can be a magnetically or mechanically operated
restriction
element, preferably a pin crossing the discharge tube 30.
Referring to Figure 2, the discharge tube 30 comprises a first discharge tube
section 38, a second discharge tube section 40 and an apex 42 formed at a
conjunction of the first and second discharge tube section 38, 40. The apex 42
is
the highest point of the discharge tube 30. The first and second discharge
tube
sections 38, 40 are directed downwardly from the apex 42.
The exit port 32 is arranged at a free end of the first discharge tube section
38,
opposed to the apex 42, and the second discharge tube section 40 is coupled to
the instrumentation tube system 12. The exit port 32 comprises a stop valve 44
for
pressure-tight sealing the discharge tube 30.
In the shown embodiment, a set of openings 46 is provided circumferentially at
the first discharge tube section 38 between the first lock element 36 and the
apex
42, namely the conjunction. Particularly, the openings 46 are realized by
boreholes
that were drilled into the first discharge tube section 38. The set of
openings 46 is
surrounded by a pressure-tight encapsulation 48, which is connected by a 212
control valve 50 to a supply 52 of pressurized gas.
Preferably, air or nitrogen is used as pressurized gas. The pressurized gas
can
be supplied from the target drive system 20.
Even though a set of openings 46 is provided in the shown embodiment, a
single opening 461s also sufficient to be connected to the supply 52, as will
become
apparent hereinafter.
In the embodiment shown in Figure 2, the first discharge tube section 38, the
second discharge tube section 40 and the apex 42 at the conjunction of both
tube
sections 38, 40 are shaped in the form of an inverse U.
Other profiles of the discharge tube 30 are also possible.
Preferably, an apex 42 is formed between the first and second discharge tube
section 38, 40, which has a radius that is sufficiently small to effectively
separate
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 17 -
the target columns in the first and second tube sections 38, 40 from each
other in
a first separation step.
The operation of the irradiation target removal system 22 of the invention is
now described in greater detail.
Irradiation targets 16, which are activated in the instrumentation finger(s)
14 for
a period of time sufficient to convert the irradiation targets 16 into the
desired
radionuclide(s), are driven out of the instrumentation finger(s) 14 into the
instrumentation tube system 12 using pressurized gas such as air or nitrogen
supplied from the target drive system 20.
The discharge tube 30 is coupled to conduits of the instrumentation tube
system 12 for receiving the irradiation targets 16 (step S1 in Figure 6). A
gate
system (not shown) such as a three-way valve can be used to guide the
irradiation
targets 16 into the discharge tube 30 of the irradiation target removal system
22.
The linear order of the irradiation targets 16 in the instrumentation
finger(s) 14 is
preserved in the discharge tube 30.
At this time, as shown in Figure 3, access to the exit port 32 of the
discharge
tube 30 is blocked by the first lock element 36, providing a stop for the
activated
irradiation targets 16 and preventing the targets 16 from leaving the
discharge tube
30 (step 82 in Figure 6).
Typically, there are so many irradiation targets 16 within the discharge tube
30,
that they pile up until a level above the set of openings 46. In this case, a
predefined
quantity 16' of the activated irradiation targets 16 can be separated from
another
quantity 16" of the activated irradiation targets 16 in the discharge tube 30
(step
S3 in Figure 6).
For this purpose, pressurized gas is supplied into the first discharge tube
section 38 through the at least one opening 46, particularly the set of
openings 46.
This drives the another quantity 16" of activated irradiation targets 16 above
the at
least one opening 46 from the first discharge tube section 38 beyond the
conjunction of the first and second discharge tube sections 38, 40, namely the
apex
42 in the shown embodiment, into the second discharge tube section 40 (as
indicated by the arrows in Figure 4).
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 18 -
The another quantity 16" of activated irradiation targets 16 is driven into
the
second discharge tube section 40 that may be populated by a third quantity 16¨
of
activated irradiation targets 16. Then, the third quantity 16" of activated
irradiation
targets 16 is driven out of the second discharge tube section 40 by the
pressurized
gas. Alternatively or additionally, the another quantity 16" of activated
irradiation
targets 16 is also driven out of the second discharge tube section 40_
For instance, an intermediate storage is provided ensuring that the another
quantity 16" of activated irradiation targets 16 and/or the third quantity 16¨
of
activated irradiation targets 16 are/is not driven back into the reactor core
10.
Finally, the first lock element 36 and the stop valve 44 are released and the
predefined quantity 16' of the activated irradiation targets 16, which is
still located
within the first discharge tube section 38, can pass under the action of
gravity into
the storage container 34 assigned to the exit port 32 (as shown in Figure 5
and
step S4 in Figure 6).
After collecting the predefined quantity 16' of the activated irradiation
targets
16, the stop valve 44 at the exit port 32 is closed for providing a pressure-
tight
sealing of the exit port 32 and the discharge tube 30, and the shielded
storage
container 34 is then removed either manually or by means of an automated
handling device.
The above process steps can then be repeated for portioning and harvesting a
further quantity of activated irradiation targets 16 until all of the
activated irradiation
targets 16 have been removed from the instrumentation tube system 12. The
system is then ready for starting a new radionuclide generation cycle.
A further embodiment of the radionuclide generation system is presented in
Figure 7.
For same parts, the same numerals are used as in the embodiments presented
above_ The same features and advantages of the equivalent parts apply here,
too.
In this embodiment, the first discharge tube section 38 exhibits a first set
of
openings 46 surrounded by a first pressure-tight encapsulation 48 and a second
set of openings 46' surrounded by a second pressure-tight encapsulation 48'.
Each
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
- 19 -
of the encapsulations 48, 48' is connected by a 2/2 control valve 50, 50' to a
supply
52, 52' of pressurized gas.
In the shown embodiment, the control valves 50, 50' and the supplies 52, 52'
of pressurized gas are independent of each other. However, they could also be
a
single control valve 50 connected to a single supply 52.
The first and second sets of openings 46, 46' are located at different heights
of
the first discharge tube section 38. Additionally, the height difference of
the first to
the second set of openings 46, 46' is different to the height difference
between the
first set of openings 46 and the first lock element 36. In this way, dependent
on at
which height pressurized gas is applied in step S3 (c.f. Figure 6), different
quantities of activated irradiation targets 16 can be kept in the first
discharge tube
section 38 and afterwards transferred to the storage container 34.
Therefore, when several times a predefined amount of activated irradiation
targets 16 are collected, it is possible to first collect an amount
corresponding to
the height difference between the first lock element 36 and the first set of
openings
46 and afterwards a second amount corresponding to the height difference
between first lock element 36 and the second set of openings 46'.
Additionally, in this embodiment a second lock element 54 is located in a
pathway 56 originating from the instrumentation tube system 12. In fact, the
pathway 56 connects the second discharge tube section 40 and the
instrumentation tube system 12.
The second lock element 54 prevents irradiation targets 16, which are pushed
out of the discharge tube 30, to flow back into the instrumentation fingers 14
of the
nuclear reactor, particularly the reactor core 10.
It is also possible that the pathway 56 exhibits further junctions to
additional
tubes to which the irradiation targets 16 can be transferred during the
separating
step S3 of Figure 6.
In another embodiment shown in Fig. 8, cartridges 58 are used that are
assigned to the irradiation targets 16. Otherwise, the radionuclide generation
system 6 exhibits the same components as described in respect to the other
embodiments and like numerals are used for referencing like parts.
CA 03136561 2021- 11- 3
WO 2020/233814
PCT/EP2019/063328
-20 -
By using the cartridges 58, the precursor materials and produced radionuclides
do not need to be able to form stable spheroids, which can withstand the
forces
occurring in the radionuclide generation system 6. Only the cartridges 58
housing
one or more of the irradiation targets 16 need to be stable enough to be
transported
from the instrumentation fingers 14 into the discharge tube 30.
CA 03136561 2021- 11- 3
