Note: Descriptions are shown in the official language in which they were submitted.
Process and installation for the treatment of solid ~artiele ag~lo-
merates suspended in a liquid9 in order to obtain a heterogeneous
mixture able to flow in lon~ ducts without cau~ing depo~it~.
DESCRIPTION.
The invention relates to a process for proce~sing agglomerates in
solid particle form suspended in a liquid, in order to break or
divide them up and in this way obtain a heterogeneous mi~ture able
to flow in ducts or pipes of considerable length without any depos-
ition risk. This process is more particularly applicable to the
reprocessing of irrsdiated nuclear fuels, following the cutting
up of the latter, their dissolving in a nitric solution and their
settling in a clarifier. The invention also relates to an installa-
tion for performing this process.
In particular when it iR necessary to displace in long ducts liquids
containing solid particles, the latter tend to agglomerate with
one another and form heaps in areas ~here turbulent flow conditions
are not ensured. Due to the agglomeration, these heaps te~d to
form heaps ha~$ng a density lower than that of the particles forming
them. The agglomeration mechanisms are not well known, but the
bonds invol~ed are~mainly of two types, namely chemical bonds which,
when the said bonds are broke~, do not re-form in rapid manner and
Van Der Walls-t~pe bonds~which, when broken, can rapidly re-form.
The treatment proce~s according to the inYention makes it possible
to break these bonds by utilizing the characteristics of the equi-
pment used. This process is more particularl~ applicable to thetreatment of agglomerates~of fines encountered in the reprocessing
of irradiated nucleàr fuel~.
urlng their reprocessing, the irradiated~nuclear fuels are cut
up and then dissolred in hot nitric solutions. Following the
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dissolving operation, solid products called shells are obtained
and which are constituted by fuel can fragments and nitric solutions
containing agglomerates of solid particles ha~ing a limited grain
size and known as fines. These solid psrticle~ are based on zircon-
ium, molybdenum, ruthenium and other metals from the structure ofthe fuels.
Before being passed to extraction co:Lumns of the solvent, the nitric
dissolving solutions are settled in a clarifier, e.g. constituted
by a centrifugal, swinging settling tank. Thi3 clarifier makes
it possible to separate the clear nitric solutions to be passed
to the extraction columns from the fines which are then in the form
of sludges or solutions of varying thickness and agglomerated to
a varying e~tent.
In ~iew of their Yer~ high radioacti~it~, the fines must be incor-
porated in a glass ~atri~ with the fis d on products resulting from
the e~traction processes. For this purpose the~ are transferred
from the clarifier to the ~itrification site by transfer pipes.
On the ~itrification site, the said pipes issue into storage tanks,
where the solutions of fines are continuously stirred for nuclear
safety reasons, e.g. using pulsing mea~s.
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Such an installation suffers from numerous disadYantages. Firstl~,
the fines are abr~sive particles which, with increasing size) brin8
about ever gr~ater wear of the pipes, particularly in their curved
parts.
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In addition, when the fines are formed from highl~ agglomerated
particles, they tend to be deposited in the pipes, particularl~
:; in ehe ~on-turbulent areas or where there are surface roughnesses.After a certain time, plugs are formed~ w~lch cause stoppages in
; the inwardly cur~ed parts of the pipes. This constitutes 2 difficult
problem, becauee the unblocking of the pipes requires inter~ention
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in cells where man is no~ allowed access. Moreover, in view of
the difficulties encountered in modelling the behaviour of fine~,
it is ~ery difficult to successfully ~odify the installations and
parameters such as the flow rate, the pressure drops in the pipes,
etc., in order to pre~ent the formation of such plugs.
Moreover, the presence of agglomerates in the solutions of fines
also tends to lead to the said agglomerates bein8 deposited in the
bottom of storage tanks located on the vitrification site. As a
result the operation of the pulsing means used for stirring the
solutions of fines is disturbed, which is agaln an important dis-
advantage, in view of the difficulties encountered in intervening
within the tanks.
The invention specifically ~ims at a process and an installation
making it possible to treat in a simple manner agglomerates of solid
particles suspended in a liquid, such as the dissol~ing fines obtai-
ned during the reprocessing of irradiated nuclear fuel~, in order
to break up the agglomerates before said particles flow in long
-ducts or pipes, e.g. in order to be transferred to the vitrificatio~
site, by using easily realizable technical means ~hich can be fitted
~0 and dismantled remotel7 with the aid of telemanipulators when an
intervention proves necessary.
According to the invention this result is obtained by ~eans of a
process for the treatment of agglomerates of solid particles suspen-
ded in a liquid, in order to obtain a heterogeneous mixture able
to flow without leaving deposits in long ducts9 characterized in
that it comprises reducing the grain size of the particles b~ making
the latter flow in a loop incorporating means or breaking up the
agglomerates and screening the particles leaving the said loop, in
order to hold back~the particles having 8 grain size exceeding a
predetermined threshold.
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The invention ad~antageously applies to the treatment of fines obt~
ained after cutting up, dissolving and settling irrsdiated nuclear
fuel~ and prior to their transfer to a storage tank.
Preferabl~, prior to makin8 the partiles circulate within ~he loop,
theY undergo a prior size reduction, e.g. using ultrasonic waYe~,
within the apparatu~ in which settling takes place.
According ~o different embodiments of the in~ention, it i~ possible
to break up the agglomerates within the loop by using ult~asonic
means, or a renturi tube de~ice optionally followed by a baffle
system. In addition, the particles are preferably screened or sifted
in an ultrasonic screening or sifting machine.
hccording to another aspect of the in~ention, an installation is
proposed for the treatment of agglomerates of solid particles suspen-
ded in a liquid, in order to obtain a heterogeneous mi~ture able
to flow without lea~ing deposits in Yery long d~ucts, ~hich is char-
acteri~ed in that it comprises a loop having a transfer tank linked
with the bottom of a settling apparatus, pwmping means and means
for breaking up the agglomerates and a particle screening machine
placed in a pipe connecting the transfer tank to a storage tank
and located in the ~icinit~ of the transfer tank.
The in~ention is descrihed in ~reater detail hereinafter relati~e
to non-limitati~e emhodiments and the attached drawings, wherein
show:
Fig. 1 diugra = tically an installation for the treatment of
dissolving fines in accordance with the inYention.
Fig. 2 a diagrammatic sectional Yiew o an ultrasonic de~ice
placed,~according to a first embod~ment of the in~ention,
in the loop of the installatlon illustrated in fi8. 1.
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Fig. 3 a diagrammatic sectlonal view comparable to fig. 2 showing
a venturl tube device placed, according to a second embodi-
ment of the in~ention, in the loop of the installation
illustrated by fig. 1.
Fig. 4 a diagrammatic sectional Yiew comparable to fig~. 2 and
3 showing a venturi tube deYice placed, according to a
third embodiment of the invention, ln the loop of the
installation illustrated ~y fig. 1.
Fi8. 5 a disgrammatic sectional view comparable to Pigs. 2 to
4 showing a baffle and Yenturi tube de~ice for placing,
according to a fourth embodiment of the in~ention, in
the loop of the installation illu~trated by fig. 1.
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Fig. 6 a disgrammatic sectional view of an ultrasonic fines scre-
ening machlne usable in the installation illustrated by
::': fi8- 1.
The dissolving fines treatment in~tallation according to the in~en-
tion wlll firstl~be~descr~bed relati~e to ig. 1. In the latter9
the reference numeral lO desi~nates a clarifier9 e.g. coDstituted
by a centrifugal,~swinging settling tan~. ~ithin the said clarifier
10, the nitric solutions from the not shown dissol~ing appara~us
are settled i~ the~con~entional ~ay and in which the irradiated
nuclear fuels ha~e pre~iously been dissolved in~ho~ nitric solutioo
a~ter~cutting~up.~ These nitric solutions;are introduced into the
clarifier 10 by 8~ pipe~l2.~
In~the clarifier ~lO~the~clear nitric soluti~ons to ~e supplied to
not shown sol~ent~e~traction colu~ns by a duct 14 are separated
from ~the dissolving~fine~. When the clarifier is con~tituted by
a centrifugsl 3winging~settl m g tank, the fines are located in the
ottom o~the~Latter in~agglomerated form a~d~form a cake. Their
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transfer to the ~itrification site i~ then made possible b~ not
shown rin~ing ramps installed in the settling tank and makinx it
possible to break up the cake. The fines are then in the Eorm of
sludges or Yar~in~ly thick or ~ar~ingly agglomerated ~olutions i
the bottom of the settling tank.
These sludges are then collected in a transfer tank 16 by a connect-
ing pipe 18. To ensure that there is no risk of the latter becoming
blocked, the transfer ~ank 16 is preferabl~ placed immediately below
the clsrifier 10, the flow of fines taking place b7 gra~ity in the
pipe 18, whose length is also as small as possible.
The transfer tank 16 form~ part of a loop 20 for th2 continuous
dilaceration of the fines sludges collected i~ said tank. This
loop 20 comprises a duct 22 in which are placed, apart from the
transfer tank 16, a p~mp 24 and a dilacerating deYice 26 making
it possible to break up the fines agglomerates. The pu~p 24 can
in particular be constructed according to FR-A-2 361 55B. Variou~
embodiment~ of the dilacerating de~ice 26 will be described herein-
after relative to figs. Z to 5.
The dilaceration loop 20 constitutes a closed circuit ~hich, as
a result of the pump 24, makes it possible to continuously rec~cle
the fines sludges in the dilacerating device 26 until the average
grain size desired is obtai~ed.
During the first passage of the fines sludges in the loop 20, the
breaking up effect of the agglomerates obtained by the dilacerating
deYice 26 is ~irtually doubled by a comparable efect obtained in
the pump 24, as a result of the suctio~ and stirring due to sludge
rotation. The number of c~cle~ is determiQed b~ the user as a func-
tion of the initial characteri~tics of the treated sludges and the
characeeristics which lt is wished to obtain prior to ~he trans~er
of these sludges to the Yitrification site. A minimuo sludge flow
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rate in the loop 20 must be respected; in order to avoid ~ediment~-
tion of the sludges in the dilacerating device 26 or in the remainder
of the loop.
The pump 24 bringing about the circulation of fines sludges in the
loop 20 can be permanentl~ operated, no matter what the ~ludge quan-
tity present in the transfer tank 16. However, it is preferable
to store the solutions of fines in the transfer tank 16 in order
to only put the pump 24 into operation when the tank i~ sufficiently
full.
When the fines sludge~ present in the storage tank 16 ha~e an a~erage
grain size below a predetermined threshold, which e.g. corresponds
to the plugging or blockage threshold of the pipes for the transfer
t:o the ~itrification site, the said transfer takes place. It is
possible to establish that said threshold ha~ been cleared either
by checking the grain size of the qludges, or by deducing said grain
size from the number of cycles performed in the loop 20, or ~i~h
the aid of these two lnformations together.
The transfer of the fines sludges to the vitrificatlon site takes
: place by a pipe 28 in which is placed, in the immediate ~icinity
of the transfer tsnk 16, a fines sifting or screening machine 30.
The end of the pipe 28 oppo~ite to the transfer tank 16 i~s~es onto
the ~itrification site in a storage tank 32, which is in conventional
manner equipped with stirring means, such as not shown pulsing means,
for nuclear safety reason~.
The fines screening machine 30 placed at the entrance of the tran~fer
pipe 28 will be:described in 8reater detail hereinafter relati~s
; to fig. 6. Its function 19 to hold back the fines, whose grain
;~ : size e~ceeds a ma~imum threshold for the transfer pipe 28 and carries
~; : out a final breaking up of the agglomerates. It is also equipped
with unclogging or:unblocking means.
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The solutions of calibrated fines leaYing the fine~ screening machine
30 can therefore pass without difficulty through the tranQfer pipe
28 up to the storage tank 32 collesting the solutions of fines to
be ~itrified. In partic~lar, there is DO risk of the pipe 28 becom-
ing blocked or of an unsati3factor~ operation of the pulsing meanæequipping the storage tank 32.
With reference to fig. 2 a description will now be gi~en of a first
embodiment of the dilacerating device 26, in which the agglomerates
are broken up by a cavitation effect using ultrasonic ~aYes. Fig.
2 shows the said device, where it is designated b7 the reference
26a.
The ultrasonic dilacerating de~ice 26a is suspended on a horizontal
concrete slab 34, which separates a man-accessible upper zone 36
from a lower cell 38 in which are located the radioacti~e solution
treatment and transfer de~ices. By being suspended on the slab
34, the device 26a is consequently placed in the cell 38.
The ultrasonic dilacerating de~ice 26a comprises a ~ertically a~ed
cylindrical tank 40, equipped at its upper end with a flange 42
resting on the slab 34 and which is tightly connected thereto, e.g.
by screws 46.
The tank 40 is sealed at its upper end b~ a plug 48, which ensures
above the said device 26a the continuation of the biological prot-
ection pro~ided by the slab 34. At least one seal 50 carried by
the plug 48 provides the necessar~ sealing between the latter and
the upper part o the tank 40, whilst still allowing the removal
and putting into place of the plug 48 with the aid of a gripping
` member 52 located on the upper face of the plug and which can be
gripped by remote handling means located in the accessible zone
~ 36.
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A ring 53 placed abo~e the plug 48 maintains in position the as~embl~
constituted by the plug 48 and the body 56, e.g. ~ith the aid of
screws 55 engaged on the flange 42.
In the Yicinity of its lower end, the tank 40 has a thicker portion
54, whose upper stepped face constitutes a bearing surfac~ for the
body 56 of the acti~e part of the device 26a, said body 56 being
fi~ed, e.8. by screws, to the lower face of the plug 48. Seals
58 carried by the bod~ 56 then bear on the upper stepped face of
part 54 of tank 40, whilst a seal 60 carried by a lower cylindrical
part of the body 56 co~es into tight contact with the inner cylindri-
cal surface of part 54 of the tank 40.
An admdssion passage 62 radially tra~erses the thickest part 54
of the tank 40 and issue~ between the seals 58 and 60. Moreover,
an evacuation passage 64 is formed in the bottom of the tank 40,
in accordance with th0 ~ertical axis of the latter.
The body 56 of the acti~e part of the device 26a, which is fit~ed
coa~ially within the tank 40 so as to be e~tractable therefrom and
put in place therein with the plug 48 has an inner passage through
which flow the solutions to be treated from the admission passage
62 to the e~acuation passage 64. This passage formed within the
body 56 has an outer annular part 66, Yhose lower end issues in
front of the ~dmission passage 62 and a central part 68, whose upper
end is linked with the upper end of the annular part 66 and whose
lower end issues in front of the evacuation passage 64. The annular
part 66 and central part 68 are arranged coa~iall~ along the vertica
a~is of the tank 40,
The solutions admit~ed into the deYice 26a consequenely firstly
: flow from bottom to top in the annular part 66 and then fro~ top
to bottom in the central part 6B of the passa~e formed in the body
30 56. It should be noted that the passages 62 and 64 can be reversed,
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so that then the flow of solutions to be treated takes place in
the reYerse direction within the de~ice 26a.
Outside the annular part 66 and in thle zone located aboYe the thick-
est part 54 of the tank 40, the body 56 has an annular recess 70
in which are recei~ed se~eral groups of ultrasonic wave emitting
transducers 72.
Each of the groups of transducers 72 is e.g. formed by se~eral trans-
ducers aligned parallel to the Yertical a~is of the device 26a,
the groups of transducers being regularly distributed o~er the entire
circumference. The number and location of the transducers 72 in
each group, as well as the number and location of these groups in
the recess 70 are determined taking account of the constraints of
the process (flow rate, velocity, number of cycles in the loop,
etc.) and the height of the annular part 66 of the passage formed
in the bod~ 56.
The arrangement of the transducers 72 in the de~ice 26a makes it
possible for them to emit ultrasonic waves in directions oriented
radially with respect to the vertical a~is of the device, so as
to create a ca~itation effect over the entire surface of the liquid
traYersed b~ the sound wave. The ultrasonic frequency is chosen
as a function of the solution to be treated, said frequency beiDg
` e.g. 20 + 5 kNz.
The form or shape of the transducers 72 is chosen, as a function
of the frequenc~, so as to obtain a maximum cavitation effec~.
These transducers can in particular be in the for~ of cylinders.
However, a ring-like or o~oid shape can also be used.
In order to protect the transducers 72 from the effects of irradia-
tion, they are adYantageously sheathed with stainless steel. In
view of the fact that the transducers are not in direct contact
wlth the llquld to be treated, there is no need to take any special
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precaution with respect to corrosion or any other damage a~ a resule
of contact.
The electric supply for the transducers 72 is pro~ided from not
shown, external electric sources located in the upper zone 36 and
using electrical conductor~ 74. The latter are adYantageously sheat-
hed so as to have a good resistance to irradia~ion. Moreover, they
traverse the plu~ 48 in helical tubes 76, which guarantee the absence
of radiation leaks of the lower cell 38 in the upper ~one 36.
The helical tubes 76 also make it possible to produce a forced flow
of a cooling fluid, such as sir, within the recess 70. This forced
flow ensures the cooling of the transducers 72, which tend to heat
up as a result of their nwmber.
As has already been stated, the actiYe part of the deYice 26a loca~ed
within the tank 40 can be easily fitted and dismantled, e.g. using
a mobile evacuation enclosure like that described in FR-A-84 03312,
or any other equivalent means. When the active part of the device
is located outside the tank 40, it is merely necessary to disengage
it from the plug 48 to haYe access to the means located ~i~hin the
body 56.
As an embodiment of the deYice 26a, such a deYice was equipped with
twel~e groups each constituted by four transducers 72 emitting at
20 kHz, the annular part 66 in which the fines sludges to be treated
flow having a diameter of 11 mm and an effective height of 160 mm.
By bringing about the circulation in said device of dissolYed fines
sludges containing 75g of solids per litre of solution and in which
85% of particles had a size exceeding 140 ~m and generall~ in the
form of agglomerates between 150 and 250 ym, it was possible ~o
reduce 95~ of the fines to a si2e between 80 and 25 pm.
A second embodiment of the dilacerating de~ice 26 used in the loop
20 of the installation illustrated in fig. 1 will now be described
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relative to fig. 3. This device, which is designated in general
terms by 26b in fig. 3, is a ~enturi tube de~ice in which the di~-
in~egration of the agglomerates is obtained under the effect of
the shear forces created by the e3isting radial velocit~ 8radient~
in the ven~uri tube.
The installation of the device 26b of fig. 3 is the same as that
of device 26a of fig. 2. Thus, the device 26b is suspended on the
hori~ontal concrete slab 34, in such a way as to be placed in the
lower cell 38 located below said slab.
The dilacerating device 26b also incorporates a vertically a~ed
cylindrical tank 140, whose upper flange 142 is fi~ed to the slab
34 by screws 146. In its lower part, the tank 140 also has a thicker
zone 154, whereof the upper stepped face keeps in place the bod7
156 of the active part oi` the device. The said body 156 i9 fi~ed
e.g. b7 screws 157 to the lower end of a sleeve 149, which projects
downwards from a plug 148 tightl~ fi~ed to the flange 142 of the
tank 140, e.g. by screws 147.
The body 156 of the actiYe part of the deYice 26b rests on the upper
face of the thicker part 154 of the tank 140 ~ia two sealing 0-rings
158. Moreover, the body 156 has a c~lindrical lower pare, which
tightly cooperates with the cylindrical internal suriace of the
part 154 of tbe tank 140 b~ a seal 150.
An admission passage 162 formed in the thicker part 154 of the tank
140 issues into a ~ower chamber 163 formed in the tank 140 below
~he seal 160. hn e~acuation passage 164, also formed in the thicker
part 154 of the tank 140, issues into the latter between the seals
158 and 160.
The lower cha~ber 163 is linked with the eYacuation opening 164
by a passage i'ormed in the bod~ 156 and which successi~el~ incorpor-
ates an injector 165, a venturi ~ube 167 and an annular passage
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169. The injector 165 and the ventu.ri tube 167 are disposed along
the ~ertical axis of the tank 140, whereas the annular passage 169
is centered on the same axis and placed around the Yenturi tube
above the injector.
More specifically, the injector 165 is formed ln a lower ~art 171
of the body 156, which is fi~ed, e.g. by screws, to the lower end
of an intermediate part 173 of said same body in which is formed
the venturi tube 167. The fines solutions admitted into the lower
tank 163 by the admission pflssage 162 enter the injector 165 by
the larger diameter, lower end thereof, before passing from bottom
to top through the lower, convergent part 175 and then the upper,
divergent part 177 of the venturi tube 167.
These solutions then pass downwards again through the annular passage
16g~ whose upper end i3 linked ~ith the upper end of the venturi
15 tube 167 and whose lower end issues between the seals 1~8 and 160
in front of the evacuation passage 164. This annular passape 169
is formed between the intermediate part 173 of the body 156 and
an upper part 179 of the latter, which carries the seals 158 and
b~ which the body 156 is fi~ed to the slee~e 149. The connection
20 between the parts 179 and 173 of the body 156 is pro~ided by tie
rods 181.
Finally, the lower end of the annular passage 169 communicates with
8 recirculation chamber 183 formed in the bod~ lSS bet~een the injec-
tor 155 and the venturi tube 167 by means o holes 185 traversing
25 the intermediate part 173 of the body 156.
The solutions of fines circ~lating in the loop 20 of fig. 1 are
: introduced into the de~ice 26b b~ the admission passage 162, prefer-
;~ : ably at a pressure of at least 300 kPa. The pressurized liquidentering the inner chamber 163 tra~erses the de~ice fro~ bottom
: ~ 30 to top, whilst passing successiYely through the injector 165 and
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the convergent ~nd divergent zone~ 175,177 respec~lvely of the ~ent-
uri tube 167. The liquid flows at high Yelocity in the injector
165 and then in the venturi tube 167. Thus, for an approsimate
flow rate of 5 m3/h for the liquid introduced into the de~ice 26b
and an outlet diameter of the injec~or 165 of appro~imatelg 10 mm,
the Yelocit~ reached by the liquid iis approxi~atel~ 18 m/s.
To the primary flow rate of the liquid traversing the injector and
then the venturi tube from bottom to top must be added the induced
flow rate resulting from the entrainment by said primary liquid
of the liquid introduced into the recycling chamber 183 through
the holes 185. Tests have shown that the induced flow rate is Yery
close to the primary flow rate. Consequently the liquid flow rate
tra~ersing the venturi tube 167 corresponds to appro~ima~ely 10
m /h in the aforementioned example.
The liquid passing at high ~elocity out of the upper end of the
venturi tubs 167 runs against the upper cup-shaped end of the part
179 of the body 156 and drops again through the annular passage
169. Part of the liquid then passes out of the deYice 26b through
the evacuation passage 164 and the other part is recycled iD chamber -
183 through holes 185.
The liquid flowing in the injeetor 165 and then in the Yenturi tube
167 has a Yery high radial ~elocit~ gradient, iOe. the flow velocit~
of the liquid along the Yertical a~is of the device is much higher -
in the immediate vicinity of said a~is than along the walls of the
injector and the ~enturi tube. ~he liquid and the agglomerated
solid particles carried therein are consequently e~posed to Yery
hi8h shear force~ within the injector 165 and the Yenturi tube 167,
which break do~n the agglomerates.
A particle exposed to these shear forces is subdiYided into smaller
particle3 until the si~e o the particles i~ sufficientl7 small
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to ensure that the shear induced b~ the radial velocit~ gradient
in the injecto~ 165 and then in the venturi tube 167 is no longer
sufficient to break up these particles.
For example, it has been found that the passage in the device 26b
of a suspen~ion containing partic~es with a mean di~neter close
to 30 ym has the effect of reducing said mean diameter to a vslue
between 10 and 15 ym following a single passage and a val~e close
to 5 ym after recycling.
In another test, the suspended particles with a diameter larger
than lO0 ~m were recorded. The liquid initially entering the device
26b contains 4% particles of this type, whereas it only contains
3% on leaYing the venturi tube 167 after a first passage, said per-
centage being reduced to 1.5% after one recycling and to 0.7% after
two recyclings.
15 As in the first embodiment described relative to fig. 2, the device
26b is designed so as to permit remote dismantling or disengagement
of the plug 148 and the active part of the device, so as to permit
the partisl or total replacement of the lat~er, when its wear due
to the abrasi~e nature of the particles present in the treated liquid
makes this necessary.
In the dilacerating device 26b described with reference to fi8.
3, the fines sludges to be treated flow from bottom to top within
the ejector formed by the injector 165 and the venturi tube 167.
Practical tests have shown that a better efficiency can be obtained
by circulating the liquid from top to bottom ~ithin said ejec~or.
For this purpose, it is clear that the positions of the injector
and the venturi tube within the bod~ containing the acti~e part
of the device can be reversed. The admission pa~sage b~ which the
liquid to be treated is ad~itted into the device is then linked
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with the injector located in the upper part of the bod~ by an snnular
passage. Thiq liquid then flows from top to bottom in the in~ector
and then the venturi tube before being evacuated by a passage formed
in the lower part of said bod~ and tlhen by an evacuation passage
formed in the bottom of the tank. A recycling of the liquid to
be treated can be obtained by pro~iding between the annular pas~age
for supplying liquid to the injector and the central passage forming
the venturi tube, a second annular passage which is linked with
each of the ends of ~he venturi tube. A deflector is then advant-
ageously formed in the body of the active part of the de~ice, below
the lower end of the venturi tube, so as to prevent particles from
being deposited at this ~evel and so as to permit the recycling
of part of the liquid to be treated by this second annular passage.
Moreover, the venturi tube dilacerating device 26b described relat-
lS i~e to fig. 3 has a non-ca-/itatin~ recirculating ejector. By modi-
fying the process parameters, said ejector can be transformed into
a cavitating recirculating ejectorO In this ca e, a even better
efficiency of the device is obtained, but the abrasion risks are
greater. Howe~er, this solutioD can be adopted ~he~ t`he liquids
to be treated only need a short operating tlme.
As a variant, it is also possible to use devices incorporating vent-
uri tubes without recirculation, when the solid particles carried
by the liquid are only slightly agglomerated. When it is vital
to obtain a ma~imum disintegration of these particles, such as is
the case for the dissolYing fines obtained during the reprocessing
of irradiated nuclear fuels, the use of recirculation ~enturi tubes
remains preferable.
Thus, as in the embodiment de~cribed relative to fig. 3, the device
26c illustrated in fig. 4 has a vertically ased cylindrical tank
318 suspended on a horizontal slab 34 and an ejector 330 interchan-
~eably received in the tank 318, the replacement of the ejector
taking place from the zone 312 located above the slab 34.
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The body of the ejector 330 comprises three parts 331,332 and 333
coa~iall~ arran8ed around the vertical a~is of the tank 318. As
in the embodiment of fi8. 3, the nuter part 333 compri~es a ring-
shaped lower portion 349 resting on a thicker part 318a of the
tank 318 by means of two seals 362. Thi9 portion 349 is extended
upwards b~ a tubular portion 350, which is sealed at i~B upper end
by a horizontal portion 351 fi~ed to the cover 324 accessible from
the zone 312.
The part 333 internally supports by welded tie rods 353, the inter-
mediate part 331, which is shaped like a hollow cylinder and whose
upper end carries in its centre an injector 336. The lower portion
of part 331 carries a seal 360, which cooperates with the part 318a
of the tank 318 below the seals 362.
The part 331 internally ~upports by tie rods 355 the central part
15 332 constituting a venturi tube 334 arranged, together with the
injector 336, coa~ially to the vertical axis of the tank 318. The
upper intake end of the venturi tube 344 is t~rned upwards and faces
the outlet end of the injector 336.
The admission passage 340 for the liquid which it i~ wishsd to treat
20 and which is formed in the thicker part 318a of the tank 318, issues
between the seals 360 and 362 preferably in a tangential direction,
so as to create a whirling movement of the liquid in ~he annular,
outer chamber 370 formed between the outer and inter~ediate parts
333,331 respectively.
At its upper end, the outer, annular passage 370 is linked with
the upper, intake end of the injector 336, which is itself connected
to the venturi tube 344.
~ The lower end of the venturi tube 344 issues in front of a deflector
: 372 formed in the lower portion of the intermediate part 331. The
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shape of said deflector 372 makes it possible to avoid an accumula-
tion of particles at this location, by forcing the liquid to carry
out a radiall~ outwards and then upwards direction change. Passages
374 formed in said lower portion of the p~rt 331 issue at their
S upper end into thP bottom of the deflector 372 and at their lower
end in a evacuation chamber 356 formed in the bottom of the tank
318 below the seal 360. These passages 374 have a common, lower
part arranged in accordance with the axis of the tank 318 and posi~-
ioned immediately abo~e an evacuation passage 358 formed, along
the said a~is, in thP bottom of the tank 3180
An inner, annular, recycling passage 376 is also formed betweenthe intermediate part 331 and the central part 332 forming the vent-
uri tube 344. At its lower end the passage 376 issues above the
deflector 372 and, at its upper end, between the injector 336 and
lS the venturi tube 344.
In the device 316 described relative to fig. 4, the liquid to be
treated, injected under pressure by the admission passage 340, firs-
tly rises by the outer, annular passage 370 within the ejector 330.
In a downward movement it then successivel~ traYerses the injector
336 and the ~enturi tube 344. At the lower end of the latter, part
of the liquid is directly eYacuated by the passages 374 and 358,
whilst another part is rec~cled into the ~enturi t~be by the annular,
recycling passage 376.
The de~ices described successi~el~ with reference to figs. 3 and
4 comprise in both cases a non-cavitating recirculation ejector
which, has been shown to be the most efficient ejector for obtaining
the desired particle disintegration.
Fig. 5 diagrammatically shows a fourth embodiment of the dilacerat-
ing de~ice 26 ~sed in the loop 20 of the treatment installation
illustrated in fig. 1. This device is designated b~ the reference
26d.
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As in the embodiment described relative to fig. 3, the body 256
of the acti~e part of the device is interchangeably placed in a
ver~ically a~ed tank 240, which is suspended on a not shown, horizon-
tal slab. An admission passage 262 formed in a thicker part 254
of the tank 240 issues into a lower chamber 263 formed in the lower
part of the tank below a seal 260. An evacuation passage 264 also
formed in part 254 of the tank 240 issues in the interior of the
tank between the seal 260 and the seals 258, which are carried by
the body 256.
The liquid to be treated flows in a passage formed in the body 256
- between the lower chamber 263 and the evacuation passage 264. S~id
passage successively has an injector 265, a Yenturi tube 267 and
a baffle syste0 287. The baffle system 287 giYes a reduced height
and an increased diameter to the upper part of the body 256.
The baffle system 287 is consti~uted by a passage 289 formed between
two facing, coasial profiles 291,293. Part of the liquid leaYing
the passage 289 is eYacuated by the eYacuation passage 264, whilst
another part of said liquid is recycled in the venturi tube 267
by the holes 285 formed be~ween the latter and the injector 265.
In the dilacerating de~ice 26d described briefly with reference
to fig. 5, ~o the agglomerated particle disintegration effect obtai-
ned by shearing in the injector 265 and the Yenturi tube 267 in
the manner described hereinbefore, is added a supplementary particle
disin~egration under the effect of the impacts of said particles
against the walls of the baffle system 287.
When the dilacerating device 26 is of the Yenturi tube type 9 like
those successively described with reference to figs. 3 to 59 advan-
tageously determination takes place of the injector dia~eter so
that the pressure in the neck of ~he Yenturi is appro~imately equal
to at~ospheric pressure, which avoids degassing and ca~itation problems.
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By using a device ha~ing a diameter 11 mm injector as~ociated in
the dilacerating loop 20 with a pump 24 deli~ering a~ appro~imately
4 bars for a flow rate of 78 m/h, it has been possible to determine
by treatin8 fines solutions of appro~imatel~ 75 g/l, that an average
operating time of 45 hours makes it possihle to brin8 about the
almost total disappearance of particles with A mean dia~eter in
excess of 25 ~m, knowing tha~ an operation lasting one hour corresp-
onds to approximately 32 passages in the loop.
Fig. 6 shows an embodiment of the fines screening or sifting machine
30 placed at the intake of the pipe 28 for transferring fines to
the vitrification site. This fines screening apparatus 30 is susp-
ended in the same way as the dilacerating deYice 26 on a biological
protection slab 34', which can in certain cases be the sa~e as the
slab 34. The screening machine 30 i~ thus located in the lower
cell 38' in which the fines are treated.
T~le fines screening machine 30 has a ~ertically a~ed tank 78, incor-
porating an upper flange 80 fi~ed to the slab 34' by screws 82.
In its median part, the tank 78 is internally provided with a shoul-
der 84, on which rests in a ~ight and detachable manner a horizon~al
plaee 86, provided in its centre with a gripping member 88 permitting
its remote fitting and dismantling ~ith the aid of appropriate hand-
ling means. The plate 86 rests on the sho~lder 84 ~ia a no~ shown
seal. At leas~ one admission passage 90 traYerses the tank 78 abo~e
the shoulder 84 and issues into the tank, preferably in a tangential
direction. A screened fluid evacuation pipe 92 issues in the immed-
iate vicinity of the conical bottom 94 of the tank 78.
The fines screening machine 30 is also equipped with an emptying
pipe 96, which in the same way as the discharge pipe 92 issues in
the i~mediate Yicinity of the co~ical bottom 94 of the tank 78,
together with a pipe 98 for the discharge of gases, which issues
abo~e the shoulder 84.
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The plate 86 contains cylindrical holes 100 of the same diameter,
which are regularly distributed over the pla~e circumference around
the ~ertical a~is of the ~ank 78. E~lch of these holes 100 reoeives
a gloYe finger-shaped filter car~rid~,e 102, whose cylindrical part
is internally coated with a filtering medium, e.g. constituted by
a wire gauze. Each of the filter cartridges 102 rests on the plate
86 by a collar for~ed on its upper, open end. Thus, the said cart-
ridges can be easily fitted and removed.
It should be noted that under certain operating conditions, the
number of filter cartridges 102 can ~e less than the number of holes
100 formed in the plate 86. Plugs are then inserted in the unoccu-
pied holes 100. An ultrasonic probe 104 is placed in each of the
filter cartridges 102. Each probe 104 has a cylindrical sheath
106 sealed at each of its ends, and an ultrasonic transducer 108
tightly placed within the sheath 106. The stainless steel sheath
106 extends over appro~imately half its height withi~ the corresp-
onding filter cartridge 102 and o~er a comparable height, abo~e
the said cartridge, so as to rest b7 a shoulder formed at its upper
end on a plate 110, which itself rests on a shoulder for~ed within
the tank 73, aboYe the admission passage 90 and the gas discharge
pipe 98. Seals 11~ and 114 respectively ensure the necessar7 sealing
between each of ~he sheathq 106 and the plate 110 and between the
plate 110 and the tank 78.
In the same way as the plate 86 suppor~ing the filter cartrid~es
102, the plate 110 supporting the ultrasonic probes 104 is centrally
provided on its upper face with a me~ber 116 permitting its gripping
b7 appropriate handling means located abo~e the slab 34'.
The lower ends of the sheaths 106 received in tbe filter cartridges
102 are separated from the latter by an annular space, iD which
can flow the solution of fines introduced into the screening machine
30 by the passage 90.
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As is illustrated by fig. 6, the u].trasonic transducers 108 are
placed in the lower par~s of the sheaths 106, ~o as to cover ~he
entire height of the ~iltering medium plared in the cyli~drical
wall of the filter cartridg~s 102. I~le shape of this preferably
S cylindrical transducer 108 is designed so as to bring about a ~aximum
cavitation in the annular ~one formed between each of the probes
104 and the corresponding filter cartridge 102.
The electrical power supply for each of the transducers 108 is pro~i-
ded by a source located in the accessible zone above the slab 34'
through an electrical conductor 118. The latter conductor tightly
traYerses the upper end of each of the sheaths 106, as well as a
plug 120 sealing the upper end of the tank 78 and thus completes
the neutron protection provided by the slab 34'.
More specifically, in the embodiment illustrated in fig. 6, a circu-
lar opening is formed in the plug 120, Yertically with respect to
each of the ultrasonic probes 104, so as to permit the fitting and
removal thereof without removing the plug 120. Each of these circu-
- lar openings is normally sealed by a small plug 122 traYersed by
the electrical conductor 118 of the corresponding probe. To avoid
radiation leaks at this level, the conduceors 118 pass through the
plugs 122 in helical tubes 124.
In order to permit the dismantling of each of ~he ultrasonic probes
104 through the hole of the plug 120, following the remoYal of the
corresponding small plug 122, each of the sheaths 106 of the probes
104 carries on its upper face a gripping member 125, which can be
grasped by an appropriate handling means located above the slab
34'~ The plate 110 on which are suspended all the ultrasonic probes
104 is fixed below the plug 120, so that remoYal of the latter gives
access to the plate 86 carr~ing the filter csrtridges 102, e.g.
for the replacement of the la~ter.
The connection bet~een the plug 120 and the plate llQ is pro~ided
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by a cylindrical e~tension of the latter, which al90 helps to keep
the ultrasonic probes 104 in place on the plate 110. Thus, for
each of the probes 104, a horizontal locking plate 126 cooperates
with said cylindrical e~tension of the plate 110 by a ba~onet conn-
ection 128. Each plate 126 supports a screw 130, which is axiallyaligned with the corresponding ultrasontc probe 104 when ~he plate
126 is in place. The screws 130 can be manipulated from the access
ible zone above the slab 34' following the remoYal of their corr-
esponding small plugs 122. ~ach of the screws 130 cooperates with
a threaded part formed on the upper end of the gripping member 125
of the corresponding probe 104, whilst the latter is immobilized
in rotation b~ the cooperation of the plate 126 with a prismatic
part formed at the base of ~he memher 125.
Consequently, an action on each of the screws 13Q makes it possible
either to disengage the pla~e 126 from the corresponding probe 104,
or conversely, by e~pansion9 to engage the latter ag~inst the plate
110 in order to lock the same. When, after remo~ing the plugs 1229
one or more screws 130 are disengaged from the corresponding probes
104, the dismantling of the latter can take place following the
removal of the locking plates 126 through ~he holes let b~ the
remoYal of the small plugs 122.
When the fines scree~ing machine is operating~ each of the ultra~
sonic probes 108 is supplied with electricity and emits ul~rason~c
waves oriented radially with respect to the probe 104, so as to
create a ca~itation effect on the liquld present in the annular
space formed between the probe and its corresponding filter cartridge
102. This liquid, introduced into the screening machine 30 by the
passage 90, is therefore exposed to a new dilaceration action after
traYersing the filtering medium lining each of the filter cartridges
102. The particles ha~ing a size greater than a threshold, which
i9 in particular predetermined as a func~ion of the sealing risks
with respect to the pipe 28 (fig. 1), are held back by the filtering
medium of each of the cartridges 102. The liquid and ~he particles
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of a sufficiently s!~ll size pass through the filter cartridge~
and drop into the conical bottom 94 c3f the tank 78, where the~ are
taken up by the evacuation pipe 92.
During the operation of the fines screening machine 30, the operating
conditions must be such that those parts of ~he probes 104 housing
the ultrasonic transducers 108 are permanently e~bedded. MoreoYer,
the pressure on the filtering medium of each of the cartrid6es 102
must be adequate to permit a correct operation thereof, whilst still
remainin~ limited, so that the particles are not engaged against
the filtering medium and authorizing an adequate cavitation, as
a function of the power of the transducers. Moreover, the solution
treated in the fines sc~eening machine must rPmain at a temperature
not causing any deterioration of the transducers. The transducers
108 are also used for unclogging the filter cartridges 102 of the
screening machine 30, when this proves necessary.
For example, use was made of 8 fines screening machi~e comprising
four filter cartridges, whose filtering medium was constituted b~
wire gauzes of 25 or 40 ~m, as a function of the desired 8rain size.
These filter cartridges had an internal diame~er of 92 mm and a
hei8ht of 160 mm. In each of these cartridges was placed a c~lindri-
cal transducer formed by ju~aposing three ceramic disks. The nomin-
al instantaneous electric power was then 7S0 W, with a charge rate
of 20% corresponding to a pulsed operation and an effecti~e inten~ity
of 0.~7 A. This pulsed operation made it possible ~o disturb the
prela~er Eormed by the largest particles, so as to permi~ the passage
of the finer particles, break up by the ca~itation effect the agglomr
erates of large particles and limit the thermal load of thP appara-
tus. Such a screening machine ~ade it possible ~o ensure the desi-
red calibration of the particles conve~ed to the vitrification site.
Advantageouslg9 the performance characteristics of the process and
in~tallation according to the inYention are further impro-Jed b7
carrying out9 within the actual clarifier 10, a prior dilaceraeion
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of the fines sludges located in the bottom of the clarifier af~er
rinsing the cake.
In this case and as is Yery diagra~malticall~ illustrated i~ fig.
1, through an opening formed in the cover of ~he clarifier 10, an
ultrasonic probe 132 is introduced into the latter. ThiA ultrflsonic
probe is formed by a stainless ~teel sheath in which is placed an
ultrasonic transducer.
In the case where the clarifier 10 is formed by a cenerifugal swing-
ing settling tank, the latter is slowly rotated, whilst actuating
the ultrasonic probe 132. At the end of a certain time and as a
result of the cavitation effect created by the transd-~cer, this
operation makes it possible to reduce the ~ize of the particles
before the solution is transferred into the transfer tank 16.
Tests carried out by means of a cylindrical transducer having an
15 instantaneous, nominal power of 500 W, a charge rate of 20% corr-
esponding to a pulsed operation and emitting a~ 20 ~z made it poss-
ible to obtain, on the basis of particles with a size initiall7
between 360 and 3000 ~m and after 5.5 h of treatmene, 45% particles
with a diameter below 40 ym, 5% particles bet~een 40 and 360 ~m
20 and 50% particles between 360 and 3000 pm. It is also possible
to make the ultrasonic fines screening machine operate without curr-
ent pulsation.
Use of an ultrasonic probe 132 ~ithin the clarifier 10 makes it
possible to further reduce the clogging or blockage risks in the
transfer pipe 28 and to reduce the treatment time of the fines in
the loop 20.
; Obriously, the invention is not limited to the embodiments describedi~ exemplified ~anner hereinbefore and i~ fac~ corers all variants.
I~ is clear that the struc~ure of the diferent equipments described
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can be substantially ~odified, more particularly as a function of
the operating conditi.ons and the results to be ob~ained.
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