IL33742A

IL33742A - Irradiation cell for continuous operation

Info

Publication number: IL33742A
Application number: IL33742A
Authority: IL
Original assignee: Commissariat Energie Atomique
Priority date: 1969-02-06
Filing date: 1970-01-20
Publication date: 1972-10-29
Also published as: FR2031747A5; DE2005294A1; ES376235A1; NL7001001A; US3655965A; BE745041A; IL33742A0; GB1269034A; DE2005294B2; OA03209A; RO59825A; CH504228A; SE359772B; LU60245A1

Description

no»jn n'npo'? πί η κη Irradiation cell for continuous operation 00I-!∑iISSARIAT A L'ENERGIE ATOMIQUE Inventors 8 Pierre ICRE Jacques LAIZIER -Phis invention relates to a cell for Irradiating a liquid product which circulates continuously at an adjus ble discharge rate and fluid velocity, especially with a beam.of accelerated electrons.

The aim of the Invention is more particularly to define the geometry pf a cell of this type in order that this latter should be well adapted to the shape of an electron beam which is employed in such a manner as to obtain within the circulating liquid product an irradiatio dose which Is both of maximum value and generally homogeneous.

Finally, although this application is not intended to imply any limitation whatsoever, the invention is primarily directed to the radlovulcanization of natural or synthetic latexes vrhic are subjected to a beam of aocelerated electrons having an energy level which is especially but. not exclusively within the range of 2 to 10 MeV, the power of which can vary between 1 and 10 H.

According to the present invention there is provided a cell for irradiating with a beam of accelerated electrons a liquid product comprising a tank, means for circulating the liquid product 'continuously at an adjustable flow rate and velooity within said tank, said tank having an elongated shape whose axis is substantially perpendicular to the direction of the electron beam, a pipe providing continuous supply o the liquid product to be irradiated connected to one end of said tank, means fitted in said pipe for distributing the flow of liquid within said tank, a discharge duct connected to the other end of said tank, an overflow orifice in said duct, discharge spout for said duct and a total-opening valve i said ■ i ■ - ' w length of the tank establishing a stable laminar flow regime within the central portion of said tank receiving the electron beam whereby the electron distribution over the flow velocity of the liquid product provides a homogeneous total dose of irradiation.

Further properties of an irradiation cell as constructed in aooordance with the invention will now beoome w apparent from the following description of one exemplified embodiment which is given solely by way of indication, reference being had to the accompanying drawings, wherein : - Fig. 1 is a diagrammatic longitudinal sectional view of the cell under consideration ; - Figs. 2, 3 and are transverse sectional views taken respectively along the lines II-II, III-III, IV-IV of Pig. 1.

As can be seen from Fig. 1, the irradiation cell considered is mainly composed of a parallelepipedal tank 1 having a generally elongated shape and preferably fabricated from burnished stainless steel in particular for the purpose of overcoming the dangers of coagulation and corrosion under radiation and in order to permit the treatment of any liquid product. The tank 1 is placed horizontally beneath an electron accelerator 2, the electron beam which is delivered by said accelerator being oriented so that the longitudinal axis of the tank 1 should be substantially perpendicular to the direction of said beam and disposed according to the scan or length range of this latter.

The tank 1 is provided at both ends with two flanges 3 and for coupling said tank to two pipes 5 and 6, the respective functions of which are to supply the tank with a liquid product to be irradiated and to discharge said product after irradiation, the liquid being circulated within the tank in continuous flow in the direction shown diagram-matically by the arrows 7. The supply pipe 5 (as shown in Fig.2) is designed in the form of a duct having a generally cylindrical shape and terminating in a coupling end-piece 8 having a transverse cross-section which is identical with 'ψ end-piece to the flange 3 "by means of a counter-flange 9. Within the end-piece 8, the pipe 5 is provided with a series of small plates 10 which are suitably oriented with respect to the axis of said pipe and disposed fanwise so as to divide the flow of liquid which penetrates into the tank into a series of unitary streams which flow in parallel relation over the whole width of the cell. The length of the pipe 5 and especially of its end-piece 8 is so determined that a stable laminar flow regime is established within the tank and more particularly within the central portion of this latter opposite to the accelerator 2, especially in order to ensure that the velocity diagram within the liquid flow in that region which is subjected to the action of the electron beam should produce a substantially homogeneous overall irradiation as a result of superimposition on the curve of electron distribution along the width and the axis of said beam.

In fact, at the surface of the liquid which is in a laminar state of flow, the stream has maximum velocity along the axis of the tank while receiving a maximum dose rate ; at the level of the wall at which the dose rate is of minimum value, the velocity is at a minimum ; similarly at the bottom of the stream, the flow velocity is of minimum value at the bottom of the tank at which the dose rate is of minimum value whereas the flow velocity in the vicinity of the surface is close to its maximum value in a zone in which the dose rate is also at a maximum.

This overlap of the curves of distribution of dose rates and of velocities both at the surface and at a depth makes it possible to optimize the dose homogeneity through Advantageously and in order to obtain the most stable and most suitable laminar flow regime within the central portion of the tank, the length of this latter can readily be adjusted by placing between the flange 3 and the counter-flange 9 any extension section or element which provides the total length of the tank with a value which is suited to the selected flow rate.

Moreover, the transverse dimensions and especially the width of the cell are determined so as to correspond substantially to the width of the electron beam ; in this respect, the geometry of the beam can easily be adapted to that of the cell simply by adjusting the height of this latter with respect to the electron accelerator or emitter, the same result being achieved by establishing the level of the liquid product to be irradiated with respect to the cone of divergence of the electron beam. Finally, the depth of liquid which is circulated within the tank is so determined as to be exactly equal to the total penetration of electrons into the liquid considered at the energy level which is adopted. In particular, the absorbed dose and heating of the liquid can readily be controlled in order to prevent coagulation.

In the central portion thereof, the tank 1 is provided opposite to the irradiation- apparatus 2 with a metallic window 11 formed by means of a very thin sheet of a suitable metal and especially of aluminum or titanium. Said sheet is maintained against the body of the tank by means of a flange 12 of rectangular shape which is fitted with a seal (not shown in the drawings). The thickness of this window is chosen as small as possible in order to cause only ne li ible deceleration of electrons at the time of enetra- tion of these latter into the tank. The characteristics of this window are determined in any case as a function of the energy of the incident beam in order to minimize radiation losses o In that portion which is remote from the window 11 , the tank 1 is additionally provided with a bottom wall 13 having a small angle of slope in the direction of the discharge pipe 6 in order to assist the flow of the liquid product. Moreover, the central zone of the tank 1 in which the irradiation is carried out is preferably cooled by a continuous flow of a suitable cooling fluid.

To this end, the tank 1 is enclosed within an outer jacket 1 forming between this latter and the wall of the tank a space 15 into which opens a supply pipe 16 and a discharge pipe 17 for a flow of coolant water ; that zone of the tank which is enclosed within the outer jacket 1 is advantageously longer than the distance scanned by the electron beam.

Fig. 4 illustrates the cross-section of the pipe 6 for the discharge of irradiated liquid which flows out of the tank in the direction of the arrows 7 . This pipe 6 is provided with a counter-flange 18 and attached by means of this latter to the flange of the tank, said pipe being provided with an overflow orifice 19 and with a discharge spout 20 associated with a valve (not shown) which serves to regulate the flo through the overflow orifice 19 and consequently to modify the depth of the liquid product in the tank 1. The pipe is provided with a viewing window 21 which also forms an inspection door for use when the irradiation cell is not in service.

Finally, the equipment of the cell is completed by out the remote measurement, control and adjustment of the operating parameters. Thus, the discharge pipe 6 is fitted with a level detector so that the depth of the irradiated liquid product may be continuously checked whilst the tank 1 . is provided downstream of the irradiation zone with an electron beam detector for checking the stability of the mean power delivered and consequently of the mean absorbed dose in respect of a given stable flow rate. Temperature control devices are also provided both upstream and down- stream of the irradiation zone .

The cell described in the foregoing makes it possible in particular to carry out the continuous irradiation of natural and synthetic latexes with a flow rate comprised between 1000 and 3000 1/h. In this case, the nominal diameter of the supply pipe is 50 mm, the length of the tank in which the flow is converted to the laminar state prior to penetration into the central irradiation zone being equal to 5>0 cm. The energy of the electron beam is chosen equal to M.5 MeV and the useful length, of the tank is 18 cm. The thickness of the circulating liquid latex is 2 .5 cm, which corresponds to the total penetration of electrons of , 4.5 MeV energy.

It will readily be understood that the invention is not limited in any respect to the exemplified embodiment as hereinabove described or to the field of application which has been more especially contemplated but extends on the contrary to all alternative forms. In particular, the cell under consideration could readily permit the irradiation of any volatile or non-volatile liquid having variable viscosity, homogeneous products, emulsions or suspensions, as subjected o

Claims

33742/2

1. A cell for Irradiating with a beam of accelerated electrons a liquid product comprising, a tankV means for circulating the liquid product continuously at an adjustable low rate and velocity within said tank, said tank having an elongated shape whose axis is substantially perpendicular to the direction of the electron beam, a pipe providing a continuous supply of the liquid product to be irradiated connected to one end of said tank, means fitted in said pipe for distributing the flow of liquid within said tank, a discharge duct connected to the other end of said' tank, an overflow orifice in said duct, a discharge spout for said duct and a total-opening valve in said spout for regulating tltte depth of liquid withi said tank, the length of the tank establishing a stable laminar flow regime within the central portion of said tank receiving the electron beam whereby the electron distribution over the flow velocity of the liquid product provides a homogeneous total dose of irradiation,

2. # An irradiation cell in accordance with claim 1, said means for distributing the flow of liquid including a series of small plates rigidly fixed to the internal wall of said supply pipe dividing the total flow into unitary streams at the entrance of said tank. 33742/2

3. An irradiation oell in accordance with claim 1 Including means for adjusting the level of the liquid ¾ithin said tank for total absorption of electrons within the depth of the liquid.

4. · An irradiation oell in accordance with claim 1 said tank having along its logitudinal dimension at least one flange and ex-tension elements connected to said flange to adapt the length of said tank to the rate of flow of the liquid product.

5. An irradiation cell substantially as herein before described by way of example and with reference to the accompanying drawings. For the Applicants BEINJEiOLD COHN & FARTHERS