APPARATUS AND METHOD

Abstract

An apparatus (10) is described for removing radioactive contamination, at least in part, from a first article (A1) comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof. The apparatus (10) comprises a heated first vessel (100A) for melting the metal, at least in part, therein, thereby providing a melt (M) therefrom. The apparatus (10) comprises casting means (200) for forming a second article (A2), particularly a sheet, having a predetermined thickness (T), from the melt, preferably wherein the casting means (200) comprises and/or is a rotatable roller (210) arrangeable to contact the melt (M) to thereby form thereon the second article (A2) and a guide (220) arranged to remove the second article (A2) from the roller (210). The apparatus (10) comprises a set of radiation detectors (300), including a first radiation detector (300A), arranged to detect a first fraction of the radioactive contamination, if present, in a first part (P1) of a set of parts of the second article (A2), preferably wherein the set of radiation detectors (300) comprises opposed first and second radiation detectors (300A, 300B) arranged to receive the second article (A2) traversing therebetween. The apparatus (10) comprises a cutter (400) arrangeable to excise the first part (P1) of the second article (A2) therefrom.

Claims

1. An apparatus for removing radioactive contamination, at least in part, from a first article comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof, the apparatus comprising: a heated first vessel for melting the metal, at least in part, therein, thereby providing a melt therefrom; casting means for forming a second article, for example a sheet, a strip or a ribbon, having a predetermined thickness, from the melt, preferably wherein the casting means comprises and/or is a rotatable roller arrangeable to contact the melt to thereby form thereon the second article and a guide arranged to remove the second article from the roller; a set of radiation detectors, including a first radiation detector, arranged to detect a first fraction of the radioactive contamination, if present, in a first part of a set of parts of the second article, preferably wherein the set of radiation detectors comprises opposed first and second radiation detectors arranged to receive the second article traversing therebetween; and a cutter arrangeable to excise the first part of the second article therefrom.

2. The apparatus according to claim 1, wherein the casting means is arranged to form the second article at a linear rate in a range from 1 to 60 m/min, preferably in a range from 5 to 30 m/min, more preferably in a range from 10 to 20 m/min.

3. The apparatus according to claim 1, wherein the casting means is arranged to form the second article having the predetermined thickness in a range from 0.25 mm to 7.5 mm, preferably in a range from 0.5 mm to 5 mm, more preferably in a range from 1 mm to 3 mm from example 1 mm, 1.5 mm or 2 mm.

4. The apparatus according to claim 1, wherein the casting means is arranged to form the second article having a width in a range from 0.01 m to 2 m, preferably in a range from 0.1 m to 1 m, more preferably in a range from 0.25 m to 0.75 m, for example 0.4 m, 0.5 m or 0.6 m.

5. The apparatus according to claim 1, wherein the set of radiation detectors comprises an ionization chamber, a gaseous ionization detector, a Geiger counter and/or a scintillation counter.

6. The apparatus according to claim 1, wherein the set of radiation detectors is arranged to detect a first fraction of the radioactive contamination, if present, across at least 90% of a width of the second article, preferably at least 95% of the width of the second article, more preferably 100% of the width of the second article.

7. The apparatus according to claim 1, wherein the set of radiation detectors is arranged to detect a second fraction of the radioactive contamination, if present, in a second part of the set of parts of the second article and wherein the cutter is arrangeable to excise the second part of the second article therefrom.

8. The apparatus according to claim 1, wherein the apparatus is arranged to control the cutter to excise the first part of the second article therefrom in response to a signal received from the set of radiation detectors; optionally wherein the signal corresponds with and/or comprises a first location of the first fraction of the radioactive contamination in the second article and the apparatus is arranged to control the cutter to excise the first part of the second article therefrom according to the first location, for example centred about the first location.

9. The apparatus according to claim 1, comprising a conveyor arranged to convey the second article past the set of radiation detectors.

10. The apparatus according to claim 1, comprising a second vessel arranged to receive at least a portion of the melt therein from the first vessel and wherein the apparatus comprises the roller, wherein the roller is immersible in the melt in the second vessel; optionally, wherein the apparatus comprises a pump arranged to pump the portion of the melt from the first vessel into the second vessel.

11. The apparatus according to claim 1, comprising an interceptor arranged to intercept dross on a surface of the melt.

12. The apparatus according to claim 1, comprising a rotatable barrel arranged to receive the second article, having the first part excised therefrom, spooled thereon.

13. A method of removing radioactive contamination, at least in part, from a first article comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof, the method comprising: melting the metal, at least in part, thereby providing a melt therefrom; forming a second article, for example a sheet, a strip or a ribbon, having a predetermined thickness, from the melt, preferably by contacting the melt with a rotating roller and removing therefrom the second article formed thereon; detecting a first fraction of the radioactive contamination, if present, in a first part of a set of parts of the second article, preferably using a set of radiation detectors, including a first radiation detector, preferably by receiving the second article traversing between opposed first and second radiation detectors of the set of radiation detectors; and excising the detected first fraction of the radioactive contamination, if present, from the second article, for example by cutting, the first part of the second article therefrom.

14. The method according to claim 13, wherein forming the second article is at a linear rate in a range from 1 to 60 m/min, preferably in a range from 5 to 30 m/min, more preferably in a range from 10 to 20 m/min.

15. The method according to claim 13, wherein forming the second article comprises forming the second article having the predetermined thickness in a range from 0.25 mm to 7.5 mm, preferably in a range from 0.5 mm to 5 mm, more preferably in a range from 1 mm to 3 mm from example 1 mm, 1.5 mm or 2 mm.

16. The method according to claim 13, wherein forming the second article comprises forming the second article having a width in a range from 0.01 m to 2 m, preferably in a range from 0.1 m to 1 m, more preferably in a range from 0.25 m to 0.75 m, for example 0.4 m, 0.5 m or 0.6 m.

17. The method according to claim 13, wherein detecting a first fraction of the radioactive contamination is by using the set of radiation detectors comprising an ionization chamber, a gaseous ionization detector, a Geiger counter and/or a scintillation counter.

18. The method according to claim 13, wherein detecting a first fraction of the radioactive contamination comprises detecting a first fraction of the radioactive contamination across at least 90% of a width of the second article, preferably at least 95% of the width of the second article, more preferably 100% of the width of the second article.

19. The method according to claim 13, comprising detecting a second fraction of the radioactive contamination, if present, in a second part of the set of parts of the second article and excising the detected second fraction of the radioactive contamination, if present, from the second article, for example by cutting, the second part of the second article therefrom.

20. The method according to claim 13, wherein excising the detected first fraction of the radioactive contamination, if present, from the second article comprises excising the first part of the second article therefrom responsive to a signal received from the set of radiation detectors; optionally wherein the signal corresponds with and/or comprises a first location of the first fraction of the radioactive contamination in the second article and wherein excising the detected first fraction of the radioactive contamination, if present, from the second article comprises excising the first part of the second article therefrom according to the first location, for example centred about the first location.

21. The method according to claim 13, comprising conveying the second article while detecting a first fraction of the radioactive contamination.

22. The method according to claim 13, wherein forming the second article from the melt is by contacting the melt with a rotating roller, wherein the method comprises stilling the melt.

23. The method according to claim 13, comprising intercepting dross on a surface of the melt.

24. The method according to claim 13, comprising spooling the second article, having the first part excised therefrom, on a rotatable barrel.

25. The method according to claim 13, comprising controlling a speed of forming of the second article.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0143] For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

[0144] FIG. 1 shows the melting point of binary Pb alloys as a function of the content of alloying additions of Sn, Bi, Te, Ag, Na, Cu and Sb;

[0145] FIG. 2 shows the dynamic viscosity η.sub.Pb of technically pure liquid lead as a function of temperature;

[0146] FIG. 3 shows the surface tension of liquid lead as a function of temperature;

[0147] FIG. 4 shows absorption of gamma rays by lead a function of energy;

[0148] FIG. 5 shows the impulse counting rate {dot over (N)}(d) as a function of thickness d;

[0149] FIG. 6 schematically depicts an apparatus according to an exemplary embodiment;

[0150] FIG. 7 schematically depicts a part of the apparatus of FIG. 6, in more detail;

[0151] FIG. 8 schematically depicts a method according to an exemplary embodiment;

[0152] FIG. 9 shows a photograph of forming a second article; and

[0153] FIG. 10 shows an Ellingham diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

[0154] FIG. 7 schematically depicts an apparatus 10 according to an exemplary embodiment.

[0155] The apparatus 10 is for removing radioactive contamination, at least in part, from a first article A1 (not shown, in this example, used Pb—4 wt. % Sb shielding bricks) comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof. The apparatus 10 comprises a heated first vessel 100A for melting the metal, at least in part, therein, thereby providing a melt M therefrom. The apparatus 10 comprises casting means 200 for forming a second article A2, particularly a sheet, having a predetermined thickness T, from the melt, preferably wherein the casting means 200 comprises and/or is a rotatable roller 210 arrangeable to contact the melt M to thereby form thereon the second article A2 and a guide 220 arranged to remove the second article A2 from the roller 210. The apparatus 10 comprises a set of radiation detectors 300, including a first radiation detector 300A, arranged to detect a first fraction of the radioactive contamination, if present, in a first part P1 of a set of parts of the second article A2, preferably wherein the set of radiation detectors 300 comprises opposed first and second radiation detectors 300A, 300B arranged to receive the second article A2 traversing therebetween. The apparatus 10 comprises a cutter 400 arrangeable to excise the first part P1 of the second article A2 therefrom.

[0156] In this example, the metal comprises Pb in an amount of at about 95 wt. %, for Pb—4 wt. % Sb shielding bricks.

[0157] In this example, the metal has a melting point of about 280° C. In this example, the first vessel 100A is heated using gas burners. In this example, the heated first vessel 100A is arranged to heat the metal to a temperature of about 380° C.

[0158] In this example, the heated first vessel 100A has a capacity in of 0.4 m.sup.3.

[0159] In this example, the apparatus 10 is arranged to drain a heel (i.e. heavy impurities) from the bottom of the melt M in the first vessel 100A, for example by comprising an outlet (not shown) proximal the base thereof. In this example, the apparatus 10 is arranged to collect dross (i.e. light impurities) from proximal a surface of the melt, for example by comprising an interceptor 110.

[0160] The apparatus 10 comprises the casting means 200 for forming the second article A2, having the predetermined thickness T, from the melt. In this example, the casting means 200 comprises a continuous casting means 200.

[0161] The formed second article A2 has the predetermined thickness T. In this example, the predetermined thickness T corresponds with at most twice a practical detection range of β and/or γ radiation, for example for single-sided detection. In this example, the casting means 200 is arranged to form the second article A2 having the predetermined thickness T in a range of 2 mm. In this example, the second article A2 is a continuous sheet. In this example, a tolerance of (i.e. a variability in) the predetermined thickness is within 10% of the predetermined thickness across at least 75% by area, normal to the predetermined thickness, of the second article A2. In this example, the casting means 200 is arranged to form the second article A2 at a linear rate in a range of 15 m/min. In this example, the casting means 200 is arranged to form the second article A2 having a width of 0.4 m.

[0162] In this example, the casting means 200 comprises the rotatable roller 210 arrangeable to contact the melt M to thereby form thereon the second article A2 and the guide 220 arranged to remove the second article A2 from the roller 210. In this example, the apparatus 10 comprises a second vessel 100B arranged to receive at least a portion of the melt M therein from the first vessel 100A and wherein the apparatus 10 comprises the roller 210, wherein the roller 210 is immersible in the melt M in the second vessel 1006; wherein the apparatus 10 comprises a pump (not shown) arranged to pump the portion of the melt, directly or indirectly, from the first vessel 100A into the second vessel 1006. In this example, the apparatus 10 comprises an interceptor 110 arranged to intercept dross on a surface of the melt.

[0163] In this example, the set of radiation detectors 300 comprises 4 off 16″×4″×2″ NaI scintillation counters. In this example, the set of radiation detectors 300 comprises opposed first and second radiation detectors 300A, 300B arranged to receive the second article A2 traversing therebetween. Particularly, two NaI scintillation counters are arranged below the second article A2 and two NaI scintillation counters are arranged above the second article A2. In this example, the opposed first and second radiation detectors 300A, 300B are mutually offset laterally to optimise detection. In this example, the set of radiation detectors 300 is calibrated using gamma ray point sources of either Cs-137 or Co-60.

[0164] In this example, the apparatus 10 comprises a conveyor 500 arranged to convey the second article A2 past the set of radiation detectors 300. In this example, the conveyor 500 is arranged to convey the second article A2 past the set of radiation detectors 300 at a linear rate in a range from 10 to 20 m/min, for example 15 m/min. In this example, the conveyor 500 is arranged to convey the second article A2 past the set of radiation detectors 300 at a same rate as a rate of forming of the second article A2. In this way, the rate of detecting matched the rate of forming the second article A2.

[0165] In this example, the cutter 400 comprises and/or is a mechanical cutter 400, for example a punch, arranged to cut around the detected first fraction of the radioactive contamination. In this example, the cutter 400 is arranged to cut a predetermined shape, for example a circle.

[0166] In this example, the set of radiation detectors 300 is arranged to detect the first fraction of the radioactive contamination, if present, across 100% of the width of the second article A2.

[0167] In this example, the set of radiation detectors 300 is arranged to detect a second fraction of the radioactive contamination, if present, in a second part of the set of parts of the second article A2 and wherein the cutter 400 is arrangeable to excise the second part of the second article A2 therefrom.

[0168] In this example, the apparatus 10 is arranged to control the cutter 400 to excise the first part P1 of the second article A2 therefrom in response to a signal received from the set of radiation detectors 300. In this example, the signal corresponds with and/or comprises a first location of the first fraction of the radioactive contamination in the second article A2 and the apparatus 10 is arranged to control the cutter 400 to excise the first part P1 of the second article A2 therefrom according to the first location, for example centred about the first location.

[0169] In this example, the apparatus 10 comprises a rotatable barrel 600 arranged to receive the second article A2, having the first part P1 excised therefrom, spooled thereon.

[0170] FIG. 7 schematically depicts a part of the apparatus 10 of FIG. 6, in more detail. Particularly, FIG. 7 shows an underneath perspective view of the first radiation detector 300A, part number 8D16X64A5 3.5 available from ANTECH, housed in a housing.

[0171] FIG. 8 schematically depicts a method according to an exemplary embodiment.

[0172] The method is of removing radioactive contamination, at least in part, from a first article comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof.

[0173] At S801, the metal is melted, at least in part, thereby providing a melt therefrom.

[0174] At S802, a second article, for example a sheet, a strip or a ribbon, having a predetermined thickness, is formed from the melt, preferably by contacting the melt with a rotating roller and removing therefrom the second article formed thereon.

[0175] At S803, a first fraction of the radioactive contamination, if present, is detected in a first part of a set of parts of the second article, preferably using a set of radiation detectors, including a first radiation detector, preferably by receiving the second article traversing between opposed first and second radiation detectors of the set of radiation detectors.

[0176] At S804, the detected first fraction of the radioactive contamination, if present, is excised from the second article, for example by cutting, the first part of the second article therefrom.

[0177] The method may include any of the steps described herein.

[0178] FIG. 9 shows a photograph of forming a second article A2, using the casting means 200.

[0179] Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

[0180] In summary, the invention provides an apparatus for, and a method of, removing radioactive contamination from a first article comprising a metal, preferably wherein the metal comprises and/or is a low melting point metal for example lead and/or an alloy thereof. In this way, the low melting point metal of the first article is formed into the second article, having the predetermined thickness (i.e. a controlled dimension). The pre-determined thickness allows through-thickness (i.e. volumetric) detection of the first fraction of the radioactive contamination, if present. In contrast, through-thickness detection of radioactive contamination therein is generally not possible. Hence, by melting the metal and forming the second article therefrom, the radioactive contamination that was internal and undetectable in the first article is now detectable in the second article, by virtue of the predetermined thickness thereof. If the first fraction of the radioactive contamination is detected, the first part of the second article, including the first fraction of the radioactive contamination, is excised, such that the remaining part of the second article has proportionately less radioactive contamination. Hence, by detecting and excising the fractions of the radioactive contamination present in the second article, the residual radioactive contamination therein is reduced.

[0181] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0182] All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

[0183] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0184] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.