US3488219A - Method and means for removal of radioactive contaminants - Google Patents

Description

Patented Jan. 6, 1970 3,488,219 METHOD AND MEANS FOR REMOVAL OF RADIOACTIVE CONTAMINANTS Rolf Moroni, Hersel, near Bonn, Germany, assignor to Collo-Rheincollodium-Koln-G.m.b.H., Hersel, kreis Bonn, Germany No Drawing. Filed Mar. 23, 1965, Ser. No. 442,212

Int. Cl. B08b 7/00 US. Cl. 1344 17 Claims ABSTRACT OF THE DISCLOSURE In research endeavors, production work, and use of radioactive substances in various applications, personnel come into some degree of contact with radioactive substances.- Radioactive materials in the form of dust or contained in liquids coming in contact with parts of the body, or forming deposits on instruments, apparatus or other objects, then are considered as and termed contaminants. Especially through atomic fission, atomic bomb or atomic energy experiments, as well as other research, contaminants unavoidably in some degree appear on the human or animal skin and as well on equipment, which penetrate more or less deeply into, or react chemically with the surface contaminated therewith, so that radioactive isotopes are incorporated in the surface material. The removal of the radioactive isotopes which have penetrated such surfaces in this manner is indispensible primarily for two reasons.

First there is the danger of physical injury to the organisrn by radiation effects either on the skin surface or through incorporation; and secondly scientific work in affected laboratories finally becomes impossible, since radioactive contaminants disturb different types of sensitive measurements in an intolerable manner.

Both of the aforementioned grounds are of equal and great importance. The firstis related to the constantly increasing radiation dosage or level, while the second is of concern even when the radiation dosage is insignificant. Therefore it is not merely a matter of concern that sufficient work has been done to meet the requirements of legal radiation protection provisions, for scientific work can become impossible even where radioactive contaminants are below the tolerance levels for the human organism established by law.

Since the half-life periods of the radioactive substances here in question can be quite different, e.g., from months to decades, there arises the danger of accumulation and therewith the danger that a toxic concentration can be attained. There is a particular problem for scientists in chemistry, in physics, medicine and biology, for example, who must work professionally with these materials. In the case of radioactive substances which are absorbed or taken up by the human or animal organism, measures must be taken for elimination of these materials from consideration of the natural catabolic and excretory processes.

Previously protective salves have been applied to the exposed skin areas of those working with or in the region of radioactive materials. These salves either in and of themselves provided a protective sheath against the penetration of radiation or contact of the contaminant with the skin, or alternatively or cumulatively provided an easy means of removal of contaminants upon removal of the salves themselves.

Many means are used in laboratories for decontamination of radioactive surfaces. In the simplest case, the contamination of the hands, a frequent washing with soap under an ample flow of water is used. But even with the use of special soaps, this method is extremely tiresome or irksome, and further strongly adherent contaminations cannot be removed in this way. Thus it is, in the case of some objects which might otherwise be cleaned with soap and water, it is preferable simply to dispose of them, rather than to attempt cleaning in this manner.

The methods of cleaning are chemical or physical. To the chemical methods belong the use of acids and bases, complexing agents or ion exchange materials. Very often hydrochloric acid is used in a 1:1 dilution, which is, however, a very uncomfortable or even painful treatment of the skin surface. To the physical methods of cleaning belong the removal of the surface layer through scouring or rubbing with emery, and also the use of pumice stone. These methods have the disadvantage that they involve a drastic treatment of the skin, and also with pumice, that the radioactive material is only incompletely removed from the skin. Moreover, with the chemical or physical treatment of many types of instruments or apparatus, there is left a rough surface.

It is an object of the invention to remove radioactive surface contaminants from the skin or from objects easily, effectively quickly and harmlessly. For the attainment of this object, it is proposed in accordance with the invention, as a method for the removal of radioactive contaminants from human or animal skin and from articles, that the skin or the object be rubbed or scrapped with a porous, medium hard to hard, open-celled organic or inorganic, natural or synthetic foam body adapted for scrubbing purposes, especially a conveniently shaped body of a synthetic plastic foam, such that the contaminants be carried away with abraded particles of the foam body.

In accordance with a further proposal of the invention, for facilitating a carrying away of the radioactive cantaminants with, if necessary, skin particles lightly scraped away, the cleaning is carried out in conjunction with a flowing liquid, in particular, a soap solution.

Particularly advantageous, and of the highest efficacy for removal of radioactive contaminants, especially from human or animal skin, is the use of a hard and rigid polyurethane-foam with a pore structure of 0.2 to 3 mm., preferably 0.5 to 1 mm. in size. An open-celled plastic form of this type, having a selected hardness, removes the contaminants from the skin by a scraping action of the sharp boundary edges of the incised or cut cells, even with a deep action, without essentially harming or carrying away the true skin, and thus a removal of contaminated skin surface proceeds withoutpain. For use in conjunction with a flushing liquid, such as water, apolyurethane base foam has additionally the advantage by virtue of its thermoplastic character, that with a cold liquid,

especially cold water, the foam is hard, and with warm or hot water is somewhat softer; so that through selection of the temperature of the liquid, the hardness and thereby the scraping effect is continually adjustable upon use. In some cases a tough foam resistant to breaking up under scrubbing action is advantageous as holding and preventing spreading of the contaminants.

Particularly for smooth hard non-absorbing surfaces or articles, the soft foam is particularly useful. If it should be desired to remove the radioactive contaminants with a very high abrading of the foam body, then in accordance with the invention it is proposed to use a phenol resin foam.

As a foam body for the removal of radioactive contaminants, in accordance with a further characteristic of the invention, there are proposed foam bodies having a polystyrene-, cellulose acetate-, polyvinylchloride-, phenol resin-, polyethylene-, vinyl acetate-, Buna-rubberor natural rubber base.

As cleaner means, bodies of synthetic plastic foam, particularly the phenol resin or polyurethane base types, have additionally the decisive advantage that substantially no activity is taken up and hence none remains in the cleaner structure.

In accordance with a further characteristic of the invention, it is proposed that the foam body be comprised of a vitreous, i.e., slaggy or glass, foam. A body of slaggy or glass based foam can be used for the removal of radioactive contaminants from objects, for example, laboratory equipment or instruments, although a foam of this type is not as pain-free as the previously proposed bodies of synthetic plastic bases when used on human or animal skin.

With the foam materials proposed for the removal of radioactive contaminants, in particular the polyurethane foam and phenol-resin foam materials, the cleaning process proceeds by attacking the fundamental cause, the time requirement is small, the treatment of the surface is mild, the same foam body is re-usable many times, and the cleaning body itself in the cleaning process picks up little or substantially no radioactive impurities. The foam bodies, as they are used up and new incised or broken cells are laid open, continually work a shaving or scraping effect and therefore are effective until completely used up.

It is further found that radioactive contaminants can also be removed from the skin or from objects with a high efiicacy by scrubbing the skin or object with a granulated form of a hard to medium hard synthetic plastic foam, particularly having a polyurethane or phenol resin base, either with a mixture of granulants of the aforementioned materials, or in conjunction with a soap, a fat, an oil, a thickening agent, an emulsifying agent, or a film forming agent or a combination of two or more of these perhaps with addition of a slight amount of water. This is especially advantageous in circumstances where no, or an insufficient amount of, water or no flowing water is available for removal of radioactive contaminants.

The materials present in the mixture with the foam granulate as thickening or swelling agents are comprised of materials per se known, in greater part organic, highmolecular materials, which swell up and finally convert into homogeneous viscous colloidal solutions. Among organic materials of this type, there are for example, natural products, semi-synthetic products, or completely synthetic preparations, and so also in the case of inorganic preparations, for example, polysilicic acids, colloidal clay or metal hydroxides. By the term emulsions is to be understood, for example, dispersions in water or solvents of benzine, turpentine and other volatile oils, fatty oils, paraffin, waxes, vegetable-, animal-, and mineral-fats, nibber, fish lever oil and so forth, with dispersing agents. The best cleaning effect is obtained with a weakly acid pH of about 4.5 to 5:0.

The further proposal in accordance with the invention, of adding a film former to the granulate plastic foam, especially a polyurethane or phenol resin foam, has the particular advantage that the contaminants cling together, and adherent to or imbedded in the film, are removed therewith from the object or skin. The cleaner compositioncomprised of the foam granulate together with the film former, either alone or in combination with the aforementioned addition materials-is rubbed onto the skin or the object by hand with a scrubbing action and after hardening or drying of the film former, the film is drawn off or by rubbing broken off the skin or the object with the granulate and radioactive contaminants and such other materials as happen to be present. Such a composition can be rubbed so long on the skin or the object that no coherent or cohesive film arises, but rather crumbs comprised of the composition and the aforementioned radioactive contaminants. These crumbs then either fall from the skin by themselves, or can be easily removed by hand or a cloth.

Particularly suitable as film formers are methyl cellulose, polyvinyl alcohol, special gelatins, Konjacku, Hei Tao, tragacanth, and so forth. To make the film more pliable, addition of glycerin is recommended.

With the use of methyl cellulose the addition of wetting and emulsifying agents is omitted, because methyl cellulose has a particular characteristic of emulsifying skin fats. Thereby upon stripping of the film no stretching of the skin results.

The combinations proposed for use where water is lacking has the advantage that the cleaning means can accommodate itself to the unevennesses of the skin, whereby the radioactive contaminants can be removed from those areas of the body or object which can only insufficiently be reached by a rigid formed foam, for example, parts of the upper or lower eyelids, or of the ears and the like. The use of a foam granulate or of a pasty mixture of a granulate with the proposed addition materials has the further advantage that sensitive areas of the body can be treated in a comparatively gentle manner.

The invention is explained in greater detail with respect to the experimental results hereinafter given. For explanation of the data, there is first described the method of measurement used. 7

The research on the human skin was carried out by experiments of the investigator upon himself as the subject. The radioactive substance in solution or in liquid carrier was applied on the skin from an injection syringe and then with a drop of a l-normal acid rubbed about on the skin. After measurement of the activity attained on the skin, there were then carried out the operations with the cleaning means as hereinafter described in detail, and then a further measurement was made of the residual activity. These procedures were repeated one or more times depending upon the cleaning effect obtained.

In most cases a gamma scintillation spectrometer served as the detector; in some cases a window counter tube; and in the case of tritium, a liquid scintillation spectrometer. The distance of the detector from the observed source on the subject was kept quite closely constant. With the liquid scintillation counter, skin traces or flakes were suspended or dissolved and brought into the counter, and in this manner the residual or remaining activity on the skin was measured. The null effect or background radiation count was from time to time separately determined for subtraction.

In the data hereinafter given, the stated error is a statistical one and indicates that the true value, with 67% probability, lies in the range of the measured value, indicated through the given error.

Investigations were carried outwith various and diverse radioactive isotopes, as given in the following material, wherein the results are assembled and prwented in tabular form. For the results set forth in the Tables I to VIII, a polyurethane base, hard, synthetic plastic foam served as the treating or cleaning body.

In the accompanying Tables I-VI and VIII, the individual measurements or experiment are serially numbered in the first column; in the second column is represented the activity applied to the skin, measured in pulses per minute (as appearing by the scintillation or other counter); in the third column, the activity remaining after a single cleaning treatment; and finally, in the fourth column, the activity measured on the treating means after a treatment.

TABLE I: Cs-137 [Background 755:3 pulses/minute] Activity of subject (pulses/minute) Before cleaning Of cleaner After cleaning Experiment No.:

1 256:1:16 Slit) 773:9 1, 5305:40 85=|=10 81:1:9 16,4201130 905:10 79=|=9 14, 2205;120 72!) 73:1:9

TABLE II: 00-60 [Background 19i3 pulses/minute] Activity of subject (pulses/minute) TABLE IV: Na-22 [Background 63i6 pulses/minute] Activity of subject (pulses/minute) Before cleaning After cleaning Of cleaner Experiment No.:

TABLE V: Th-228 [Background 186:1;14 pulses/minute] Activity of subject (pulses/minute) Before cleaning After cleaning Of cleaner Experiment No.:

3, 007:1;55 258il7 2. 12, 420:1:120 234:1:16 197:1:14 2a. l90:|:2l

TABLE VI: '1.

[Background 33=|:0.4 pulses/minute] Activity of subject (pulses/minute) Before cleaning After cleaning Of cleaner Experiment No.:

1 l, 4165;38 35:1;2 2 11, 2l3:|:1l0 37;|;3

(I) CAESIUM-l 37 Caesium-l37, having a half-life period of 30 years and emitting beta and gamma radiation, is an isotope used in practically all laboratories carrying on any research with radioactive materials. The background radiation count amounted to 75i3 pulses per minute.

The isotope was present as the chloride in l-normal hydrochloric acid. The treatment was carried out by rubbing the foam block on the affected skin area for about 10 seconds. The results showed that the activity due to the applied contaminant was completely removed, that after the treatment only the background radiation effect was present, and no activity was transferred or carried over onto the treating stone or block.

(II) COBALT-60 Cobalt-60, having a half-life period of 5.3 years and emitting beta and gamma radiation, is also a frequently used isotope, for example, for radiation therapy in medicine. For those experiments for which the individual measurements are set out in Table II, the isotope was present as a chloride in one normal hydrochloric acid solution; and the background radiation effect amounted to 19:3 pulses per minute.

In these experiments, also as shown by Table II, there again appears the radical effect of the cleaning procedure, which nonetheless proceeds quickly and in a manner sparing of the skin and surfaces. Also in this case the cleaning means was not rendered contaminated.

(III) STRONTIUM-9O This radioactive isotope possesses a very high toxicity, since together with calcium it is incorporated in the marrow of the bones, and it remains there with a half-life period of 28 years. Therefore in dealing with this isotope the highest degree of cleanliness is imperative. As it emits only fi-radiation, the investigations were carried out with a window counting tube. The isotope here was used as the nitrate in l-normal nitric acid solution. The background radiation amounted here to 186114 pulses per minute, and the data are set forth in Table III.

As seen from Table III, the cleansing result is good; and despite heavy contamination (Exp. 4), there appears a slight residual activity of 1% which however was removed completely by a second treatment. (See Exp. 4a.) This residual activity is to be attributed to or accounted for by the fact that in presence of nitric acid the activity penetrates more strongly into the surface, as is shown in detail in Table VIII. Also in these experiments of Table III, the polyurethane foam cleaner itself was not contaminated.

(IV) SODIUM-22 (V) SERIES PRODUCTS OF THORIUM-228 Thorium-2'28, radioactively decomposing with a halflife period of 1.9 years and having the gaseous product radon-220, finds application in the so-called Thorium.

emanation devices, inasmuch as the decomposition product of this gas, which again is radioactive, is deposited on corresponding pins and so continually is produced as a new radioactive preparation. In the manipulation of such apparatus, the contaminations cannot always be avoided. These contaminants contain several isotopes (lead-212, bismuth212, thallium-208, and others), all present in the elemental form. Alpha, beta and gamma radiations are emitted.

Table V presents the results obtained by the use of a window counting tube. The background radiation amounted to 186:14 pulses per minute.

The cleaning process is also quite clear here. For the heavy contamination, after the first cleaning (Exp. 2), there remains about 1% radioactivity, which is removed by a second cleaning (see Exp. 2a). The cleaning means picks up substantially no radioactivity.

7 v1 TRITIUM Tritium is a beta emitter with a half-life period of 12.3 years, the radiation of which has only a slight energy and is, therefore from the standpoint of the radiation effects, relatively speaking not dangerous. 'It finds extensive applications in tracer techniques and in investigations of exchange processes in the atmosphere and hydrosphere. The most highly sensitive apparatus is necessary for its measurement, so that the error of a measurement through the slightest radioactive contamination becomes quite questionable. The need for the highest cleanliness in this case is therefore founded upon measurement techniques. The measurements presented in Table VI were undertaken in the manner described in the section given above on the measurement method. The background radiation of the equipment amount to 3310.4 pulses per minute.

The cleansing result is here also quite uncomplicated. A subsequent measurement of a possible contamination of the polyurethane foam here was not possible for technical reasons.

(VII) RADIUM-226 TABLE VII: Ra-226 [Background 186 :l: 14 pulses/minute] Activity (pulses/ minutes) of subject Initial contamination 32, 625:1:190 1. cleaning 1, 512:1:40 2. cleaning 317:1:18 3. cleaning 210:1:15 Contamination on cleaner 232:1:16

After three cleanings, each of about 10 seconds duration, the contamination was removed from the skin. The cleaning means showed a light contamination, about 1% of the activity cleaned, which however is not very heavy.

The accompanying Table VIII presents data indicating that radioactive isotopes are differently incorporated in the surface dependent upon the chemical conditions under which they are applied to the surface material. In these experiments, to the radioactive isotope applied to the skin surface there was further added one drop of a 10% or half-concentrated acid and this was rubbed on the skin. Cobalt-60 was used in conjunction with hydrochloric, sulfuric and nitric acids, and the background effect amounted to 21:2 pulses per minute.

Activity of subject (pulses/minute) Experiment No.

and Acid Before cleaning After cleaning Of cleaner ai t i ig 19' i ii 455:7

i :i: 24, 319:1:160 128:1:13 20, 1673:145 128:1:13 93:1:10 31, 78131180 1425;13 25, 6 5:k160 :1: 6a 98:1:10

It is to be observed that the contaminants adhere more firmly (compare for example Table II), above all with the use of nitric acid. But here also the residual activity is removed (see Exp. 6a) through one or two further treatments with the polyurethane foam body. The activity pick-up of the cleaning means is here somewhat greater.

The accompanying Tables IX and X show data obtained with decontamination carried by cleaning means other than polyurethane foams. Therein attention should 5 be particularly given above all to the cleaning effect and the occasional contamination of the cleaner.

BLE IX I [Background 2612 p.lmin.] 10 Initial activity. 1,637 .1: 41 p./minute.

H01 (1:1) 1st cleaning 759 :l: 28 p./minute. 2nd cleaning 215 :1: 1 p./minute. 3rd cleaning 38 :1: 7 p./minute. Initial activity. 39,271 :1: 200 pJminute. 1st cleaning 597 :1.- 25 p./minute. 2nd cleaning- 167 d: 13 p./minute. 15 Pumice Stone Initial aetivity..-. 8,584 i 93 p./minute. 1st cleaning 293 :l: 18 p./minute. 2nd cleaning. 202 i 15 p./minute.

2 Activity pick-up of the Pumice by the above cleaning operations, 12,869 i 11 5 p./ minute.

Initial activity. 25,786 :1: 160 pJminute. 1st cleaning 602 :1: p./minnte. 25 Polyurethane 2nd cleaning 363 d: 20 p./minute.

Initial activity---- 15,852 i 130 p./minute. i 1st cleaning 303 :l: 18 p./minute. 2nd cleaning 184 :1: 14 p./minute.

Activity pick-up of the Moltopren by the above cleaning operations, 267i 17 p./ minute.

Initial activity 28,857 :1: 170 p./minute. First Expt. with Mixture 1st cleaning 6,916 :1: 84 p./minute. of Alusilikate Phosphate. 2nd cleaning- 5,795 i 76 p./minute. Th it th 1 3rd cleaning 5,116 :1: 72 p./minute.

erea er e c eaning tifdtittlfg treatmen g g Polyurethane 3rd cleaning 47 :1: 7p. minute.

H Initial activlty. 22,090 :1: 150 pJminute. 40 Second Expt. with Mixture 1st cleaning 3,361 :1: 58 p./minute. of Alusilikate Phosphate. 2nd cleaning- 2,498 :l: 50 p./minute. 3rd cleaning.- 1,931 :l: 44 p./minute. Further cleaning with 1st cleaning. 728 :1: 27 p./minute. Polyurethane foam. 2nd cleaning- 348 :l: 19 pJminute.

3rd cleaning 58 :l: 8 p./minute.

45 TABLE X [Background 19:i:l.4 p./min.]

Activity of Subject (pulses/min.)

Before After 0t Experiment No. Cleaning Cleaning Cleaner 1. PHENOL RESIN FOAM 2. SLAG FOAM 23, 644:1:160 178:1:14 (2nd cleamng).. 30:1:6 aoifi 2 18, 703:1:140 47:1:7 (2nd cleaning) 355:6

6O 3. SYN THETIO PUMICE 210591170 27am 62=i=8 Subsequent cle th Polyurethane foam-.- 30:1:6 65 4. SOFT POLYURETHANE PLUS CORUNDUM OVE RLA YE R 1 35, 513:1:190 1, 447:1:39 384:1:20 Subsequent cleaning with Phenol resin ioam...... 5:10 32, 992:1:185 1, 494:1:39 384:1;20 Subsequent cleaning with Polyurethane team (hard) 38:1:7

5. SEMI-HARD POLYURETHANE 1 27, 723i170 469:|:22 2 23, 801:1:160 40821 Subsequent cleaning with polyurethane foam (hard) 87:1:10

TABLE XContinued Activity of Subject (pulses/min.)

7. STEEL WOOL PLUS SOAP 1 3, 7s5=e65 635:8 2 4, 0353165 aria} Measurement on Polyurethane foam after all above cleaning operations, 42:7.

In Table IX are presented successively the individual cleaning means with their cleaning effects and the occasional contamination of the cleaner. The background effect amounted to 26:2. pulses per minute.

The data of Table X shows the utility of different materials for decontaminating the skin surface of radioactive impurities or contaminations. The investigations were undertaken with a scintillation spectrometer and the use of cobalt-60 isotope in l-normal hydrochloric acid. The background effect or radiation amounted to 1911.4 pulses per minute. For the rest, as to the measurement method, the above given description also is here applicable.

From Tables IX and X it is to b Observed that none of the cleaning means therein appearing attains the results of polyurethane foam. A phenol resin foam however is well suited, but still its mechanical wearing away is much more marked than in the case of a polyurethane foam. Also it is apparent that by repeated use a residual activity remains in the phenol resin foam. With all the other materials used for the cleaning means, clearly no thorough-going removal of the radioactive contaminants after one treatment is to be obtained. Furthermore, in the case of a slaggy foam there is evident a strong contamination of the cleaning material, above all in the case of synthetic pumice stone. Also for natural pumice stone, it is evident that a great part of the activity remains, and therefore its use for decontamination is eliminated from consideration.

In the case of aluminum silicates, phosphates and mixtures of these materials, it is established that the cleaning effect proceeds very slowly; and moreover as a very great disadvantage, a portion of the activity combines rather strongly with the skin surface. This disadvantageous characteristic is so strong that even the subsequent cleaning with the far preferable polyurethane foam or phenol resin foam is made difficult.

The data show that the polyurethane foam produced in hard condition best fulfills the requirements for a cleaning means for radioactive contaminants, since it removes them quickly and at the same time is easy on the skin surface. This is surprising, as the comparison, for example, with the decontamination concentrate and with the pumice shows. An unpleasant disadvantage of pumice stone is that it itself takes up a great part of the activity to be removed, making it non-reusable. For a polyure thane foam this disadvantage either is not present or only appears to a negligible degree. The disadvantage of the investigated decontamination concentrate is its relatively weak cleaning power, moreover the residual activity bites into the skin surface more strongly, so that even with polyurethane foams it is more difficult to remove. Upon consideration of different chemical compositions, it is evident that in the case of nitric acid the contaminants are quite strongly adherent. But a repeated treatment by polyurethane foam removes the residual activity also.

While in the treatment with the previously known cleaning means, the cleaning effect drops off perhaps exponentially, so that repeated cleanings, ten times and more, were necessary, on the other hand with the polyurethane foam the process goes forward essentially more quickly, easily and in a manner sparing the surfaces treated. The foam materials proposed by this invention for the removal of radioactive contaminants from the skin or from objects, particularly foams of synthetic plastic, specifically are extremely light, easy to use, practically unlimited in storability, and extremely insensitive to moisture and to heat.

The synthetic plastic foam materials, capable of scraping and fabricated from medium to hard, as proposed for decontamination purposes, are at the same time suited also for the removal of non-radioactive contaminants from the skin. It is noted that as a convenient form of cleaning means the foam material in say rectangular block form may have one side out across to provide a cleaning face in which broken or intersected edges of the cells are exposed for scraping action; and on the op posite side or face there is applied a film or foil, impenetrable to the fluids, dust or other form in which the radioactive contaminants might pass through the body of the foam, thereby providing on the side opposite the cleaning face a barrier to further migration of the contaminants. This contributes to safety for the user, also to limitation of spreading of the contaminant material which has been picked up. Similarly the foam in one form or the other may be applied to a pressure plate or base provided with a handle for use in mopping operations on floors, walls or ceilings.

Moreover it appears that certain of these foams, particularly the synthetic plastic organic foams such as polyurethane may take a granular or quasi-powdered form, which may be made up into tablets or into salves or pastes and still have some advantages by a'bsorbtive or protective properties apart from cleaning in the sense previously described by the abrading, scraping action. The particles making up the tablet form, upon consumption of the tablet and its disintegration in the human body, are released and are able to some degree to absorb from the walls and linings of the throat, stomach and intestine radioactive contaminants there contained. Being so absorbed, they then pass out with the granular material carrier through the intestinal canal.

On the other hand such materials included in pastes or salves can increase the shielding effect of the salve because of their somewhat greater ability to absorb radiation. Also in some pastes or salves which are hardenable and applied before radiation or contamination exposure, the particles obviously provide a barrier to contact of these materials with the skin. After exposure has occurred the hard material is simply broken or flaked off taking the radioactive deposits or contaminants therewith. On the other hand, where there are applied and hardened after exposure has occurred, they may first be rubbed on with an opportunity to pick up the radioactive contaminants in the particles, then permitted to harden, and thereafter broken away generally serving to remove the material cleanly.

In the accompanying Table XI there are given the results of using a granulate of a hard to medium hard polyurethane base plastic foam along with a slight amount of water to make the granulate pasty, as well as the use of a mixture of a foam granulate with synthetic soap, a fat cream, and a vegetable oil.

The experiments on the human skin again were carried out on the body of the investigator himself. Cobalt- 60 was used as the radioactive isotope, to which a drop of 10% or half-concentrated acid Was added followed by rubbing on the skin. The background radiation effect amounted here to 21:2 pulses per minute.

TABLE XI [Background 215:2 p./min.]

Activity of Subject (pulses/ min.)

Expt Before After Cleaning Means No. cleaning cleaning Polyure. foam granulate, no water flush. g 'a 3%; 2a 76:1:8

Polyure. foam granulated plus syn. 1b 103:1:11 soap with release agent, no water 2 559=l=24 ll3=l=l1 flush. 2a 63:8 2b 555:8

Polyure. foam granulated fatty cream, 11 4333:21 1405:12 no water flush. l2 429:1;21 81:1:9

Polyure. foam granulate plus veget. oil, la 40221 no water flush 2 6, 3503:80 827129 Here an almost complete removal of radioactive contaminants is attained. A like result is attained with a polyurethane granulate in combination with a fat cream. Also the mixture of a polyurethane foam granulate with vegetable oil, e.g., sunflower oil, provides a comparatively good removal of radioactive contaminants from the human skin. In view of the facts that the proposed synthetic foam granulate in a mixture with a fat, oil, a soap, or a thickening agent, or an emulsifying agent, or a film former, as either single or joint additions, is completely harmless to and treats or affects the skin gently, this proposal of the invention is particularly important.

I claim:

1. Means for removing radioactive contaminants from the human skin mechanically by scrubbing rubbing, comprising: a foam material open-pored on its scrubbing surface and fabricated to be from medium hard to hard so as to crumble at the surface during scrubbing, with formation by the foam cell walls at the surface of sharp, skin-scraping and -removing edges,

which crumble away in crumb-like fashion during rubbing upon the skin,

whereby on the one hand fresh cells lying beneath the rubbing surface are broken up and the radioactive contaminants gathering in the pores are carried away with the cell walls crumbling off providing constant renewal of the effective foam material surface, said foam material being selected from the group consisting of polyurethane foam, phenol resin foam, polystyrene foam, buna rubber base foam, natural rubber base foam, and vitreous foam materials.

2. Means in accordance with claim 1, wherein said foam material is selected from the group consisting of polyurethane foam and phenol resin foam materials.

3. Means in accordance with claim 1, wherein said foam material is selected from the group consisting of slag foam and glass foam materials.

4. Means in accordance with claim 1, foam material is a body of polyurethane pore size of from 0.2 to 1.5 mm.

5. Means in accordance with claim 1, comprised of a body of said foam material, and on a surface of said body opposite the rubbing surface covered with a film impermeable to liquids and dust niigratable from the rubbing surface through the body.

6. A decontamination device adapted for removal of wherein said foam with a radioactive materials from the surfaces of human skin by a rubbing-scraping operation comprised of a body of hard and rigid foam material, said material as described in claim 1, and to provide a cleansing face, having a cut face with exposed interrupted cut cell walls affording initial scraping edges.

7. A device as described in claim 6, wherein a body face, opposite the cut face providing said scraping edges, is overlaid by foil means bonded thereto and impervious to liquids, dust and other finely divided material migrating from the cleaning face through the foam body.

8. Means in accordance with claim 1, wherein said foam material is in granulated form.

9. A cleaning composition for removal of radioactive contaminants from the surface of human skin consisting essentially of a granulated foam material as described in claim 1 and a film former in an effective amount.

10. A method for removing radioactive contaminants from the human skin comprising the steps of: rubbing the area to be decontaminated with a foam material at least superficially open-celled and fabricated to be from medium hard to hard so as to crumble at its surface during rubbing with foamation by the foam cell walls at the surface of sharp skin-scraping and -removing edges,

which crumble away in crumb-like fashion during rubbing upon the skin,

whereby on the one hand fresh cells lying beneath the rubbing surface are broken up and the radioactive contaminants gathering in the pores are carried away with the cell walls crumbling off providing constant renewal of the effective foam material surface, said foam material being selected from the group consisting of polyurethane foam, phenol resin foam, polystyrene foam, buna rubber base foam, natural rubber base foam, and vitreous foam materials.

11.'A method as described in claim 10, wherein the rubbing is carried out in conjunction with a small amount of added water on the skin.

12. A method as described in claim 10, with said material granulated, wherein a film forming material is used with said granulated material as it is rubbed on said area, leaving said materials spread over said area and permitting the film former to harden to form a film with the granulated material; and stripping the film with the embedded granules and therewith the contaminates from said surface.

13. A method as described in claim 10, with said material granulated, wherein a film forming material is mixed with said granulated material; and the rubbing of the mixed materials on said surface is continued until through hardening of the film former, loose crumbs are formed comprised of the mixture applied to the said surface and contaminants picked up therein.

14. A composition as in claim 9, including sunflower oil.

15. A composition as in claim 9, including a thickening agent.

16. A composition as in claim 9, including a skin oil emulsifier.

17. A composition as described in claim 9, including glycerine.

References Cited UNITED STATES PATENTS 1,882,741 10/1932 Beller et al. 252-311 1,934,494 11/1933 Gillespie 1347 2,591,481 4/1952 Webster 15506 2,877,131 3/1959 Overholt et al. 134-4 3,047,434 7/1962 Bulat 1347 3,088,158 5/1963 I Boyle et al. 15506 3,112,219 11/1963 Politzer et a1 252-91 3,149,364 9/1964 Baptist et al. 15--506 3,169,905 2/1965 Lambert 25289 (Other references on following page) 13 FOREIGN PATENTS 760,232 10/1956 Great Britain. 930,370 7/1963 Great Britain.

OTHER REFERENCES r Myers et a1., Synthetic Resins as Exchange Adsorbents, 0

14 LEON D. ROSDOL, Primary Examiner W. SCHULZ, Assistant Examiner US. Cl. X.R.