RADIUM-WATER GENERATORS HERMAN SCHLUNDT, RALPH G. FULTON,
AND
FRANK BRUNER
University of Missouri, Columbia, Missouri
We have determined (a) the quantity of radon present in the activated water, expressing it as millimiaocuriest per liter; and (b) the quantity of radium per g., or millimiaoliter expressed as micrograms, grams, g., per liter. The activity of water samples was determined by measuring electroscopically the quantity of radon dissolved in the water after it had stood in contact with the radioactive source for a definite period. The apparatus for such determination was an improved form of the apparatus described by Schlundt and Moore and others for separating quantitatively radon + + + + + + from water samples ( I ) , (Z), (3), ( 4 ) . The collected NDER the title "Radium-Water Generators" gases containing the radon are introduced into an evacwe have included the various types of apparatus uated chamber of a standardized electroscope through a dwina train, and and appliances which have been devised (and thiee hours later most of them patented*) for rendering ordinary water readings of the drift radioactive. The generators fall into two classes: of the charged leaf ( 1 ) those in which water stands in contact with the of the electroscope source of radioactivity, and (2) those which employ are made. Workradium emanation (radon) in making the water radioing with calibrated active. In the latter, the water to be activated does electroscopes t h e not come in contact with radium, the parent of radon, radium content of at all. In this type of generator the therapeutic agent the water sample is the radioactive gas, radon, and its disintegration can be calculated, products, RaA, RaB, and RaC. Since radon has a . assuming that the relatively short life, compared with radium, it follows n e t r a t e of disthat water made radioactive by dissolved radon is charge of the eleccharacterized by temporary radioactivity. Radon Fmms 1 troscope is propordecays spontaneously to half value in 3.85 days. Hence, we find that bottled water, whether it has been tional to the radon in the ionization chamber. made radioactive artificially with radon or is natural The first generator, A, tested consisted of an aluwater free from radium but possessing activity due to minum container of about four liters capacity, the dissolved radon, gradually loses its activity, and in the design of which is shown in Figure 1. The water comcourse of a month becomes practically inactive. partment, A, is made of double-walled aluminum, the On the other hand, water containing even minute space between the walls being filled with heat-insulattraces of radium compounds retains a permanent ing material, inasmuch as the generator is also inactivity as long as the radium salts remain in solution. tended to keep ice water. The double-walled lid, B, The radioactive elements present in water of permanent is similarly insulated. C is the water tap and D, activity are radium, and its transformation products, the radioactive brick. The radon produced by the radon, RaA, RaB, RaC. Thorium-bearing ores, or radioactive material in the brick diffuses into the water mesothorium concentrates, have been rarely used as and is taken into the system by drinking the water. activators in radium water generators. Whether After standing in the generator for one day, a twoor not the activity is permanent, can be readily de- liter sample of water was drawn off and tested for termined by boiling off the radon, sealing the water activity. The radon content was found to be too small sample for a time and determining whether there is a to be detected. Since such a time interval represents recovery of activity. approximately that which would occur if the generator Our analytical determinations have been confined One millimiaocurie radon, MpC, or 10-'C., is the quantity to three representative generators of the lirst type. of tradon in equilibrium with one milliminogram, lo-' g., radium -
Three representative radium-water generators were Tha quantities of (1) radium emanation (radon) and (2) radium (element) actually present in water samples were determined when the generators were operated according to directions of the makers. It is concluded that steady drinkers of water from men the most active type of generators do not stand in danger of contracting radium fioisoning. The alleged therapeutic value of slightly radioactive waters probably rests more on the larger daily doses of water drunk than on the radon contained therein.
tested for radioactivity.
u
* Some of the trade names of water activators are: Radium Emanator, Radium Cone, Radium Ore Revigator, Radiumator, Radium Urn Vitalizer, Radonizer, Liquid Sunlite, Radium Spa, and others.
(element). One micro-minocurie, ppC, or 10-'2C., is the quantity of radon in equilibrium with one micro-microgram, 10-la g., radium. One millimicrocurie radon per liter of water equals 2.75 Mache Units.
were in daily use, it is obvious that the generator is practically worthless as far as its emanating power is concerned. Another sample of the same volume, left standing in the generator for a week, gave a radon content of such a value that the equilibrium amount, or maximum obtainable, would be 17.9 ppC (17.9 X 10-12 curies) per liter, and this could only be obtained by allowing the water to stand in the generator for a month. The quantity of radium which goes into solution is too small to be detected in a four-liter sample of water. The radium content of the radioactive brick was determined by the bisulfate fusion method (5) and found to be 8.98 X 10-l2 g. of radium per gram sample. Since the brick weighed 570 g., its total radium content is 5.1 millimicrograms, and this amount of radium should produce 5.1 millimicrocuries of radon at equilibrium. Since 17.9 X 10-l2 curies of radon per liter were found, four times this amount, or 71.5 X 10-12 curies, were present in the four liters of water contained in the generator. The efficiency was therefore only 71.5 X 10-12/5.1 X lo-', or 1.4 per cent. The low value was probably largely due to the lack of porosity of t h e brick. The radon produced within it is practically all retained. Taking the value of radium as $100 per milligram, the value of radium in the brick is onehalf cent. The second generator,B, tested was of quite diierent design, andis shown FIGURE 2 in Figure 2. The container of the generator is made of stoneware. It is divided into two compartments by the removable stoneware partition, A . This partition is made tight by means of a circular rubber gasket, B, which fits between the partition and the girdle, C, of the container. The partition is held firmly in position by the anchor rod, D, which is fastened to the bottom of the container, passes through a hole in the center of the partition, and terminates with a leather washer, a metal washer, and a wing nut, E, as shown. Vent, F, is a metal tube, flush at the under side of the partition, passing through it, and closed by a valve cap. A cut-off valve, G, makes it possible to connect the two compartments. The water tap is shown at H, and S is the source of radium and radon. I t consists of ground carnotite ore firmly packed in a porous clay box and held in place by a porous lid, thus resembling a brick. The generator is set up by first inserting the radioactive brick and filling up with water to the girdle. The rubber gasket is then put on and the partition, A, put into place. The cut-off valve, G, is then opened so as to connect the upper and lower compartments.
Vent, F, is then opened and the partition is fastened securely in place by means of the wing nut on the anchor rod. The cut-off valve and vent are then closed, and the compartment tested for air leaks by opening the tap. If connections are tight no water will run out of the tap. When the compartment is air-tight, the cut-off valve and vent are opened and the upper compartment is filled with water up to the level of the vent cap. The cut-off valve and vent are then closed, and the lid put in place, and the generator is ready for use. When water is to be drawn, the cut-off valve and tap are opened. The water which is drawn is replaced by water from the upper compartment, and the lower compartment is always kept completely filled with water. This fact, together with that of the compartment being air-tight, insures that all radon discharged into the water is being retained by the water, since it does away with loss by diffusion into the air. Water must be added to the upper compartment from time to time to replace that consumed, and the water level should not be allowed to fall below the opening of the cut-off valve. This generator produced water much more radioactive than the former one, 77.5 millimicrocuries of radon per liter being obtainable at equilibrium; a value 4300 times as large as that obtained from geuerator A . The carnotite ore which serves as the source of radon in this generator assayed 7.3 per cent. uranium, and weighed nearly 450 g. Its radium content then is that in equilibrium with 33 g. of uranium in a natural mineral which is given by 33 X 3.4 X lo-', or 11.2 X 10W8 g. This amount of radium should produce 11.2 microcuries (11.2 X curies) of radon a t equilibrium. Since 77.5 X 10-9 curies of radon per liter were found, 4.6 times this amount or 35.7 X curies were present in the 4.6 liters of water contained in the generator. Its radon efficiency is therefore or 3.2 oer cent. At 5100 oer 35.7 X 10-8/11.2 X milligram the value of the radium in the brick is about $1.10. Water remaining in generator B for four days would contain 40 mpC of radon per liter. A person drinking six glasses of water a day as the directions suggest, would ingest a daily dose of radon amounting to about 75 mpC. To generate this amount of radon per day calls for 450 mpg of radium when we assume that aU of the radon produced finds its way into the water. Taking the value of radium as $100 a milligram, this would represent a value of 5 cents. Under normal operating conditions the activated water in this generator was found to contain 6 X lo-# g. radium per liter. A person drinking six glasses of water, 1800 cc., would be taking in 11 millimicrograms of radium daily, and in the course of a year of steady use 4 micrograms of radium would be ingested. The third generator, C, Figure 3, looks like a mere toy in comparison with the dimensions of generators A and B. This radium water activator consists of a cut glass tumbler, T , holding 70 cc. of water. It is fitted with a bakelite top, C, carrying a rubber gasket,
,G, which can be clamped down air-tight by means of a yoke, Y,attached to the base, B. Fastened to the top by metal mountings is a white porous earthenware cylinder, S, open a t the bottom, 2.5 cm. in diameter and 4.5 an.tall. The radium source, a slightly soluble salt of radium, e . g., the carbonate, is incorporated in the walls of the porous cylinder. Since the directions advise drinking two glasses of water a day, the radon determinations were made at intervals of twelve hours. Likewise the radium content of the water was determined after an exposure of twelve hours. Before making the radon determinations the generator was operated for several days, by changing the water every twelve hours. In making radon determinations it was found necessary to reduce the volume of water to 1 cc. The total radon dissolved in 70 cc. of water was found to be 2237 mpC for an exposure of twelve hours, which corresponds to an equilibrium amount of 26,000 m& or 26 pC, and a concentration of 370,000 mpC or 370 PC, per liter, a value nearly 4800 times the activity of the water capable of being produced in generator B and 22 million times as active as the water of generator A. A small fraction of the radium in the core goes into solution. We determined the permanent activity of water activated in this generator by boiling off first all the radon which had accumulated in a 70-cc. sample in twelve hours. The completely de-emanated sample was then sealed and allowed to stand for a definite period, 4 to 6 days. The growth of radon in the sample was measured by boiling off again the radon which had accumulated and measuring it electroscopically. It was found that the actual radium dissolved in 70 cc. of water was 34.7 mpg. Hence, of the equilibrium amount of radon, 26,000 mpC, scarcely 0.2 per cent., is generated by the radium which goes into solution to activate the water permanently. Finally, the radium content of the active source was determined. The core was detached, sealed in an 8-inch test-tube and after a month its gamma-ray activity was compared with a radium standard by means of a special type of gamma-ray electroscope ( 8 ( 9 Measured in this way the core contained 31.5 pg of radium (element). Since the equilibrium amount of radon, the amount which would accumulate in one tumbler full of water, is 26 $2, it is seen that the free emanating power of the radium in the core is unusually high, 82 per cent. The foregoing results are summarized in the following table :
A
m
y
Ro C o n r a n of Ccnnolor
AniucSouru
G&N~ATDRS
01 RADIW WATBP
Radon oar Litn or Ecuilibrium
Doily Dornga Daily Doraga sfRodon of Rodium
Water activated in generator B has an activity as high as some of the more active spring waters whose radioactive properties have been extolled. Since radium poisoning results from a deposit of the element radium in the bony skeleton, to the amount of several micrograms, let us consider whether a danger lurks in the permanent activity of the water activated in generator C. (It is evident that the quantities of radium in water activated in generator A are negligible.) Drinking two glasses a day of the activated water introduces 70 millimicrograms of radon into the system daily, which totals from 20 to 25 micrograms of radium during a year of steady use. Soluble radium salts taken into the system by mouth are rapidly eliminated during the first week after ingestion. The experiments of Seil, Viol, and Gordon (6) show that only 25 to 35 per cent. of radium taken orally remains in the system for longer than five days. Later the rate of elimination is somewhat less than one per cent. per day. Our own experiments and those of Barker and Schlundt (7) show a rate of elimination somewhat higher. A second factor must be considered: by the process of solution the store of radium in the radium-bearing source becomes depleted daily. According to our determinations steady service for a year would reduce the radium source to one-fifth its initial value, and thus leave the generator quite impotent. With both of these factors operative, the risk of contracting radium poisoning even by drinking water from this unusually active generator must be regarded as rather remote. LITERATURE CITED
Scn~mml,H., AND MOORE, R. B., "Radioactivity of some deep well and mineral waters," J. Phys. Chem., 9, 320 ( 1 0nFA
SCHLUNDT, H., m MOORE,R. B., "Radioactivity of the
thermal waters of Yellowstone National Park," B d . 395, U. S. Geological Survey (1909).
P ~ S O NCS 'L.,'MOORE. , R. B . , ' L ~S. , C., AND SCRAEPER, 0. C., "Extraction and recovery of radium, uranium, and
, U. S. Bureau of
BARKER,H. H., "The hisulfate method of determining radium." I.Ind. Eng. Chem., 10,525 (1918). SEIL,H. A.. VIOL, C. H., AND GORDON, M. A,, "The elimination o f soluble radium salts taken intravenously and per os," Neu York Med. J., 101, 896 (1915); also Radium, 5, 40 (1915). BARKER, H. H., AND SCHLUNDT, H., "The detection, estimation and elimination of radium in living persons given radium chloride internallv. 11." Am. I. Roenl~enol. & Radium Therapy, 24,418 (1930): Cmm. MME.M., "Les Mesures en RadioactivitC et L'Ctalon du Radium," J. phys. radium [5], 2,795-826 (1913). BARKER. H. H.. AND SCHLUNDT. H.. "The extraction and ~~~reco& of iadium from typicai American carnotite ores," Bull. U&. Mo., 24, No. 26 (1923).
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