THE COLLECTION OF LONG-LIVED NATURAL RADIOACTIVE …

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NRL REPORT 4069

THE COLLECTION OF LONG-LIVED NATURAL RADIOACTIVE PRODUCTS

FROM THE ATMOSPHERE Peter King, Luther B. Lockhart, Jr.,

Richard A. Baus, and Robert L. Patterson, Jr.

High Polymers Branch Chemistry Division

and

Herbert Friedman and Irving H. Blifford, Jr.

Electron Optics Branch Optics Division

October 20, 1952

NAVAL RESEARCH LABORATORY

WASHINGTON, D.C.

en

ABSTRACT

Long-lived radium decay products (RaD, RaE, Po) were

collected from the atmosphere by the use of air filters and rain water. A workable procedure was developed to separate traces of these active materials from rain water through use of aluminum hydroxide floc as a preliminary concentrating agent.

Rain effectively removes significant quantities of RaD, RaE, and Po from the atmosphere. The first part of the rain removes a relatively larger portion than later parts of the rain, but all fractions of the rain contain some activity (RaE). The RaD-RaE activity as collected by rain has been found to vary widely at different geographical locations and at different times at any given locality. There is no simple correlation of the activity collected with the character of the rain, the seasons, or the quantity of dirt present in the collection. The average RaD-RaE activity in disintegrations per minute per gallon varied from about 2 at Samoa to 20 at

Glenview and NRL.

PROBLEM STATUS

This is an interim report: work on this problem is

continuing.

AUTHORIZATION

NRL Problem C10-02 RDB Project NR 410-020

Manuscript submitted September 17, 1952

UNCLASSIFIED

Naval Research Laboratory. Report 4069.

THE COLLECTION OF LONG-LIVED NATURAL RADIOACTIVE PRODUCTS FROM THE ATMOSPHERE, by P. King, L. B. Lockhart, Jr., R. A. Baus,

R. L. Patterson, Jr., H. Friedman, and I. H. Blifford,Jr.

11 pp. & figs., October 20, 1952. Long-lived radium decay products (RaD, RaE, Po)

were collected from the atmosphere by the use of air filters and rain water. A workable procedure was developed to separate traces of these active materials

from rain water through use of aluminum hydroxide

floc as a preliminary concentrating agent. Rain effectively removes significant quantities of

RaD, RaE, and Po from the atmosphere. The first part

of the rain removes a relatively larger portion than

1. Radioactive

substances—

Measurement

2. Atmosphere- Radioactivity —

Measurement

I. King, P.

I. Lockhart, L. B., Jr.

Ill.Baus, R. A.

V. Friedman, H.

VI.Blifford, I. H., Jr.

IV.Patterson,R.L., Jr.

UNCLASSIFIED


THE COLLECTION OF LONG-LIVED NATURAL

RADIOACTIVE PRODUCTS FROM THE ATMOSPHERE,

by P. King, L. B. Lockhart, Jr., R. A. Baus,


11 pp. & figs., October 20, 1952.

Long-lived radium decay products (RaD, RaE, Po)

were collected from the atmosphere by the use of air

filters and rain water. A workable procedure was

developed to separate traces of these active materials


floc as a preliminary concentrating agent.

Rain effectively removes significant quantities of

RaD, RaE, and Po from the atmosphere, The first part


1. Radioactive substances—

Measurement

2. Atmosphere-

Radioactivity — Measurement

I. King, P. .

II. Lockhart, L. B., Jr.

Ill.Baus, R. A.


V. Friedman, H.


(Over, (Over)

UNCLASSIFIED UNCLASSIFIED

|

UNCLASSIFIED UNCLASSIFIED

Naval Research Laboratory. Report 4069. THE COLLECTION OF LONG-LIVED NATURAL RADIOACTIVE PRODUCTS FROM THE ATMOSPHERE, by P. King, L. B. Lockhart, Jr., R. A. Baus,

R. L. Patterson, Jr., H. Friedman, and I. H. Blifford,Jr. 11 pp. & figs., October 20, 1952.



filters and rain water. A workable procedure was developed to separate traces of these active materials


floc as a preliminary concentrating agent. Rain effectively removes significant quantities of



(Over) UNCLASSIFIED

1. -Radioactive substances—

Measurement

2. Atmosphere—

Radioactivity — Measurement

I, King, P.

Il. Lockhart, L. B., Jr.

IlIl.Baus, R. A.

V. Friedman, H. VI.Blifford, I. H., Jr.



THE COLLECTION OF LONG-LIVED NATURAL .

RADIOACTIVE PRODUCTS FROM THE ATMOSPHERE, by P. King, L. B. Lockhart, Jr., R. A. Baus,


11 pp. & figs., October 20, 1952. ;



filters and rain water. A workable procedure was.

developed to separate traces of these active materials


floc as a preliminary concentrating agent.

Rain effectively removes significant quantities of



(Over) UNCLASSIFIED

1. Radioactive substances —

Measurement

2. Atmosphere—

Radioactivity —

Measurement

I. King, P. It. Lockhart, L. B., Jr.

Ill.Baus, R. A.


V. Friedman, H.


UNCLASSIFIED

later parts of the rain, but all fractions of the rain contain some activity (RaE).

The RaD-RaE activity as collected by rain has been found to vary widely at different geographical locations and at different times at any given locality. There is no simple correlation of the activity collected with the character of

the rain, the seasons, or the quantity of dirt present in the collection. The

average RaD-RaE activity in disintegrations per minute per gallon varied

from about 2 at Samoa to 20 at Glenview and NRL.

UNCLASSIFIED

UNCLASSIFIED

later parts of the rain, but all fractions of the raincontain some activity (RaE).

The RaD-RaE activity as collected by rain has been found to vary widely at

different geographical locations and at different times at any given locality.

There is no simple correlation of the activity collected with the character of


average RaD-RaE activity in disintegrations per minute per gallon varied


UNCLASSIFIED

UNCLASSIFIED

later parts of the rain, but all fractions of the raincontain some activity (RaE). The RaD-RaE activity as collected by rain has been found to vary widely at

different geographical locations and at different times at any given locality.

There is no simple correlation of the activity collected with the character of the rain, the seasons, or the quantity of dirt present in the collection. The

average RaD-RaE activity in disintegrations per minute per gallon varied from about 2 at Samoa to 20 at Glenview and NRL.

UNCLASSIFIED

UNCLASSIFIED

later parts of the rain, but all fractions of the rain contain some activity (RaE). The RaD-RaE activity as collected by rain has been found to vary widely at

different geographical locations and at different times at any given locality. There is no simple correlation of the activity collected with the character of


average RaD-RakE activity in disintegrations per minute per gallon varied


UNCLASSIFIED

THE COLLECTION OF LONG-LIVED NATURAL RADIOACTIVE PRODUCTS FROM THE sO

INTRODUCTION

A survey of the chemical literature covering the past 45 years revealed many refer- ences concerning the amounts of the short-lived RaB and ThB in the atmosphere, but no information on the quantities of the longer lived RaD, RaE, and Po. This dearth of information prompted us to utilize facilities available at several Naval bases in different parts of the world to collect atmospheric radioactivity for subsequent analysis at NRL. These

- collections of activity were made by either, or sometimes by both, of two methods. The first method used high-capacity air filter units with filter paper as the collecting medium. The second involved the collection of large volumes of rain water, between 100 to 1000 gallons, and the concentration of the activity with aluminum hydroxide floc. The collecting methods, particularly the rain-water method, afford a means of securing large samples with a minimum of effort. As a result of the chemical methods used, the activity from 1000 gallons of rain water or 10° to 10’ cu ft of air is finally concentrated on 50 to 100 mg of carrier. Counting of the separated © and # activity and comparison with similar standards gave reasonably accurate measures of the concentration of MBSE products in the atmosphere.

RAIN-WATER COLLECTION

. Rain was. collected on 500 to 1000 sq ft roofs made of aluminum sheeting and conveyed by aluminum gutters and pipes to aluminum collecting tanks. For some of the collections made at the Naval Research Laboratory, automatic controls were used to divert different . portions. of the rain into three different tanks (Figure 1) so as to compare the activities collected during different parts of the rain. However, since the rains were not always continuous but often consisted of a series of showers, it is possible that the activity collected in the last two tanks does not actually represent the continued Bones of the same volume of air as did the rain collected in the first tank.

In most of the eullectigns: more rain fell than could be contained in the tanks and much was lost through overflow. The collections represent the water remaining in the tanks at © the end of the collection period.

FLOCCING PROCEDURE

The rain water in the tanks was stirred with a jet of compressed air anda solution of aluminum sulfate was added to make the final concentration approximately 0.2 gram Al, (SO, ), - 18 H,O per gallon of rainwater. The pH was adjusted to 7.0 + 0.1 with a sodium. carbonate solution using LaMotte standards with bromthymol blue indicator. Stirring was continued for 45 to 60 minutes and then the treated water was allowed to settle undisturbed overnight. After settling, the clear supernate was removed by syphoning and the Al(OH),

_ floc transferred to glass bottles for further settling and concentrating. The floc from 1000

gallons of water could generally be concentrated to a volume of 2 to 5 gallons.

1

2 aie NAVAL RESEARCH LABORATORY

Figure 1 - NRL rain-water collection tanks

These procedures have been checked by adding small amounts (50-100 mg) of lead and bismuth to 100 gallons of water and then collecting them with aluminum hydroxide floc as described in Appendix I. At the concentrations used (0.6-1.1 x 10-° moles/1), recoveries were approximately 70 to 90 percent, including all losses due to separation of the floc and chemical separation of the material.

BLOWER COLLECTION

Air taken from outside was passed through a 400 sq in. filter paper at about 2000 eu ft/min and vented in such a manner that it was not again drawn into the system (Figure 2). At the end of the collection period the filter paper was removed and put into solution the Pband Biwere separated in the same manner as from the floc (Appendix I).

DETERMINATION OF ACTIVITY

Measurements were made on the Pb and Bi fractions for the -8-activity of RaE (the RaD £ was too weak to measure with end-window G-M tubes) and on the Bi fraction for Po (a) activity. Because of the elapsed time between the Pb-Bi separation and counting, the RaE was distributed between the two fractions generally predominating in the Bi fraction. The Po was primarily in the Bi,.O, fraction but accurate determinations of the quantity were not obtained because of the large amount of carrier present., In some cases the Po was further carried on a smaller quantity of Te and in a few cases samples were separated free

-of carrier and with much higher counts than the original Bi,O, samples. :

For the most accurate Senet Hani nile the RaF(Po*’°) should be separated carrier -free, The RaD (Pb7!°) and RaE (Bi’*° ) cannot be separated carrier-free with any success. The considerable quantities of dirt collected in these large samples often contain appreciable | amounts of lead and bismuth contaminants.

NAVAL RESEARCH LABORATORY 3

_ RESULTS

The results listed in the following tables give the activity of the various radioactive products interms of counts per minute (8) of the RaE measured at approximately 10% geometry and counts per minute (a) of Po measured at about 50% geometry with no corrections applied for absorption and backscattering.

Table 1 lists some of the data collected in a qualitative examination of rain water for the long-lived decay products of the radium series. Complete separation of the RaE (Bi?'°) from the lead fraction was not obtained. The g-activity builds up in the Pb fraction from the 22-year Pb?’° (RaD) and the rate of buildup was followed for a sufficient length of time to identify the 5- day RaE. The §-activity in the bismuth fractions decayed with a 5-day half-life. Considerable a-activity (Po?!° ) was found in the bismuth fractions.

Similar results wereobtained with filter paper collections (Table 2). Con- siderable amounts of air were processed in these. long collections but only rough estimates of the volumes have been made. ~ The quantity of dust, etc., picked up caused ‘the flow-rate to decrease continuously.

Figure 2 - NRL air filter system

A number of studies were made on the distribution of the RaE (probably in

equilibrium with the RaD) in different portions of the rain (Table 3). Generally the acid- insoluble portion of the collected dirt was neglected since it was found to contain relatively little of the activity. There seemed to be no correlation between the concentration of activity in the sample and the quantity of dirt, character of the rain, or time between rains. In general, however, the first portion of the rain contained the greatest amount of insoluble. material and the highest concentration of eae

Collections of RaE activity made at a pomibes of different sites are compared in Table 4. Some variations are to be noted at each site though they are not as great as the differences between collections at different locations. Rain-water collections from inland sites such as Glenview, Illinois and Washington, D. C. contained the highest concentration of activity, those on the coast (Panama) or on larger islands (Hawaii, Phillipine Islands, Kodiak) showed less activity and the collection made on a relatively small land mass far removed from conti- nental areas (Samoa) showed the least activity. All of the bismuth fractions that were checked showed some @-activity (Po?’°), 3

As considerable time elapsed between the dates of collection at these sites and analysis at NRL, the RaD-RaE equilibrium had been re-established and the RaE (Bi7*° ) measurements were essentially the measurements of the RaD parent in the sample.

TABLE 1 Long-Lived Natural Activity From Some Rain Water

Collections Made at NRL

ee Pb fraction : Bi fraction A Volume HCl-insoluble te

Sample | C = , a Collected. | residue (ignited) Recovery | 8 activity a activity Bi,Os Recovery | # activity @ activity

oe ae eee (g) | (%) (c/min) (c/min) (mg) (%) (c/min) | (¢/min)

RW-16 | Oct 6, 14, 340 19.2 oe 934 Ol OT S06 . 91 75.9 92 1300 TW.

25, 1949

Rw-18* | Jan 12-30 340 170° 48 140 3 63.4 77 920 356 1950 : ares

RW-19 | Mar 31- 220 108 85 4 69.4 102 1457 300

Apr 24

1950 3

RW-20 | May 3-12 | 260 ? 214 Bo eyoh 90s |. 08 1424 246 1950

* Roof and tank cleaned January 6, 1950

| | TABLE 2 Long-Lived Natural Activity From Filter Paper

Collections Made at NRL

: - Bi fraction

ah . valine’ Ph fraction _ | B activity (c/min)

Sample Collected Processed | Recovery | 8 activity aactivity | Bi,O, Recovery Corrected a activity

(1950) (cu ft) (%) (c/min) (c/ min) (mg) (%) Exp for decay** (c/min)

MSP-2 Mar 2 tse 10% 286 196 1 80.3 118 477 724 2

MSP-4 | Mar S10" | 122 96 2 . 67.7 100 204 56 21-31 . |

MSP-5* | Mar 21- | 2.5 x 10’ 123 9 1 67.1 99 =| 121 i7 Apr 24

Msp-6 | Mar 31- | 2 x10’ 163 Al 4 78.7 116 851 137 Apr 24 a

VP-1 Apr 1.5 x 107 71.3 105° 50)! pea 64 3-15 , eae | 3

* Filter used behind the MSP-4 filter and. then the MSP-6 filter 7k

Count corrected to time of Pb-Bi separation

AUOLVUOSREVI

HIUYVASAY IVAUN

TABLE 3 Distribution of RaE(Bi?’°) Activity Among Rainwater

Fractions Collected at NRL

AMUOLVYUORE

VI HIUVASAY

TVAVN

Bi,O, Fraction “f

B activity (¢/min) B activity (c/min/gal)

Date Rainfall Data Volume Weight Recovery E Corrected for Corrected for Tank A Tank B Tank C Total

aa “hoon (in.) Collected (gal) Residue (g) (mg) (%) C decay** decay & yield Collection

RW-21 June 18 : 350 12.0 67.8 100 | 553 572 572

_ 30 12.5 67.2 90 155 174 ~ 193 6.4

RW-22 June 29 60 2.9 71.0 104 155 174 174 2.8 2.9

: & 150 1.4 10.3 103 275 320 320 2.1

30 0.8 61.2 90 27 108 120 4:0." |

RW-23 July 9 - 60 0.8 66.5 98 4 |: 16 16 ie. Oud 0.6

225 2.4 24.7 36 4 16 45 0.2

40 7.0 70.0 103 232 236 236 5.9

RW-24 July 15-16 1.5 55 wail 71.0 104 121 123 123 2.2 1.7

300 0.9 71.6 105 302 308 308 1.0 -

40 7.6 42.2 62 127 143 230 5.7 RW-25 July 20 1.4 60 1.7 41.3 61 117 132 216 7 3.6 1.9

300 1.7 73.0 107 288 324 324 1.1

RW-26 July 24 1-hour rain t 40 1.5 90.5 133 126 128 128 3.2

40 27.1 77.6 114 | 191 214 214 5.3 RW-27 | Aug 10 [30-minrain? | 60 5.5 69.5 102 124 139 139 2.3

; 4 ak 40 25.0 96.8 141 151 170 170 4,3

RW-28 Aug 19 ( an ) 60 3.6 79.1 ioe 96 108 108 1.8 1.3

Re 275 3.0 80.5 117 194 218 218 0.8

1.35 40 4.9 72.9 | 107 246 276 276 6.9 RW-29 Aug 23 2-hour rain 60 1.4 72.8 107 157 176 176 P amose 4.0

(continuous) 275 2.0 47.6 70 663 745 1064 3.9

40 5.3 - 69.7 102 25 25 25 0.6 RW-30 Sept 11 - 115 3.0 76.3 112 78 "79 79 _0.7TT 0.9

275- 2.0 68.8 101 259 264 264 1.0

40 12.5 67.4 96 99 128 133 a3 RW-31 Sept 21 0.86 60 2.1 65.7 94 127 164 174 2.9 3.0

275 Soil 60.5 86 550 710 825 BOY ine

40 7.6 63.9 91 103 116 128 3.2 RW-32 Oct 8-9 0.54 60 3.5 65.0 92 77 87 95 1.6 1.2

275 2.5 54.2 17 155 174 226 0.8

40 4.0 1.7 2.4 5 5.6 200 5.8

RW-33 Oct 23 1.86 60 6.2 62.6 89 149 168 189 SAB 2.0

275 3.0 58.2 83 251 282 340 ise

; 40 5.3 11.2 101 197 222 222 5.6

RW-34 Nov 20 0.55 60 13.7 69.1 98 143 161 164 221 2.2

i 150 2.8 69.9 99 ahoiss . 156 158 1.0.

y Average (without RW-26 and RW-27) 4.7 DAD 1.5 2.0

*New aluminum roof (1000 sq ft) and aluminum tanks used in all collections.

** count corrected to time of Pb-Bi separation. :

TSome rainwater lost through leakage. °

tt Controls failed to work properly—indeterminate quantity of rain overflowed.

TABLE 4

Distribution of Natural Activity at Various Locations " Bi,O, Fraction

B activity (c/min)

Date ; Volume Location Collected Rainfall Collected | Residue wt Recovery | Corrected for | Corrected for : ali: @ Activity

(1950) (in.) (gal) (g) (mg) (%) me decay** decay audyteld |: C/E BIB Lo /eaiay

Glenview, Ill. Jan 265 Sol. 73.3 89 528 587 660 2.5 31

Insol. 81.6 99 ii 12 12 3

June 2-13 Squall 1.6 564 38.9 66.6 95 722 1245 1310 ea -

June 24-30 Flash showers 563 - 53.9 76 675 1040 1370 2.4 -

July 6-19 Scattered showers Meee 563 6.6 15.0 22 110 124 564 1.0 -

F 2.1

Panama Mar 7-14 0.48 iB 170 0.1 69.4 102 46 47 47 0.28 13

Mar 16-Apr 24 250 0.8 65.1 96 109 218 227 © 0.9 =

May 18-27 Continuous 15.96 500 0.3 _ 59.4 87 40 52 60 0.12 e

June 28-July 20 Continuous 10.78 500 ES 69.0 101 171 192 192 0,38 es

July 20-Aug 14 Continuous 16.17 500 0.5 65.5 96 114 116 121 0.24 -

Nov 24-Dec 15 20.27 500 4.5 55.4 79 56 85 107 0.21 -

Jan 5-Feb 6 (1951) | Showers 1.75 500 * 58.2 83 47 94 113 0.23 =

0.4

Hawaii Mar 8-Apr 7 Scattered 400 * 72.8 107 128 131 131 0.33 a4

May 2-June 12 Scattered 350 0.2 68.1 100 18 72 72 0.21 -

Aug 13-Sept 18 Scattered 400 5.0 61.7 89 165 435 489 1.2 -

Sept 18-Dec 11 Continuous 300 16.7 60.8 90 327 480 534 1.8 -

: 0.9

Philippine Islands| May 4-25 Scattered 270 * 103.0 152 186 209 209 0.8 -

July 4-Aug 2 Continuous 270 * 73.3 108 120 207 207 0.8 -

Aug 2-30 Continuous for two weeks 270 * 97.5 143 99 228 228 0.8 -

Oct 3-25 Scattered 270 * 66.5 94 255 287 306 ee =

Oct 30-Nov 30 Scattered 270 3.4 63.9 94 191 282 300 1.1 -

0:3,

Samoa Jan 6-31 400 21.1 84.5 124 82 - - - ii

Feb 1-28 400 * 111.0 163 80 - - - 9

Mar 1-31 Daily 400 - 45.0 66 227 - - - 35

Apr 1-30 Daily 400 96.5 143.9 204 130 296 296 0.74 -

May 1-31 Daily 400 * 71.9 106 29 33 33 0.08 -

June 1-30 Daily 400 * 63.1 90 20 26 29 0.06 -

July 1-31 Daily 400 0.7 64.3 92 16 42 46 0.11 -

Aug 1-31 Daily 400 0.4 68.1 97 9 16 “li 0.04 -

Sept 1-30 Daily 400 4.5 67.3 95 94 96 101 0.25 -

0.21

Kodiak Apr 11-24 Scattered 1.6 500 * 97.4 143 530 - - - 108 °

June 6-19 Scattered 2.3 400 4.8 61.0 90 209 235 262 0.65 -

. June 19-July 5 Scattered 3.3 500 1.7 72.9 107 225 230 230 0.46 -

July 7-17 Scattered 1.9 500 6.8 67.9 100 120 155 155 0.31 -

Sept 11-25 Continuous 7.6 500 1.0 62.5 89 295 307 345 0.69 -

Oct 23-Nov 6 Scattered 0.4 500 5.5 62.4 89 503 565 635 12m -

Dec 5-27 Scattered 2.1 500 4.0 TLA 101 145 259 259 0.52 0.65 =

* Residues dissolved completely by wet ashing and fusions, where necessary

** Count corrected to time of Pb-Bi separation

AUOLVY¥OREVIT

HOIUVISAY

TIVAUN


An attempt was made to determine the quantity of Po relative to the RaD-RaE collected. The following assumptions were made recognizing that they are only approximations: (1) counting efficiency for the Po (a) is 50% andfor RaE (8) is 10%, (2) absorption corrections for the Po (@) in the large Bi,O, samples follow the experimentally determined curve (Fig-

~ ure 3), (3) the decay of RaE following its separation was estimated though exact decay times on many of the samples are not available, (4) loss of Po during ignition of the Bi,O, is neg- _ ligible (this is true if the temperature is below 500°C-—some samples were ignited at 600- 800°C however, and losses could have occurred). An attempt to determine the average time that the Po had been growing into equilibrium with the RaD-RaE series from the ratio of disintegrations per minute (d/min) of @ to B gave times of 7 to 84 days with an average value of 43 days (Table 5). Some of the lower values are unreasonable since the samples are known to have had more time for Po growth than is indicated by the calculations. It is felt that the average life of the series in the atmosphere may be readily obtained through procedures such as these but that the present work has not been done with sufficient accuracy to givea reliable value for this life. Other work at this Laboratory on the RaA-RaE series indicates a somewhat shorter life for natural radioactive products in the atmosphere.!

E)

EN

Gs

oO

75

50

25

Be

RATIO

OF COUNTS

OF SAMPLE TOSTANDARD

(PERC

O 10 20 30 BigO3 SAMPLE THICKNESS (Mg/CGm®)

Figure 3 - Self-absorption of Po ( @) mounted with various weights of BizO,

1 ; Blifford,I. H., Jr., Lockhart, L. B., Jr., and Rosenstock, H. B., “On the Natural

Radioactivity in the Air,” NRL Report 4036, September 1952

8 NAVAL RESEARCH LABORATORY

TABLE 5

Comparison of the Amounts of Rae and Po in the Atmosphere

Date Source | Collected ao ___RaE (8) Po (a) aie

(1950) mg) | c/min | d/min | c/min | d/min | @ B

NRL (water) aot 63.4 1060 |. 10600 356 3740 | 0.35

Apr 69.4 1550 15500 300. 3530 | 0.23 May 70.0 . 1640 16400 246 -2900 | 0.18

NRL (paper) Mar 80.3 724 7240 2 27 | 0.04

Mar 67.7 300 3000 56 660 | 0.22 Apr 67.1 130 1300 17 190 | 0.15 Apr 718.7 900 9000 137 1830 | 0.20 Apr 71.3 — 600 6000 64 780 | 0.13

Glenview eg ‘water) Jan 73.3 672 6720 34 470 | 0.07

Panama (water) Mar 69.4 © 47 470 BBCi 153 | 0.33

Hawaii (water) Mar 69.4 131. -- 1310 24 290 | 0.22

Kodiak (water) Apr . ‘97.4 650 6500 108 1660 | 0.26

Samoa (water) Jan 84.5 100 1000 11 157 | 0.16

. Feb — 111.0 100 1000 9 144 | 0.14 Mar 45.0 500 5000 35 264 | 0.05 |

Since most of the natural activity has been found to be attached to particles of the order of 0.01-0.02 micron, 2 it is not unreasonable to expect the average life of these particles in the air to be long. However, it would be surprising to find equilibrium between the RaD- RaE-Po series to be established since the parent radon is continually being added to the atmosphere and the intermediate members of the series are continually being removed by rain and fall out on dust particles.

CONCLUSIONS

1. High-capacity air filters and rain-water collections are effective methods of obtain- ing large samples of airborne natural radioactive decay products.

2. Rain effectively removes significant quantities of RaD, RaE, and RaF (Po””° ) from the atmosphere. The first part of the rain removes a relatively larger portion than later parts of the rain, but all fractions of the rains contain some moeetty (RaE).

2 Wilkening, M. H., “Natural Radioactivity as a Tracer in the Sorting of Aerosols According

to Mobility,” Rev. Sci. Instr., 23:13-16 (1952)


3. The RaD-RaE activity as collected by rain has been found to vary widely at different geographical locations and at different times at any given locality. On the basis of the present information, there is no simple correlation of the activity collected with the character of the rain, the seasons, or the quantity of dirt present in the collection.

4. The average RaD-RaE activity in disintegrations per minute per gallon varied from about 2 at Samoa to 20 at Glenview and NRL. Other sites (Panama, ers

Philippine Islands, Kodiak) Baye intermediate values.

* KK

APPENDIX I Analysis of Flocs For RaE and Po

SOLUTION OF SAMPLES

The Al(OH); floc is acidified with HC1 until strongly acid, then boiled gently for 15 minutes during which time 5 ml each of standardized Bi and Pb carrier solutions are added (equivalent to about 75 mg each of Bi,O, and PbSO,). A 10 to 20 ml portion of 30%

HO, is cautiously added over a period of 10 minutes and the mixture is boiled for 10 minutes to decompose excess peroxide. The solution is filtered with suction through Whatman #41-H paper; the residue is ignited at 700°C and weighed on a rough balance.

The residue is fumed with HNO; -HF-H,SO, in a Vycor beaker. After cooling, any insoluble matter is filtered off,ignited, fused with Na, CO, in a platinum crucible, and finally treated with HNO, -HF-H,SO,. Generally no further fusions are Pee heS: These solutions are combined with the HC] filtrate.

PRELIMINARY SEPARATIONS

The pH of the above filtrate is adjusted with NaOH and HCl! until the hydroxides just remain in solution (pH 2-3). The filtrate is then diluted to 4 to 8 liters, depending on amount of aluminum present, and heated nearly to boiling; some macerated filter paper

- is added and the solution gassed with a rapid stream of H,S for an hour while cooling. After settling for at least two hours (preferably overnight), this solution is filtered with suction using #42 paper. The filtrate is discarded.

The paper and precipitate are transferred to a 400-ml Vycor beaker, treated with 20 ml HNO, and 20 ml H,SO,, and digested on a hot plate until all the paper is in solution. After removal of this solution from the hot plate, some HNO, and about 2 ml HF is cautiously added. The beaker is then covered with a Vycor plate and the contents digested until all organic matter has been oxidized by cautious additions of HNO; to the hot solution. Heating is continued until all HF has been volatilized and the H,SO, fumes strongly. The hot solution is then removed from the hot plate and about 1 gram of solid ammonium per- sulfate is added to decompose the nitroso-sulfuric acid complex. After the solution is allowed to cool, it is diluted to 200 ml and allowed to stand (1-2 hours) until PbSO« has settled. It is then filtered through #42 paper, washed thoroughly with 10% H 250, solution, and the precipitate ignited in a pee crucible below 600° C.

SEPARATION OF Bi

NH.OH is added to the above filtrate until the first permanent hydroxide precipitate is obtained, then the precipitate is redissolved by addition of a small quantity of dilute H,SO,. At this point the pH should be 2 to 3. About 0.2 gram thioacetamide is added (gassing with H,S is satisfactory); the solution is boiled gently for 30 to 40 minutes, allowed to settle five minutes, and filtered through #40 paper. The paper and the Bi,S, precipitate are transferred to the original beaker; 25 ml HNO, 1:1 is added and heated

10


gently on a hot plate until the Bi,S, has dissolved. The solution is filtered through #41-H paper into a 400-ml beaker and the residue is washed thoroughly with dilute HNO, (2%). The filter paper and residue are discarded. NH,OH is added to the filtrate until the hydroxides begin to separate; then the precipitate is redissolved with dilute HNO, and the solution is diluted to 250 ml. After a slight excess of (NH,4), CO; has been added, the solution is heated to 90°C to coagulate the precipitate and is filtered through #40 paper. The precipitate is dissolved from the paper with HNO, 1:1, the paper is washed thoroughly, and finally the _bismuth is reprecipitated with (NH,), co, as before. The precipitate is ignited below 500°C. A weighed sample of Bi,O, is transferred to a plastic sample holder, mounted with collodion, and counted immediately after drying. If @-counting is to be done, the sample is mounted on a 2-cm diameter aluminum dish and the powapr anchored with a small amount of dilute collodion solution.

PURIFICATION OF PbsO,

The crucible containing the ignited sulfates is filled about 2/3 full with solid ammonium acetate and about 3 ml water is added; the solution is stirred to break up lumps and digested | at 80-90°C for 30 minutes with occasional stirring. It is filtered through #42 paper and the

- residue is washed thoroughly with hot 20% ammonium acetate solution. H,SO,(20 ml) is » carefully added to the filtrate and evaporated to fumes of SO,. The solution is cooled, diluted to 200 ml, allowed to settle, and filtered through #42 paper. The residue is washed with 10% H,SO, and ignited below 600° C. The sample is weighed, mounted and counted as described above. seen

NAVY-DPPO PRNC, WASH., D.C.

&

.&% APPENDIX C

Collection and Measurement of RaA and RaC!

After the importance of RaA and RaC'! in producing

internal radiation had been pointed out to us; this question was

investigated in several uranium mines. Preliminary experiments

showed that large amounts of short-lived, alpha-emitting substances did exist in mine atmospheres and work was begun to develop a field method, utilizing available instruments, that would evaluate

the atmospheric concentrations of these elements.

‘In its present stage of development the method consists

esentially of the following steps:

1. Air is drawn through a one- -inch diameter circle of

Whatman 41 filter paper at a measured rate (14-23 liters per minute) by a hand-cranked pump for either a 5 or 10 minute period.

2. The alpha activity on the filter paper is measured by a

field instrument (the Juno and the Mark II Alpha Radiac have both

been satisfactory for this purpose) at measured times after collection.

These instruments are calibrated against a methane flow proportional

counter to obtain disintegrations per minute, using radon daughter products collected on a filter paper as a source of alpha radiation.

3. The calculation of alpha emitting radon daughters in

the atmosphere is based upon a mathematical treatment by Dr. John H. Harley, Chief, Analytical Branch, Health and Safety Division, AEC. He presents three derivations, namely:

(1) "The build-up of activity on the filter paper from the start of sampling until equilibrium is established between the rate of deposit and the rate of decay of the activity."

(2). "The decay of the equilibrium activity after sampling

is stopped. "

(3) "The decay of the activity present when sampling is stopped at any time before equilibrium is reached."

From the equations in (3) above, theoretical decay curves were plotted for 5 and 10 minute samples. Data obtained from mine

filter paper samples were plotted on the same graphs, which are

attached. (Figures 1 and 2) As these data appeared to agree with the theoretical curves, the decay curves were used as the basis

for construction of correction curves (Figure 3) to correct the observed dpm at time i to dpm at time 0 (time 0 is the moment at

which sampling was stopped).

From the equations presented in (1) above, the activity on the filter paper at the end of any sampling time may be expressed as percentage of final or equilibrium activity. This turns out to be 10% and 18% for 5 and 10 minute samples, respectively.

"For an equilibrium sample, if we can determine the initial activity (at the end of sampling) this activity may be substituted into the expression, (16) curies/liter - 5.95 x 10-15 (dpm)

7 Vv

(v = sampling rate in 1 pm) to obtain the radon concentration. "

For our work it appeared that expressing the alpha

activity in terms of RaA and RaC' would be more useful than expressing it as radon, especially as we are certain that in the mines radon is not in equilibrium with its decay products. Therefore,

by multiplying by 2, and dividing by the fraction of final wae we obtain for a 5 minute sample

uucuries of RaA + RaC! = 0.12 (dpm) and for a 10 minute sample Seg ee Pes :

0. 066 (dpm) Vv

uucuries of RaA + RaC!

. The following is an example of the method:

A sample was taken from 10:03 to 10:13 at a sampling rate of 18.5 liters per minute and at 10:45 the Juno read 26 x 100. From

the calibration curve, disintegrations per minute = 640,000. The correction

factor for 32 minutes (10:45 - 10:13) was 1.8, so the alpha activity at 10:13 was 1.8 x 640,000 dpm. Substituting into the above formula

micromicrocuries of RaA # RaC! = 0.066 (1,152,000) = 4100. 18.5

The Seeking method of calculating is based on the assumption

that RaA and RaC! are in equilibrium with each other. This

assumption is probably not entirely valid in mines with good venti-

lation, but from the data obtained thus far, it does not seem that it

introduces serious error.

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- SUGGESTED PROCEDURE FOR COLLECTION OF ATR SAMPIES FOR DETERMINATION OF RADON CONTENT. |

Definitions

The following definitions are given to insure a clear understanding of certain terms used in the procedures out- lined below:

1. Breath Samples: A breath sample is a sample of expired air collected from an individual for the purpose of determining the radon content thereof,

Re Control Area: A control area is an area to which employees are brought for the purpose of having samples of expired air collected. It should be well ventilated and removed as far as possible from radioactive material of any kind, particularly the working areas eogulardy occupied by

these employees.

Ba Control Sample: A control sample is a sample of the air collected from the location within the control area occupied by employees awaiting the collection of breath samples, It should be taken immediately before the collection of the first of the expired air samples.

4. Workroom Air: A workroom air sample is a sample of air from the working area of a radium paint shop, storage space, or other radium processing room taken under normal working conditions,

Breath Samples’

A breath sample is collected from an individual by re- quiring: him to exhale into a collapsed regulation basketball bladder, or thin rubber balloon of approximately the same volume, until it is sufficiently distended to be free from wrinkles. This will provide sufficient air to fill the glass sampling flask completely. To transfer the air to the flask, the neck of the bladder (or balloon) should be "pinch- ed off" and then pushed over the end of the free glass tube of the stopcock at the top of the flask. If, however, the neck of the bladder (or balloon) is of such: size as not to fit ‘securely on the glass tube of the flask, a suitable re-

ducing coupling should be used with a short piece of rubber tubing to fit both the coupling and the glass tube of the flask. Since the opposite glass tube of the flask is closed by a rubber cap, the air will flow into the flask when the sto peock is turned to the open position, in accordance with the instructions on the card enclosed with the flask. Samples should not remain in the rubber bladder (or balloon) any longer than hecessary to effect the collection of the breath sample and its transfer to the glass flask, since the rubber slowly absorbs radon, If there is any reason to believe that the radon content of a breath sample of an individual will be high, the bladder (or balloon) into which he exhales should not be used for the collection of a breath sample of any other employee. In any event, the bladder (or balloon) should be flushed several times after each person uses it to avoid possible erroneous value for the breath sample of the next employee for whom it is used. Flushing consists of inflating with tanked gas, such as oxygen, nitrogen, or argon and then completely deflating by rolling or praaesns the bladder (or balloon) out flat.

A breath sample taken at the beginning of the ecole. before the subject is permitted to enter the working area, will give a more representative value of the radon due to radium retained in the system. A sample taken during the day after the subject has been inhaling the workroom air may be misleading. 3 ;

It would be more desirable to obtain breath samples at the beginning of the work week when the employees have been away from all sources of radiation for two or more “days.

If there is reason to believe that a particular breath Sample, or group of such samples, will have a high radon content, such information should accompany the flask, or flasks, so that the Radon Testing Laboratory can make the measurements with equipment especially designed for high concentration samples, The test of an extremely high sample might be lost if an attempt is made to measure it with equipment used for the average breath samples, aside from the fact that it is likely to contaminate and permanently incapacitate laboratory equipment for further use.

It is exceedingly important that breath samples be returned to the Radon Testing Laboratory of this Bureau immediately after sealing. Samples must be measured within approximately one week of the sampling date to permit evalua- tion with sufficient accuracy to warrant the issuance of a

repgrt.

Control Samples

All breath samples taken on a particular day and in the same control area may be accompanied by a control samples

If a control sample is to have any significance the subject with whose breath sample it is to be compared should be required to remain in the control area at least ten minutes before the breath sample is taken. This will permit practically a complete change of air in the lungs. /

The filter tube furnished with each flask must be used when taking control samples; otherwise, airborne radioactive particles may be introduced into the flask, In such a case the value observed by the Radon Testing Laboratory would be high and the measuring equipment possibly contaminated.

To collect an air sample at the point in the room where sampling is desired, it is only necessary to turn the stopcock on the top of the flask to the open position, as indicated by the instructions on the card enclosed with the flask. After the air in the flask has come to atmospheric pressure, the stopcock is turned to the closed position and the flask is ready to be returned to the Radon Testing Laboratory for measurement.

Room Air Samples

Samples of workroom air should be collected in the manner described above for the collection of control samples, being certain that the filter is always used. These flasks should not be used in areas'where a heavy concentration of radon might be expected, as, for example, in a radium storage safe where a leaking preparation might be suspected, In such cases, the Radon Testing Laboratory should be notified and a suitable flask will be furnished,

If room air samples are to be submitted periodically as a check on the radon content of the air in the working area, care should be taken that subsequent samples from any one area be secured under the same conditions as previous samples from the same area, iae., time of day, location within the room, degree of ventilation and so forth.

Radon Testing Laboratory Radioactivity Section

June, 1950 NATIONAL BUREAU OF STANDARDS Washington 25, De C.

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