Regulatory Guide 4.3

Measurements of Radionuclides in the Environment Analysis of I-131 in Milk

ML13350A246
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Issue date:	09/30/1973
From:	US Atomic Energy Commission (AEC)
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RG-4.003
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September 1973 U.S. ATOMIC ENERGY COMMISSION

REGULATORY

DIRECTORATE OF REGULATORY STANDARDS

GI JIDE

REGULATORY GUIDE 4.3 MEASUREMENTS OF RADIONUCLIDES IN THE ENVIRONMENT

ANALYSIS OF 1-131 IN MILK

A. INTRODUCTION

relation to benefils to lite public heallh and saflby and in relation to the utilization of atomic energy in the General Design Criterion 64. "Monitoring public interest.

Radioactivity Releases," of Appendix A to 10 CFR Part The procedure for the determination of 1-131 in

50, "General Design Criteria for Nuclear Power Plants," milk described in this glide constitutes a method requires that means he provided for monitoring (hfe plant acceplable to the Regulatory staff for measuring 1.131 as environs or lighl.water.cooled nuclear power plants for may he required by the ahove regnilalions or orders or radioactivity that may be released from normal license conditions imposed pursuant thereto.

operations, including anticipated operational occurrences, and from postulated accident

B. DISCUSSION

Paragraph (a)(2) of § 50.36a of 10 CFR Part 50

provides that technical specifications For each license In accord wilh the Commission's policy (f keeping will include a requirement that the licensee submit a exposure of man to radioactive materials released from report to the Commission within 60 days after January I licensed activities, including the operation of production and July I of each year which, in addition to specifying or utilization facilities, as low as practicable, licensees the quantity of each of the principal radionuclides should make every reasonable effort to limit the release released to unrestricted areas in liquid and airborne of radioactive materials in effluents to unrest. -led areas effluents during the last six months of operation, as far below the limits specified by the Comm. qion as provides sufficient information to estimate annual practicable. Iodine-131 requires special at:*-ntion radiation doses to the public resulting from effluent because it is one of 'he more significant radionuclides releases. present in releases from nuclear power plants, and it can Paragraph (e) of § 20.106 of 10 CFR Part 20 be concentrated through the air.vegetation.cow.milk provides that the Commission may limit the quantities pathway and potentially contribute to the thyroid dose.

of radioactive materials released in air or water by Although most milk data have indicated little or no licensees during a specified period of time if it appears 1.131, milk monitoring at the suggested improved level that the daily intake of radioactive materials from air, of sensitivity would provide direct evidence that the water, or food by a suitable sample of an exposed potential exposure due to 1-131 does not exceed population group. averaged over a time period not predicted values.

exceeding one year, would otherwise exceed specified Current guidelines' for 1-131 dose it) the thyroid of quantities. Section 20.201 of 10 CFR 20 requires that a infants require that the sensitivity for measuring 1.131 in licensee conduct surveys of levels of radiation or milk be improved over conventional direct gamma concentrations of radioactive material as necessary for counting of the raw milk sample. Low-level beta compliance with AEC regulations in Part 20. Paragraph counting techniques with a detection sensitivity about (c) of § 20.1 of 10 CFR Part 20 states that every an order of magnitude better than conventional gamma reasonable effort should be made by AEC licensees to counting techniques can be used to attain the desired maintain radiation exposures, and releases of radioactive sensitivity. In the analysis of 1.131 in milk, it may be materials in effluents to unrestricted areas, as far below the limits specified in Part 20 as practicable, i.e., as low 'Regulatory Guide 1.42. "Interim Licensing Policy on As as is practicably achievable, taking into account the state Low As Practicable. for Gaseous Radioiodine Releases front of technology, and the economics of improvements in Light-Water-Cooled Nuclear Power Reactors."

Copies of published guidas may be obtained by request indicaing the divitions USAEC REGULATORY GUIDES deored to the U.S. Alomic Energy Commlsston. washington, D.C. 20-6, Atteion: Director of Regulatory Standards. Com,wents end 1,-491400s lot Ragi4a10o'V Gukis we issued to describe end rmke raillable to the public Improveflmnts In these guides warefiotifegd and should be sent to the Secretary methods aceptb*le to the AEC Regultaory staf of ianmtemenling specific parts of of tha Commission, U.S. Atomic Energy Commission, Wtrhinglon, D.C. 20645, the Cormmission's regulations, so delineate techniques used by the staff In Attention: Chief, Public Pm'eWp Staff.

eVAluating Specific problems or postulated accidents, or to provide guidance to aplicants. Regulatory Guides are not subtitut*es for reg"uations and complince The guides ae issued In the following ton broad divisions:

with them Isnot required. Methods and solutions different fromn thoe set out to In the guidin will be acceptable if they provide a beut, for the findings requisite 1. Powdr Reactors B. Products

7. Transportation the issuance or continuance of a permit or lics% by the Commission. 2. Aesarcd* and Test Reaacts

3. Fuels and Materlals Facilites

a. Occupational Heahh

4. Environmental and Siting 9. Antitrust Review Publlshed =uideswill be revised periodlcally. asappropriate. toa*sommodate 6. Materialk and Plant Protection 10. General crnnftsl lad to reflect new Inforsntlotn at experience.

necessary in some instances to measure 1-131 in tile .worthwhile to do ,this only, wihen the net count. is more presence of i-129 2-as Well as other radioisotopes of than about 0.3 cpm. If, after the second count, it is iodine; since the usual beta counting methods are determined that the activity is not decaying with a nonspecific, provisions for the resolution of such a half-time of about 8 days, a third count made 4-5 days potential mixt'jre of isotopes should be included in the after the second count can provide the basis for a rough procedure. In most instances, however, radioisotopes of graphical resolution of 1-131 activity. In any case, it iodine other than 1-131 and possibly 1-129 are not would be desirable to hold the sample for at least a year expected to be of significance in the milk pathway to permit possible identification of the long-lived because of their short half-lives. Also, under normal component should the need arise.

operating conditions of nuclear power plants, the contribution from 1-129 will be negligible, the potential significance of 1.129 being associated primarily with fuel

C. REGULATORY POSITION

.reprocessing plant:i. It is probable, therefore, that any radioiodine detected in milk sampled from the environs of nuclear power plants will be primarily 1-131. The procedure for the analysis of 1-131 in milk Nevertheless, because of the nonspecificity of heta described in the appendix to this guide is acceptable to counting methods, as a minimum. decay checks should the Regulatory staff as a basis for meeting analytical be performed. performance standards which are compatible with A simple check for isolopic purity can be performed established guidelines.' Other procedures selected for by recounting the sample for radioactive decay. A analyzing 1.131 in milk should provide levels of half.time of 8 days would be a good indication that the analytical sensitivity and specificity similar It) those for activity is due to 1-131. However, since it is not practical the method described in the appendix.

to attempt to monitor decay half-times when the sample net counting rate is less titan about 0.3 cpm. it would be ISee footnote on page 4.3-1

'A regulatory guide for the analysis of 1-129 in milk is in preparation.

4.3-2

Ao UNITED STATES

• *,*NUCLEAR REGULATORY COMMISSION

0

) 0 WASHINGTON. D. C. 20555.

9ýl4 OP *December 1, 1976 REGULATORY GUIDE DISTRIBUTION LIST (DIVISION 4)

The Nuclear Regulatory Commission staff has withdrawn Regulatory Guide

4.3, "Measurements of Radionuclides in the Environment, Analysis of

1-131 in Milk." This guide was issued in September 1973 to describe one acceptable method for the determination of iodine-131 in milk which would meet the guidelines for iodine-131 dose to the thyroid of infants as given in Regulatory Guide 1.42, "Interim Licensing Pol- icy on as Low as Practicable for Gaseous Radioiodine Releases from Light-Water-Cooled Nuclear Power Reactors." With the adoption of Appendix I to 10 CFR Part 50 as an effective rule and the adoption of a series of implementing guides, there was no longer a need for Regulatory Guide 1.42, and it was withdrawn. Since Regulatory Guide

4.3 .was issued, a number of acceptable alternative methods and tech- niques for the determination of low levels of iodine-131 in milk have been demonstrated, including the analysis of milk containing preserva- tives and the use of beta-gamma coincidence counting techniques. Also since Regulatory Guide 4.3 was issued, there has been a recognition of the need to consider the effects of relatively high and variable con- centrations of stable iodine in milk on the calculated radiochemical recovery and of the resultant need for determinations of stable iodine in milk. Because of the existence of acceptable alternative procedures, and the general recognition of the practicality of determining low levels of iodine-131 in milk, the detailed procedural guidance of Regu- latory Guide 4.3 is no longer needed. Current licensing commitments based on Regulatory Guide 4.3 will not need to be reexamined as a result of this withdrawal.

Regulatory guides may be withdrawn when they are superseded by the Commission's regulations, when equivalent recommendations have been incorporated in applicable approved codes and standards, or when changes in methods and techniques have made them obsolete.

Sincerely, Robert B. Minogue, Director Office of Standards Development

APPENDIX

IODINE-131 ANALYSIS OF MILK AT CONCENTRATIONS

DOWN TO 0.25 PICOCURIE PER LITER

The direct ion exchange method fCo separating A graphical resolution of 1.131 activity based on these iodine from raw milk requires that the iodine he in a three points mnay he performed. The sample should be readily exchangeable anionic form. Radiviodine tracer held for at least a year to permit possible identitication experiments on cows' 2 -' have shown that 0-10 percent of thie long.lived component should the need arise.

of the iodine in milk may he protein bound, rendering this fraction essentially unavailable for exchange with the ion exchange resin. However, this uncertainty of up to 10 percent in the 1-131 determination will not Abstract of the Procedure significantly affect data interpretation and therefore is Iodine-131 is removed from milk by concentrating the considered to be acceptable. Nevertheless, for the sake iodine on an anion exchange resin column and of accuracy, it is recommended that a fixed correction subsequently removing it from the resin by batch factor of 1.05(1/0.95 = 1.05) be applied to the counting extraction using NaOCI. After reduction to 12 by data to compensate for this effect. hydroxylamine hydrochloride, the iodine is extracted Also, there may be instances where milk samples

• may curdle to varying degrees in the interim between into CC14 . reduced with bisulfite. and back extracted into water. The iodine is precipitated as palladous collection arid analysis. Milk in this condition is iodide. Chemical yield based on the added carrier iodine unsuitable for analysis by the direct ion exchange is determined gravimetrically. The 1.131 concentration is method. A fresh sample should be obtained should this determined by counting the palladous iodide precipitate occur. If clabbering continue. it) be a problem, the ion in a low-background beta counter. The yield for the exchange separation should be performed at the sample procedure is 70 to 85'7r.

collection point and the ion exchange resin column shipped to the laboratory for processing. If this cannot be done, the milk sample should be frozen prior to shipment to the analytical laboratory. Special Apparatus The procedure described in this appendix was adapted from a procedure entitled "Determination of I. Ion exchange column, 2 cm dia. by about 10 cm

1-129 in Milk and Water Samples" developed by the long with standard taper fittings Radiological Sciences Laboratory. Division of 2. Four-liter reservoir with standard taper fitting Laboratories and Research, New York State Department 3. Assorted sizes of glass beakers of Health It was tested at the Battelle Memorial 4. Hot plate Institute Pacific Northwest Laboratories and shown to 5. Magnetic stirrer be adequate to measure 1-131 in milk at the 0.25 6. Suction filtering apparatus picocurie per liter concentration level. This sensitivity is 7. 250-ml and 125-ml separatory funnels

• based on using a 4.liter milk sample and beta counting

8. Clinical centrifuge

• for 1000 minutes or longer in a low-background counter 9. Low-baCkground beta counter (nominal background with a nominal background count rate of 0'5.1 count 41 count per min.)

per minute (cpm). The analytical sensitivity can be 10. Nylon rings and discs,,Mylar, glass fiber paper (2.8 further improved by using more than 4 liters of milk and cm) (see HASL 300)

counting for longer than 1000 minutes.

. A recount for decay check should be performed

7-10 days after the first count. However, because it is not practical to do. this for net counting rates of less Reagents and Chemicals than about 0.3 cpm, a recount should be made only when the initial net counting rate is greater than 0.3 I. Iodide carrier, 10 mg/ml -dissolve 1.181 grams Nal cpm. If. after the second count, it is determined that the in 100 ml water activity is not decaying with a half-life of 8 days, a third 2. Dowex I x 8. 20.50 mesh. Cl" form count should be made 4.5 days after the second count. 3. 2M NaCI . dissolve 116.9 grams NaCI in I liter water

4. NaOCl, 5-6% (commercial strength)

'Murthy. G. K.. ei at "Method for Removing Iodine-131 5. HNO.t, concentrated from Milk," Journal or Dairy Science. 45:1066 (1962) 6. Hydroxylamine hydrochloride, crystals

2 7. CCI4 Salki' M.. Omomo. Y.. "Determination of Iodine-131 in Milk, Quick Mcthod. for Radlochemical Analysi.," Technical 8. IM NaHSO1 - dissolve 1.041 grams of NaHSO 3 in Reportr. Series No. 95, JAFA, 1969. 10 ml water (prepare daily)

3'Bretthauer. F.. W.. Mullen. A. L.. Molghiss, A. A. "Milk

• Trantfer Comparison.s of Dirfereni Chemckal Forn*s . or 9. Palladous chloride, 10 mg/ml -dissolve 1.66 grams Radloiodine."' Health Physics, 22:257 (1972) ofPdCl 2 in 100 nil of water

4.3.3

a.,:

Procedure .18. Mount the precipitate on a nylon disc, cover with:*

Mylar (1/4 mil thick), and fasten with ring. (This

1. Prepare an ion exchange column 2 cm in diameter . procedure is described in HASL 300.) j by 10 cm long and fill to a height of 5 cm with 19. Count in a low-background counter for I00%1 Dowex I x 8. 20-50 mesh. CI" form. Add the resin minutes.

from a water slurry. 20. If net counting rate of sample is greater than 0.3

2. Add 1-2 ml of iodine carrier (10 mg 1'/ml) to 4-liter cpm. recount after 7-8 days.

..,ilk sample and stir thoroughly. Accurately 21. Calculate as picocuries 1-131 per liter of milk at measure and record exact volume of carrier added. time of sampling.

• Pass through the column at a flow rate of about 30

nml per minute and discard effluent.

3. Wash the column with 500 ml hot (500 C) distilled Notes water followed by .100 ml of 2M NaCI. Discard washes. I. This is most easily accomplished by using a

4. Transfer the resin to a 250-ml beaker using 50 ml of polyethylene squirt bottle to dispense the NaOCI.

5-6% NaOCI. (Note 1) 2. Resin should be very light straw color after NaOCI

. 5. Place a small ("2 cm long) magnetic st,.ring bar in extraction, if not light colored, the NaOCI is below

• the beaker and stir vigorously for 5 minuies on a strength, and a fresh solution should be obtained.

magnetic stirrer. Commercial grade Clo.rox has been found to be

6. Filter the resin slurry. through a suction filter and adequate.

retain the NaOCI solution. (Note 2) 3. Add the acid slowly with stirring until the vigorous

7. Reextract the resin by repeating steps 4. 5. and 6. reaction subsides. Perform in well ventilated hood.

8. Discard the resin, combine the two 50-ml solutions, 4. Proceed with caution in this step. Excessive gas and carefully add 20 ml or conc. H,N0 3 . (Note 3) formation during the extraction can cause the

9. Pour the acidified NaOCI solution into a 250-ml stopcock or cap on the separatory funnel to "pop"

• separatory funnel and add 50 ml of CCI 4 . with consequent loss of samp!

e. Start by gently

10. Add 1.5 gm of hydroxylamine hydrochloride and swirling the solution to effect mixing. Invert the shake (Note 4). Extract the iodine into the organic separatory funnel with the stopcock pointing up phase (about 2 min. equilibration). (Note 5) and release the pressure by opening the stopcock.

l1. Drain lower organic, phase into a clean 250-ml Close the stopcock, shake, and repeat the pressure

. . separatory funnel and save. release sequence.

12. Add 50 ml CC14 and I gm hydroxylamine 5.. Organic phase should be deep red: if not, add hydrochloride to the aqueous phase in the first additional gram of NH2 OH.lHCI.

separatory funnel and reextract. Combine organic 6. After back extraction into water, CC14 should be phases and discard aqueous phase. colorless; if not add additional NaHS.0 3 and

, 13. Add 25 ml H20 and 10 drops of freshly prepared reextract.

IM NaHSO 3 to the separatory funnelcontaining the 7. HASL 300 "Procedure Manual" Health and Safety combined CC14 and shake. Equilibrate for.. 2 Laboratory, U.S. Atomic Energy Commission, 376 minutes. Discard organic (lower) phase. (Note 6) Hudson St., New York, New York 10014.

14. Transfer the aqueous (upper) phase into a clean

50-ml centrifuge tube and add I ml of conc. HNO3 and 10 ml of PdCI2 solution. Stir and let stand for 5 Calibration and Standardization of Beta Counter minutes.

15. Centrifuge Pdl 2 precipitate discarding supernate. Counter standardization should be performed with 1-131 Wash precipitate by. stirring with 10 ml of H2 0. standard obtained from the National Bureau of

16. Using a filter funnel setup similar to that (Teflon or Standards (NBS)or with one which Is relatable to NBS.

polyethylene - nylon) described in HASL 300. An example of a relatable standard is a secondary or

"Procedure Manual'" USAEC, filter with suction tertiary standard which has been calibrated against a through a tared glass fiber paper (2.8 cm diameter), primary NBS standard.

using a water wash bottle to effect the transfer.

(Note 7) A self-absorption calibration curve should be

17. Dry precipitate for 20 minutes in an ovenset at constructed using at least 4 points. A useful curve can be

• .I10Cand weigh to the nearest 0.1 milligram. constructed by plotting counter efficiency against mass.

(Alternatively, the sample may be dried on a hot The counter efficiency can then be read off the curve as

• plate at low heat for about 30 minutes.) a function of the gravimetric yield.

.4.3-4

I Example of Calculation of Results The activity in picocurics per liter at the time the milk was collected is determined by calculations based tn the observed net counts per minute of 1-131. The calculation requires correction for chemical yield, protein-bound iodine, counter efficiency, decay since sampling, and the sample volume.

An example of a calculation of the 1-131 concentration in a sample and the error (standard deviation )Iassociatedwith tile measurement follows:

= .8 mg

,, of ppt.

Wl I

Chem ical yield 14.83"

F'nh!ppt is not Stoichii nntrically Pdlt. and this value is a deIermined empirical yield l'r 100u5 r1c,a ry: 14.83 mgi%i', Ihw determined weight of PdIc for 10 ml! of I.

I. Chemical yi!J = 0.78

2. Counter efficiency 7 0.35

3. Counter hackground 00.6 cpm

4. Counting time = 1000 minutes

5. Radioactive decay - 8.05 days

6. Sample net coun:s - 0.6- cpn (fIor a I-lialf-life decay period)

Gross counts for I000-min interval = (background cpm + net cpm) (counting tin..)

0 = (0.6 + 0.6))1000 = 1200

The net counts - 1200 - 600 = 600 corrnts per 1000 minutes or 0.6 cpnm Standard deviation = gross counts + background counts

12600++600=42 Net count with error limit - 600 +/- 42 (net counts) (factor for protein-bound fraction)

Net pCi/liter (count time)(chem yield)(counter efflt sample volhIdecay )(dpil/pCi)

(600 +/- 42) (1.05)

( 1000)(0.78)(0.35)(4)(0.50)(2.22)

= 0.5 pCi/liter with standard deviation of +/- 7r;"

4.3-5