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
Download: ML13350A246 (6)

{{#Wiki_filter:U.S. ATOMIC ENERGY COMMISSION REGULATORY GI DIRECTORATE OF REGULATORY STANDARDS REGULATORY GUIDE 4.3 MEASUREMENTS OF RADIONUCLIDES IN THE ENVIRONMENT ANALYSIS OF 1-131 IN MILK September 1973 JIDE

A. INTRODUCTION

General Design Criterion 64. "Monitoring Radioactivity Releases," of Appendix A to 10 CFR Part 50, "General Design Criteria for Nuclear Power Plants," requires that means he provided for monitoring (hfe plant environs or lighl.water.cooled nuclear power plants for radioactivity that may be released from normal operations, including anticipated operational occurrences, and from postulated accidents.

Paragraph (a)(2) of § 50.36a of 10 CFR Part 50 provides that technical specifications For each license will include a requirement that the licensee submit a report to the Commission within 60 days after January I and July I of each year which, in addition to specifying the quantity of each of the principal radionuclides released to unrestricted areas in liquid and airborne effluents during the last six months of operation, provides sufficient information to estimate annual radiation doses to the public resulting from effluent releases.Paragraph (e) of § 20.106 of 10 CFR Part 20 provides that the Commission may limit the quantities of radioactive materials released in air or water by licensees during a specified period of time if it appears that the daily intake of radioactive materials from air, water, or food by a suitable sample of an exposed population group. averaged over a time period not exceeding one year, would otherwise exceed specified quantities.

Section 20.201 of 10 CFR 20 requires that a licensee conduct surveys of levels of radiation or concentrations of radioactive material as necessary for compliance with AEC regulations in Part 20. Paragraph (c) of § 20.1 of 10 CFR Part 20 states that every reasonable effort should be made by AEC licensees to maintain radiation exposures, and releases of radioactive materials in effluents to unrestricted areas, as far below the limits specified in Part 20 as practicable, i.e., as low as is practicably achievable, taking into account the state of technology, and the economics of improvements in relation to benefils to lite public heallh and saflby and in relation to the utilization of atomic energy in the public interest.The procedure for the determination of 1-131 in milk described in this glide constitutes a method acceplable to the Regulatory staff for measuring 1.131 as may he required by the ahove regnilalions or orders or license conditions imposed pursuant thereto.

B. DISCUSSION

In accord wilh the Commission's policy (f keeping exposure of man to radioactive materials released from licensed activities, including the operation of production or utilization facilities, as low as practicable, licensees should make every reasonable effort to limit the release of radioactive materials in effluents to unrest. -led areas as far below the limits specified by the Comm. qion as practicable.

Iodine-131 requires special at:*-ntion because it is one of 'he more significant radionuclides present in releases from nuclear power plants, and it can be concentrated through the air.vegetation.cow.milk pathway and potentially contribute to the thyroid dose.Although most milk data have indicated little or no 1.131, milk monitoring at the suggested improved level of sensitivity would provide direct evidence that the potential exposure due to 1-131 does not exceed predicted values.Current guidelines' for 1-131 dose it) the thyroid of infants require that the sensitivity for measuring 1.131 in milk be improved over conventional direct gamma counting of the raw milk sample. Low-level beta counting techniques with a detection sensitivity about an order of magnitude better than conventional gamma counting techniques can be used to attain the desired sensitivity.

In the analysis of 1.131 in milk, it may be'Regulatory Guide 1.42. "Interim Licensing Policy on As Low As Practicable.

for Gaseous Radioiodine Releases front Light-Water-Cooled Nuclear Power Reactors." Copies of published guidas may be obtained by request indicaing the divitions deored to the U.S. Alomic Energy Commlsston.

washington, D.C. 20-6, Atteion: Director of Regulatory Standards.

Com, wents end 1,-491400s lot Improveflmnts In these guides w are fiotifegd and should be sent to the Secretary of tha Commission, U.S. Atomic Energy Commission, Wtrhinglon, D.C. 20645, Attention: Chief, Public Pm'eWp Staff.The guides ae issued In the following ton broad divisions: USAEC REGULATORY GUIDES Ragi4a10o'V Gukis we issued to describe end rmke raillable to the public methods to the AEC Regultaory staf of ianmtemenling specific parts of the Cormmission's regulations, so delineate techniques used by the staff In eVAluating Specific problems or postulated accidents, or to provide guidance to aplicants.

Regulatory Guides are not for reg"uations and complince with them Is not required.

Methods and solutions different fromn thoe set out In the guidin will be acceptable if they provide a beut, for the findings requisite to the issuance or continuance of a permit or lics% by the Commission.

Publlshed =uides will be revised periodlcally.

as appropriate.

toa crnnftsl lad to reflect new Inforsntlotn at experience.

1. Powdr Reactors 2. and Test Reaacts 3. Fuels and Materlals Facilites 4. Environmental and Siting 6. Materialk and Plant Protection B. Products 7. Transportation a. Occupational Heahh 9. Antitrust Review 10. General necessary in some instances to measure 1-131 in tile presence of i-129 2-as Well as other radioisotopes of iodine; since the usual beta counting methods are nonspecific, provisions for the resolution of such a potential mixt'jre of isotopes should be included in the procedure.

In most instances, however, radioisotopes of iodine other than 1-131 and possibly 1-129 are not expected to be of significance in the milk pathway because of their short half-lives.

Also, under normal 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.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.Nevertheless, because of the nonspecificity of heta counting methods, as a minimum. decay checks should be performed.

A simple check for isolopic purity can be performed by recounting the sample for radioactive decay. A half.time of 8 days would be a good indication that the activity is due to 1-131. However, since it is not practical to attempt to monitor decay half-times when the sample net counting rate is less titan about 0.3 cpm. it would be'A regulatory guide for the analysis of 1-129 in milk is in preparation..worthwhile to do ,this only, wihen the net count. is more than about 0.3 cpm. If, after the second count, it is determined that the activity is not decaying with a half-time of about 8 days, a third count made 4-5 days after the second count can provide the basis for a rough graphical resolution of 1-131 activity.

In any case, it would be desirable to hold the sample for at least a year to permit possible identification of the long-lived component should the need arise.C. REGULATORY POSITION The procedure for the analysis of 1-131 in milk described in the appendix to this guide is acceptable to the Regulatory staff as a basis for meeting analytical performance standards which are compatible with established guidelines.' Other procedures selected for analyzing 1.131 in milk should provide levels of analytical sensitivity and specificity similar It) those for the method described in the appendix.ISee footnote on page 4.3-1 4.3-2 Ao UNITED STATES 0* REGULATORY COMMISSION) 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 iodine from raw milk requires that the iodine he in a readily exchangeable anionic form. Radiviodine tracer experiments on cows' 2 -' have shown that 0-10 percent 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 significantly affect data interpretation and therefore is considered to be acceptable.

Nevertheless, for the sake of accuracy, it is recommended that a fixed correction factor of 1.05(1/0.95 = 1.05) be applied to the counting data to compensate for this effect.Also, there may be instances where milk samples* may curdle to varying degrees in the interim between collection arid analysis.

Milk in this condition is unsuitable for analysis by the direct ion exchange method. A fresh sample should be obtained should this occur. If clabbering continue.

it) be a problem, the ion exchange separation should be performed at the sample 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.

The procedure described in this appendix was adapted from a procedure entitled "Determination of 1-129 in Milk and Water Samples" developed by the Radiological Sciences Laboratory.

Division of Laboratories and Research, New York State Department of Health It was tested at the Battelle Memorial Institute Pacific Northwest Laboratories and shown to be adequate to measure 1-131 in milk at the 0.25 picocurie per liter concentration level. This sensitivity is* based on using a 4.liter milk sample and beta counting* for 1000 minutes or longer in a low-background counter with a nominal background count rate of 0'5.1 count per minute (cpm). The analytical sensitivity can be further improved by using more than 4 liters of milk and 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 than about 0.3 cpm, a recount should be made only when the initial net counting rate is greater than 0.3 cpm. If. after the second count, it is determined that the activity is not decaying with a half-life of 8 days, a third count should be made 4.5 days after the second count.'Murthy. G. K.. ei at "Method for Removing Iodine-131 from Milk," Journal or Dairy Science. 45:1066 (1962)2 Salki' M.. Omomo. Y.. "Determination of Iodine-131 in Milk, Quick Mcthod. for Radlochemical Analysi.," Technical Reportr. Series No. 95, JAFA, 1969.3 'Bretthauer.

F.. W.. Mullen. A. L.. Molghiss, A. A. "Milk* Trantfer Comparison.s of Dirfereni Chemckal .or Radloiodine."' Health Physics, 22:257 (1972)A graphical resolution of 1.131 activity based on these three points mnay he performed.

The sample should be held for at least a year to permit possible identitication of thie long.lived component should the need arise.Abstract of the Procedure Iodine-131 is removed from milk by concentrating the iodine on an anion exchange resin column and subsequently removing it from the resin by batch extraction using NaOCI. After reduction to 12 by hydroxylamine hydrochloride, the iodine is extracted into CC1 4.reduced with bisulfite.

and back extracted into water. The iodine is precipitated as palladous iodide. Chemical yield based on the added carrier iodine is determined gravimetrically.

The 1.131 concentration is determined by counting the palladous iodide precipitate in a low-background beta counter. The yield for the procedure is 70 to 85'7r.Special Apparatus I. Ion exchange column, 2 cm dia. by about 10 cm long with standard taper fittings 2. Four-liter reservoir with standard taper fitting 3. Assorted sizes of glass beakers 4. Hot plate 5. Magnetic stirrer 6. Suction filtering apparatus 7. 250-ml and 125-ml separatory funnels

8. Clinical centrifuge

9. Low-baCkground beta counter (nominal background 41 count per min.)10. Nylon rings and discs,,Mylar, glass fiber paper (2.8 cm) (see HASL 300)Reagents and Chemicals I. Iodide carrier, 10 mg/ml -dissolve 1.181 grams Nal in 100 ml water 2. Dowex I x 8. 20.50 mesh. Cl" form 3. 2M NaCI .dissolve 116.9 grams NaCI in I liter water 4. NaOCl, 5-6% (commercial strength)5. HNO.t, concentrated 6. Hydroxylamine hydrochloride, crystals 7. CCI 4 8. IM NaHSO 1 -dissolve 1.041 grams of NaHSO 3 in 10 ml water (prepare daily)9. Palladous chloride, 10 mg/ml -dissolve 1.66 grams ofPdCl 2 in 100 nil of water 4.3.3 a.,: Procedure 1. Prepare an ion exchange column 2 cm in diameter by 10 cm long and fill to a height of 5 cm with Dowex I x 8. 20-50 mesh. CI" form. Add the resin from a water slurry.2. Add 1-2 ml of iodine carrier (10 mg 1'/ml) to 4-liter.. ,ilk sample and stir thoroughly.

Accurately measure and record exact volume of carrier added.* 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 (50 0 C) distilled water followed by .100 ml of 2M NaCI. Discard washes.4. Transfer the resin to a 250-ml beaker using 50 ml of 5-6% NaOCI. (Note 1).5. Place a small ("2 cm long) magnetic st,.ring bar in* the beaker and stir vigorously for 5 minuies on a magnetic stirrer.6. Filter the resin slurry. through a suction filter and retain the NaOCI solution. (Note 2)7. Reextract the resin by repeating steps 4. 5. and 6.8. Discard the resin, combine the two 50-ml solutions, and carefully add 20 ml or conc. H ,N0 3.(Note 3)9. Pour the acidified NaOCI solution into a 250-ml* separatory funnel and add 50 ml of CCI 4.10. Add 1.5 gm of hydroxylamine hydrochloride and shake (Note 4). Extract the iodine into the organic phase (about 2 min. equilibration). (Note 5)l 1. Drain lower organic, phase into a clean 250-ml..separatory funnel and save.12. Add 50 ml CC1 4 and I gm hydroxylamine hydrochloride to the aqueous phase in the first separatory funnel and reextract.

Combine organic phases and discard aqueous phase., 13. Add 25 ml H20 and 10 drops of freshly prepared IM NaHSO 3 to the separatory funnelcontaining the combined CC1 4 and shake. Equilibrate for.. 2 minutes. Discard organic (lower) phase. (Note 6)14. Transfer the aqueous (upper) phase into a clean 50-ml centrifuge tube and add I ml of conc. HNO 3 and 10 ml of PdCI 2 solution.

Stir and let stand for 5 minutes.15. Centrifuge Pdl 2 precipitate discarding supernate.

Wash precipitate by. stirring with 10 ml of H2 0.16. Using a filter funnel setup similar to that (Teflon or polyethylene -nylon) described in HASL 300."Procedure Manual'" USAEC, filter with suction through a tared glass fiber paper (2.8 cm diameter), using a water wash bottle to effect the transfer.(Note 7)17. Dry precipitate for 20 minutes in an ovenset at*.I10C and weigh to the nearest 0.1 milligram.(Alternatively, the sample may be dried on a hot* plate at low heat for about 30 minutes.).18. Mount the precipitate on a nylon disc, cover Mylar (1/4 mil thick), and fasten with ring. (This.procedure is described in HASL 300.) j 19. Count in a low-background counter for I0 0%1 minutes.20. If net counting rate of sample is greater than 0.3 cpm. recount after 7-8 days.21. Calculate as picocuries 1-131 per liter of milk at time of sampling.Notes I. This is most easily accomplished by using a polyethylene squirt bottle to dispense the NaOCI.2. Resin should be very light straw color after NaOCI extraction, if not light colored, the NaOCI is below strength, and a fresh solution should be obtained.Commercial grade Clo.rox has been found to be adequate.3. Add the acid slowly with stirring until the vigorous reaction subsides.

Perform in well ventilated hood.4. Proceed with caution in this step. Excessive gas formation during the extraction can cause the stopcock or cap on the separatory funnel to "pop" with consequent loss of samp!e. Start by gently swirling the solution to effect mixing. Invert the separatory funnel with the stopcock pointing up and release the pressure by opening the stopcock.Close the stopcock, shake, and repeat the pressure release sequence.5.. Organic phase should be deep red: if not, add additional gram of NH 2 OH.lHCI.6. After back extraction into water, CC1 4 should be colorless; if not add additional NaHS.0 3 and reextract.

7. HASL 300 "Procedure Manual" Health and Safety Laboratory, U.S. Atomic Energy Commission, 376 Hudson St., New York, New York 10014.Calibration and Standardization of Beta Counter Counter standardization should be performed with 1-131 standard obtained from the National Bureau of Standards (NBS)or with one which Is relatable to NBS.An example of a relatable standard is a secondary or tertiary standard which has been calibrated against a primary NBS standard.A self-absorption calibration curve should be constructed using at least 4 points. A useful curve can be constructed by plotting counter efficiency against mass.The counter efficiency can then be read off the curve as 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 )Iassociated with tile measurement follows: Wl of ppt. mg Chem ical yield = ,, .8 I 14.83" F'nh! ppt is not Stoichii n ntrically Pdlt. and determined weight of PdIc for 10 ml! of I.I. Chemical yi!J

3. Counter hackground

4. Counting time 5. Radioactive decay 6. Sample net coun:s Gross counts for I 000-min interval The net counts Standard deviation Net count with error limit Net pCi/liter this value is a deIermined empirical yield l'r 100u5 r1c, a ry: 14.83 mgi% i', Ihw= 0.78 7 0.35 0 0.6 cpm= 1000 minutes-8.05 days-0.6- cpn (fIor a I-lialf-life decay period)= (background cpm + net cpm) (counting tin..)= (0.6 + 0.6))1000 = 1200-1200 -600 = 600 corrnts per 1000 minutes or 0.6 cpnm= gross counts + background counts 1 2600++600=42 -600 +/- 42 (net counts) (factor for protein-bound fraction)0 (count time)(chem yield)(counter efflt sample vol hIdecay )(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}}