Regulatory Guide 4.3
| ML13350A246 | |
| Person / Time | |
|---|---|
| Issue date: | 09/30/1973 |
| From: | US Atomic Energy Commission (AEC) |
| To: | |
| References | |
| RG-4.003 | |
| Download: ML13350A246 (6) | |
U.S. ATOMIC ENERGY COMMISSIONREGULATORY GIDIRECTORATE OF REGULATORY STANDARDSREGULATORY GUIDE 4.3MEASUREMENTS OF RADIONUCLIDES IN THE ENVIRONMENTANALYSIS OF 1-131 IN MILKSeptember 1973JIDE
A. INTRODUCTION
General Design Criterion 64. "MonitoringRadioactivity Releases," of Appendix A to 10 CFR Part50, "General Design Criteria for Nuclear Power Plants,"requires that means he provided for monitoring (hfe plantenvirons or lighl.water.cooled nuclear power plants forradioactivity that may be released from normaloperations, including anticipated operationaloccurrences, and from postulated accidents.Paragraph (a)(2) of § 50.36a of 10 CFR Part 50provides that technical specifications For each licensewill include a requirement that the licensee submit areport to the Commission within 60 days after January Iand July I of each year which, in addition to specifyingthe quantity of each of the principal radionuclidesreleased to unrestricted areas in liquid and airborneeffluents during the last six months of operation,provides sufficient information to estimate annualradiation doses to the public resulting from effluentreleases.Paragraph (e) of § 20.106 of 10 CFR Part 20provides that the Commission may limit the quantitiesof radioactive materials released in air or water bylicensees during a specified period of time if it appearsthat the daily intake of radioactive materials from air,water, or food by a suitable sample of an exposedpopulation group. averaged over a time period notexceeding one year, would otherwise exceed specifiedquantities. Section 20.201 of 10 CFR 20 requires that alicensee conduct surveys of levels of radiation orconcentrations of radioactive material as necessary forcompliance with AEC regulations in Part 20. Paragraph(c) of § 20.1 of 10 CFR Part 20 states that everyreasonable effort should be made by AEC licensees tomaintain radiation exposures, and releases of radioactivematerials in effluents to unrestricted areas, as far belowthe limits specified in Part 20 as practicable, i.e., as lowas is practicably achievable, taking into account the stateof technology, and the economics of improvements inrelation to benefils to lite public heallh and saflby andin relation to the utilization of atomic energy in thepublic interest.The procedure for the determination of 1-131 inmilk described in this glide constitutes a methodacceplable to the Regulatory staff for measuring 1.131 asmay he required by the ahove regnilalions or orders orlicense conditions imposed pursuant thereto.
B. DISCUSSION
In accord wilh the Commission's policy (f keepingexposure of man to radioactive materials released fromlicensed activities, including the operation of productionor utilization facilities, as low as practicable, licenseesshould make every reasonable effort to limit the releaseof radioactive materials in effluents to unrest. -led areasas far below the limits specified by the Comm. qion aspracticable. Iodine-131 requires special at:*-ntionbecause it is one of 'he more significant radionuclidespresent in releases from nuclear power plants, and it canbe concentrated through the air.vegetation.cow.milkpathway and potentially contribute to the thyroid dose.Although most milk data have indicated little or no1.131, milk monitoring at the suggested improved levelof sensitivity would provide direct evidence that thepotential exposure due to 1-131 does not exceedpredicted values.Current guidelines' for 1-131 dose it) the thyroid ofinfants require that the sensitivity for measuring 1.131 inmilk be improved over conventional direct gammacounting of the raw milk sample. Low-level betacounting techniques with a detection sensitivity aboutan order of magnitude better than conventional gammacounting techniques can be used to attain the desiredsensitivity. In the analysis of 1.131 in milk, it may be'Regulatory Guide 1.42. "Interim Licensing Policy on AsLow As Practicable. for Gaseous Radioiodine Releases frontLight-Water-Cooled Nuclear Power Reactors."Copies of published guidas may be obtained by request indicaing the divitionsdeored to the U.S. Alomic Energy Commlsston. washington, D.C. 20-6,Atteion: Director of Regulatory Standards. Com, wents end 1,-491400s lotImproveflmnts In these guides w are fiotifegd and should be sent to the Secretaryof 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 GUIDESRagi4a10o'V Gukis we issued to describe end rmke raillable to the publicmethods to the AEC Regultaory staf of ianmtemenling specific parts ofthe Cormmission's regulations, so delineate techniques used by the staff IneVAluating Specific problems or postulated accidents, or to provide guidance toaplicants. Regulatory Guides are not for reg"uations and complincewith them Is not required. Methods and solutions different fromn thoe set out Inthe guidin will be acceptable if they provide a beut, for the findings requisite tothe 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 Reactors2. and Test Reaacts3. Fuels and Materlals Facilites4. Environmental and Siting6. Materialk and Plant ProtectionB. Products7. Transportationa. Occupational Heahh9. Antitrust Review10. General necessary in some instances to measure 1-131 in tilepresence of i-1292-as Well as other radioisotopes ofiodine; since the usual beta counting methods arenonspecific, provisions for the resolution of such apotential mixt'jre of isotopes should be included in theprocedure. In most instances, however, radioisotopes ofiodine other than 1-131 and possibly 1-129 are notexpected to be of significance in the milk pathwaybecause of their short half-lives. Also, under normaloperating conditions of nuclear power plants, thecontribution from 1-129 will be negligible, the potentialsignificance of 1.129 being associated primarily with fuel.reprocessing plant:i. It is probable, therefore, that anyradioiodine detected in milk sampled from the environsof nuclear power plants will be primarily 1-131.Nevertheless, because of the nonspecificity of hetacounting methods, as a minimum. decay checks shouldbe performed.A simple check for isolopic purity can be performedby recounting the sample for radioactive decay. Ahalf.time of 8 days would be a good indication that theactivity is due to 1-131. However, since it is not practicalto attempt to monitor decay half-times when the samplenet counting rate is less titan about 0.3 cpm. it would be'A regulatory guide for the analysis of 1-129 in milk is inpreparation..worthwhile to do ,this only, wihen the net count. is morethan about 0.3 cpm. If, after the second count, it isdetermined that the activity is not decaying with ahalf-time of about 8 days, a third count made 4-5 daysafter the second count can provide the basis for a roughgraphical resolution of 1-131 activity. In any case, itwould be desirable to hold the sample for at least a yearto permit possible identification of the long-livedcomponent should the need arise.
C. REGULATORY POSITION
The procedure for the analysis of 1-131 in milkdescribed in the appendix to this guide is acceptable tothe Regulatory staff as a basis for meeting analyticalperformance standards which are compatible withestablished guidelines.' Other procedures selected foranalyzing 1.131 in milk should provide levels ofanalytical sensitivity and specificity similar It) those forthe method described in the appendix.ISee footnote on page 4.3-14.3-2 Ao UNITED STATES0* REGULATORY COMMISSION) 0 WASHINGTON. D. C. 20555.9ýl4OP *December 1, 1976REGULATORY GUIDE DISTRIBUTION LIST (DIVISION 4)The Nuclear Regulatory Commission staff has withdrawn Regulatory Guide4.3, "Measurements of Radionuclides in the Environment, Analysis of1-131 in Milk." This guide was issued in September 1973 to describeone acceptable method for the determination of iodine-131 in milkwhich would meet the guidelines for iodine-131 dose to the thyroidof infants as given in Regulatory Guide 1.42, "Interim Licensing Pol-icy on as Low as Practicable for Gaseous Radioiodine Releases fromLight-Water-Cooled Nuclear Power Reactors." With the adoption ofAppendix I to 10 CFR Part 50 as an effective rule and the adoptionof a series of implementing guides, there was no longer a need forRegulatory Guide 1.42, and it was withdrawn. Since Regulatory Guide4.3 .was issued, a number of acceptable alternative methods and tech-niques for the determination of low levels of iodine-131 in milk havebeen demonstrated, including the analysis of milk containing preserva-tives and the use of beta-gamma coincidence counting techniques. Alsosince Regulatory Guide 4.3 was issued, there has been a recognition ofthe need to consider the effects of relatively high and variable con-centrations of stable iodine in milk on the calculated radiochemicalrecovery and of the resultant need for determinations of stable iodinein milk. Because of the existence of acceptable alternative procedures,and the general recognition of the practicality of determining lowlevels of iodine-131 in milk, the detailed procedural guidance of Regu-latory Guide 4.3 is no longer needed. Current licensing commitmentsbased on Regulatory Guide 4.3 will not need to be reexamined as a resultof this withdrawal.Regulatory guides may be withdrawn when they are superseded by theCommission's regulations, when equivalent recommendations have beenincorporated in applicable approved codes and standards, or when changesin methods and techniques have made them obsolete.
Sincerely,Robert B. Minogue, DirectorOffice of Standards Development APPENDIXIODINE-131 ANALYSIS OF MILK AT CONCENTRATIONSDOWN TO 0.25 PICOCURIE PER LITERThe direct ion exchange method fCo separatingiodine from raw milk requires that the iodine he in areadily exchangeable anionic form. Radiviodine tracerexperiments on cows' 2 -' have shown that 0-10 percentof the iodine in milk may he protein bound, renderingthis fraction essentially unavailable for exchange withthe ion exchange resin. However, this uncertainty of upto 10 percent in the 1-131 determination will notsignificantly affect data interpretation and therefore isconsidered to be acceptable. Nevertheless, for the sakeof accuracy, it is recommended that a fixed correctionfactor of 1.05(1/0.95 = 1.05) be applied to the countingdata to compensate for this effect.Also, there may be instances where milk samples* may curdle to varying degrees in the interim betweencollection arid analysis. Milk in this condition isunsuitable for analysis by the direct ion exchangemethod. A fresh sample should be obtained should thisoccur. If clabbering continue. it) be a problem, the ionexchange separation should be performed at the samplecollection point and the ion exchange resin columnshipped to the laboratory for processing. If this cannotbe done, the milk sample should be frozen prior toshipment to the analytical laboratory.The procedure described in this appendix wasadapted from a procedure entitled "Determination of1-129 in Milk and Water Samples" developed by theRadiological Sciences Laboratory. Division ofLaboratories and Research, New York State Departmentof Health It was tested at the Battelle MemorialInstitute Pacific Northwest Laboratories and shown tobe adequate to measure 1-131 in milk at the 0.25picocurie 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 counterwith a nominal background count rate of 0'5.1 countper minute (cpm). The analytical sensitivity can befurther improved by using more than 4 liters of milk andcounting for longer than 1000 minutes..A recount for decay check should be performed7-10 days after the first count. However, because it isnot practical to do. this for net counting rates of lessthan about 0.3 cpm, a recount should be made onlywhen the initial net counting rate is greater than 0.3cpm. If. after the second count, it is determined that theactivity is not decaying with a half-life of 8 days, a thirdcount should be made 4.5 days after the second count.'Murthy. G. K.. ei at "Method for Removing Iodine-131from Milk," Journal or Dairy Science. 45:1066 (1962)2Salki' M.. Omomo. Y.. "Determination of Iodine-131 inMilk, Quick Mcthod. for Radlochemical Analysi.," TechnicalReportr. Series No. 95, JAFA, 1969.3 'Bretthauer. F.. W.. Mullen. A. L.. Molghiss, A. A. "Milk* Trantfer Comparison.s of Dirfereni Chemckal .orRadloiodine."' Health Physics, 22:257 (1972)A graphical resolution of 1.131 activity based on thesethree points mnay he performed. The sample should beheld for at least a year to permit possible identiticationof thie long.lived component should the need arise.Abstract of the ProcedureIodine-131 is removed from milk by concentrating theiodine on an anion exchange resin column andsubsequently removing it from the resin by batchextraction using NaOCI. After reduction to 12 byhydroxylamine hydrochloride, the iodine is extractedinto CC14.reduced with bisulfite. and back extractedinto water. The iodine is precipitated as palladousiodide. Chemical yield based on the added carrier iodineis determined gravimetrically. The 1.131 concentration isdetermined by counting the palladous iodide precipitatein a low-background beta counter. The yield for theprocedure is 70 to 85'7r.Special ApparatusI. Ion exchange column, 2 cm dia. by about 10 cmlong with standard taper fittings2. Four-liter reservoir with standard taper fitting3. Assorted sizes of glass beakers4. Hot plate5. Magnetic stirrer6. Suction filtering apparatus7. 250-ml and 125-ml separatory funnels8. Clinical centrifuge9. Low-baCkground beta counter (nominal background41 count per min.)10. Nylon rings and discs,,Mylar, glass fiber paper (2.8cm) (see HASL 300)Reagents and ChemicalsI. Iodide carrier, 10 mg/ml -dissolve 1.181 grams Nalin 100 ml water2. Dowex I x 8. 20.50 mesh. Cl" form3. 2M NaCI .dissolve 116.9 grams NaCI in I liter water4. NaOCl, 5-6% (commercial strength)5. HNO.t, concentrated6. Hydroxylamine hydrochloride, crystals7. CCI48. IM NaHSO1 -dissolve 1.041 grams of NaHSO3 in10 ml water (prepare daily)9. Palladous chloride, 10 mg/ml -dissolve 1.66 gramsofPdCl2in 100 nil of water4. a.,:Procedure1. Prepare an ion exchange column 2 cm in diameterby 10 cm long and fill to a height of 5 cm withDowex I x 8. 20-50 mesh. CI" form. Add the resinfrom a water slurry.2. Add 1-2 ml of iodine carrier (10 mg 1'/ml) to 4-liter.. ,ilk sample and stir thoroughly. Accuratelymeasure and record exact volume of carrier added.* Pass through the column at a flow rate of about 30nml per minute and discard effluent.3. Wash the column with 500 ml hot (500C) distilledwater followed by .100 ml of 2M NaCI. Discardwashes.4. Transfer the resin to a 250-ml beaker using 50 ml of5-6% NaOCI. (Note 1).5. Place a small ("2 cm long) magnetic st,.ring bar in* the beaker and stir vigorously for 5 minuies on amagnetic stirrer.6. Filter the resin slurry. through a suction filter andretain 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 ,N03.(Note 3)9. Pour the acidified NaOCI solution into a 250-ml* separatory funnel and add 50 ml of CCI4.10. Add 1.5 gm of hydroxylamine hydrochloride andshake (Note 4). Extract the iodine into the organicphase (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 CC14 and I gm hydroxylaminehydrochloride to the aqueous phase in the firstseparatory funnel and reextract. Combine organicphases and discard aqueous phase., 13. Add 25 ml H20 and 10 drops of freshly preparedIM NaHSO3 to the separatory funnelcontaining thecombined CC14 and shake. Equilibrate for.. 2minutes. Discard organic (lower) phase. (Note 6)14. Transfer the aqueous (upper) phase into a clean50-ml centrifuge tube and add I ml of conc. HNO3and 10 ml of PdCI2 solution. Stir and let stand for 5minutes.15. Centrifuge Pdl2 precipitate discarding supernate.Wash precipitate by. stirring with 10 ml of H2 0.16. Using a filter funnel setup similar to that (Teflon orpolyethylene -nylon) described in HASL 300."Procedure Manual'" USAEC, filter with suctionthrough 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.) j19. Count in a low-background counter for I0 0%1minutes.20. If net counting rate of sample is greater than 0.3cpm. recount after 7-8 days.21. Calculate as picocuries 1-131 per liter of milk attime of sampling.NotesI. This is most easily accomplished by using apolyethylene squirt bottle to dispense the NaOCI.2. Resin should be very light straw color after NaOCIextraction, if not light colored, the NaOCI is belowstrength, and a fresh solution should be obtained.Commercial grade Clo.rox has been found to beadequate.3. Add the acid slowly with stirring until the vigorousreaction subsides. Perform in well ventilated hood.4. Proceed with caution in this step. Excessive gasformation during the extraction can cause thestopcock or cap on the separatory funnel to "pop"with consequent loss of samp!e. Start by gentlyswirling the solution to effect mixing. Invert theseparatory funnel with the stopcock pointing upand release the pressure by opening the stopcock.Close the stopcock, shake, and repeat the pressurerelease sequence.5.. Organic phase should be deep red: if not, addadditional gram of NH2 OH.lHCI.6. After back extraction into water, CC14 should becolorless; if not add additional NaHS.03 andreextract.7. HASL 300 "Procedure Manual" Health and SafetyLaboratory, U.S. Atomic Energy Commission, 376Hudson St., New York, New York 10014.Calibration and Standardization of Beta CounterCounter standardization should be performed with 1-131standard obtained from the National Bureau ofStandards (NBS)or with one which Is relatable to NBS.An example of a relatable standard is a secondary ortertiary standard which has been calibrated against aprimary NBS standard.A self-absorption calibration curve should beconstructed using at least 4 points. A useful curve can beconstructed by plotting counter efficiency against mass.The counter efficiency can then be read off the curve asa function of the gravimetric yield..4.3-4 IExample of Calculation of ResultsThe activity in picocurics per liter at the time the milk was collected is determined by calculations based tn theobserved 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 withtile measurement follows:Wl of ppt. mgChem ical yield = ,, .8 I14.83"F'nh! ppt is not Stoichii n ntrically Pdlt. anddetermined weight of PdIc for 10 ml! of I.I. Chemical yi!J2. Counter efficiency3. Counter hackground4. Counting time5. Radioactive decay6. Sample net coun:sGross counts for I 000-min intervalThe net countsStandard deviationNet count with error limitNet pCi/literthis value is a deIermined empirical yield l'r 100u5 r1c, a ry: 14.83 mgi% i', Ihw= 0.787 0.350 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 minutesor 0.6 cpnm= gross counts + background counts1 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