P. Andrew Karam Ph.D., CHP Paksbi@rit.edu Andrewkaram

P. Andrew Karam Ph.D.,CHPpaksbi@rit.eduwww.andrewkaram.com

Composition is Al2SiO4(F,OH)2 Will also have trace impurities that vary fromlocation to locationThese impurities can affect color and activationproductsPure topaz is colorless or pale yellow Blue topaz can occur naturally, but is usuallyproduced via irradiation

Reactor-irradiated, using neutrons Accelerator-irradiated, using electrons Produces “Swiss blue” (a deep blue)Produces “London blue” or “sky blue” (a lightershade of blue)Gamma-irradiated, using Cs-137 Also produces London blue and sky blue

Mineral color is a result of physical structure(e.g. opal) and/or the interactions of light withelectric fields in a mineralExposure to ionizing radiation can alter amineral’s distribution of electric chargeExposure to particle radiation (especially largeparticles) can also change a crystal’s physicalstructureImpurities can also affect color by stressing thecrystal structure and influencing electronconfiguration

Red/Pink - ChromiumBlue - Titanium & IronYellow - Iron & UnknownOrange - Chromium & IronViolet/Purple - Chromium & Titanium and/orIronGreen - Iron

Neutron irradiation produces a deeper bluethan irradiation by gammas or electronsbecause Neutrons are more heavily ionizing,Neutrons induce more change to the crystalstructureNeutrons penetrate the whole crystal (unlikeelectrons)

Gemstones mined, cleaned, and sortedCutting and polishingIrradiation at reactor or acceleratorGemstones set at factory (often in China) Small number of gems remain loose as replacementsor for settingSet jewelry may be electroplated, requiring thoroughcleaningFinished product shipped to US for sale toretail outlets

Radiation safety Health and safety ContaminationRadionuclide concentrations and dosesDose to end usersDose to workersRegulatory compliance Possession (state)Exempt distribution (NRC)

Most stones are cut and polished prior toirradiationNO stones are cut or polished by PAJIn addition, any items that are to beelectroplated must be rigorously cleaned toensure proper adhesion of electroplated metals.Accordingly, there should be no contamination This should be checked by manufacturer, prior toshipping

These will vary, depending on the impurities(activation targets) and neutron fluenceNuclide 752115Exempt 50.050.020.2Maximum /expected nuclideconcentration onreceipt(3 weeks 0.020.18Maximum / expectednuclide concentration attime of transfer to nonlicensed customer(6 weeks 40.0190.16

2Ta-182115TotalRadiation Г (mR/hr per Expected activity inemitted μCi at 30 cm) one item of narioIntegrated 1-year radiation doseOn contact with skin(Varskin 3)shallowdeepExemption limits (worstcase)Expected concentrationsAt a distance of 4 cm(MicroShield)shallowdeep3700 mR388 mR137 mR24 mR760 mR29 mR34 mR1.8 mR

No contamination is expectedRadionuclide concentrations will likely be onlya fraction of exempt concentrationsRadiation dose and dose rates expected to below, even for large quantities of gemstones May have over 500 kg of irradiated gemstones onhand at any given time, and more before holidays(Christmas, Valentine’s Day, Mother’s Day)

Most gemstones are held for a few weeks postirradiation to cool offSome producers will not ship gems until grossradionuclide concentrations are less than 74pCi/gmIn actuality, gems will not reach the US until afew months post-irradiation, allowing forconsiderable decay of shorter-lived nuclides

We can calculate radiation dose from 500 kg ofirradiated gemstones that contain exemptconcentrations of the “big 5” nuclidesUsing MicroShield and calculations using theappropriate gamma constants, we should seeup to 5 mR/hr at a distance of 1 meter from apoint source, soon after irradiation.Actual measurements are much lower becauseof decay ( 1 mR/hr)

Not from radiation

NRC guidance documents date back about 20years, and assume that gems will be irradiatedin the USIn reality, gems are now irradiated overseasand undergo considerable decay beforeimportationMuch of the NRC licensing guidance isappropriate; some is not

The purpose of the NRC license is to importgems, characterize the radionuclideconcentrations (hopefully less than exemptionlimits), and then distribute as exemptradioactive materialsThis means that the licensee must be able toshow that they are capable of performingreceipt surveys and (more difficult) determinethe radionuclide concentration in these gems

Ideally, the licensee will characterize everygemstone with respect to radionuclide ID andconcentrationsThis would involve performing gammaspectroscopy on every gemstoneIn reality, this is nearly impossible because of thevery large number of gems, the cost of gammaspec equipment, and lack of HP trainingLuckily, the NRC does not seem insistent on thispoint, and seems willing to accept a sampling plan

The day I visited, two pallets of earringsarrivedEach pallet held 20 boxesEach box contained over 200 cards, each with 5sets of earrings Only 1 set per card contained blue topazOther packages may contain up to 10,000bracelets, each with 6 stonesSurveying every individual item isprohibitively time-consuming

Need to be able to demonstrate that “hot” gemsdo not escape detectionNeed to be able to demonstrate that gems donot exceed exempt concentrations for anynuclides (the “sum of fractions” rule applies)Need to demonstrate that the licensee can makethese determinations to the satisfaction ofregulators

Must be able to show that the licensee cansafely possess and secure radioactive materialsTotal activity is less than that of most soildensity gauges, so this is not difficult

The packagingarea – too manypeople (and toolittle dose) to berad workers.Receive packages,awaiting surveying

Jewelry comespackaged in severallayers of ziploc bags

Topaz (and some other gems) may beirradiated to cause it to change colorIrradiation can induce radioactivity, albeit inexempt concentrationsIrradiated gems exhibit only low levels ofradiation and do not pose a health riskProspective licensees must be able to convincethe regulators that they are competent todetermine that gems are exempt fromregulation

Reactor-irradiated, using neutrons Produces “Swiss blue” (a deep blue) Accelerator-irradiated, using electrons Produces “London blue” or “sky blue” (a lighter shade of blue) Gamma-irradiated, using Cs-137 Also produces London blue and