Information Notice 1986-23, Excessive Skin Exposures due to Contamination with Hot Particles
UnS 0 1AL SSINS No.: 6835IN 86-23UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555April 9, 1986IE INFORMATION NOTICE NO. 86-23: EXCESSIVE SKIN EXPOSURES DUE TOCONTAMINATION WITH HOT PARTICLES
Addressees
- All nuclear power reactor facilities holding an operating license (OL) or aconstruction permit (CP).
Purpose
- This information notice is provided to alert recipients of a potentiallysignificant problem pertaining to skin contamination incidents. It is expectedthat recipients will review this information for applicability to their facili-ties and consider action, if appropriate, to preclude a similar problem occur-ring at their facilities. However, suggestions contained in this notice do notconstitute NRC requirements; therefore, no specific action or written responseis required.
Description of Circumstances
- Three reactor licensees recently have reported excessive skin exposures toindividuals as a result of contamination from single hot particles of radioac-tive material. (See Attachment 1 for a more detailed description of theseevents.) Hot particles are small (in some cases microscopic) particles ofradioactive material with a high specific activity.All three licensees have concluded that the hot particles in those contamina-tion events most probably were transferred to the individual from "clean"protective clothing (which are intended to prevent skin contamination). Reviewof the events discussed in Attachment 1 indicates the following additionalcommon considerations:1. Plants with hot particle problems experience multiple contaminationevents. Once hot particles are loose in the plant they are difficult todetect and control. Plants with a potential for generating hot particles(those with stellite components or poor fuel performance) should consideradditional contamination control measures such as providing temporarycontainment for "hot" jobs, where feasible. The INPO Significant EventReport (SER) 42-85, "Personnel Skin Contaminations Due to ActivatedStellite Particles," includes a discussion on minimizing the introductionof stellite to a reactor system.8604040321 IN 86-23April 9, 1986 . It is believed that the insides of protective clothing are being contami-nated in the laundry system. Reliance on the laundry process monitors inthe cleaning fluid path and/or bulk gamma surveys of "clean" protectiveclothing is ineffective for detecting hot particles. Licensees may wantto segregate highly contaminated clothing from potentially contaminatedclothing and launder each group separately to reduce the chance of trans-ferring hot particles.3. In all the reported events, a need for more vigilance in personnel contam-ination control (self-frisking, protective clothing removal procedures,etc.) is evident.A hot particle on the skin produces a very steep dose gradient with the dosedropping off rapidly as distance from the particle increases. The NCRP doselimit recommendations in NBS Handbook 59 (which provide the basis for thecurrent NRC regulations) assumes that the critical area of the skin is 1.0 cm2and that the radiosensitive basal layer of cells is at a depth of 7mg/cm2 belowthe surface. For purposes of showing compliance with 10 CFR 20.101(a), calculat-ing a skin dose averaged over 1.0 cm2 at a depth of 7 mg/cm2 is appropriate.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact the RegionalAdministrator of the appropriate regional office or this office.dward .ordan, DirectorDivisi n/of Emergency Preparednessand i gineering ResponseOffice of Inspection and EnforcementTechnical Contacts: Roger L. Pedersen, IE(301) 492-9425James E. Wigginton, IE(301) 492-4967
Attachments:
1. Description of Events2. List of Recently Issued IE Information Notices Attachment 1IN 86-23April 9, 1986 DESCRIPTION OF EVENTSMcGuire:On June 5, 1985, a contractor employee supporting the plugging operation of asteam generator at Duke Power Company's McGuire Station discovered a small areaof skin contamination under the arm. The contamination was detected by acontamination portal monitor when the individual exited the controlled areaafter removal of three sets of protective clothing. Further detailed surveysof the contaminated skin area showed the following results: 0.5 mR/hr gamma,58 mrad/hr beta, and greater than 50,000 cpm with a pancake G-M detector. Thecontamination was successfully removed using adhesive tape. Further evaluationshowed that the contamination was a single particle 40 microns in diameter withan activity of 1.2 microcuries (uCi) of Co-60. Calculation of the absorbeddose to 1 cm2 of skin resulted in a skin dose of 10.6 rad. This exceeded themaximum allowable dose of 7.5 rem in a quarter [10 CFR 20.101(a)].Prior to the June event, a number of similar contamination incidents with hotparticles of cobalt-60 had occurred but with lesser dose consequences. Thelicensee's investigation led to the preliminary conclusion that the cobalt-60particles were transferred to the individual from the "clean" protectiveclothing. The licensee has identified other Co-60 particles in the plantlaundry area. The licensee thus far believes the source of contamination to bestellite valve seats with high cobalt content in the primary coolant system.Small particles of stellite may have been dislodged and transported to thecore, where they would have been activated to Co-60. Subsequently, theseparticles became trapped in protective clothing during maintenance activitiesand were not removed during normal laundering.The licensee subsequently initiated the following protective measures:1. Disposal of all cotton protective clothing in use at the time of theevent;2. Increased surveillance of protective clothing after laundering (includingcomprehensive surveys of both the inside and outside of laundered protec-tive clothing using pancake probe G-M meters);3. Increased vigilance in self-frisking procedures when exiting contaminatedarea and when traversing between frisking locations within contaminationcontrol zones; and4. Further evaluations to determine where stellite valve seats are used andwhere they could possibly be eliminated.San Onofre:On October 30, 1985, a firewatch employee found contamination while "friskingout" of the radwaste building (RWB). Investigation showed the contaminant tobe a small speck of material attached to the outside back of the individual's Attachment 1IN 86-23April 9, 1986 modesty garment worn under protective clothing. Frisker readings near theparticle were in excess of 50,000 cpm beta-gamma. An alpha count with a SAC-4survey instrument yielded 2,000 cpm. Gamma spectrometric analysis showed about4 uci of material made up of Nb-95, Zr-95, Ru-103, Ru-106, Ba-140, La-140,Ce-141 and Ce-144. This composition suggests that the hot particle is a tinyfragment of fuel rather than the normal mix of activation and fission productswhich originate within the reactor coolant system. Careful frisking by person-nel at the RWB exit point turned up a few more hot particles on modesty garmentsand shoes. Extensive surveys pointed to the fuel reconstitution equipment andwork area in the Unit 3 FHB as the most significant sources of hot particles.Unit 3 has experienced significant fuel integrity problems. Recently San Onofreperformed fuel reconstitution in the spent fuel pool by replacing defective fuelpins in the affected fuel assemblies.On November 19, two additional instances of personnel contamination with hotparticles were detected. On November 21, a similar personnel contamination wasdetected. Additionally, two more hot particles were found in the FHB. Workwas halted and the FHB was isolated. Access to the FHB is presently limited torequired operator surveillances with constant HP coverage. The licenseedetermined that these skin contaminations resulted from hot particles transferredfrom "clean" protective clothing. Checks of protective clothing on theready-to-issue shelves revealed two cases where protective clothing (which metthe "return to normal service" criteria of less than 5,000 cpm/probe area) werefound, upon very slow and careful frisking (15 minutes), to have hot particleswith activities that exceeded this value. Accordingly, a program is beingimplemented to withdraw all protective clothing presently in use for thoroughsurvey under more restrictive criteria. The clothing will be replaced withprotective clothing that has been out of service since Unit 3 fuel reconstitu-tion was initiated or with one-time-use disposal garments.A preliminary assessment of the dose received by the two individuals involvedin the November 19 events indicates 1.3 rem to the skin of the whole body and 7rem to the skin of an extremity. These are below the dose limits set in 10 CFR20.101(a). However, these dose calculations are currently under review by theNRC.Other actions taken by the licensee include:1. An extensive, special survey program (of workplace and protective cloth-ing) is being maintained to assure the prompt detection and removal ofadditional hot particles.2. Full face respirators are required in FHB during work involving theremoval of reconstitution tools.3. A special instruction was given to station personnel stressing the impor-tance of good frisking practices, use of protective clothing, contamina-tion control, and other H.P. practice Attachment 1IN 86-23April 9, 1986 Dresden:On December 11, 1985, a hot particle was found near the abdomen area on theoutside of an individual's undershirt. The contamination was initially foundby a portal monitor. On analysis, the hot particle was determined to contain110 nanocuries (nCi) of Co-60. The licensee concluded that the particle wasmost likely transferred from protective clothing to this undershirt. Based onthe individual's work activities an exposure time of 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> was estimatedresulting in a skin dose of less than 1 rem.On January 4, 1986, a hot particle (44 nCi CO-60 and 1 nCi Cs-137) was found ona contract worker's abdomen while passing through a whole body frisker. Thelicensee performed instrument response checks on the whole body friskers,postal monitors, and laundry monitors using the collected hot particle. Thelicensee concluded that the particle was transferred from protective clothingto the worker's skin. During interviews the worker admitted that he routinelyomitted frisking after removing his protective clothing at step-off pads. Withthe particle replaced near its original position the licensee had the workerpass through whole body friskers several times; an alarm was received about 50percent of the time. The licensee estimated the maximum probable time ofexposure to be 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />, resulting in a calculated skin dose of less than 5rems.Actions taken by the licensee to prevent reoccurrence include:1. Initiating a more aggressive laundry monitoring program; and2. Emphasizing to contractors the need for worker compliance with radiologi-cal control Attachment 2IN 86-23April 9, 1986LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to86-2286-2186-20Underresponse Of RaditionSurvey Instrument lo HighRadiation FieldsRecognition Of AmericanSociety Of MechanicalEngineers AccreditationProgram For N Stamp HoldersLow-Level Radioactive WasteScaling Factors, 10 CFRPart 61Reactor Coolant Pump ShaftFailure At Crystal RiverNRC On-Scene Response DuringA Major EmergencyUpdate Of Failure Of Auto-matic Sprinkler System ValvesTo Operate3/31/863/31/863/28/863/21/863/26/863/24/8686-1986-18All power reactorfacilities holdingan OL or CP andresearch and testreactorsAll power reactorfacilities holdingan OL or CP and allrecipients of NUREG-0040 (white book)All power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CP86-1786-16Failures To Identify Contain- 3/11/86ment Leakage Due To InadequateLocal Testing Of BWR VacuumRelief System ValvesLoss Of Offsite Power Caused 3/10/86By Problems In Fiber OpticsSystems86-1586-14PWR Auxiliary Feedwater Pump 3/10/86Turbine Control ProblemsOL = Operating LicenseCP = Construction Permit