Information Notice 1996-35, Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training

Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training

ML031060046
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000442, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	06/11/1996
From:	Cool D A NRC/NMSS/IMNS
To:
References
IN-96-035, NUDOCS 9606060078
Download: ML031060046 (8)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDSWASHINGTON, D.C. 20555June 11, 1996NRC INFORMATION NOTICE 96-35: FAILURE OF SAFETY SYSTEMS ON SELF-SHIELDEDIRRADIATORS BECAUSE OF INADEQUATE MAINTENANCEAND TRAINING

Addressees

All U.S. Nuclear Regulatory Commission irradiator licensees and vendors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice (IN) to alert addressees to two incidents where safety interlocks onself-shielded irradiators (Category I) failed to prevent inadvertent exposure.The causes of these exposures stemmed from a lack of appropriate maintenanceand/or worker training. The incidents include a broken spring -- possiblycausing malfunction of the safety interlock -- and a worker who intentionallybypassed a safety interlock. It is expected that recipients will review theinformation for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained inthis information notice are not NRC requirements; therefore, no specificaction nor written response is required.

Description of Circumstances

The first incident occurred when an operator may have been able to open theshielded door of an irradiator with the sources in the exposed position.After irradiation of several pocket dosimeters, the operator opened theshielded door of the irradiator to retrieve the dosimeters, but did notperform a radiation survey, as required by the facility's internal procedures,before opening the door. Twice, the operator placed one hand inside theirradiator to retrieve the dosimeters. Subsequently, the operator observedthat the unit timer continued to count, indicating that the sources remainedin the exposed position. The operator checked his personal pocket dosimeter,but did not note an unusual reading. However, the operator did not report theincident until questioned by the radiation safety officer, who had noted anunusually high dosimetry report of 3.55 millisievert (355 mrem) deep doseequivalent for the worker. The dose to the right hand was calculated to be amaximum of 12.5 millisievert (1.25 rem).The design of the irradiator includes two interconnected interlock systems,intended to prevent unshielded exposure of the sources. These include a doorinterlock system -- designed to allow opening of the shielded door only afterthe sources are placed in the fully shielded position -- and a source exposure-.interlock system -- designed to secure the sources in the fully shieldedtDR FE E NO r/C9 03 ?C 0t, II

kk JIIN 96-35June 11, 1996 position whenever the shielded door is open or unlocked. The manufacturer ofthe irradiator indicated that under normal operations, either systemindividually wouldiprevent inadvertent access to the unshielded sources.Following the incident, the manufacturer of the irradiator was requested toperform an onsite inspection of the irradiator and facilities. During theinspection, the manufacturer noted:(1) the irradiator was located in an area that was not climate-controlled;(2) internal components of the irradiator were in a degraded state;(3) maintenance of the irradiator had last been performed approximately10 years ago; and(4) a return spring, integral to the source exposure safety interlocksystem, was broken. The manufacturer indicated that the lack ofenvironmental control may have accelerated the degradation of theinternal components of the irradiator, and that the lack of periodicmaintenance of the irradiator may have contributed to the failure ofthe return spring.The broken return spring may have caused the source securing mechanism of thesource exposure interlock system to malfunction, possibly allowing exposure ofthe sources after the shielded door was unlocked and opened. However, duringthe post-incident investigation, neither the manufacturer nor the licenseewere able to identify a failed component of either interlock system that couldhave allowed the shielded door to be opened with the sources in the exposedposition. The manufacturer indicated that the design of the source exposuremechanism -- the operator must manually move the sources from the shielded tothe exposed position with a lever -- would have provided the operator with apositive indication of source position even if the interlock systems failed.Source position would have been further provided by a series of green and redsource position lights on the irradiator.The operator's actions indicate either a lack of training on the properfunctioning and use of the irradiator, a lack of understanding of the trainingprovided, and/or a disregard for following the established operating andsafety procedures. The operator indicated that the timer continued to countwhen the shielded door was opened. However, the manufacturer reported thatthe timer automatically activates whenever the source lever is manually movedto one of the two source exposed positions and the lever is fully engaged inthe source slot, and stops counting as soon as the lever is moved from thefully engaged position. The fact that the timer continued to count indicatesthat the operator had not moved the sources from the fully exposed and engagedposition. The licensee reported that the operator had been trained in theoperation of the irradiator and was listed as an authorized user, but that theirradiator was used infrequently and that this was only the operator's seconduse of the irradiator since being trained.The second incident occurred when a maintenance worker preparing to performmaintenance on an irradiator bypassed the irradiator door interlock system toobserve movement of the inner irradiation chamber. The maintenance was being

K>IN 96-35June 11, 1996 performed to correct previous maintenance that resulted in the irradiator notfunctioning properly. The maintenance worker was unaware that, although thesources remained shielded during movement of the irradiation chamber from theload to irradiate position, high levels of radiation scatter would be present.The maintenance worker, upon hearing the in-room monitor alarm, immediatelyreturned the radiation chamber to the 'load' position (maximum shielding).Although the maintenance worker was familiar with the operation of theirradiator and had been responsible for its maintenance for nearly 15 years,the worker apparently had not been given formal training on radiation safetyor the operation and maintenance of the irradiator. The maintenance workerwas not aware of the scatter radiation and assumed that since the sources werenot directly exposed, radiation from the sources would be contained within thedevice.During this incident, another worker, hired to perform contract maintenance onthe irradiator, was also in the room near the irradiator. Neither worker woredosimetry nor had any documented training in radiation safety. Therefore,their doses could only be calculated based on their recollection and wereestimated to both be approximately 4 microsievert (0.4 mrem) whole body.DiscussionAlthough neither incident resulted in doses in excess of regulatory limits,the doses received in both incidents were unnecessary and possibly could havebeen avoided with proper training and routine equipment maintenance. Asimilar incident in 1984, where a door interlock failed, resulted in theoperator being exposed to 222 terabequerel (6000 curies) of cesium-137.The first incident clearly demonstrates the need to perform appropriatemaintenance on these types of units. Even though these units are designedwith interlocks and safety features intended to prevent inadvertent exposures,the components of these systems depend on adequate maintenance to functionproperly. Failure to properly maintain these systems and provide appropriatetraining could result in unnecessary exposures. Manufacturers of these typesof irradiators frequently provide initial and periodic training on theoperation of their units and, in some cases, training on other manufacturers'units, as well. Initial training is typically a condition of the license and,therefore, must be provided to all irradiator users and maintenance personnel.Periodic refresher training is also beneficial as a reminder for workingsafely around the irradiator and provides for a means to receive ordisseminate additional or updated information.In addition, most manufacturers have a recommended schedule of maintenanceand/or recommended preventative/periodic maintenance that should be performed.Users of these types of irradiators should evaluate their usage to determinethe applicability of the recommended maintenance to their situation and usage.Users who operate their unit more than usual or who use their units underharsh conditions should consider the need for stepped-up maintenance or

'-> IN 96-35June 11, 1996 shortened maintenance intervals. In addition, each manufacturer's recommendedmaintenance may vary according to the specific unit or type of use.Therefore, personis performing maintenance on their unit may require specificmaintenance training for their unit.Users who are not aware of the required training for their unit, or who wishto receive information concerning training in general, should consult theirlicense, licensing authority, or the manufacturer of the unit. RegulatoryGuide 10.9, provides additional guidance in this area and may assist personswho wish to develop a training and maintenance program. Users who wish toreceive additional information concerning recommended maintenance for theirunit should contact the manufacturer of the unit. In addition, third-partyservice companies may also be available for training and maintenance servicesfor these types of irradiators.This information notice requires no specific action nor written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate regional office.I3W¶flstn8by9WWstIADonald A. Cool, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Material Safetyand SafeguardsTechnical contacts: Douglas Broaddus, NMSS(301) 415-5847Internet:dab~nrc.govAnthony Kirkwood, NMSS(301) 415-6140Internet:ask~nrc.govAttachments:1. List of Recently issued NMSS Information Notices2. List of Recently issued NRC Information NoticesDOCUMENT NAME: 96-35.INTo receive a copy of this document, Indicate In the box: C' = Copy without attachment/enclosure *E' -Copy with attachmentjendosure N

• No copy* See previous concurrenceOFFICE IIMAB* [ClIMAB* [C Tech Editor* l IMOB* [C IMNS* I C,NAME IDBroaddus* LCamper lEKraus _KRamsey jDCof'DATE 14/17/96 5/28/96 4/01/96 5/31/96 6/4 96 11OFFICIAL RECORD COPY

j;IN 96-XXMay XX, 1996 IN 96-XXMay XX, 1996 KUJ KUAttachment 1IN 96-35June 11, 1996 LIST OF RECENTLY ISSUEDNMSS INFORMATION NOTICESInformation ' Date ofNotice No. Subject Issuance Issued to96-33Erroneous Data from Defec-tive Thermocouple Resultsin a Fire05/224/96All material and fuel cyclelicensees that monitor tem-perature with thermocouples96-2896-2196-2096-18Suggested Guidance Relat-ing to Development andImplementation of Correc-tive ActionSafety Concerns Relatedto the Design of the DoorInterlock Circuit onNucletron High-Dose Rateand Pulsed Dose RateRemote Afterloading Brachy-therapy DevicesDemonstration of Associ-ated Equipment Compliancewith 10 CFR 34.20Compliance With 10 CFRPart 20 for AirborneThoriumIncident ReportingRequirements forRadiography Licensees10 CFR 34.20; FinalEffective DateHandling UncontainedYellowcake Outside of aFacility Processing CircuitRecent Incidents InvolvingPotential Loss of Controlof Licensed Material05/01/9604/10/9604/04/9603/25/9601/10/9612/18/9512/6/9510/27/95All material and fuel cyclelicenseesAll NRC Medical Licenseesauthorized to use brachy-therapy sources in high-and pulsed-dose-rate remoteAll industrial radiographylicensees and radiographyequipment manufacturersAll material licenseesauthorized to possess anduse thorium in unsealed formAll Radiography Licenseesand Manufacturers ofRadiography EquipmentIndustrial RadiographyLicensees.All Uranium RecoveryLicensees.All material and fuel cyclelicensees.96-0495-5895-5595-51 K> -iKJAttachment 2IN 96-35June 11, 1996 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to96-3496-3396-3296-3196-30Hydrogen Gas Ignitionduring Closure Weldingof a VSC-24 Multi-AssemblySealed BasketErroneous Data FromDefective ThermocoupleResults in a FireImplementation of 10 CFR50.55a(g)(6)(ii)(A),"Augmented Examinationof Reactor Vessel"Cross-Tied Safety Injec-tion AccumulatorsInaccuracy of DiagnosticEquipment for Motor-Operated Butterfly ValvesRequirements in 10 CFRPart 21 for Reporting andEvaluating Software ErrorsSuggested Guidance Relatingto Development and Imple-mentation of CorrectiveActionPotential Clogging of HighPressure Safety InjectionThrottle Valves DuringRecirculationRecent Problems with Over-head CranesTransversing In-Core ProbeOverwithdrawn at LaSalleCounty Station, Unit 105/31/9605/24/9606/05/9605/22/9605/21/9605/20/9605/01/9605/01/9604/30/9604/30/96All holders of OLs or CPsfor nuclear power reactorsAll material and fuel cyclelicensees that monitor tem-perature with thermocouplesAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor pressurized waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor nuclear power reactorsAll material and fuel cyclelicenseesAll holders of OLs or CPsfor pressurized waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor nuclear power reactors96-2996-2896-2796-2696-25OL -Operating LicenseCP -Construction Permit