Information Notice 1994-89, Equipment Failures at Irradiator Facilities

Equipment Failures at Irradiator Facilities

ML031210550
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/28/1994
From:	Paperiello C J NRC/NMSS/IMNS
To:
References
IN-94-089, NUDOCS 9412210186
Download: ML031210550 (9)

-/UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDSWASHINGTON, D.C. 20555December 28, 1994NRC INFORMATION NOTICE 94-89: EQUIPMENT FAILURES AT IRRADIATOR FACILITIES

Addressees

All U.S. Nuclear Regulatory Commission irradiator licensees.PurRoseThe U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to several equipment failures -- some of which havegeneric implications -- that involve wet source storage irradiators. It isexpected that all recipients (including dry source storage irradiatorlicensees) will review the information for applicability to their facilitiesand consider actions, as appropriate, to avoid similar problems. However,suggestions contained in this information notice are not new NRC requirements;therefore, no specific action or written response is required.Descrition of CircumstancesThe first equipment failure involved the time delay system required in 10 CFR36.23(f). The second equipment failure involved two incidents where thecontrol console provided false indications of irradiator condition. The finalequipment failure involved a source rack that failed to return to its shieldedposition after the comnand was initiated at the control console.1. Fault in the Operational Time Delay Reset Power Supply.In this incident, a fault in the control console circuitry occurred at alicensee's facility when an external electrical power surge caused a fuse toblow in the operational time delay reset power supply. This circuit had beenrecently installed to meet the requirements of 10 CFR Part 36. Theoperational time delay circuit prevents the control console from activatingfor a preset time after being initiated by the operator in the irradiationroom, thereby preventing source rack movement per 10 CFR 36.23(f). Inaddition, the operational time delay circuit of this irradiator must beoperational for the audible and visual warning circuit and the door interlockcircuit to function properly. The audible and visual warning systems aredesigned to activate whenever the irradiator door is opened and sourcemovement is initiated. Nevertheless, the audible and visual warning systemsdid not activate when the operator left the irradiation room, until thecontrol console was turned 0ON6 with the console key. The planned irradiationwas performed, however, since the audible warning system did activate beforeirradiation, per the requirement In 10 CFR 36.31(a).9412210186 PDR ZV > cL(~ (l4eX am t31195 IN 94-89December 28, 1994 The operational time delay circuit was also designed to reset after anirradiation to prevent the control console from being re-energized andallowing additional source movement. The control console should not re-energize until the circuit is again initiated by the operator In theirradiation room. However, in this incident, the control console was able tobe re-energized before the time delay circuit was initiated. The blown fusein the reset power supply prevented the time delay circuit from resetting asdesigned.To prevent reoccurrence, a surge protector was installed to protect the entiresystem from external power surges, and the time delay circuit was redesignedto disable the control console, audio and visual safety circuits, and thesource positioning system, in case the fuse blows again. This alerts theoperator to a fault and prevents source movement until the fuse is replaced.2. False Indications of Source Rack Position.A false indication of source rack position (rack not in the fully downposition) was received at the control console of a wet source storage licenseewhen the wire that carries the source position signal shorted because of worninsulation. Vibration in the system caused the wire to rub against nearbymetal and wore away the insulation. The short-circuit also caused an initialintermittent false indication of a collision between the source rack and thecarrier. The licensee verified that the sources were in the shielded positionand traced the fault to the damaged wire. The wire was replaced and reroutedthrough a flexible conduit to reduce the possibility of additional wear.A second false indication of source rack position occurred at the samefacility when the plunger of a source rack down-position switch failed toextend and thereby did not properly indicate the true position of the sourcerack. The plunger failed to extend because of corrosion between the plungerand sleeve causing increased friction. The irradiator licensee receivedconflicting signals when the lower position switch indicated that the sourcerack was not fully down, but the upper position switch Indicated that thesource rack was fully down. The installed radiation monitors and subsequentsurveys performed outside of the cell indicated that the source rack wasshielded. Further visual analysis confirmed that the source racks were in thefully shielded position.The licensee concluded that the lower source rack position switch wasmalfunctioning and replaced the switch. On further analysis of the switch, itwas determined that green corrosion deposits on the brass sleeve and steelplunger of the switch caused the plunger to stick in the retracted position,preventing it from springing back to the extended position. With the plungerin the retracted position, the switch indicates the source rack is not in thefully down position. The Irradiator vendor, Nordion International, Inc.(NII), was notified and has issued Service Bulletin IND-93-2, which isincluded as Attachment 1 to this information notice. Service Bulletin IND-93-2 advises all users of NIl pool type irradiators containing these plunger-typeposition indicators to check the switches for evidence of corrosion, clean theswitches if corrosion is found, and replace the switches as soon as possible.

IN 94-89December 28, 1994 In addition, NII has provided replacement switches constructed of corrosion-resistant materials (porcelain sleeve and stainless steel plunger) to allusers whose irradiators contain the non-corrosion-resistant switches, and hasprovided instructions for installation and initial testing of the newswitches.3. Failure of Source Rack to Return to the Shielded Position.In this incident, a source rack at a licensee's facility failed to return tothe shielded position. This occurred when an air solenoid valve failed tofully return to the exhaust position and stuck in an intermediate positionthat blocked any air passage through the valve, thereby trapping air pressurein the line between the valve and source rack hoist. During a typicalirradiation, the licensee noted an irregular reading on the control console(not related to source rack position) and pressed the emergency stop button.The source rack position indication on the control console indicated that oneof the two irradiator source racks failed to return to the fully down/shieldedposition. The installed radiation monitors, the position of the source rackcable on the roof of the irradiator builcing, and subsequent radiation surveysperformed outside the Irradiation cell confirmed that one source rack hadremained in the up/unshielded position. Further investigation revealed thatpressure remained in the air line to the source rack hoist, keeping the rackin the exposed position, when this pressure should have been released. Thelicensee cut the air line to release the pressure, and the source rackreturned to the fully down/shielded position. The licensee determined thatone or both of the air solenoid valves in the supply line failed to move tothe exhaust position when the source down command was initiated, thereby notlowering the source rack. Both valves were replaced and the source hoistsystem operated normally.The irradiator vendor, NII, was notified and both solenoid valves werereturned to NII for further investigation. NII determined that the solenoidvalves that were indicated to be four-way, two-position (exhaust/pressurize),five-port valves could in certain circumstances, operate as four-way, three-position (exhaust/pressurize/neutral), five-port valves. A two-position valvewould exhaust pressure in the air line to the source rack hoist upon loss ofsupply air pressure, regardless of valve position. The neutral position of athree-position valve would maintain pressure In the air line to the sourcerack hoist regardless of supply air pressure. Therefore, a three-positionvalve would not allow for a fail-safe operation. The circumstance thatallowed the valve to operate as a three-position valve was attributed to thedeterioration and hardening of the seals in the valve spool, causing the valvespool to stick in the neutral position. Nil's investigation showed that itis unlikely that the ingress of contaminants caused the valve spool to stickin the 'neutral position. However, NII did not rule that out as acontributing factor. According to NII, harding of the seals is thought to becaused by oxidation over time of the seal material. One of the spools, in usefor over 5 years, showed considerable hardening of the seal material, whereasthe seals of the other spool, in use for only 14 months, had become hardened,but not as hard as the first valve's seals.

...jIN 94-89December 28, 1994 As a result of this incident, NII issued Service Bulletin IND-94-1, which isincluded as Attachment 2 to this information notice. To preclude futurefailures of this nature, NlI recommends that Norgren part 54237-56 valvespools no longer be used in Norgren Nugget 200 Series Source Hoist Valves,part K71EAOO KSI AECKGI, and that Norgren part 54237-58 spools be used asreplacement spools in existing and all new valves of this type used in NIIpool type irradiators.The 54237-58 spools allow for the exhaust of air in all positions, thuseliminating the possibility of pressure remaining in the air line to thesource rack hoist on removal of supply air pressure. In addition, NIIrecommended in their report to the licensee, that the spools be replacedperiodically to reduce the possibility of additional failures because of sealhardening. NII's investigation revealed that detectable hardening of the sealmaterial has occurred, in at least one case, within 14 months of use.However, the valve in that case continued to operate without failure.In addition, NII reports that licensees who have ordered replacement valvesfor the original installed valves (part K71EAOO KSI AECKGI), may have receivedreplacement valves labeled with Norgren's off-the-shelfl part numbers.Therefore, Norgren Nugget 200 Series Source Hoist Valves with part numbersK71EAOO KS6 KQI, K71EAOO KS6 AECKGI, and any other variants of the K71EAOOvalves used for these operations should have their valve spools replaced also.NII asserts that the construction and operation of these valves are identicalto the K71EAOO KSI AECKGI valves.Discussion:The failures of the audible and visual warning systems and operational timedelay to initiate properly were caused by a blown fuse in the operational timedelay reset power supply, failing to cause the timer to reset. This allowedthe control console to be energized and source movement to occur before theoperational time delay being re-initiated, contrary to Part 36 requirements.The redesigned circuit prevents this situation from occurring by not allowingthe control console to re-energize if this fuse blows again. The controlconsole is designed such that source movement cannot occur unless the controlconsole is energized. Irradiator users should evaluate all possible failuremodes of source positioning control circuitry and interlocks, or circuitrythat supports these systems, upon installation and whenever modifications aremade.The worn insulation that caused the short in the source rack positionindication circuit did not cause a situation in which the source racks were inthe exposed position unintentionally. However, the licensee was required tobypass safety interlocks (using appropriate safety measures) to verify thetrue position of the source rack. Users should be aware of and takeprecautions against conditions (e.g., wear caused by vibration, excessiveheat, embrittlement caused by high radiation, etc.) which could cause thefailure of essential electrical components and indicators.

IN 94-89December 28, 1994 Users of NII pool-type irradiators containing source down-position indicationswitches constructed of non-corrosion-resistant materials should be aware thatif the recommendations contained in NII Service Bulletin IND-93-2 are notfollowed, the potential for false or conflicting source rack position signalsexists. If a false signal is received, the operator may be required to bypasssafety interlocks (using appropriate safety measures) to verify the trueposition of the source rack.The most likely cause of the corrosion was the close proximity of the switchto the water line and high humidity in the irradiation room. To date, NII isnot aware of any indications of corrosion developing in the upper sourceposition switch, which is constructed using materials similar to the originalbottom source down-position switches. The upper switch is located away fromthe water line and is exposed to higher temperatures and lower humidity whenthe source rack is in the raised/exposed position. However, if conditionsexist in the area around the upper switch that are favorable to corrosion(e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type irradiators containing Norgren part 54237-56 valvespools used in Norgren Nugget 200 Series Source Hoist Valves, part K71EAOO,should be aware that if they do not follow the NII recommendation to replacethe 54237-56 spools with 54237-58 spools, the source racks may become stuck inthe exposed position. Licensees may have to cut the air line to the sourcerack hoist to return the source rack to the shielded position. In addition,the licensees should consider NII's recommendation that the spools be replacedon a periodic basis to reduce the possibility of failure, according to theirspecific operation. If not replaced, the replacement valve spools could failbecause of seal material hardening, although such failure would not causepressure to remain trapped in the air line.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate regional office.Carl J. perie o, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Materials Safetyand SafeguardsTechnical contact: Douglas Broaddus, NKSS(301) 415-5847Attachments:1. Nordion International Inc., Service Bulletin IND-93-22. Nordion International Inc., Service Bulletin IND-94-13. List of Recently issued NMSS Information Notices4. List of Recently issued NRC Information Notices

<_4 _ 94-89December 28, 1994 Users of NII pool-type irradiators containing source down-position indication switchesconstructed of non-corrosion-resistant materials should be aware that if therecommendations contained in NII Service Bulletin IND-93-2 are not followed, thepotential for false or conflicting source rack position signals exists. If a falsesignal is received, the operator may be required to bypass safety interlocks (usingappropriate safety measures) to verify the true position of the source rack.The most likely cause of the corrosion was the close proximity of the switch to thewater line and high humidity in the irradiation room. To date, NII is not aware of anyindications of corrosion developing in the upper source position switch, which isconstructed using materials similar to the original bottom source down-positionswitches. The upper switch is located away from the water line and is exposed to highertemperatures and lower humidity when the source rack is in the raised/exposed position.However, if conditions exist in the area around the upper switch that are favorable tocorrosion (e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type irradiators containing Norgren part 54237-56 valve spools used inNorgren Nugget 200 Series Source Hoist Valves, part K71EA00, should be aware that ifthey do not follow the NII recommendation to replace the 54237-56 spools with 54237-58spools, the source racks may become stuck in the exposed position. Licensees may haveto cut the air line to the source rack hoist to return the source rack to the shieldedposition. In addition, the licensees should consider Nil's recommendation that thespools be replaced on a periodic basis to reduce the possibility of failure, accordingto their specific operation. If not replaced, the replacement valve spools could failbecause of seal material hardening, although such failure would not cause pressure toremain trapped in the air line.This information notice requires no specific action or written response. If you haveany questions about the information in this notice, please contact the technical contactlisted below or the appropriate regional office.Carl J. Paperiello, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Materials Safetyand SafeguardsTechnical contact: Douglas Broaddus, NMSS(301) 415-5847Attachments:1. Nordion International Inc., Service Bulletin IND-93-22. Nordion International Inc., Service Bulletin IND-94-13. List of Recently issued NMSS Information Notices4. List of Recently issued NRC Information NoticesDOCUMENT MANE: 94-89.INTechnical Editor*EKraus11/16/94 *See previous concurrencecop without at L. 6* WM attachs t L. BE- a Co p1* ous 'on cOFC IMOB* IMOB* SCDB* lKE INS IKANE KRamsey/l GPangburn FCombs RBaer MFederline EBrach CPa p 110DATE 11/15/94 11/29/94 11/30/94 12/09/94 12/09/94 Not In 124l1V9= _ _ _ _ _ _ FLRoffice j

~'IN 94-~ December , 1994 Users of NII pool-type irradiators containing source down-position indicationAiltdas. constructed of non-corrosion-resistant materials should be aware thatif the recommendations contained In NII Service Bulletin IND-93-2 are notfollowed, the potmntial for false or conflicting source rack position signalsexists.- IfMa false signal Is received, the operator may be required to bypasssafety interlocks (using appropriate safety measures) to verify the trueposition of the source racukThe most likely cause of the corrosion was the close proximity of the switchto the water line and high humidity In the irradiation room. To date, NII isnot aware of any Indicattons of.corrosion developing in the upper sourceposition switch, which Is constructed using Oateri as similar to the originalbottom source down-position switches. The upper switch is located away fromthe water line and Is exposed to higher toWperatures and lower humidity whenthe source rack Is in the raised/exposed position. However, if conditionsexist in the area around the upper switch that are favorable to corrosion(e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type irradiators containing Norgren part 54237-56 valvespools used In Norgren Nugget 200 Series Source Hoist Valves, part K71EA00,should be aware that if they do not follow the NII recommendation to replacethe 54237-56 spools with 54237-58 spools, the source racks may become stuck inthe exposed position. Licensees may have to cut the air line to the sourcerack hoist to return the source rack to the shielded position. In addition,the licensees should consider NII s recommendation that the spools be replacedon a periodic basis to reduce the possibility of failure, according to theirspecific operation. If not replaced, the replacement valve spools could failbecause of seal material hardening, although such failure would not causepressure to remain trapped In the air line.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice please contactthe technical contact listed below or the appropriate reglonal office.Carl J. Paperiello, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Materials Safetyand SafeguardsContact: Douglas Broaddus, NMSS(301) 415-5847Attachments:1. Nordion International Inc., Service Bulletin IND-93-22. Nordion International Inc., Service Bulletin IND-94-13. List of Recently issued NMSS Information Notices4. List of Recently issued NRC Information NoticesDOCUMENT NAME: G:IM-IRRAD.KNRTechnical Editor*EKraus11/16/94 *See previous concurrencewithout t GP With, tt tu. upt

• U _ ___OFC J IMOB* SCW .M lM"+)KANE KRamsey/ll GPangburn FCombs RBaer NFederline c C'peuelloDATE 11/15/94 11/29/94 11/30/94 129/94 1209/94V94 94^ -OFFI:'CIAL RECOR COP

IN 94-November , 1994 aware of any Is4kcations of corrosion developing in the upper source positionswitch, whicd is coestructed using materials similar to the original bottomsource do"w#mpositls switches. The upper switch Is located away from the waterline and Is exposed to higher taperatures and lower humidity when the sourcerack is In the ralse/Uxposed position. However, if conditions exist In the areaaround the upper switch that are vorable to corrosion (e.g., high humidity ora caustic atmosphere), this switc could corrode also.Users of KIU pool-type irradiato containing Norgren part # 54237-56 valvespools used I. Korgren Nugget 200 rios Source Hoist Valves, part # K71EAOO,should be aware that If they do not fllow the NII recommendation to replace the54237-S6 spools with 5423748 spo4ls, the source racks may become stuck In theexposed position. Licensees may hav to cut the air line to the source rackhoist to return the source rack to shielded position. In addition, thelicensees should consider NII's recoe ation that the spools be replaced on aperiodic basis to reduce the possibility of failure, according to their specificoperation. If not replaced, the replace nt valve spools could fail because ofseal material hardening, although such fa ure would not cause pressure to remaintrapped In the air line.This information notice requires no specifi action or written response. If youhave any questions about the information n this notice, please contact thetechnical contact listed below or the appro Wate regional office.Carl J. periello, DirectorDivision f Industrial and* Medical uclear SafetyOffice of uclear Materials Safety andSafeguaContact: Douglas Broaddus, NKSS(301) 415-5847Attachments:1. Nordion International Inc., Service Bulleti IND-93-22. Nordion International Inc., Service Bulletin IND-94-13. List of Recently issued NISS Information Hoti es4. List of Recently issued NRC Information Notic sDISTRIBUTION:\INOB r/f SCOB r/f iNKS r/fDOCIMENT NAME: G:IN-RRAD.KN\Technical Editor*EKraus11/16/94 ,mc'. Caov ulthout attedaclMmtc. -V a Caw wifth mttclumVc.qCuu _U_______-!gOFC IM I IO M0BEI l -_ I I S INNS IINANE IKRUSseYIll 6Pnbr cobS , K\ E~aCh Pe110-ngur k t _ -.drC~peielDAE 11/15/94 11/29/94 I~D AT E I 9 li994 1 1 194 -/q/ 1 I 1 I IOFFICM R ECOD COP

K>IN 94-November , 1994 aware of any indications of corrosion developing in the upper source pos itonswitch, which is constructed using materials similar to the original ottomsource down-position switches. The upper switch is located away from e waterline and is exposed to higher temperatures and lower humidity when e sourcerack is In the raised/exposed position. However, if conditions exis in the areaaround the upper switch that are favorable to corrosion (e.g., h humidity ora caustic atmosphere), this switch could corrode also.Users of NII pool-type irradiators containing Norgren par t 54237-56 valvespools used In Norgren Nugget 200 Series Source Hoist Va es, part t K71EA00,should be aware that if they do not follow the NII rec ation to replace the54237-56 spools with 54237-58 spools, the source racksay become stuck in theexposed position. Licensees may have to cut the ai line to the source rackhoist to return the source rack to the shielded p ition. In addition, thelicensees should consider NII's recommendation tha the spools be replaced on aperiodic basis to reduce the possibility of failure, in their specificapplication. If not replaced, the replacement alve spools could fail becauseof seal material hardening, although such fa ure would not cause pressure toremain trapped in the air line.This information notice requires no sped c action or written response. If youhave any questions about the informati in this notice, please contact thetechnical contact listed below or the ipproprate regional office.Carl J. Paperiello, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Materials Safety andSafeguardsContact: Douglas Broaddu , NMSS(301) 415-5847Attachments:1. Nordion Intern lonal Inc., Service Bulletin IND-93-22. Nordion Inte ational Inc., Service Bulletin IND-94-13. List of Rec tly Issued NHSS Information Notices4. List of Re ntly issued NRC Information NoticesDISTRIBMTON:/INOB r/f SCDB r IHNS r/fDOCUKENT NARE: 6: IRRAD.KKRTechnical EditoEKraus/ /IC/94%'On CpY WitMou sttaduasnwInc. 8E

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