Information Notice 1986-68, Stuck Control Rod

Stuck Control Rod

ML031250095
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	08/15/1986
Revision:	0
From:	Jordan E L NRC/IE
To:
References
IN-86-068, NUDOCS 8608130205
Download: ML031250095 (3)

SSINS No.: 6835IN 86-68UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555August 15, 1986IE INFORMATION NOTICE NO. 86-68: STUCK CONTROL ROD

Addressees

All boiling water reactor facilities holding an operating license or aconstruction permit.

Purpose

This notice alerts addressees to the potential for a stuck control rod anddamaged control rod drive as a result of closed manual isolation valves on thehydraulic control unit. Recipients are expected to review the information forapplicability to their facilities and consider actions, if appropriate, topreclude similar problems occurring at their facilities. However, suggestionscontained in this information notice do not constitute NRC requirements;\ therefore, no specific action or written response is required.

Description of Circumstances

During a full scram preoperational test (before fuel loading) on April 29, 1986,the Clinton nuclear power plant found that rod 08-25 was stuck at position 06.Attempts to move the rod by gradually increasing drive water pressure wereunsuccessful.Investigation revealed that the 112 valve (scram discharge riser manual isolation)on the hydraulic control unit was in the closed position despite verificationthat the valve was in the proper (open) position. The closed 112 valve causeda very high pressure to develop in the control rod drive, crushing the cylindertube. Because the surface area above the piston is smaller than that below thepiston, a closed 112 valve can cause pressures above the piston to be severaltimes as large as the 1850 psi applied at the bottom of the piston by the scrmaccumulators. The above-the-piston water surrounds the cylinder and can partiallycrush the cylinder. The crushed cylinder tube caused interference with themovement of the piston and thus the stuck rod.Subsequent unsuccessful attempts were made to insert the partially withdrawncontrol rod into its drive by removing temporary blade guide assemblies andapplying force from above with a specially constructed tool. The rod wasultimately removed by cutting the index tube into two pieces and removing. itfrom the drained reactor vessel.if_., -eff C IN 86-68August 15, 1986 The licensee has adopted a number of corrective measures. The manual isolationvalves are locked open once they are verified to be in the proper position.The personnel access control to the hydraulic control units has been tightened.In addition to the normal independent verification of valve position, the start-up organization has instituted a temporary measure of having managementpersonnel make additional random checks.Discussion:Although not always causing damage to the control rod drive as occurred atClinton, there have been several instances of manual isolation valves on thehydraulic control units causing failure to scram of individual control rods.Among the other instances when problems with the manual isolation valves on thehydraulic control unit have prevented a rod from scraming are:Date Plant Event-Failure to Scram One RodOctober 20, 1984 Dresden Unit 3 Manual isolation valve discseparated from valve stemOctober 24, 1984 Quad Cities Unit 2 Scram inlet isolation valve closedApril 11, 1985 Perry Inadvertently closed 112 valve -CRDM damaged, index tube cut toremoveThere are other valves on the hydraulic control unit that could prevent a scramor cause damage to the control rod drive mechanism. Some of these valves couldbe discovered by problems with normal rod movement before a scram. However, aclosed 112 valve does not cause problems with normal rod movement. Becauselarger pressures are applied to the control rod drive during the scram, damagecaused by closed valves on the hydraulic control unit is most likely to occurduring the scram.No specific action or written response is required by this information notice.If you have questions about this matter, please contact the Regional Adminis-trator of the appropriate NRC regional office or this office.ard Jordan, DirectorDivisi of Emergency Preparednessand Engineering ResponseOffice of Inspection and Enforcement

Technical Contact:

Eric Weiss, IE(301) 492-9005

Attachment:

List of Recently Issued IE Information Notices Attachment 1IN 86-68August 15, 1986LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to86-6786-6686-6586-6486-6386-6286-6186-6086-31Sup. 1Portable Moisture/Density 8/15/86Gauges: Recent Incidents AndCommon Violations Of Require-ments For Use, Transportation,And StoragePotential For Failure Of 8/15/86Replacement AC Coils SuppliedBy The Westinghouse ElectricCorporation For Use In ClasslE Motor Starters AndContractorsMalfunctions Of ITT Barton 8/14/86Model 580 Series SwitchesDuring Requalification TestingDeficiencies In Upgrade 8/14/86Programs For Plant EmergencyOperating ProceduresLoss Of Safety Injection 8/6/86CapabilityPotential Problems In West- 7/31/86inghouse Molded Case CircuitBreakers Equipped With AShunt TripFailure Of Auxiliary Feed- 7/28/86water Manual Isolated ValveUnanalyzed Post-LOCA Release 7/28/86PathsUnauthorized Transfer And 7/14/86Loss Of Control Of IndustrialNuclear GaugesAll NRC licenseesauthorized to possess,use, transport, andstore sealed sourcesAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll PWR facilitiesholding an OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdinga CPAll power reactorfacilities holdingan OL or CPAll NRC generallicensees that possessand use industrialnuclear gaugesOL = Operating LicenseCP = Construction Permit