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
From:	Jordan E NRC/IE
To:
References
IN-86-068, NUDOCS 8608130205
Download: ML031250095 (3)

SSINS No.: 6835 IN 86-68 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 August 15, 1986 IE INFORMATION NOTICE NO. 86-68: STUCK CONTROL ROD

Addressees

All boiling water reactor facilities holding an operating license or a

construction permit.

Purpose

This notice alerts addressees to the potential for a stuck control rod and

damaged control rod drive as a result of closed manual isolation valves on the

hydraulic control unit. Recipients are expected to review the information for

applicability to their facilities and consider actions, if appropriate, to

preclude similar problems occurring at their facilities. However, suggestions

contained 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 were

unsuccessful.

Investigation revealed that the 112 valve (scram discharge riser manual isolation)

on the hydraulic control unit was in the closed position despite verification

that the valve was in the proper (open) position. The closed 112 valve caused

a very high pressure to develop in the control rod drive, crushing the cylinder

tube. Because the surface area above the piston is smaller than that below the

piston, a closed 112 valve can cause pressures above the piston to be several

times as large as the 1850 psi applied at the bottom of the piston by the scrm

accumulators. The above-the-piston water surrounds the cylinder and can partially

crush the cylinder. The crushed cylinder tube caused interference with the

movement of the piston and thus the stuck rod.

Subsequent unsuccessful attempts were made to insert the partially withdrawn

control rod into its drive by removing temporary blade guide assemblies and

applying force from above with a specially constructed tool. The rod was

ultimately removed by cutting the index tube into two pieces and removing. it

from the drained reactor vessel.

if_., -eff C

IN 86-68 August 15, 1986 The licensee has adopted a number of corrective measures. The manual isolation

valves 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 management

personnel make additional random checks.

Discussion:

Although not always causing damage to the control rod drive as occurred at

Clinton, there have been several instances of manual isolation valves on the

hydraulic control units causing failure to scram of individual control rods.

Among the other instances when problems with the manual isolation valves on the

hydraulic control unit have prevented a rod from scraming are:

Date Plant Event-Failure to Scram One Rod

October 20, 1984 Dresden Unit 3 Manual isolation valve disc

separated from valve stem

October 24, 1984 Quad Cities Unit 2 Scram inlet isolation valve closed

April 11, 1985 Perry Inadvertently closed 112 valve -

CRDM damaged, index tube cut to

remove

There are other valves on the hydraulic control unit that could prevent a scram

or cause damage to the control rod drive mechanism. Some of these valves could

be discovered by problems with normal rod movement before a scram. However, a

closed 112 valve does not cause problems with normal rod movement. Because

larger pressures are applied to the control rod drive during the scram, damage

caused by closed valves on the hydraulic control unit is most likely to occur

during 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, Director

Divisi of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Eric Weiss, IE

(301) 492-9005 Attachment: List of Recently Issued IE Information Notices

Attachment 1 IN 86-68 August 15, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-67 Portable Moisture/Density 8/15/86 All NRC licensees

Gauges: Recent Incidents And authorized to possess, Common Violations Of Require- use, transport, and

ments For Use, Transportation, store sealed sources

And Storage

86-66 Potential For Failure Of 8/15/86 All power reactor

Replacement AC Coils Supplied facilities holding

By The Westinghouse Electric an OL or CP

Corporation For Use In Class

lE Motor Starters And

Contractors

86-65 Malfunctions Of ITT Barton 8/14/86 All power reactor

Model 580 Series Switches facilities holding

During Requalification Testing an OL or CP

86-64 Deficiencies In Upgrade 8/14/86 All power reactor

Programs For Plant Emergency facilities holding

Operating Procedures an OL or CP

86-63 Loss Of Safety Injection 8/6/86 All PWR facilities

Capability holding an OL or CP

86-62 Potential Problems In West- 7/31/86 All power reactor

inghouse Molded Case Circuit facilities holding

Breakers Equipped With A an OL or CP

Shunt Trip

86-61 Failure Of Auxiliary Feed- 7/28/86 All power reactor

water Manual Isolated Valve facilities holding

a CP

86-60 Unanalyzed Post-LOCA Release 7/28/86 All power reactor

Paths facilities holding

an OL or CP

86-31 Unauthorized Transfer And 7/14/86 All NRC general

Sup. 1 Loss Of Control Of Industrial licensees that possess

Nuclear Gauges and use industrial

nuclear gauges

OL = Operating License

CP = Construction Permit