Information Notice 1986-34, Improper Assembly, Material Selection, & Test of Valves & Their Actuators

Improper Assembly, Material Selection, & Test of Valves & Their Actuators

ML031250019
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, 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:	05/13/1986
From:	Jordan E NRC/IE
To:
References
IN-86-034, NUDOCS 8605090010
Download: ML031250019 (3)

LIS SSINS No.: 6835 IN 86-34 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 May 13, 1986 IE INFORMATION NOTICE NO. 86-34: IMPROPER ASSEMBLY, MATERIAL SELECTION,

AND TEST OF VALVES AND THEIR ACTUATORS

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This notice is being issued to advise recipients of potential problems resulting

from improper material selection and improper assembly procedures for

safety-related power actuated valves. This information is applicable to valves

at the time of initial installation and during post-maintenance reassembly or

test. Although both the cited facilities are BWRs, it appears that PWRs may be

equally vulnerable.

It is expected that recipients will review the information for applicability to

their facilities and consider actions, if appropriate, to determine if similar

problems exist at their facilities. However, suggestions contained in this

notice do not constitute NRC requirements; therefore, no specific action or

written response is required.

Description of Circumstances

In the recent past, River Bend and Shoreham have reported operational problems

and structural integrity problems with safety-related valves and their

actuators. Both BWR facilities are currently in the startup and initial

operational period and have reported significant problems with severe vibration

of components and systems. These vibrational problems appear to exacerbate but

not directly cause the identified valve problems.

At Shoreham on September 25, 1985, when a valve in the RHR system was being

operated from the control room, a response feedback signal was not received.

Local inspection disclosed that the bolts connecting the actuator to the valve

yoke were broken and the actuator was completely detached from the valve.

The valve was a relatively small "mini-flow" valve.

At River Bend on January 5, 1986, a similar event occurred involving a 20-inch

main feedwater system containment isolation valve.

8605090010

IN 86-34 May 13, 1986 (

Discussion:

Licensee evaluation efforts at River Bend disclosed that manufacturer's

instructions on actuator valve assembly were generally vague and sometimes the

information furnished by the actuator manufacturer was contradictory to that

supplied by the valve supplier. The 20-inch valve at River Bend has a Limitorque

SMB-4 actuator on a Velan valve. The mounting capscrews are 1-4inch diameter, high strength steel, threaded into the 35,000 psi strength cast iron actuator

housing. The valve manufacturer specified assembly torque of 1270 ft-lb. The

installed bolts did not have the normally specified 11/2 diameters thread engagement, and as part of the failure analysis, the licensee calculated that the preload

stress on the engaged cast iron threads would approximate the specified ultimate

strength of the cast iron. The failure which allowed the actuator to become

detached was the capscrews tearing out of the cast iron. Subsequently the

licensee, the valve supplier, and the actuator supplier agreed that a proper

installation torque for the valve-actuator combination would be 700 ft-lb.

During reassembly of the 20-inch valve at River Bend, the licensee discovered

that the mating flanges did not come together at the specified 700 ft-lb torque

value. Review of the actuator vendor installation and maintenance instructions

disclosed a caution that final assembly torque should be applied with the valve

stem at about midstroke. If the valve is closed, the bolt preload may be

transferred through the stem to the valve disc. When the valve is next opened, the bolts are relaxed and have low (or no) preload. Such a condition, particularly in the presence of high vibration, will cause early fatigue

failure of the bolts.

Examination and testing of other valve assemblies at these sites showed some

with very high torque levels and others where some of the capscrews were found

to be broken. The failures appeared to be caused by overload on some mild

steel, low strength bolts or fatigue for higher strength bolts. In some cases

it appears that bolting material specifications were missing or not adhered to.

Material traceability problems with bolts and other fastenings are discussed

in IE Information Notice 86-25, "Traceability and Material Control of Material

and Equipment, Particularly Fasteners." River Bend and Shoreham have established

specific programs to ensure that in the future proper bolts are used and are

properly torqued.

IN 86-34 May 13, 1986 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

94 Director

Divi n of Emergency Preparedness

an 'Engineering Response

Office of Inspection and Enforcement

James B. Henderson, IE

(301) 492-9654 Attachment: List of Recently Issued IE Information Notices