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)

L I S 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

Technical

Contact: James B. Henderson, IE (301) 492-9654 Attachment:

List of Recently Issued IE Information

Notices