Information Notice 2009-04, Age-Related Constant Support Degradation

Age-Related Constant Support Degradation

ML090340754
Person / Time
Issue date:	02/18/2009
From:	Mcginty T Division of Policy and Rulemaking
To:
Beaulieu, D P, NRR/DPR, 415-3243
References
IN 2009-04
Download: ML090340754 (4)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001 February 18, 2009 NRC INFORMATION NOTICE 2009-04: AGE-RELATED CONSTANT SUPPORT

DEGRADATION

ADDRESSEES

All holders of operating licenses or construction permits for nuclear power reactors, except

those who have permanently ceased operations and have certified that fuel has been

permanently removed from the reactor vessel.

PURPOSE

The Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to a possible age-related degradation of mechanical constant supports that may

adversely impact design stresses on piping systems. It is expected that recipients will review

the information for applicability to their facilities and consider actions, as appropriate, to avoid

similar problems. However, suggestions contained in this information notice are not NRC

requirements; therefore, no specific action or written response is required.

DESCRIPTION OF CIRCUMSTANCES

During the fourteenth refueling outage at the Palo Verde Nuclear Generating Station, Unit 2, Arizona Public Service (the licensee) tested four safety-related constant supports as part of an

investigation for failures on these components and associated beam attachments for these

supports. The testing performed by the licensee measured deviations in the supporting force of

between 8.7 and 13.3 percent. The allowable deviation of the supporting force, including

friction, specified in American Society of Mechanical Engineers (ASME)Section III, Division I,

Subsection NF, is 6 percent. The licensee and the vendor preliminarily concluded that

deviations in the supporting force resulted from wear on the linkages and increased friction

between the various moving parts and joints within the constant support. The wear on the

linkages may have been caused by cyclic loading or vibration, from the main steam lines. The

measured vibrations on the main steam lines were below the analyzed values of displacement

and velocity but were above the ASME OM-3 value of 0.5 inches per second.

The licensee conducted physical inspections and engineering evaluations to determine whether

any structural damage to the main steam piping had occurred. It did not identify any main

steam line piping operability concerns, although analyzed margins to ASME code allowable

stresses were reduced. The licensee subsequently restored these constant supports and

evaluated the effect on the steam generator nozzles with the measured deviations of supporting

force to ensure that ASME code limits were not exceeded.

BACKGROUND

Constant support hangers are designed to provide a substantially uniform supporting force for a

piping system throughout its full range of pipe movement. This is accomplished through the use

of a spring operating in conjunction with a lever, in such a way that the spring force times the

distance to the main lever pivot is always equal to and opposite of the pipe load times its

distance from the main pivot point (see illustration below). These constant support hangers

have been used to limit nozzle loads on pipes that experience large thermal variations from cold

conditions to normal operating conditions.

DISCUSSION

The licensee for Palo Verde does not routinely test these mechanical constant supports, and

these supports are not part of any routine preventive maintenance program. The vendor, ITT-

Grinnell (now Anvil), did not require any routine maintenance on these supports. The physical

condition of the constant supports is visually examined as required by the ASME Section XI,

Subsection IWF, which calls for inspecting a certain number of supports every outage. This

required visual inspection does not determine whether these supports exceed ASME code

allowable load deviation of 6 percent. Although there is no regulatory requirement to do so, licensees may wish to consider testing the constant supports (e.g., displacement testing while

measuring load) to identify constant supports that exceed the ASME code allowable load

deviation of 6 percent.

The licensee and the vendor have preliminarily determined that deviations in the supporting

force resulted from wear on the linkages and increased friction between the various moving

parts and joints within the constant support. This age-related degradation mechanism may

affect the supporting force provided by constant supports and can adversely affect the analyzed

stresses of connected piping systems.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

/RA/

Timothy J. McGinty, Director

Division of Policy and Rulemaking

Office of Nuclear Reactor Regulation

Technical Contacts: Jim Melfi, Region IV Gerond George, Region IV

623-386-3638 817-276-6562 E-mail: Jim.Melfi@nrc.gov E-mail: Gerond.George@nrc.gov

Alexander Tsirigotis, NRR

301-415-2258 E-mail: Alexander.Tsirigotis@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

/RA/

Timothy J. McGinty, Director

Division of Policy and Rulemaking

Office of Nuclear Reactor Regulation

Technical Contacts: Jim Melfi, Region IV Gerond George, Region IV

623-386-3638 817-276-6562 E-mail: Jim.Melfi@nrc.gov E-mail: Gerond.George@nrc.gov

Alexander Tsirigotis, NRR

301-415-2258 E-mail: Alexander.Tsirigotis@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

Distribution: IN Reading File Albert Wong

ADAMS Accession Number: ML090340754 OFFICE RIV:DRP TECH EDITOR EMCB:DE BC:EMCB:DE D:DE

NAME JMelfi KAzariah-Kribbs ATsirigotis KManoly PHiland

DATE 02/03/2009 email 02/11/2009 email 02/06/2009 02/12/2009 02/12/2009 OFFICE BC:RER2 PGCB:DPR PGCB:DPR BC:PGCB D:DPR

NAME RAuluck DBeaulieu CHawes MMurphy TMcGinty

DATE 02/17/2009 02/17/2009 02/18/2009 02/18/2009 02/18/2009 OFFICIAL RECORD COPY