ML090340754 

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. 
IN 2009-04 

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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, ITTGrinnell (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. 
IN 2009-04 

Page 3 of 3 

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. 
IN 2009-04 

Page 3 of 3 

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