United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-05: Main Steam Safety Valve Test Failures and Ring Setting Adjustments

                                                            SSINS No: 6835 
                                                            IN 86-05       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, DC 20555

                              January 31, 1986

Information Notice No. NO 86-05:   MAIN STEAM SAFETY VALVE TEST FAILURES AND
                                   RING SETTING ADJUSTMENTS 

Addressees: 

All pressurized-water-reactor (PWR) facilities holding an operating license 
(OL) or a construction permit (CP) 

Purpose: 

This notice is being provided to alert recipients of a potentially 
significant problem pertaining to spring-actuated main steam safety valves 
that may possess less than the full-rated flow capacity It is expected that
recipients will review the information for applicability to their facilities
and consider actions, if appropriate, to preclude a similar problem at their
facilities However, suggestions contained in this information notice do not
constitute NRC requirements; therefore, no specific action or written 
response is required NRC is continuing to obtain and evaluate pertinent 
information If specific actions are determined to be required by NRC, an 
additional notification will be made 

Description of Circumstances: 

In the fall of 1984, Public Service of New Hampshire sent the main steam 
safety valves (MSSVs) for its Seabrook plant to Wyle Laboratories for 
full-flow testing to determine the proper vent stack size To determine full
flow, Wyle measured disc travel of the model number 6R1O valves manufactured
by the Crosby Valve and Gage Company The results of the tests indicated 
that the valves could not achieve the required disc travel with the 
factory-set ring setting (+155 notches) The disc travel achieved was 50% of 
the full lift necessary to develop required steam flow capacity Adequate 
lift was not attainable even with the largest diameter tailpipe 

Additional tests were done in July 1985 to determine the appropriateness of 
the ring settings Specifically, the tests were to determine if the 
"as-shipped" ring settings of the valves would allow the required disc 
travel with minimum tailpipe backpressure and to determine the effects on 
valve disc travel for a range of backpressures between 180 and 390 psig 
During these tests, the upper (guide) ring setting was adjusted from +155 to 
O and then to +25 to achieve the required disc travel This is a substantial 
adjustment Subsequently, the 



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                                                           IN 86-05        
                                                           January 31, 1986 
                                                           Page 2 of 2     

licensee consulted with the valve manufacturer and agreed on ring settings 
of +25 for the guide ring and -25 (the original setting) for the lower 
(nozzle) ring (see figure 1) 

Full flow, full size tests of the sort described in this notice are not 
normally performed by the licensee or valve vendor for large secondary 
safety valves, nor are they required by the ASME Code, Section III Instead 
the valves are certified by extrapolations on data from tests of smaller 
valves 

The MSSVs on most PWRs, while not necessarily the same model or manufacturer
as those at Seabrook, are generally at the upper end of the valve size 
range This raises the concern that full-sized flow demonstration may never 
have been performed for many MSSVs and these may have incorrect ring 
settings In addition, similar problems with ring settings have been found 
when full-size tests were performed for PWR primary safety valves Thus, 
these MSSVs may not be capable of providing full-relief capacity in 
accordance with facility design requirements 

NRC is continuing to obtain and evaluate pertinent information If specific 
actions are determined to be required by NRC, an additional notification 
will be made 

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 



                                   Edward L Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Mary S Wegner
                    (301) 492-4511

Attachments:
1   Figure 1, Typical Main Stream Safety Valve
2   List of Recently Issued IE Information Notices

Page Last Reviewed/Updated Tuesday, November 12, 2013