United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-92: Pressurizer Safety Valve Reliability

                                                            SSINS No.:  6835
                                                            IN 86-92 

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                              November 4, 1986



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


This notice is provided to inform recipients of potentially significant 
problems pertaining to the reliability of pressurizer safety valves. It is 
expected that recipients will review the information for applicability to 
their facilities and consider actions, if appropriate, to preclude a similar 
problem from occurring at their facilities. However, suggestions contained 
in this information notice do not constitute NRC requirements; therefore, no
specific action or written response is required. 

Description of Circumstances: 

St. Lucie 2: 

On April 17, 1986 while shut down for refueling, St. Lucie 2 personnel bench
tested three pressurizer safety valves that have a technical specification 
(TS) set point of 2515 <+/-> 1% psig. Valve V-1200 lifted at 2554 psig (14 
psi above the maximum TS set point, valve V-1201 lifted at 2893 psig (353 
psi above the maximum TS set point), and valve V-1202 was leaking too much 
to test. The problem with V-1201 was attributed to a hole in the bellows 
which allowed boric acid to contaminate and corrode the valve internals 
causing them to bind. The seat of V-1202 was badly steam cut. The minor set 
point drift of V-1200 was considered normal for 18 months operation. All 
valves were repaired before replacing them in service. 

McGuire 1: 

On September 2, 1986, McGuire 1 reported that a pressurizer safety valve had
lifted at 2375 psig, 85 psi below the 2485 <+/-> 1% TS required set point. 
The primary system depressurized to 1800 psig before the valve fully closed.
This event occurred during pressurization for an inservice leak test. During
subsequent bench testing of that valve, the as-found set point was 
determined to be 2320 psig. Analysis showed that the three lifts used to 
determine the valve set point at the last test were trending downward. 
Cocking of the spring, probably because of debris under the spring or a 
burr, was considered to be the cause of the set point "drift." When the 
spring was properly seated, the set point stabilized. 


                                                       IN 86-92 
                                                       November 4, 1986 
                                                       Page 2 of 2 

The low pressure at which the valve reclosed is attributed by the licensee 
to the setting of the blowdown adjusting ring, which deviated from the 
vendor's recommended setting by 137 notches. The remaining pressurizer 
safety valves on unit 1 were inspected and one other had misadjusted ring 
settings. The misadjustment was attributed to on-site readjustment by 
maintenance personnel. The correctly set rings on the third valve were set 
by the vendor's representative. Unit 1 valves will be repaired and reset. 

Unit 2 had two pressurizer safety valves set by the vendor's representative 
and one set by plant maintenance personnel. The plant technician had 
recorded the ring settings, which were the same as the vendor's 
recommendation. Therefore, Unit 2 valves were determined to be operable. 

Arkansas Nuclear One, Unit 2: 

On September 15, 1986 while at 29% power, ANO 2 experienced a spurious 
openng and rapid reseating of two pressurizer safety valves, which resulted 
in an increase in level and pressure in the quench tank and a 4 psig drop in 
reactor coolant pressure. On September 25, 1986 following a reactor trip, 
quench tank parameters and tail pipe temperatures indicated that one or both
pressurizer safety valves had lifted. Licensee tests showed that the 
setpoints of the valves were lower than the TS required 2485 psig <+/-> 1%. 
One valve lifted at 2365 psig and the other between 2430 and 2455 psig. It 
was determined that the wrong test equipment had been used to set the lift 
pressure of the valves at the outage prior to these events. The valve 
manufacturer sent a representative to the site with the correct equipment. 
The valves have been correctly reset. 

A search of licensee event reports from January 1, 1983 to the present shows
that 20 other events involving 32 valves occurred. The problems were: 18 
valves with set point drift, 12 valves with seat leakage, 1 valve with set 
pressure high and 1 valve designated as inoperable. Attachment 1 contains 
the details of this compilation. Other information on the subject of safety 
valve performance and reliability may be found in information notices 86-05; 
86-05, Supplement 1; and 86-56, the subject of which are main steam safety 

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, IE 
                    (301) 492-4511 

1.   Other Pressurizer Safety Valve Problems 
2.   List of Recently Issued IE Information Notices

                                                       Attachment 1 
                                                       IN 86-92 
                                                       Page 1 of 1 


             PLANT                 NO. VALVES

          SEQUOYAH 1                    1

          SALEM 2                       3 
          SALEM 1                       3 
          MILLSTONE 2                   1 
          SEQUOYAH 2                    1 
          SEQUOYAH 2                    1
          BEAVER VALLEY 1               1 
          SUMMER                        1
          SEQUOYAH 2                    1

          CALVERT CLIFFS 2              1 
          BEAVER VALLEY 1               1

          FT CALHOUN                    1 
          SALEM 2                       3 
          SALEM 1                       3 
          MILLSTONE 2                   1 
          PALISADES                     1 
          SUMMER                        1 
          YANKEE-ROWE                   1 

          ANO 1                         1 
          SEQUOYAH 1                    1 
          SEQUOYAH 2                    3 

          YANKEE-ROWE                   1

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