View source for PNO-V-88-031, on 880512,engineering Walkdowns of Pipe Whip Restraints Identified That Pressurizer Surge Line in Contact W/Upper Shim Pack of Pipe Whip Restraint 1.2.Possibly Caused by Difference Between Pressurizer & Hot Leg

{{Adams
| number = ML20154C732
| issue date = 05/12/1988
| title = PNO-V-88-031:on 880512,engineering Walkdowns of Pipe Whip Restraints Identified That Pressurizer Surge Line in Contact W/Upper Shim Pack of Pipe Whip Restraint 1.2.Possibly Caused by Difference Between Pressurizer & Hot Leg
| author name = Barr R, Mendonca M
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION V)
| addressee name = 
| addressee affiliation = 
| docket = 05000344
| license number = 
| contact person = 
| document report number = PNO-V-88-031, PNO-V-88-31, NUDOCS 8805180285
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 1
}}
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I PRinL{MINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-88-31 MN                 M Date 05/12/88 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information presented is as initially received eith u t verification or evaluation and is basically all that is known by Region V staff on this date.
FACILITY: PORTLAND GENERAL ELECTRIC COMPANY             Emergency Classification TROJAN                                         Notification of Unusual Event DOCKET NO. 50-344                              Alert PRESCOTT, OREGON                               Site Area Emergency General Emergency XX Not Applicable

==SUBJECT:==
UNEXPECTED PRESSURIZER SURGE LINE PIPE D:SPLACEMENT Uith the plant in Mode 6 and the Reactor Coolant System (RCS) temperature at approximately 80 F, engineering walkdowns of pipe whip restraints identified that the pressurizer surge line was in contact with the upper shim pack of pipe whip restraint 1.2.        The inspection of pipe whip restraints was a result of the licensee's long term action plan in response to pipe support problems identified in the 1987 refueling outage. No pipe contact was observed for the seven other restraints on the surge line. The licensee determined that 4771 pounds force was required to push the pipe off the contact point. After the removal of two shims from the pipe whip restraints 1.2 upper shim pack, the pipe moved 3/8 of an inch in the upward direction. The design cold gap was 9/16 of an inch. Inspection of the "B" RCS loop hot leg pipe whip restraint and steam generator upper and lower support ring revealed no other pipe movement outside expected ranges.
The licensee has developed an action plan to assess the cause, significance, and corrective actions for this event. One of the potential causes being investigated is thermal stratification in the surge line during heatup, particularly when a bubble is being formed in the pressurizer. At that time, a temperature difference in excess of 300 F exists between the pressurizer and the RCS hot leg. The possibility of thermal stratification was apparently not considered in the NSSS piping analysis. The licensee indicated that Westinghouse, the NSSS supplier, has previously identified the issue of thermal stratification and discussed this with the hRC staff. As part of its action plan, the licensee will make a determination as to the continued operability of the surge line, will make changes to piping supports as appropriate, and has plans to implement a monitoring program for temperature and deflection data for the surge line.
Problems with RCS thermal expansion at Trojan were encountered in 1986. Review of these problems concluded that the RCS had been overrestrained. Adjustments were made to the RCS restraints and an ongoing tronitoring program was implemented. Licensee actions will be followed by the resident inspectors, Region V, and NRR. The licensee's current schedule shows unit startup from the refueling outage on June 1.
This information is current as of 9:30 am (PST), May 12, 1988.
CONTACT:    M. Mendonca                    R. Barr FTS 463-3720                   503-556-3751 DISTRIBUTION BY 5520:                                      FAX T0:
Date d A Time /.n                                    Date r/mTime r. /[
Chairman Zech          EDO      RI                    INP0 Comm. Roberts         AE00      RII                  NSAC Comm. Bernthal         PA0      RIII                 LICENSEE Comm. Carr            SLITP     RIV                  RESIDENT INSPECTOR Comm. Rogers          NRR       GPA                  HQS. OPERATIONS OFFICER SECY                   NMSS     ACRS CA                    ARM       RES                  MAIL T0:                                     #
POR                    01       OIA                  va (Uriginal)                                    1 8805180285 880512                               DOT:(Trans. Only, Applicable State)           l PDR    I&E PNO-V-G8-031         ECD RV FORM 211 Revised: 8/19/87
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