United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 82-16: HPCI/RCIC High Steam Flow Setpoints

                                                            SSINS No.: 6835 
                                                            IN 82-16 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                                May 28, 1982 

Information Notice No. 82-16:   HPCI/RCIC HIGH STEAM FLOW SETPOINTS 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided as an early notification of a 
potentially significant problem pertaining to incorrect setpoint values for 
isolation of the high pressure coolant injection system and reactor core 
isolation cooling system used in boiling water reactors. It is expected that 
recipients will review the information for applicability to their 
facilities. No specific action or response is required. 

Description of Circumstances: 

On February 11, 1982, Power Authority of the State of New York (PASNY), 
licensee of the J. A. FitzPatrick (JAFP) plant, reported finding incorrect 
steam flow high differential pressure settings on the high pressure coolant 
injection (HPCI) system. The high steam flow trip is provided to detect, a 
break in the HPCI steam supply line and initiate closure of the steam supply
isolation valves. A similar feature exists in the reactor core isolation 
cooling (RCIC) system. 

The high steam flow setpoints are normally derived by design calculations 
(performed by GE) and confirmed or revised based on start up testing at the 
individual BWR facilities. According to GE, the design calculated setpoints 
are normally stated in the Final Safety Analysis Report (FSAR). After 
obtaining the startup steam flow data, the appropriate setpoints should be 
determined and the FSAR should be amended with the revised information. The 
setpoints are typically established at 300 percent of measured rated steam 
flow. 

Individual plant high steam flow setpoint values are determined based on 
data obtained by measuring the differential pressure (dp) across the HPCI 
(or RCIC) steam line elbow tap during rated steam flow conditions. The 
measured dp is then multiplied by an appropriate factor corresponding to 300 
percent flow and adjusted to account for possible instrument inaccuracies. 
The setpoint values are directly dependent on the exact configuration of the
elbow tap holes and associated instrumentation. It is for this reason that 
the setpoint values are not accurately predictable in all cases and must be 
established by actual testing. At JAFP plant, the design calculated setpoint
was 230 inches of water differential. However, the initial 230-inch setpoint
and the actual high differential pressure settings were not revised to 
reflect the measured 

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                                                           IN 82-16 
                                                           May 28, 1982  
                                                           Page 2 of 2 

data. The licensee's corrective action included measuring rated steam flow 
differential pressures and reestablishing appropriate settings during 
startup from the recent refueling outage. 

Although the JAFP high differential pressure settings were nonconservative, 
some diverse protection was provided by isolation signals on low steam line 
pressure and high ambient and/or delta temperatures. On the other hand, 
lowering the setpoints increases the likelihood of spurious isolation trips 
that result from pressure transients associated with quick starts of the 
system. At some BWRs, such spurious isolation are a significant concern 
because they occur often, reducing the reliability of the HPCI to operate on
demand. Spurious isolation are believed to result from various causes (such 
as condensation in the instrument lines, an effect which may be aggravated 
by the orientation of the taps on the elbow). To overcome the effects of 
pressure transients and setpoint drifts initiating spurious isolation, some 
BWRs have incorporated time delays in this instrumentation system by use of 
orifice snubbers and/or electronic timers. 

General Electric recommended that its customers review the startup test data
to verify that the FSAR-defined HPCI and RCIC steam flow setpoints are 
consistent with startup data. Where any setpoint values are found to be 
inconsistent, action should be taken to correct the discrepancy. Regarding 
this recommendation at this time, we would caution that any setpoint changes
and related testing should include consideration of the potential problem of
spurious isolation. Such consideration should include an awareness of Item 
II. K.3.15 of NUREG 0737, "Clarification of TMI Action Plan Requirements," 
that describes requirements on modifications of steam supply line break 
detection logic to prevent spurious isolation of HPCI and RCIC. In this 
regard, consideration should be given to including an electronic time delay 
in the high steam flow instrumentation system to decrease the chance of 
spurious isolation. (A time delay of 3 seconds was recommended by GE and 
included in the INPO/NSAC Significant Operating Experience Report 81-13 on 
HPCI/RCIb malfunctions.) 

No written response to this information is required. If you need additional 
information regarding this matter, please contact the Regional Administrator
of the appropriate NRC Regional Office. 



                                   Edward L. Jordan, Director 
                                   Division of Engineering and  
                                     Quality Assurance 
                                   Office of Inspection and Enforcement 

Technical Contact:  C. J. DeBevec 
                    301-492-4870 

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