United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 96-22: Improper Equipment Settings due to the use of Nontemperature-Compensated Test Equipment

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR REACTOR REGULATION
                         WASHINGTON, D.C.  20555-0001

                                April 11, 1996


NRC INFORMATION NOTICE 96-22:  IMPROPER EQUIPMENT SETTINGS DUE TO THE USE OF   
                               NONTEMPERATURE-COMPENSATED TEST EQUIPMENT


Addressees

All holders of operating licenses or construction permits for nuclear power
reactors.

Purpose

The U. S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for improper calibration and
setting of safety-related equipment setpoints as a result of using
nontemperature-compensated measuring and test equipment.  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

On October 5, 1995, the licensee for the Farley Nuclear Plant determined that
nontemperature-compensated pressure gauges of various ranges and by different
manufacturers were in use at the plant.  An investigation revealed that these
gauges had been used for testing and calibration of safety-related equipment
without correcting the readings for temperature effects.  Nontemperature-
compensated gauges were used in testing and/or calibration of reactor trip
system transmitters, engineered safety features actuation system transmitters,
main steam safety valve lift settings, and pressure instruments used for
calorimetric calculations.  

The licensee conducted an evaluation of the use of nontemperature-compensated
pressure gauges in these applications.  After accounting for the additional
uncertainties associated with the gauges, the current safety analysis and
technical specification limits and nominal trip setpoints remained acceptable;
however, the calculated setpoint margins were reduced.

On February 10, 1995, during a refueling outage at the Surry Power Station,
Unit 2, the as-found calibration test data for the three safety-related
pressurizer pressure transmitters were not within the allowable tolerance.   
A root cause evaluation team determined that the error in the allowable
tolerance was caused, in part, by using a nontemperature-compensated pressure
gauge to calibrate each of the three transmitters after installation. 


9604050336.                                                            IN 96-22
                                                            April 11, 1996
                                                            Page 2 of 3


The transmitters provide pressurizer pressure input to the reactor trip system
and the engineered safety features actuation system.  An assessment of the
safety implications of these errors determined that Unit 2 had exceeded
Technical specification values and, therefore, margin was reduced.  However,
operation remained within design basis and safety analysis limits.  

Discussion

At both the Farley and Surry plants, the licensees used measuring and test
equipment in environments in which corrections for temperature should have
been made to ensure the accuracy of setpoints of safety-related equipment.
Specifically, at the Surry plant, the catalog of the pressure test gauge
vendor (HEISE) specifies that the nontemperature-compensated test gauge was
accurate to specified values at a reference calibration temperature of 
73 degrees F.  For a 3000-psig range HEISE gauge, environmental temperature
variances can cause up to a 3 psig error for each 5 degrees F change from the
reference temperature.

To maintain the accuracy of measuring and test equipment used in calibrating
safety-related devices, all factors, including the environmental temperature
at which the safety-related equipment will operate, are normally identified in
plant calibration procedures.  Also, there are several nuclear industry
references that provide guidance on proper methods of addressing environmental
effects on measuring and test equipment stored and used at nuclear plants. 

The Institute of Electrical and Electronic Engineers Standard 498-1975, "IEEE
Standard Supplementary Requirements for the Calibration and Control of
Measuring and Test Equipment Used in the Construction and Maintenance of
Nuclear Power Generating Stations," specifically addresses temperature
compensation of measuring and test equipment.  Section 3.2 of this document
titled "Environmental Controls" states, in part, that "measuring and test
equipment and reference standards shall be transported, stored and calibrated
in environments which will not adversely affect their accuracy.  Environmental
factors which shall be considered include, but shall not be limited to:
temperature, [and] humidity......When inaccuracy of measuring and test
equipment or reference standards, because of environmental effects, cannot be
avoided, compensating corrections shall be determined and applied." 

The Instrument Society of America's "Setpoints for Nuclear Safety Related
Instrumentation Used in Nuclear Power Plants," ISA-S67.04 (1982), has been
endorsed by the NRC in Regulatory Guide 1.105, "Instrument Setpoints for
Safety-Related Systems."  Section 7.3 of the standard states that "A system
shall be established to ensure the accuracy and adequacy of the test equipment
used to verify setpoints and tolerances of safety-related instrumentation." 
Test equipment accuracy directly affects setpoint calculations.  Among the
factors which affect the accuracy of measuring and test equipment is the
temperature at which a calibration is actually performed..                                                            IN 96-22
                                                            April 11, 1996
                                                            Page 3 of 3


This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
the technical contacts listed below or the appropriate Office of Nuclear
Reactor Regulation project manager.


                                          signed by

                                       Dennis M. Crutchfield, Director
                                       Division of Reactor Program Management
                                       Office of Nuclear Reactor Regulation

Technical contacts:  Morris W. Branch, RII
                     (804) 357-2101 
                     Internet:mxb2@nrc.gov

                     Stephen G. Tingen, NRR
                     (301) 415-1280
                     Internet:sgt@nrc.gov

                     S. V. Athavale, NRR
                     (301) 415-2974
                     Internet:sva1@nrc.gov
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