ML20235G965

SER Re Setpoint Methodology for Rosemont Replacement Transmitters.Licensee Proposed Methodology Not Adequate to Allow Approval to Be Used in Application of Units

ML20235G965
Person / Time
Site:	Seabrook
Issue date:	09/24/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235G961	List: ML20235G958 ML20235G965
References
NUDOCS 8709300314
Download: ML20235G965 (3)

Text

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ENCLOSURE 1 8" kg UNITED STATES NUCLEAR REGULATORY COMMISSION g

n .g ,j WASHINGTON. D. C. 20555 y

4*****$ SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON PUBLIC SERVICE OF NEW HAMPSHIRE SEABROOK NUCLEAR GENERATING PLANT, UNIT NO. 1 DOCKET N0. 50-443 SETPOINT METHODOLOGY FOR ROSEMOUNT REPLACEMENT TRANSMITTERS

1.0 INTRODUCTION

By letter dated February 14, 1986 Public Service of New Hampshire (PSNH) responding to the staff's RAI 420.8, verified that the existing safety-related l instrument channel setpoints as specified in their technical specifications were developed by utilizing the Westinghouse (W) setpoint methodology that had been approved by the staff. According to the licensee this methodology provides two methods of combining error contributors in an instrument measuring I loop. One method is by statistically combining independent (not interactive) errors using the Root Sum Squares (RSS), and the other method is by adding the dependent error components arithmetical 11y.  ;

In a later letter dated December 23, 1986, PSNH responded to a request from the  !

staff for additional information concerning the proposed setpoint methodology that they intended to use for recently purchased Rosemount transmitters and described a methodology which differed from the W methodology discussed above.

Specifically, PSNH states that based on test results in Rosemount Report 08300076 (" Accuracy of Pressure Transmitters") Revision A dated June 6,1973 they now consider transmitter error from LOCA/HELB conditions to be statistically independent and as such will be combined with other statistically independent channel error in a measuring loop by placing this error contributor under the radical (RSS method). This method of combining the error contributor from LOCA/HELB conditions is considered nonconservative with respect to the W method that combines the same error contributor by adding the error value arithmetical 11y.

8709300314 870924 DR ADOCK 0500 3

l Additionally, the licensee states that their intent is to use this same methodology for all future setpoint calculations at Seabrook Station when applied to Rosemount transmitters. ICSB has reviewed this latter methodology proposed by PSNH and finds that there is not an adequate basis to allow staff approval for it to be used for the replacement Rosemount transmitter at this time. ICSB's evaluation of this issue is discussed below.

2.0 EVALUATION The setpoint methodology that the licensee is proposing for the replacement transmitters from Rosemount is based on data obtained from LOCA/HELB tests of six transmitters tnd described in Rosemount reports D8300040 and 08600010.

Our review of the test results indicate that the drift error of the units during the run of the LOCA/HELB test is not independent but random in nature.

However, the staff believes that the data submitted thus far are insufficient to support this randomness classification, and, therefore find the setpoint methodology proposed by the licensee to be unacceptable at this time. In this regard the licensee may want to conduct additional tests to obtain more supporting data for future Rosemount applications at the Seabrook Station.

One additional concern the staff has considered in determining the acceptability of the proposed setpoint methodology is that the licensee has stated that if the proposed methodology was found to be acceptable by the staff then they intend to use this less conservative approach for all future applications of Rosemount transmitters. The staff does not concur in this generalistic approach. The staff believes that since the proposed setpoint methodology is less conservative than the current method, the licensee, as a minimum to satisfy the concern for

, the health and safety of the public, should study each application of the Rosemount transmitters on a case-by-case basis.

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3.0 CONCLUSION

l In summary, the ' staff finds the licensee's proposed methodology for establishing setpoint values for the. replacement transmitters from Rosemount not to have an

. adequate basis, at this time, to allow approval for it to be used in the application of these' units to measure pressurizer pressure and steam generator water level at the Seabrook Station.

-. Principal ~ Contributor . Vincent D. Thomas

. Dated:-

SE 241987

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