ML20236N257
Text
. O -19 % IL)
August 7, 1997 MEMORANDUM TO:
Herbert M. Berkow, Director Project Directorate FD 11-2 Division of Reactor Projects 1/Il FROM:
Jared S. Wermiel, Chief Instrumentation and Controls Branch Division of Reactor Control And Human Factors
SUBJECT:
TASK INTERFACE AGREEMENT (TIA 97-07) EVALUATION REGARDING REACTOR TRIP AND ENGINEERED SAFETY FEATURES ACTUATION SYSTEMS INSTRUMENTATION SETPOINTS FOR VOGTLE UNITS 1 AND 2 (TAC NOS. M98528 AND M98529)
By merhorandum (TIA) dated March 28,1997, Region !! requested that NRR provide an evaluation of the Vogtle Electric Ger.:.ating Plant Units 1 and 2, licensee's practice of establishing reactor trip system and ESFAS instrument setpoints as nominal values with tolerances beyond the Technical Specifications (TS) Trip Setpoint maximum or minimum value. The TlA stated that the licensee's position is that current plant procedures and Technical Specification Bases define the trip setpoint as a nominal value bounded by a channel calibration accuracy band and is properly adjusted when the "as-left" setpoint is within this band. Attached is the staff's response to the subject TIA. This completes our i
effort in response to your request.
l Docket Nos.: 50-424 and 50-425
Attachment:
As stated CONTACT:
Cliff Doutt, HICB 415 2847 DISTRIBUTION:
Central Files HlCB RF L. Spessard/C. Thomas DOCUMENT NAME: VOGTLE 97-76 n
h,..
,v.,tu.
.ine w
h.m c c, iin.ut.n.ch-.ni/.ew.u r - c., with.tt. chm.nt/.ncio.ur.
- 0f",N. copy 0FFICE HICB/0RQt,,,
lE HICB/DRCit,,.l E HICB/DRCN_ _ l6 ADPR/TSB m6 l
@C l
NAME CDoutt /\\*(,A JMauck 61 JWermiel M WBeckner'
('.eSe h.,,,
DATE 07/2g /97~ b 07/zs/97 0 07/2fr /97 07/SI /97
$/ 7 /97 0FFICIAL RECORD COPY t
9807150066 900624 h R h -155 PDR
$/fA l
~
TASK INTERFACE AGREEMENT (TIA-9707) EVALUATION BY THE OFFICE OF NUCLEAR FsEACTOR REGULATION VOGTLE UNITS 1 AND 2 DOCKET 50-424 AND 50-425 l
By memorandum dated March 28,1997, Region 11 requested NRR's position on the license 6's practice of establishing procedures with reactor trip system (RTS) and 4
engineered safety features actuation system (ESFAS) system instrument setpoints as nominal values with tolerances beyond teciinical specification (TS) maximum and minimum
" allowed values". The concern resulted from an inspection conducted as a follow up to an issue at Watts Bar and Sequoyah, which have similar RTS and ESFAS TS.
The TIA request noted that the licensee's procedures contain setpoint tolerance bands specifying setpoint ranges that the Region interprets could result in the licensee setting setpoints outside of the specified TS limit. However, the inspection also showed that in no case has the licensee taken advantage of procedure tolerances and set instrument trip setpoints beyond the TS " allowed value." Further, the Region sta'ad that the licensee maintains that the TS Bases document provides guidance that a measured setpoint that does not exceed the " allowed value"is considered operable.
l In response to the TIA, the staff reviewed Vogtle RTS and ESFAS TS, TS Boses and setpoint methodology documents. The Vogtle TS Bases state the following:
"The Trip Setpoints are the nominal values (emphasis added) at which the bistables are set. Any bistable is considered to be properly adjusted when the "as left" value is within the band for CHANNEL CALIBRATION accuracy."
i Based on the above TS Bases statement and our review of the associated license documents, the staff finds that the setpoint methodology and the TS Bases are in agreement that the TS Trip Setpoint is a nominal value. However, the staff notes Vogtle RTS and ESFAS TS limits, which are presented in the accompanying LCOs as " Trip Setpoint" and " Allowable V:'ve" table entries, specify Trip Setpoint minimum or maximum values (inequalities) for each function, rather than Trip Setpoint nominal values. The Vogtle TS Bases also state the following about nominal Trip Setpoints:
"The Trip Setpoints used in the bistables are based on the analytical limits stated in Reference 1. The selection of these Trip Setpoints is such th6t adequate protection is provided when all sensor and processing time delays are taken into account. To allow for calibration tolerances, instrement uncertainties...... the Trip Setpoints and Allowable Values specified in Table 3.3.1-1 in the accompanying LCO are conservatively adjusted with respect to the analytical limits. The actual nominal Trip Setpoint entered into the bistable is more conservative than that specified by the Allowable Value to account for changes in random measurement errors detectable by a COT."
ATTACHMENT l
O 2-10 CFR 50.36(a) states that specifications require summary statements of the bases or reasons for specifications, other than those covering administrative controls, but do not become part of the technical specifications. Thus, the Vogtle TS Trip Setpoint inequalities specified for RTS and ESFAS functions are TS limits which cannot be altered by the Bases discussion. For this reason, the staff interprets the Vogtle TS Tsip Setpoints to represent the most limiting setting that is allowed for the Trip Setpoint.
Furthermore, by the Bases noted above, it is apparent that specifying Vogtle TS Trip l
Setpoints as inequalities represents a departure from the approved setpoint methodology.
In order to satisfy the TS setpoint inequality requirement, the licensee's practice has been to routinely set the Tnp Setpoint value conservatively to the TS Trip Setpoint value inequality. The staff finds this acceptable provided the licensee setting is bounded by the l
setpoint methodology calibration tolerance and procedures (in the appropriate direction and magnitude). Therefore, it is the staff position that TS compliance can be met by establishing appropriate controls to limit the resetting of the Trip Setpoint consistent with the TS inequality value.
We' also campared Vogtle TS Bases, RTS and ESFAS Setpoint and Allowable Value TS limits to the setpoint methodology in response to the Region statement that the licensee maintains that the TS Bases document provides guidance that a measured setpoint that does not exceed the " allowed value"is considered operable. The Vogtle TS Bases state the following:
1 "Sepoints in accordance with the Allowable Value ensure that SLs (safety limits) are not violated during AOOs (and that the consequences of DBAs will be acceptable, providing the unit is operated from within the LCOs at the onset of the AOO or DBA and the equipment functions as designed). Note that in the accompanying LCO 3.3.1, the Trip Setpoints of Table 3.1.1 1 are the LSSS."
The staff review concludes that the licensee position is supported by the licensed setpoint methodology. However, the assignment of the Limiting Safety System Setting (LSSS) as the nominal Trip Setpoint in the Vogtle TS is inconsistent with the setpoint methodology for Vogtle (WCAP-11269) which recognizes the Alloweble Value as the LSSS. The Vogtle l
setpoint methodology considers the Trip Setpoint value to be the " nominal safety system setting" which is considered the desired Trip Setpoint for the variable. By classifying the Trip Setpoint as the LSSS in the TS Bases, the Trip Setpoint, with inequality, becomes a l
d defined operability limit per 10 CFR 50.36 (which requires incorporation of the LSSS in TS). Because the Trip Setpoint is listed as the LSSS and is further defined by an inequality, exceeding the inequality by the calibration tolerance or finding the nominal Trip Setpoint greater than the Vogtle TS inequality, results ir TS noncompliance and puts the licensee into the appropriate LCO remedial action. The first condition can occur when the nominal trip setpoint as-left value is set greater than the nominal Trip Setpoint inequality value but within the nominal trip setpoint calibration tolerance. In this case, the instrument setpoint is set within the assumption of the setpoint methodology (as-left) and is conservative to the Allowable Value, but the instrument could still be declared I
O 3
. inoperable. In this regard, it is the staff position that the Vogtle TS Bases are inconsistent with the licensing basis topical report setpoint methodology for LSSS and the licensee should undertake an action to reconcile the Vogtle TS Bases with the approved setpoint methodology.
In conciusion, the staff finds the licensee procedures for setting the nominal Trip Setpoint to have no adverse impact on safety and to satisfy the requirements of the referenced setpoint methodology and Vogtle TS. However, since the Trip Setpoint is the LSSS in the Vogtle TS, the licensee shall consider the Trip Setpoint inequality as the setpoint upper limit (as-left) to satisfy the TS format and the operability requiremmts of 10 CFR 50.36.
Additionally, the setpoint calibration tolerance (now essentially single sided) for the Trip Setpoint must be maintained in the appropriate direction and magnitude to be consistent with the Vogtle setpoint methodology values.
s Docket Nos.: 50-424 and 50-425
Contact:
Cliff Doutt, HICB (301) 415-2847 Carl Schulten, TSB (301) 415-1192 l
i e
i