ML20058E369
| ML20058E369 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 11/01/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058E361 | List: |
| References | |
| NUDOCS 9011070146 | |
| Download: ML20058E369 (3) | |
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NUCLEAR REGULATORY COMMISSION j
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.135 TO FACILITY OPERATING LICENSE NO. 'DPR-46 NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. 50-298
1.0 INTRODUCTION
1 By' letter dated April 3,1990, as supplemented by letter dated August 17, i
1990, Nebraska public Power District (NPPD) requested an. amendment to the TechnicalSpecifications(TSs)appendedtoFacilityOperatingLicenseNo.
DPR-46fortheCooperNuclearStation(CNS). The proposed amendment would change.the Technical Specifications to clarify that the definition of the l
term " Instrument Calibration".in Specificati.on 1.1.2 involves only the
' verification of the operability for resistance temperature detectors and-thermocouples used as sensors in instrument channels rather than removal and calibration of these sensors.
2.0 DISCUSSION
-This proposed ch.. ige was triggered by a concern which was initially raised during a regional; inspection of the licensee's compliance to Regulatory Guide 1.97. During that-inspection, the NRC-inspection team questioned the adequacy of the licensee's instrument channel calibration procedures which were developed for measuring systems that use non-adjustable Resistance Temperature Detectors'(RTDs) or Thermocouples (TCs) as the sensing device.
According to the licensee. they maintain that since non-adjustable sensing devices such as-RTDs and TCs have fixed outputs to given input responses,
'the sensors cannot be adjusted, and replacement of the sensorLis the only corrective measure to take when a channel measurement becomes suspect. An-instrument: channel'becomes' suspect when its output reading. deviates more than.an acceptable margin from'other instrument channel output readings that correlate.to the channel in question. For this reason, the licensee concludes.that calibration of these non-adjustable sensors is neither warranted, required, nor possible. Confronted with the definition of-the L
term '? Instrument CalibratiN". in the Technical Specifications for CNS at the time, which stated that " calibration'shall encompass the entire L
instrument including sensor, --," the regional ~ inspection team challenged the licensee's calibration procedures which did not include the sensor u
l portion of the measuring system when performing required periodic-L:
surveillance tests on RTD or TC measuring systems.
In their attempt to clarify.the above calibration issue, the licensee submitted a proposed modification of the definition of " Instrument Calibration" to the NRC for acceptance by their April 3, 1990 letter.
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.During the staff's' review of the licensee's proposed change, two concerns were raised by the staff and-later discussed with representatives of NpFD during'a telephone conversation on August 10, 1990. The first concern deals with the ambiguity of statement " adjustment as necessary of the remaining adjustable devices in the [ instrument] channel," and the second concern deals with the methodology the licensee is im)1ementing to achieve
.' verification of operability' of the sensing element i.e., RTD or TC)."
In response to these concerns, the licensee submitted a revised version
.of the definition for " Instrument Calibration" for staff review and acceptance by letter dated August 17, 1990.
The revised definition for Technical Specification 1.1.2. states in part:
Instrument Calibration
.... Calibration of instrument channels with resistance temperature detector (RTD) or thermocouple sensors shall consist of verification of operability of the sensing element, and normal calibration of the remaining adjustable devices in the channel.
g The staff has reviewed the revised Technical Specification 1.1.2 for CNS and finds.the definition as written to be acceptable. However, the staff believes that since it is impractical to detail the methodology the licensee. intends,to implement when " verifying the operability" of the sensor devices in the technical specification, a discussion on this verification of RTDs and TCs is included herein to document the mutual L
understanding between this licensee and the staff. During a telephone conversation on September 11, 1990, the licensee and'the staff agreed that the non-adjustable sensing devices such as those-installed RTDs at CNS being used to monitor Drywell ambient temperature conditions and suppression water temperature will be subjected to cross calibration checks at least-,
once each refueling cycle. Cross calibration is a method for in-situ /on-line testing to verify accuracy'of the installed RTDs..However,-this. cross calibration check must always be conducted such that the outputs measured from the'RTDs under test are compared to at'least one independently calibrated (to known accepted standards) and carefully installed RTD.
Additionally, since the full operating range ofERTDs in service monitoring Drywell and. suppression pool conditions is relatively narrow'(90 to 150"F, and;90 to 135"F, respectively), at least two point cross calibration checks will be conducted during each refueling cycle that utilize at least two temperature points to cross calibrate the the sensor. One point may be measured during' shutdown and the other during plant operations. This can be accomplished by ' employing the independently calibrated RTD discussed above as one point and thereafter a cross calibration check between similar RTDs during steady state plant conditions. Their data should be recorded and used as "as left" versus "as found" data for future sensor drift information.
Known sta6dards such as ice baths, boiling water, and other known isothermal conditions are considered acceptable calibration standards for RTDs but are not encouraged because the RTD under test cannot be tested in its normal installation configuration.
Past experience has shown that many errors
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(response time, temperature errors, etc.) have arisen because of poor post installation controls after removing RTDs for test. Rigid and careful post installation procedures for verification of RTD operability is both time consuming and not at all conclusive in returning the RTD to the previous service after test.
.The staff has reviewed both the April 3, 1990 proposed change and the supplement dated August 17, 1990. Discussions have been held with the licensee representatives and the regional inspectors from Region IV, and the. staff has concluded that the amendment to Technical Specification 1.1.2 for CNS as discussed above, is acceptable subject to the discussion herein..
'3.0. ENVIRONMENTAL CONSIDERATION The amendment: involves.a change in a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements.
The staff.has determined that the amendment involves no significant increase. in the amounts, and no significant change in the types, of any effluents.that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposures.
The Commission has previously issued a proposed finding that the amendment involves _no.significant hazards consideration'and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria.for categorical exclusion set forth in 10 CFR Section 51.22(c)(9).
'Pursuantto10CFR51.22(b),noenvironmentalimpactstatementorenviron-
' mental assessment need be prepared in connection with the issuance of the amendment.'
4.0 CONCLUSION
.The st'aff has concluded, based on the considerations' discussed above, that:
-(1);there is reasonable assurance that the health and safety of the public
-will not be endangered by operation in the proposed manner, and (2)'such' activities will be conducted in compliance with the Commission's regulations, and the:1ssuance of the amendment will not be inimical to the common defense and security or-to the health and safety of the'public.
. Dated:-Novembetr 1,1990
- Principal Contributor: Vincent Thomas
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