LIC-94-0164, Part 21 Rept Re Nonconformance in Potentiometers W/ Attachable Switches Mfg by Ohmite & Supplied by Abb C-E. Nonconforming Components Returned to Abb C-E & Abb C-E Issued Info Bulletin 94-02,providing Appropriate Guidance
| ML20072N802 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 08/24/1994 |
| From: | William Jones OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-94 IEB-94-002, IEB-94-2, LIC-94-0164, LIC-94-164, NUDOCS 9409060293 | |
| Download: ML20072N802 (5) | |
Text
_ . . _ _ _ . .
- o Omaha Public Power District C"H8mCJane5 444 South 16th Street Mall
- * " " " Omaha. Nebraska 68102-2247 402/636-2000 August 24, 1994 LIC-94-0164 U. S. fluclear Regulatory Commission ATTil: Document Control Desk Mail Station Pl-137 Washington, DC 20555
References:
- 1. Docket flo. 50-285
- 2. Letter from OPPD (W. C. Jones) to NRC (Document Control Desk) dated June 21, 1994 (LIC-94-0141).
Gentlemen:
SUBJECT:
10 CFR Part 21 Report Concerning flonconforming Components Manufactured by Ohmite Omaha Public Power District (OPPD) has investigated a material nonconformance in potentiometers with attachable switches manufactured by Ohmite and supplied by ABB Combustion Engineering, and determined the nonconformance to be reportable pursuant to 10 CFR Part 21. OPPD notified the f1RC Operations Center on July 26, 1994. Attached is information required pursuant to 10 CFR 21.21(c)(4).
Please contact me if you have any questions.
Sinc rel ,
f hjp W.C.Janeh LW Senior Vice g President J ,
WCJ/brh !
Attachment ;
1 c: LeBoeuf, Lamb, Greene & MacRae l S. D. Bloom, f1RC Project Manager l L. J. Callan, NRC Regional Administrator, Region IV i R. P. Mullikin, NRC Senior Resident Inspector l M. J. Sponzo, Manager - Muclear Spare Parts, ABB-CE fjlO C !i b l l
9409060293 940024 PDR ADOCK 050002 % .
c; FDR l gt 45 5124 Employment with Equal oppo# tun:ty l tAaie/ Fema:e i
m 1
US Huclea'r Regulatory Commission LIC'94-0164 Page 2 This report is submitted pursuant to 10 CFR 21.21(c)(4). The items identified address the specific information requested by 10 CFR 21.21(c)(4) as follows:
(i) Identification of individual or individuals providing this notification:
W. C. Jones Senior Vice President Omaha Public Power District 444 South 16th Street Mall Omaha, NE 68102-2247 (ii) Basic components containing defect:
Ohmite model CU1021 and CU1031 potentiometers and model CS-1 switches, supplied as attachable to the potentiometers, were found to be in nonconformance with the required function for which they were supplied for the Fort Calhoun Station.
(iii) Identification of supplier:
The subject Ohmite parts were supplied by ABB Combustion Engineering under OPPD Purchase Orders S075870 and S039124.
(iv) Nature of Defect:
Source of Discrepancy The switchpotentiometer is attachab (lepot) to and switches an entire are modular series such that the which of potentiometers CS-1 includes the above listed models. The pot / switch assembly functions such that when the potentiometer shaft is rotated fully counter-clockwise (CCW) the switch is operated and " captures" the adjustment knob in the full CCW position. The potentiometer adjustment will thus be captured at one extreme of its adjustable range, OPPD attempted to install a pot / switch assembly, and the assembly would not pass its post-maintenance test. When the pot / switch was installed it was identified that in the full CCW position the switch was open but the potentiometer was not "zerced," and the resistance value of the potentiometer could be changed without opening the switch. OPPD discussed this discrepancy with ABB Combustion Engineering, who informed OPPD that Ohmite changed the manufacturing facility for these items from Mexico to Canada. The model numbers for the affected items were not changed. The components of different origin (i.e.,
manufactured at different facilities) appear to have the same external physical characteristics and can be assembled together, but will not function correctly.
The assembly of a Canadian potentiometer and a Mexican switch will not allow for the potentiometer wiper arm to make contact with the switch.
The potentiometer will appear to function but will not operate the switch and will thus not be captured in the "off" position.
These pots / switches are used on the Power Ran e Nuclear Instrumentation (PRNI), Wide Range Nuclear Instrumentation WRNI) drawers, and on the Reactor Protective System Calibration and i dication Panel (RPSCIP).
US fluclear Regulatory Commission LICE 94-0164
[
Page 3 Potential Safety Significance The potential safety significance has been evaluated assuming that the switch and potentiometer are assembled and installed into the circuit.
Since the potentiometer will appear to function but will not operate the switch, it was assumed that the switch is in the position it was in when received from the supplier. Therefore, the switch could aither be in the "open" or " closed" position when assembled. Both possibilities t>elow in the (switch open or closed)lhoun applications at Fort Ca Station.and the consequences are outlined Wide Ranqe Nuclear Instrumentation (WRNU.
The CU1031 potentiometer application in the WRNI drawer is used as the period trip test potentiometer. This potentiometer in conjunction with the CS-1 switch provides a simulated additive signal to the period rate circuit. The signal is used for calibration and function tests associated with the WRNI high power rate of change signal. The potentiometer is isolated from the supply voltage when the integral switch is open (i.e., the switch is in the off position).
The inadvertent installation of a faulty potentiometer / switch combination in this application would not pose any safety significance.
If installed with the switch in the open position, rotating the potentiometer knob would not provide any input signal. If installed with the switch in the closed position, an additive test signal would be provided that would reduce the margin to trip which is conservative for nuclear safety.
A CU1021 potentiometer is used on the WRNI for the level (or wide range
% power) trip test potentiometer. The use and function of this potentiometer is very similar to that previously discussed for the period trip test potentiometer.
A nonconforming potentiometer / switch in this application would not pose any safety significance. If installed with the switch open, no input signal would be provided. With the switch closed, the potentiometer could be positioned to provide an additive power level signal which would impact the Zero Power Mode (ZPM) bypass function and the automatic bypass of the High Power Rate of Change signal to the RPS.
This potential impact would not pose any safety significance.
Reactor Protective S_ystem Calibration and Indication Panel (RPSCIP)
The CU1031 potentiometer application in the RPSCIP provides a simulated test input signal for the Thermal Margin / Low Pressure (TMLP) trip function. The signal developed from this potentiometer when the switch is in the closed position is added to the value of the variable low pressure trip limit (Po ) in the TMLP calculator. This limit is auctioneered with a fixed low pressure trip limit (P,,,,,) and the higher of the two values is provided to the RPS trip unit as P, (See USAR Section 7.2.3.7).
e i
US Nuclea'r Regulatory Commission LICE 94-0164 Page 4 The inadvertent installation of a faulty potentiometer / switch combination in this application would not pose any sa,fety significance.
If installed with the switch in the open position, rotating the potentiometer knob would not provide any input signal. If installed with the switch in the closed position, an additive test signal would be provided which would increase the setpoint and thus reduce the margin to trip which is conservative for nuclear safety.
The CU1021 potentiometer application in the RPSCIP provides a simulated test input signal for the Delta-T power signal. Delta-T power is auctioneered with NI power in the TMLP calculator to develop a "Q" power signal which is used as the process input to RPS high power trip unit and is an input to the Axial Power Distribution (APD) and TMLP trip function calculations.
The inadvertent installation of a faul ty potentiometer / switch combination in this application could create an adverse safety impact.
If installed with the switch in the open position, rotating the potentiometer knob would not provide any input signal. If installed with the switch in the closed position it is possible to introduce a nonconservative error in the Delta-T power signal. After the potentiometer is used for the required setting, the potentiometer could introduce a signal which would be added to the Delta-T power causing a higher than actual (conservative) power signal on that channel.
During the daily NI/ Delta-T calibration the channel would be compared to the other channels and the value of the affected channel would be reduced by an amount equal to the error. If a test is then conducted which moved the potentiometer, it could be left in a position with a lower setpoint (nonconservative) until the next daily NI/ Delta-T calibration corrected it.
Power Ranne Nuclear Instrumentation (PRNI)
The CU1021 potentiometer application in the PRNI provides a simulated test input for the respective subchannel (upper or lower, therefore there are two CU1021 potentiometers per PRNI channel). The PRNI trip test potentiometers supply an additive test input signal to the respective subchannel. The CS-1 switch serves to provide an alarm and power trip test interlock function and to capture the potentiometer in the "off" or "zero input" full CCW position.
The inadvertent installation of a faulty potentiometer / switch comuination in this application could create an adverse safety impact.
If installed with the switch in the closed position, an alarm condition would alert the control room operators to an abnormal condition on one of the NI channels and the trip units would be tripped for the affected channel and could not be reset. This condition could not go undetected and would not pose any adverse safety impact.
If installed with the switch in the open position, the potentiometer would not be captured at the "zero input" position and the alarm condition would be reset. Thus a simulated subchannel signal could be provided without intended precautionary alarms / trips. The impact of an inadvertent simulated subchannel input would be an elevated value for NI power that would reduce the margin to trip which is conservative for nuclear safety. However, the subchannel input to the Axial Shape Index (ASI) calculation would also be affected by the erroneous input.
l
t- .
US Nuclear Regulatory Commission L IC-94-0164 Page 5 This impact would be to calculate an ASI value that is inappropriately skewed either positive or negative depending upon the subchannel affected. The impact on ASI could be nonconservative. There could be an adverse safety impact to an axial power transient in the opposite direction of the simulated power. There is also an APD input to the iMLP calculator; however, any error introduced is negligible when compared to the conservative error introduced by the increase in NI Power.
Based on the above evaluation OPPD has determined that a substantial safety hazard, as defined by 10 CFR Part 21, could exist.
(v) Date information of defect was obtained:
OPPD discovered the discrepancy on April 22, 1994 and provided an interim report pursuant to 10 CFR 21.21(a)(2) on June 21,1994 (LIC 0141). The evaluation which determined that the discrepancy was a defect was completed oa July 20, 1994. The Senior Vice President, who is the responsible officer in OPPD with executive authority over Part 21 issues, was, informed on July 25, 1994.
(vi) Number and Location of components containing defect:
It has been verified that the potentiometers /swikh combinations are not installed at Fort Calhoun Station in a location which could have an adverse safety implication. The time frame that Ohmite changed manufacturing facilities, and any other utilities which might have the subject components, is not known by 0 PPD.
(vii) Corrective action which has, or is being taken:
After the discrepancy was identified, the potentiometers / switches purchased under Purchase Orders S075870 and S039124 still in inventory, were returned to ABB Combustion Engineering. ABB Combustion Engineering has issued ABB-CE Infobulletin 94-02 dated August 12, 1994 which provides recommended corrective actions.
(viii) Advice related to defect to be given to licensees:
ABB Combustion Engineering has issued ABB-CE Infobulletin 94-02 dated 1 August 12, 1994 which provides appropriate guidance. j l
I