Source: https://www.nrc.gov/reading-rm/doc-collections/event-status/part21/1999/1999480.html
Timestamp: 2019-10-15 19:17:02
Document Index: 540291495

Matched Legal Cases: ['art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21']

NRC: Part 21 - 1999-48-0
Home > NRC Library > Document Collections > Event and Status Reports > Part 21 Reports > 1999 > 1999-48-0
ACCESSION #: 9910280183
TELEPHONE: (626) 934-1600 OR (626) 961-9221
October 21, 1999 FAX: (626) 961-2538
Subject: 10CFR Part 21 Report, Containment Monitoring System Model 225 CMA-X
Reference: Teledyne's Engineering Evaluation Letter, from K. Johns to R. Khajavi, Dated 5 October 1999 (Exhibit 1)
Teledyne Electronic Technologies, Analytical Instruments hereby notifies and submits a 10CFR Part 21 Report to the U.S. Nuclear Regulatory Commission (NRC) of a problem identified by the Carolina Power & Light Corporation and communicated to Teledyne Analytical Instruments on September 22, 1999. We are not certain whether this event warrants 10CFR Part 21 Report. In our opinion, this problem does not introduce a substantial safety hazard and it is detectable during the routine calibration, therefore, precluding its use. Nevertheless, Teledyne Analytical Instrument felt that it was prudent to advise the NRC and the affected Customers, as a minimum.
On September 22, 1999 Carolina Power & Light Corporation notified Teledyne Analytical Instruments that they were experiencing non-linear oxygen readings with two (2) Model 225 CMA-X Containment Monitoring Systems (oxygen application only) at the Brunswick Nuclear Power Plant. This behavior was witnessed during their routine calibration when replacing an old fuel cell with a new fuel cell. In reviewing our product field performance records, Teledyne has not received any customer reports or advisory indicating the same non-linearity experience on Model 225 CMA-X Containment Monitor.
Teledyne's investigation (Exhibit 1) revealed that the non-linear response is caused by the high gain produced by the 10K resistor (P/N: R3 11) across the second stage amplifier. This anomaly occurs if the fuel cell (oxygen application only) installed has an output close to 50 microamps. To preclude recurrence, Engineering drawings will be revised to replace the 10K resistor with a 7.5K resistor (P/N- R406) which will reduce the gain by 25%. Testing was conducted and validated the effectiveness of corrective action. In addition, all affected Customers will be advised on the Teledyne's corrective action.
Reference #: RK 10-99-023
Subject: 10CFR Part 21 Report, Containment
Monitoring System Model 225 CMA-X
The following lists the customers planned for problem notification and corrective action:
- Carolina Power & Light - Bernische Kraftwerk AG
- Taiwan Power Co. - Vermont Yankee Nuclear Power Corp.
- Niagara Mohawk Power Corp. - Nuclenor, Spain
In summary, Teledyne has identified the root cause, will revise the engineering drawings to reflect the planned corrective action and notify affected customers no later than 10 November 1999.
Should further questions arise, please do not hesitate to contact Kim Johns, Nuclear Systems Engineer, at (626) 934-1611 or myself at (626) 934-1502.
Reference #: RK: 10-99-023
TO: Ray Khajavi
CC: Al Pichelli, Ed Chu, Jeff Burks, Ron Downie
SUBJECT: Engineering evaluation of problems reported in Carolina Power & Light Corp. E-mail dated September 22, 1999 to Jeff Burks.
On September 22, 1999 an F-mail was received from Carolina Power & Light Corp. (CPLC) which stated that they were experiencing nonlinear O2 readings due to high O2 fuel cell outputs associated with the two (2) Model 225 CMA-X Containment Monitoring Systems at the Brunswick Nuclear Plant. The nonlinear O2 readings were found during the routine calibration when replacing an old cell with a new cell. The worst case- non-linearity reported was 8%.
The nuclear O2 fuel cell is Teledyne Electronic Technologies/Analytical Instruments (TET/AI) P/N C23831. The fuel cell, for an concentration of 20.9% O2, has a specified output of 28 to 50 microamperes at atmospheric pressure and a temperature of 25 degrees C. For recent manufacturing lots, the fuel cell outputs have been measured to be on the high end of the range between 40 to 50 microamperes. Fuel cells with an output close to 50 microamperes may cause the second stage amplifier of the O2 detector amplifier printed circuit board assembly (TET/AI P/N A23860) to become saturated. This would make the O2 readings nonlinear.
The fuel cells in question at CPLC had lot numbers 214702, 313077, 313078 and 313079. Tests were performed on September 27 and 28, 1999 to verify that the recent manufacturing lots of fuel cells had acceptable temperature characteristics. The fuel cells that were tested had lot numbers 313085, 313086, and 313087. The tests showed that the recently manufactured cells had identical temperature characteristics as the fuel cells that were originally qualified.
The gain of the 02 detector amplifier printed circuit board assembly was lowered by 25% by changing the feedback resistor of the first stage amplifier front 10,000 ohms to 7,500 ohms. The amplifier was tested with a precision current source at 25 microamperes and at 50 microamperes. The test verified that the amplifier performed within specification over this range.
The non-linearity of the 02 reading would normally be found during routine calibration. In order to prevent this occurrence, TET/AI recommends that the feedback resistor of the first stage amplifier on the 02 detector amplifier printed circuit board assembly (TET/AI P/N A23860) be changed front 10,000 ohms (TET/AI P/N R311) to 7,500 ohms (TET/AI P/N R406). This will lower the gain by 25% and prevent the second stage amplifier from saturating for fuel cells with an, output close to 50 microamperes. In addition the gain will still be high enough from cells that have an output on the lower end of the acceptable range of 28 microamperes.
Reference #: RKJ:991005A
SUBJECT: Nonlinear O2 Readings
The following standard documents identify the location of the first stage amplifier feedback resistor as reference designator R1.
A23860 O2 Control Unit Detector Amplifier P.C. Board Assembly
B24635 O2 Amplifier Schematic
The above documents are used on standard systems. If the system is customs the description and location of the resistor would be similar.
The 7,500 ohm resistor is available fully dedicated for use on class 1E safety related, equipment as TET/AI P/N R406.