ML20149K778
| ML20149K778 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 07/24/1997 |
| From: | Heider K YANKEE ATOMIC ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYR-97-035, BYR-97-35, NUDOCS 9707300149 | |
| Download: ML20149K778 (3) | |
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- YANKEE ATOMIC ELECTRIC COMPANY r.,.n-,n.
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g('l HC87 Box 160, Rowe, Massachusetts 01367
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July 24,1997 BYR 97-035 i
U.S. Nuclear Regulatory Commission Document Control Desk Washington,DC 20555
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Subject:
Special Report - Meteorological Instrumentation (Air Temperature Delta T) Operability
Dear Sir / Madam:
The Yankee Nuclear Power Station (YNPS) Off-Site Dose Calculation Manual (ODCM) requires YNPS to submit a Special Report if one or more of the required meteorological monitoring channels is inoperable for more than seven days (ODCM Control 5.5, Action a). The attached report describes the operability of the Air Temperature Delta T channel which was determingd to be inoperable between May 20,1997 and July 14,1997. The Air Temperature Delta T channel indicates the temperature difference between the top and bottom of the meteorological tower.
In February 1992, YNPS permanently ceased power operations and initiated spent fuel storage and decommissioning operations. The Air Temperature Delta T channel is not required to support either of these operations. The Defueled Emergency Plan, which was approved by the Nuclear Regulatory Commission, eliminated the need to perform offsite dose assessments following the limiting design basis event (spent fuel handling accident), eliminating the need to use the meteorological tower temperature difference for offsite dose assessment. The meteorological data are trended and maintained available for estimating potential radiation doses as a result of release of radioactive materials to the atmosphere.
If you have any questions or require further information, please contact E. L. May of my staff at 413-424-2223.
Sincerely, tW S U
enneth J. I eider Site Manager and Manager of Operations
Enclosure:
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NSARC Chairman (YAEC)
USNRC Region I y
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Special Report:
Meteorological Instrumentation (Air Temperature Delta T) Operability BACKGROUND The Yankee Nuclear Power Station (YNPS) Off-Site Dose Calculation Manual (ODCM) requires YNPS to submit a ten day Special Report if one or more of the required meteorological monitoring channels is inoperable for more than seven days (ODCM Control 5.5, Action a). On July 14,1997, wiring from the Air Temperature Delta T channel was discovered to be reversed following relocation of the channel indication to a new panel on May 20,1997. The Air l
Temperature Delta T channel indicates the temperature difference between the top and bottom of the meteorological tower. The reversed wiring inverted the temperature difference indication (e.g., negative temperature differences were indicated as positive values). The Air Temperature Delta T channel was inoperable between May 20,1997 and July 14,1997. This report presents the cause of the inoperability and the date the channel was returned to service.
In February 1992, YNPS permanently ceased power operations and initiated spent fuel storage and decommissioning operations. The Air Temperature Delta T channel is not required to support either of these operations. The Defueled Emergency Plan, which was approved by the Nuclear Regulatory Commission, eliminated the need to perform offsite dose assessments i
following the limiting design basis event (spent fuel handling accident), eliminating the need to i
use the meteorological tower temperature difference for offsite dose assessment. The meteorological data are trended and maintained available for estimating potential radiation doses as a result of release of radioactive materials to the atmosphere.
DISCUSSION On May 20,1997 as part of the Control Room Relocation Project, Yankee removed the YNPS meteorological instrumentation (including the Air Temperature Delta T channel) from service to relocate the meteorological instrumentation panel and associated instrumentation channels from the original Control Room to the Screenwell House. This work was conducted in accordance with Engineering Design Change Request 96-302, " Control Room Relocation," and Implementing Procedure OP-5000.455, " Installation of Control Room Meteorological PC and Modification of PLC Communication Network." On May 22,1997, the meteorological instrumentation was declared operational following completion of procedures OP-5000 455 and OP-4150, " Vendor Calibration and/or Maintenance of the Meteorological Data Gathermg System Instrumentation."
Routine evaluation of meteorological data following the relocation indicated that Air Temperature Delta T channel data appeared to be inconsistent with expected results. The data exhibited a negative differential temperature in the morning instead of a positive value and conversely a positive value in the evening instead of a negative value. On June 30,1997, TRC Environmental Corporation, the vendor that calibrates and maintains the meteorological instrumentation, verified the proper operation of the lawer and upper aspirator motors / fans and
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Special Report: MeteorologicalInstrumentation (Air Temperature Delta T) Operability July 24. I997 Page 2 recalibrated the Air Temperature Delta T channel. The data following the inspection continued to exhibit an unexpected response.
On July 14,1997, TRC provided additional troubleshooting of the channel, including evaluation of the channel wiring. During this effort the sensor input wiring was determined to be reversed. The wiring configuration was corrected and the instrumentation indicated the appropriate temperature difference. The Air Temperature Delta T channel was declared operable on July 14,1997.
The Air Temperature Delta T channel indication is available in the YNPS Control Room and is reviewed routinely by the Yankee Nuclear Services Division with other meteorological data, However, the indication is not used for any spent fuel storage or decommissioning activity at YNPS. Changes to the YNPS Emergency Plan after the permanent shutdown eliminated the need for this indication for offsite dose projection. The data from the period when the channel indication was inverted may be used by simply changing the sign of the indication; the absolute j
valut of the indication is correct.
1 CAUSE OF THE INOPERABILITY The root cause of the inoperable Air Temperature Delta T channel was reversed input wiring to the channel occurring during relocation from the Original Control Room to the Screenwell House. The reversed wiring was not detected during post-installation testing.
SCHEDULE FOR RESTORATION The Air Temperature Delta T channel operability was restored on July 14,1997 after confirmation of the reversed wiring.
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