ML051670202

Special Report Meteorological Tower 10-60M Air Temperature Delta-T Inoperable

ML051670202
Person / Time
Site:	Callaway
Issue date:	06/09/2005
From:	Keith Young AmerenUE
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC05160
Download: ML051670202 (3)

Text

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Union Electric PO Box 620 Callaway Plant Fulton, MO 65251 June 9, 2005 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 ULNRC05 160 Ladies and Gentlemen:

wAmeren Uf DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

FACILITY OPERATING LICENSE NPF-30 SPECIAL REPORT METEOROLOGICAL TOWER 10-60M AIR TEMPERATURE DELTA-T INOPERABLE Enclosed is a Special Report documenting the Inoperability of 10-60 Meter Meteorological Monitoring Delta-T Instrumentation on the Primary Meteorological Tower and the actions taken to restore this circuitry to an Operable status. This report is submitted in accordance with Final Safety Analysis Report 16.3.3.3.

If you have any questions or require additional information, please contact Mr. Mark Reidmeyer, Supervisor, Regional Regulatory Affairs at (573) 676-4306.

This letter does not contain new commitments.

Sincerely, Mangr D ung Manager, Regulatory Affairs Enclosure 1,21---

asubsidiary ofAmeren Corporation

ULNRC05160 June 9, 2005 Page 2 cc: U.S. Nuclear Regulatory Commission (Original and 1 copy)

Attn: Docuiimrent Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)

Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360

ULNRC05160 June 9, 2005 Enclosure ENCLOSURE Special Report The Meteorological Instrumentation Limiting Condition For Operation (LCO) (Final Safety Analysis Report Section 16.3.3.3) requires the meteorological monitoring instrumentation channels to be operable at all times. With one or more required meteorological monitoring channels inoperable for more than 7 days, LCO Action 'a' requires a Special Report to be submitted to the Commission within the next 10 days outlining the cause of the malfunction and the plans for restoring the channel(s) to an operable status.

On May 31, 2005, with Callaway Plant in Mode 1, the Primary Met Tower 10-60 meter Delta-T was determined to be inoperable. This Delta-T instrument channel measures the temperature difference between the 10 and 60 meter tower elevations.

While reviewing the real-time data for the 10-60 meter Delta-T, it was determined that the data trend did not look as responsive as expected when compared with past channel behavior or the 10-90 meter Delta-T channel. Further investigation determined the change started approximately 0916 on May 11, 2005. The date of failure is considered as May 11, 2005.

Plans for restoration to Operable status:

A station work request was generated on May 31, 2005 to repair the instrumentation.

Repairs were made on June 3, 2005. The Primary Met Tower 10-60 Meter Delta-T channel was declared Operable at 1659, June 3, 2005.

Cause of the malfunction:

A communications problem between the meteorological tower and the plant computer was identified. No failure of any meteorological instruments nor the local recorder occurred. The most likely cause of the channel failure was the input card to an analog to digital converter. The input card consists of a collection of mercury-wetted relays which gate the meteorological signals to the analog to digital card.

The communication problem was not evident to site personnel because the data was generally tracking the day-to-day transitions of the normal Delta-T data. The communications problem was also masked in the 15-minute average data. The local tower recorder was recording accurate data and would have been available for use in an emergency. The 10-90 meter Delta-T channel was operable. This operable channel is relied upon for assessment of radioactive releases should they occur. Failure of the 10-60 meter Delta-T did not adversely affect the ability to assess radioactive releases.