Document: NRC Regulatory Guide
Document ID: 29acb072-d497-44e6-ac1c-a053c0a468a0
Document Type: regulatory_guide
Title: Meteorological Monitoring Programs for Nuclear Power Plants + HISTORY - HISTORY DG-1164 , Third Proposed Revision 1, published 10/2006 Draft ES 926-4 , Second Proposed Revision 1, entitled "Meteorological Measurement Program for Nuclear Power Plants," published 04/1986 Draft SS 926-4 , First Proposed Revision 1, entitled "Meteorological Programs In Support of Nuclear Power Plants," published 09/1980 Revision 0, entitled "Onsite Meteorological Programs," was issued as Safety Guide 23
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0625/ML062540408.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.23
CFR Part: 
CFR Title: 

Content:
freezing conditions. 4. Instrument Accuracy and Range The time-average accuracies for digital systems should meet the criteria listed in Table 2. These accuracies are stated in terms of overall system accuracies and should include, where applicable, the errors introduced by sensors, cables, signal conditioners, temperature environments for signal conditioning and recording equipment, recorders, processors, data displays, and the data reduction process. The instrumentation should be capable of operating over the expected range of climatic conditions based on regional climatology. If the accuracies of the signal conditioning equipment and/or data acquisition system are sensitive to changes in temperature, they should be housed in a climate-controlled environment. 9 The use of redundant sensors and/or recorders is an acceptable approach to achieve the 90-percent data recovery goal. DG-1164, Page 10 Table 2. Meteorological System Accuracies and Resolutions Measurement System Accuracy Measurement Resolution Wind Speed ±0.22 m/s (±0.5 mph) for speeds < 2.2 m/s (5 mph) ±5% for speeds $ 2.2 m/s (5 mph) starting threshold < 0.45 m/s (1 mph) 0.1 m/s or 0.1 mph Wind Direction ±5 degree starting threshold < 0.45 m/s (1 mph) 1.0 degree Temperature ±0.5 EC (±0.9 EF) 0.1 EC or 0.1 EF Vertical Temperature Difference ±0.1 EC (±0.18 EF) 0.01 EC or 0.01 EF Dew Point ±1.5 EC (±0.27 EF) 0.1 EC or 0.1 EF Wet-Bulb Temperature ±0.5 EC (±0.9 EF) 0.1 EC or 0.1 EF Relative Humidity ±4% 0.1% Precipitation (water equivalent) ±10% for a volume equivalent to 2.54 mm (0.1 in.) of precipitation at a rate < 50 mm/h (<2 in./h) 0.25 mm or 0.01 in. Time ±5 min 1 min 5. Instrument Maintenance and Servicing Schedules Meteorological instruments should be inspected and serviced at a frequency that will ensure data recovery of at least 90 percent on an annual basis.9 The 90-percent rate applies to the composite of all variables (e.g., the joint frequency distribution of wind speed, wind