05000454/FIN-2015008-01
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Finding | |
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| Title | Question Regarding the Maximum Wet Bulb Temperature Value Assumed in the SXCT Tornado Analysis |
| Description | Question Regarding the Maximum Wet Bulb Temperature Value Assumed in the Emergency Service Water Cooling Tower Tornado Analysis Introduction: The team identified an unresolved item (URI) regarding the maximum wet-bulb temperature value assumed in the SXCT tornado analysis. Specifically, the team noted the analysis used a value which was less restrictive than the highest 3-hour wet-bulb temperature recorded for the site as described in the UFSAR. Description: In Section 3.5.4 of the UFSAR, Analysis of Missiles Generated by a Tornado, stated that, An analysis of the UHS cooling capability for a tornado missile event has been made. It also stated that, A maximum outside air wet-bulb temperature of 78 degrees Fahrenheit is assumed and is conservatively held constant throughout the transient. In addition, this UFSAR section stated that, The analysis was performed using service water cooling tower performance curves generated using the method described in UFSAR Section 9.2.5.3.1.1.2 [...]. The analysis of the UHS cooling capability for a tornado missile event was calculation BYR09-002, UHS Capability with Loss of SX [Emergency Service Water] Fans due to a Tornado Event, which used a constant maximum outside air wet-bulb temperature value of 78 degrees Fahrenheit consistent with UFSAR Section 3.5.4. However, the team noted the assumed maximum outside air wet-bulb temperature value of 78 degrees Fahrenheit appeared to be inconsistent with the method described in UFSAR Section 9.2.5.3.1.1.2, Steady State Tower Performance Analysis. Specifically, it stated that, The design wet-bulb temperature during warm weather operation is 82 degrees Fahrenheit (Refer to UFSAR Section 2.3.1.2.4). In Section 2.3.1.2.4 of the UFSAR, Ultimate Heat Sink Design, stated that, This analysis [described in Section 9.2.5.3.1.1] includes scenarios with the highest 3-hour wet-bulb temperature, 82 degrees Fahrenheit, which was recorded on July 30, 1961, at 3:00 pm. This UFSAR section also stated that, Per Regulatory Guide 1.27, the ultimate heat sink must be capable of performing its cooling function during the design basis event for this worst case 3-hour wet-bulb temperature. In addition, it stated, However, the design operating wet-bulb temperature of the ultimate heat sink is 78 degrees Fahrenheit (ASHRAE 1 percent exceedance value). This issue is unresolved pending further review by the Office of Nuclear Reactor Regulation (NRR) of the licensing basis related to the wet-bulb temperature value applicable for the SXCT tornado analysis, and the team determination of further NRC actions to resolve the issue. (URI 05000454/2015008-01; 05000455/2015008-01, Question Regarding the Maximum Wet-Bulb Temperature Value Assumed in the SXCT Tornado Analysis) |
| Site: | Byron  |
|---|---|
| Report | IR 05000454/2015008 Section 1R21 |
| Date counted | Sep 30, 2015 (2015Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | A Della Grecab Palagi C Lipa D Betancourt J Leivo M Jones N Feliz-Adornoa Dunlopc Thompson D Strohmeyer E Duncan G Edwards G Hansen J Draper J Mcghee K Walton L Cender M Jones |
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Finding - Byron - IR 05000454/2015008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2015Q3
Self-Identified List (Byron)
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