05000348/FIN-2014007-07
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Finding | |
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| Description | Introduction: The team identified an unresolved item (URI) regarding the lack of evaluations to ensure the CCW system was capable of withstanding the forces resulting from a reactor coolant pump (RCP) thermal barrier break hydraulic transient. Specifically, this event can lead to a thermal-hydraulic transient and its effects may not have been evaluated. Description: The team reviewed section 9.2.2 of the UFSAR, Cooling System for Reactor Auxiliaries, which states High pressure switches on the return line from each reactor coolant pump thermal barrier cooling coil and a high flow switch on the common return from all three pumps will initiate the rapid closure of isolation valves to isolate the reactor coolant pumps in the event of a leak in the thermal barrier. Calculation 36.7, Setpoint Basis for CCW Thermal Barrier Isolation Pressure Switches PSH-3184A,B,C, concluded that the pressure drop in the CCW line is sufficient to prevent any pressurization to the point of over stressing the lower design pressure piping and that the pipe schedule is sufficient to protect against erosion in the pipe due to high flow. The calculation assumed the closure time of these isolation valves (i.e., HV-3184 and HV-3046) was 10 seconds. Section 13.6.2 of the Technical Requirements Manual, Containment Isolation Valves, included a requirement to verify these isolation valves close within 10 seconds. Recent test results showed these valves close in about 2.5 to 5 seconds. In addition, Calculation 36.7 determined that the maximum flow from a thermal barrier rupture to the 2.5 inch CCW piping would be 275 gpm of RCS water at 2235 psig and 550 degrees F. Normal service conditions at the CCW piping would be about 40 psig. However, the team noted these conditions had the potential to result in significant steam void formation at the CCW piping. Specifically, a simplified thermodynamic analysis performed by the inspection team, and assumed initial and final saturation conditions of 550 and 200 degrees F, respectively, determined that approximately 36% of the leaked water mass would evaporate. However, the resulting steam volume would be about 547 times greater than the initial water volume at 550 degrees F. The team noted this condition and its potential effects were not evaluated. The transient could be caused by a steam void collapse upstream of the valve following the rapid valve closure of HV-3184 and downstream of the valve due to potential condensation-induced water hammer when the steam void collapses while combining with colder CCW water at a larger process line. Section 9.2.2 of the UFSAR states System components are designed to the codes given in Table 9.2-10. Table 9.2-10 identified ASME Section III as the applicable code for the CCW piping. The licensee indicated the specific code of record is the 1971 Edition through the summer 1971 Addenda. Impact loading for class 3 piping, such as CCW piping, is addressed in Section ND-3600, which referred to the requirements of NB-3600. Section NB-3622.1, Impact, stated Impact forces caused by either external or internal conditions shall be considered in the piping design. Based on this information, the team determined additional information is required to assess the potential for a thermal-hydraulic transient and its effects to CCW. The licensee captured the team concerns in their CAP as CR 834119. This issue is unresolved pending further licensee analysis to resolve the issue and to determine if a performance deficiency exists (URI 05000348, 364/2014007-07, Potential Effects of an RCP Thermal Barrier Break to the CCW System Were Not Evaluated). |
| Site: | Farley  |
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| Report | IR 05000348/2014007 Section 1R21 |
| Date counted | Jun 30, 2014 (2014Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | D Mas E Stamm G Macdonald M Yeminy N Feliz _Adorno R Nease S Kobylarz T Lightyk Miller P Niebaum R Patterson S Sandal |
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Finding - Farley - IR 05000348/2014007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Farley) @ 2014Q2
Self-Identified List (Farley)
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