Event 48018 – June 12, 2012 – Palisades – TECHNICAL SPECIFICATION REQUIRED SHUTDOWN
“At 1456 hours on June 12, 2012, the plant commenced a shutdown due to water leakage from the SIRW [Safety Injection Refueling Water] tank exceeding the operational decision-making issue process trigger point of 31 gallons per day causing it to be declared inoperable and requiring entry into Technical Specification (TS) 3.5.4, Condition B. TS 3.5.4 Condition B requires the SIRW Tank to be returned to operable status within one hour or entry into Condition C that requires the plant to be in Mode 3 within 6 hours and Mode 5 within 36 hours.
“Actual leakage from the SIRW Tank was measured at approximately 31.4 gallons per day. This event had no impact on the health and/or safety of the public.
“The NRC Senior Resident Inspector has been notified.”
The licensee believes that the tank is leaking from several locations. However, at this time, they cannot determine exact locations. The refueling water has minor tritium contamination.
The refueling water is being collected in a reservoir and then pumped into a holding tank. The licensee will be shutting down to cold shutdown.
The SIRW Tank is an integral part of the Emergency Core Cooling System and serves as its source of Borated Water (285,000 Gallons) to mitigate LOCA, SGTR, Excess Steam Demand, and other postulated events. Further, it provides the water necessary to carry on Refueling Operations because it’s inventory is used to fill the Refueling Pool.
Adjunct functions of the SIRW Tank include normal makeup for Reactivity Control during plant operation.
The SIRW Tank also serves as a volume for Testing ECCS Pumps on different flow paths to validate their pump curve performance. The SIRW Tank Instrumentation initiate Long Term Sump Recirculation during a LOCA. The SIRW Tank, like all ECCS components meet strict Seismic Requirements.
No leakage is tolerated.
Leakage of this magnitude may invalidate all abovementioned (brief list) of functions.
The SIRWT is monitored in part by the Plant’s Structural Monitoring Program and Maintained by the Water Chemistry Program in accordance with the Renewed Palisades License. The Palisades Plant’s License was Renewed in January 2007 until 2031.
1.2.4 NUCLEAR STEAM SUPPLY SYSTEM (NSSS)
10. Safety Injection System
Four safety injection tanks are provided, each connected to one of the four reactor inlet lines. Each tank has a volume of approximately 2,000 cubic feet containing approximately 1,000 cubic feet of borated water at a concentration of 1,720-2,500 ppm and pressurized by approximately 1,000 cubic feet of nitrogen at approximately 200 psia.
In the event of a large Loss of Coolant Accident, the borated water is forced into the Primary Coolant System by the expansion of the nitrogen. The water in three tanks will adequately refill and reflood the entire core.
In addition, borated water will be injected into the reactor vessel to cool the core via the same nozzles used by the SI tanks by two low-pressure and two high-pressure injection pumps taking suction from the 285,000-gallon safety injection and refueling water storage tank (SIRW). For maximum reliability, the designed capacity from the combined operation of one high-pressure and one low-pressure pump provides adequate injection flow for any Loss of Coolant Accident.
Upon depletion of the storage tank supply, the high-pressure pump suction automatically transfers to the containment sump and the low pressure pumps are shut down. One high-pressure pump has sufficient capacity to maintain the core water level at the start of recirculation. In the event of a DBA, at least one high-pressure and one low-pressure pump would receive power from the emergency power sources.
Both high- and low-pressure injection pumps are located outside the containment building to permit access for periodic testing during normal operation.
The pumps discharge into separate headers which lead to the containment. Test lines are provided to permit running the pumps for test purposes during Plant operation.
FSAR CHAPTER 6 – ENGINEERED SAFEGUARDS SYSTEMS
6.1.2 SYSTEM DESCRIPTION AND OPERATION
184.108.40.206 General Description
1. Emergency Core Cooling
The SIRW tank is located between the reactor building and turbine building above the control room on the auxiliary building roof. The safety injection pumps and all other components of the Safety Injection System are located at the lowest level of the auxiliary building in a tornado-proof area.
This location maximizes pump suction head when recirculating from the containment sump. The safety injection equipment inside the auxiliary building is located in two water-tight rooms. Sufficient space is provided around equipment in these rooms to permit installation of temporary shielding for maintenance.
Valves required to isolate equipment are provided with remote operators. An interconnection is provided from the Chemical and Volume Control System to allow testing of the injection line inner check valves during reactor operation; however, in practice, the check valves are tested in the cold shutdown mode (partial stroke test) or in the refueling mode (full stroke test).
220.127.116.11 Component Design
1. Safety Injection and Refueling Water (SIRW) Tank The SIRW tank contains a minimum of 250,000 gallons of water containing boron in the range of 1,720 ppm to 2,500 ppm. This is sufficient water to fill the refueling cavity.
When the tank reaches the recirculation actuation setpoint (RAS), the safety injection and containment spray pump suction will be switched to the containment sump. The actual time that RAS occurs will vary depending on tank level and pump flow rates.
The minimum time is approximated to be 20 minutes. This assumes that the tank is at its minimum level and all pumps are operating at near runout conditions.
The tank is constructed of aluminum and is cathodically protected with insulating flanges. Heating steam is provided to maintain the tank above 40°F to prevent freezing. It is field fabricated to the requirements of ASA B96.1. The SIRW tank design parameters are shown in Table 6-1 (Attached).
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