Reduced Inventory Flashcards
Describe the purpose and applicability of 40OP-9ZZ16, RCS Drain Operations.
The purpose of this procedure is to place the plant in a drained condition, from 10% Pressurizer level (117 ft elevation), down to the minimum RCS level allowed at Mid-Loop (101 ft 6 inches elevation). The procedure supports plant activities that require an RCS drain down be performed, with or without fuel in the Reactor Vessel.
Define the following terms: • Partially Drained • Lowered Inventory • Reduced Inventory • Mid Loop • Vortexing • Level Change • Bulk Temperature
Partially drained:
RCS level less than 10% Pressurizer level, or less than 117 ft elevation but greater than 114 ft.
Lowered Inventory:
RCS level less than or equal to 114 ft, but greater than 111 ft.
Reduced Inventory:
RCS level less than or equal to 111 ft elevation, but greater than 103 ft 1 inch, with fuel in the Reactor Vessel.
Mid-Loop:
RCS level less than or equal to 103 ft 1 inch elevation, but greater than or equal to 101 ft 6 inches with fuel in the Reactor Vessel.
Vortexing:
The whirlpool effect on the water at the SDC Pump suction connection at the RCS Hot Leg, which is caused by low RCS levels in conjunction with high SDC system flow rates.
Level Change:
Deliberate or inadvertent actions that results in a change in RCS inventory. Variations in level due to temperature changes are not considered a Level Change, although they may result in the need for one.
Bulk Temperature:
The actual temperature in the core. This is indicated at the CETs with no RCS flow or at SIA-TI351X/SIB-TI-352X, SDC Heat Exchanger inlet temperature with SDC flow.
State the bands of allowable SDC flowrates during RCS draindown.
Generally speaking, the bands of allowable SDC flow during draindown are limitations based on elevations to preclude vortexing:
• Above elevation 107 ft, SDC flow should be between 3,780 to 5,000 gpm.
• Between elevations 103 ft 1 in to 102 ft, SDC flow should be between 3,780 to 4,600 gpm.
• Between elevations 102 ft to 101 ft 6 in, SDC flow should be between 3,780 to 4,150 gpm.
However, there is more to consider with respect to the low end of the SDC flow band. A SDC flow of 3,780 gpm is considered to be “Reduced SDC Flow”. Although the allowable range, by Tech Specs, starts at 3,780 gpm, if the flow is reduced below the “normal” flow of about 4,000 gpm too soon after shutdown, the SDC loop may not be able to maintain RCS temperature in the desired band.
Identify critical systems, parameters and instruments that should be monitored during RCS Drain operations.
Critical indications to observe include water inventory/level instrumentation, water temperature both in and out of the SDC heat exchangers, SDC pump amps and flow.
With fuel in the vessel, two independent means of determining RCS level must be in service before entering Reduced Inventory Operations, <111 ft elevation.
Prior to entering reduced inventory or mid-loop conditions, a minimum of 2 CETs are required to be operable for monitoring core temperatures
Describe how indicated Pressurizer Level is used during the performance of 40OP-9ZZ16 including:
• Maximum allowable deviation of PZR level channels
• Who may allow continued draindown if the maximum allowable deviation is exceeded.
Corrected Pressurizer level maximum deviation is less than 3% between level channels RCALI-110X and RCB-LI-110Y, when compared to RCN-LI-103.
If anomalies exist in Pressurizer level readings or correlations, draining operations are required to be suspended until ONE of the following:
The cause of the discrepancy is identified and corrected.
The cause of the discrepancy is identified, and authorization to continue is obtained from the Unit Operations Manager.
Describe how the RWLIS functions to support RCS drain down operations.
Each train provides indication for BOTH of the following:
• Wide Range, read on RCN-LI-752B
• Narrow Range, read on RCN-LI-752A
The power supply for RWLIS level transmitters RCN-LT-752A and RCNLT752B is NNN-D12 52-02 with the flow compensation being powered by PNA-D25 and PNB-D26.
Describe what is required per 40OP-9ZZ16 when RCS level cannot be displayed from the Control Room.
When no means of displaying RCS level in the Control Room is available, local monitoring and recording at least once every 15 minutes is required to be performed.
State the maximum permissible drain rate with fuel installed in the Reactor.
The maximum drain rate with fuel installed in the Reactor, using only the RV head vent orifice, is less than or equal to 40 gpm.
The maximum drain rate with fuel installed in the RV and the Grayloc hubs open is less than or equal to 135 gpm.
Describe the makeup flowpaths required during reduced inventory in accordance with 40OP-9ZZ16.
- Two makeup paths are required, with one being a gravity makeup path.
- Gravity makeup and High Pressure Safety Injection (HPSI) makeup can NOT be aligned to the same train.
Identify the parameters which directly affect the potential for vortex formation at the suction of the SDC pumps.
The two main parameters associated with vortex formation are:
- RCS level: The lower the level the greater the chance of vortex formation.
- RCS flowrate: The greater the flowrate the greater the chance of vortex formation.
Describe the phenomenon known as Surge Line Flooding and its potential impact on RCS level and indication.
Should boiling occur the possibility exists of escaping steam velocity in the 12” surge line to not allow water to drain back down from the pressurizer into the RCS. This is known as “surge line flooding”.
40OP-9ZZ16, Appendix I - RWT Gravity Makeup To SDC Suction Header, Table 7 defines minimum level requirements in the RWT such that water elevation will provide sufficient head to overcome internal RCS pressure due to surge line flooding.
Define the term “Closed Containment” and describe when it must be in place and how it is tracked in accordance with 40DP-9ZZ30.
Closed Containment — A containment that provides at least one integral barrier to the release of radioactive material. Sufficient separation of the containment atmosphere from the outside environment is provided such that a barrier to the escape of radioactive material is reasonably expected to remain in place following a core melt accident.
Describe the requirements associated with the Containment Equipment Hatch.
The following requirements apply to the Containment Equipment Hatch:
• The Unit Operations Manager is responsible to authorize opening Containment Equipment Hatch whenever the RCS is in Reduced Inventory.
• The Shift Manager has the following responsibilities:
• Authorize opening the Containment Equipment Hatch when RCS level is greater than the 111 ft.
• Obtains authorization from the Unit Department Leader to allow opening the Containment Equipment Hatch when RCS level is in Reduced Inventory Condition, less than the 111 ft.
All containment penetrations, including the Equipment Hatch, must be capable of being closed by the time core boiling starts after a loss or impairment of shutdown cooling or within 60 minutes whichever is more limiting. (Time Critical Action-TCA-86).
The Equipment Hatch is considered is closed and held in place by a sufficient number of bolts (at least 4 bolts approximately equally spaced) such that no gaps exist in the sealing surface.
The determined time to boil shall be greater than 30 minutes to ensure sufficient time exists to close and secure the Containment Equipment Hatch before boiling occurs
