ML18233A533
| ML18233A533 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 01/03/2019 |
| From: | Prosanta Chowdhury NRC/NRO/DLSE/LB1 |
| To: | |
| Chowdhury P/nro/ 415-1647 | |
| References | |
| Chapter 13 | |
| Download: ML18233A533 (38) | |
Text
- 13.1.4.1 Combined License Information Items 13.1.4.1.1 Management and Technical Support Organization
13.1.4.1.2 Operating Organization
- 13.2.4.1 Combined License Information Items 13.2.4.1.1 Licensed and Non-licensed Plant Staff Training Programs
- Federal Register Federal Register 13.3.4.1 Technical Support Center
TSC equipment, such as engineering workstations and communications equipment, are components of the MCS, PCS, and communications system (COMS). Power is supplied to these systems from the normal DC [direct current] power system (EDNS).
As described in FSAR Tier 2 Section 8.3.2.1.2, the EDNS consists of batteries, battery chargers, and inverters. The EDNS battery chargers are normally supplied from the low voltage AC electrical distribution system (ELVS). Following a loss of AC electrical power supply to the EDNS battery chargers, the batteries automatically assume the loads for a minimum duration of 40 minutes.
Additionally, in the event of a loss of normal onsite AC power, backup power to the ELVS can be provided by the backup power supply system (BPSS). Spare battery and charger terminal connection points are also provided for connection to mobile battery and charging units if necessary. The BPSS design is described in FSAR Tier 2 Section 8.3.1.1.2.
The TSC and the main control room (MCR) share the control room ventilation system (CRVS), as described in FSAR Tier 2 Section 9.4.1. Upon detection of a high radiation level in the outside air intake, the normal outside air flow path is isolated and 100 percent of the outside air is bypassed through the air filtration unit to filter outside air and minimize radiation exposure to personnel within the MCR and TSC. This mode of operation allows the CRVS to continue providing breathable air to the MCR and TSC personnel and maintain the MCR and TSC at positive pressure with respect to the outside environment. This design meets the requirements of NUREG-0696, Section 2.6. 13.3.4.2 Operational Support Center
13.3.4.3 Emergency Operations Facility 13.3.4.4 Technical Support Center Engineering Workstations The reference to the safety display and indication system (SDIS) in Section 13.3 is being changed to refer to the technical support center (TSC) engineering workstations, which are part of the module control system (MCS) and plant control system (PCS). The post-accident monitoring (PAM) variables displayed on SDIS in the main control room are also displayed on MCS or PCS and are available to the TSC engineering workstations. The PAM instrumentation includes the required functions, range, and accuracy for each variable monitored.
Variables and their type classification are based on their accident management function as identified in abnormal operating procedures, emergency operating procedures, and emergency procedure guidelines. The PAM Type B, C, D, and E variables are summarized in FSAR Tier 2 Table 7.1-7.
The engineering workstation PCS displays in the technical support center (TSC) provide monitoring functionality to plant processes and equipment.
There is a unidirectional communication interface between the MCS and PCS networks and the plant network. The MCS and PCS systems provide monitoring data via one-way communication interfaces to the plant network which provides data recording, trending, and historical retention that can be called up on the TSC engineering workstations 13.3.4.5 Emergency Response Data System An emergency response data system compliant with Section VI of 10 CFR [Part]
50, Appendix E, provides a direct near-real-time electronic data link of selected parameters between the onsite computer system and the NRC Operations Center in the event of an emergency.
Additionally, there is a link from the plant network to the NRC emergency response data system (ERDS) via dedicated communications servers that connect to the plant network and provide data communication of required plant data to off-site emergency response facilities as shown in FSAR Tier 2 Figure 7.0-1.
13.3.4.6 Enhanced Emergency Response Capabilities for Beyond-Design-Basis Events 13.3.4.7 Decontamination Facilities
13.3.4.8 Process Sampling System
13.3.4.9 Inspections, Tests, Analyses, and Acceptance Criteria
- 13.5.4.1 Combined License Information Items 13.5.4.1.1 Administrative Procedures
13.5.4.1.2 Operating and Maintenance Procedures
13.5.4.2 NuScale Generic Technical Guidelines
13.5.4.2.1 Critical Safety Functions
The remove fuel assembly heat critical safety function includes the aspects of reactor coolant system (RCS) integrity. This is due to the integral nature of emergency core cooling system (ECCS) and RCS integrity-actuating ECCS opens valves to allow steam release to the containment and return of water back to the RCS-it is done to maintain core cooling and protect the fuel clad fission product barrier. This is automatically actuated when there is an existing loss of RCS as indicated by low reactor pressure vessel (RPV) riser water level or high containment water level. RCS integrity is addressed under the core heat removal CSF by ensuring that the low temperature overpressure (LTOP) system automatically actuates when required. The LTOP system fully actuates ECCS when pressure is above the temperature dependent pressure setpoint. When ECCS actuates, an intentional hydraulic connection between the RCS and CNV occurs which establishes a natural circulation heat removal path outside of the RCS, but within the containment. A pressurized thermal shock event is not credible at NuScale because of the following factors:
All sources of makeup are isolated by the containment isolation system.
Actuation of the ECCS system precludes pressurization of the RCS system.
The NuScale reactor pressure vessel is designed to withstand the maximum passive system cooldown rate.
13.5.4.2.2 Methodology to Identify Operator Actions ********
13.5.4.2.3 Critical Safety Function Flowchart Logic and Operator Actions
Containment Integrity Safety Function
Reactivity Safety Function At full power, the core exhibits a large negative temperature coefficient, even at beginning of cycle conditions. The initial loss of feedwater, due to the containment isolation, causes a loss of RCS cooling which results in a rise in RCS temperature. Due to the negative temperature coefficient, the core is subcritical shortly after the loss of feedwater, even without inserting control rods. The long-term ATWS response is unique because of the excess heat transfer capacity of the passive cooling systems. This excess heat transfer results from the relatively small core size, a large coolant mass-to-power ratio, and the efficient passive heat transfer systems. Return to power occurs only after passive heat transfer to the ultimate heat sink (UHS) has been established and RCS temperature is significantly reduced. The strong negative temperature coefficient and reduction in RCS temperature causes core fission power to increase until it is in equilibrium with the passive heat removal capacity. The core fission power never exceeds the passive heat removal capacity for an extended duration. The resulting fission power is well within the capacity of the passive cooling systems and UHS, and the core is protected.
Core Heat Removal Safety Function
Miscellaneous Items ****