PRHRS system

Passive residual heat removal (PRHR) system ... 

The plant response following an SGTR until the primary-to-secondary break flow is terminated is analyzed with the LOFTTR2 program. The LOFTTR2 program is modified to model the PRHR system, core makeup tanks, and protection system actions appropriate for the APIOOO. 

The ADS and PRHR system are design features that can be used to prevent high-pressure core melt in a severe accident. 

The safety analysis of the TMSR-SF has also drawn much attention. Three types of transient conditions including ULOF, UOC, and UTOP were examined on the TMSR-SF by an FHR safety analysis code named the FHR Safety Analysis Code (FSAC Xiao et al., 2014). The station blackout anticipated transient without scram (SBO-ATWS) accident was analyzed by the modified RELAP5/MOD 4.0 code with the responses of the passive residual heat removal (PRHR) system (Jiao et al., 2015). 

Fig. 6J-3 The In-Containment Passive Safi System IRWST, PRHR HX ami the...

Fig. 37. Schematic representation of the in-containment passive safety injection system (PS1S). 1RWST = in-containment refueling water storage tank. PRHR-HX = passive residual heat removal heat exchanger. ADS = automatic depressurization system (four stages). (Westinghouse)...

Passive Residual Heat Removal System (PRHRS)... 

If feed water systems or steam generator heat removal is not available, two PRHR heat exchangers provide decay heat removal. The system is located above the Reactor Coolant System (RCS) and forms a closed loop at full system pressure using natural convection circulation. The... 

Decay heat removal Passive Residual Heat Removal System (PRHR) Passive Non-LOCA heat removal... 

Passive residual heat removal system (PRHRS) X 3 channels 1 channel on the reactor, 2 channels to the secondary circuit 1 loops... 

Decay Heat Removal Passive heat removal system, PRHRS Passive Self-actuates at P = 0 6 MPa, 2x2 5 m ... 

A 3-3 Primary pressure control Implemented system (Name) - ARHRS, PRHRS... 

Strong negative reactivity coefficients L Pnmary Transients - Great primary mertia, CPS actuation, PRHR actuation L Secondary Transients - Great primaiy mertia, CPS and PRHR actuation L Loss of Electric Sources - Implementation of passive systems (battery power sources) Total Loss of heat sink not cntical ... 

Debris cooling system (name) PRHRS, AHRS... 

Self sufficiency (h) 24 through each train Safety graded Yes A3 3 Primary pressure control Implemented system (Name) PCPS, PRHRS a Actuation mode (manual/automatic) Automatic... 

If the duty systems are unavailable, or are imable to control the ult, passive residual heat removal (PRHR) is initiated and the CMTs actuated to inject borated water into the reactor coolant system (RCS). In most cases this will be sufficient to manage the fault for at least 72 hours. 

Results of the analysis for the postulated feedwater line rupture show that the capacity of the PRHR heat exchanger is adequate to remove decay heat, to prevent overpressurising the reactor coolant system, and to maintain the core cooling capability. Radioactivity doses from mptures of the postulated feedwater lines are less than those presented for the postulated main steam line break and meet US regulatory criteria. Fiuther consequence analysis will be conducted to demonstrate that the results meet the relevant UK criteria. 

The results of this analysis show that inadvertent operation of the core makeup tanks or CVS during power operation does not adversely affect the core, the reactor coolant system, or the steam system. The PRHR heat removal capacity is such that reactor coolant water is not relieved from the pressuriser safety valves. DNBR always remains above the design limit values, and reactor coolant system and steam generator pressures remain below 110 percent of their design values. 

A scaled-down test facility has been established comprehensive tests using this facility will produce data on the whole system interaction, performance behaviour of the self-controlled pressurizer (PZR), indirect performance effect of passive residual heat removal system (PRHRS), natural circulation effects, etc. 

The major auxiliary systems of SMART consist of a component cooling system (CCS), purification system and make-up system. The function of the CCS is to remove heat generated in the main coolant pumps (MCPs), control element drive mechanisms (CEDMs), pressurizer (PZR), and the internal shielding tank. Feedwater supplied from the condensate pump of the turbo-generator is used as the coolant to remove heat. The purification system purifies the primary coolant and controls water chemistry to provide reliable and safe operation of the reactor core and all equipment in any mode of operation. The make-up system fills and makes-up the primary coolant in case of a primary system leak and supplies water to the compensating tanks for the PRHRS it consists of two independent trains, each with one positive displacement makeup pump, a makeup tank, and piping and valves. 

Besides the inherent safety characteristics of SMART, its safety is further enhanced by highly reliable engineered safety systems. These are designed to function passively on demand and consist of a reactor shutdown system, passive residual heat removal system (PRHRS), emergency core cooling system (ECCS), safeguard vessel, reactor overpressure protection system (ROPS) and containment overpressure protection system (COPS). 

The fluid flow through the core, through the SG and the PRHRS HEX, is characterized by flow through parallel channels. The channels in the core are formed by the fuel rods and those in the SG and PRHRS by closed flow-tube channels. Such flow configurations, parallel flow channels, are susceptible to instabilities for single-and two-phase flows. Under long-term safe shut-down conditions the PRHRS is expected to be a two-phase flow system. 

For Gen IV systems that have an integral containment and for the case of a piping break internal to the containment, three coupled NCLs must correctly operate to ensure removal of the energy from the core. An opening low in the RPV must be provided so that the expelled coolant can return from the containment back to the core region for the SG to transport energy to the PRHRS HEX. 

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