4.0 Steam and Power Conversion System

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Objectives1. State the purposes, and describe the operation of, the

following steam and power conversion systems:

• Main steam supply system,• Condensate and feedwater system,• Condenser circulating water system, and• Emergency feedwater system.

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2. Explain the purposes of, and describe the operation of, the main steam relief trains.

3. Describe the major differences between the design of the US-EPR steam and power conversion system and those of currently operating PWRs.

Fig. 4-1 Turbine-Generator Package

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Main Steam Supply System

Safety-Related Functions:

• Main steam isolation to prevent li f t l t

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overcooling of reactor coolant

• RHR by venting steam via MSSVs & MSRTs

• Steam-side isolation during an SGTR

Fig. 4-2 Main Steam Supply SystemDesign5.17x106 lb/hr1435 psig592oF

MSIV:

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• MSIV:– Hydraulic-pneumatic gate valve– Warming line with isolation & control valves

• Main Steam Isolation Signals:– Rapid SG pressure drop (all SGs)– Low SG pressure (all SGs)– SG isolation signal (partial cooldown + high SG level

or high steam line radiation) (affected SG)

Two trip Systems (1 shown)De-energize to Trip

N2 is the Closing Force(Manually added as needed)

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Close in 5 Sec with, 5x106 lb/hr Flow and 1320 psid in either direction

Gate Valve

Partial Closure orSlow Closure

(2)

Fig. 4-4 MSIV Actuator

Fig. 4-2 Main Steam Supply System

MSSV S i l d d t ti

1460 psig 1490 psig

2.84x106 lb/hr

1.42x106 lb/hr/valve

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• MSSVs: Spring loaded, overpressure protection

• MSRT: MSRIV (open/shut) + MSRCV (modulates)– Overpressure protection (1370-psig setpoint)

– RHR (controlled steam release to atmosphere)

– Partial cooldown (180°F/hr for 20 min after SIS)

– Radioactivity containment (SG isolation signal raises MSRIV relief setpoint to 1435 psig)

Angled Globe Valve

Fig. 4-3 MSRIV Actuator

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Fig. 7-2 Partial Cooldown

Steam Header Pressure

Tavg:

>60% 594°F

Fig. 4-5 Main Steam Bypass Control

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Steam Header Pressure LowTurbine Control Valves Close

60% 5935-60% 587-594°F25-35% 587°F

6 valves, ~ 60% of full-load steam capacity

Condensate & Feedwater System

Safety-Related Functions:

• Main feedwater isolation as necessary

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• Containment isolation of SG blowdown cooler supply & return lines

Fig. 4-6 Condensate & Feedwater System

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To SG Blowdown Coolers

Fig. 4-6 (cont’d)

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To 1st-Stage FW Heaters

To Deaerator

Fig. 4-6 (cont’d)

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To SG Warming Headers

Fig. 4-6 (cont’d)

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To MFW Headers Via HP FW Heaters

Fig. 4-6 (cont’d)

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Fig. 4-7 Condensate & Feedwater System

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5 – 20%

0 – 5%

Fig. 4-7 (Cont’d)

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●●●● ●

●

20 – 100%

Fig. 4-7 (Cont’d)

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Fig. 4-8 Condenser Circulating Water System

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Fig. 4-9 Condenser Circulating Water System

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Emergency Feedwater SystemSafety-Related Functions:

• Provides flow to SGs to cool down RCS (via MSRTs) to RHRS initiation conditions under transient & accident conditions

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• Isolates EFWS flow to the affected SG following an MSLB

• Isolates EFWS flow to an SG with an SGTR

• Provides sufficient inventories in storage pools to support cooldown requirements

~110,000 gal

400 gpm FCV LCV Isolation

Discharge Header normallyIsolated between S/Gs

~95,600 gal

~95 600 gal

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Start Signals: LOOP w/ SI (all SGs)<40% WR (individual SG)

Isolation Signals (affected SG): >89% WR; (1) partial cooldown initiated + (2) high SG level or high steam line radiation (SGTR indication).

Suction Header normally Isolated between storage pools

~95,600 gal

~110,000 gal

Fig. 4-10 EFWS