About Zwentendorf Nuclear Power Plant

ZNPP

G. Weimann

June 26th, 2013 Zwentendorf NPP

Hot Water Reactor Technology

§  „In a hot water reactor, heated water is pumped into the pressure container of the reactor. Here the fuel is uranium oxide enriched up to 4.02% by uranium 235. The pressure vessel is two-thirds filled with water. Through core decaying heat, parts of the water are vaporised into steam which drives the turbine--in Zwentendorf a pressurised turbine and three low-pressure turbines. Afterwards, water vapour leaves the turbine-about 7000 tonnes per hour-which is then cooled in the condenser and recycled. The advantage of hot water is that only water is needed, and they are simple to construct, but a disadvantage is radiation exposure in the steam turbines, although the steam has relatively little radioactivity.“ EVN-Website 2013

.

Basic concept Nuclear energy è Thermal energy è Electric energy The fundamental concept is similar to the concept used for conventional large thermal power plants –

of e.g. the Benson Boiler type.

Zwentendorf NPP

Danube River Offgas Stack

Reactor Building Turbine Hall

Control Room Building Hot Shop

Cold Shop Emergency Diesel Bld.

Startup Transformer Main Transformer

House Load Transformer Transformer

Startup-Boiler

Boiling Water Reactor: April 4th,1972 •  Turn key plant: AEG-GE modification: Siemens-KWU-BWR Vintage 69 •  Power 723 / 692 MWe net

•  Investment 1,044 bill. € total 5 bill. € •  Owners: 50% grid operator 50% regional electricity suppliers •  1 out of 3 planned in Austria 1986 Abandoned November 15th, 1978

For Boiling Water Reactor Designs

§  All operate on the same principles:

•  High coolant pressure is maintained by controlled coolant boiling

•  Heat transfer from fuel to the reactor coolant water to produce steam

•  The nuclear power conversion is controlled by the water circulated and control rods absorbing neutrons

•  Emergency systems are installed, capable to shut the reactor down and remove residual and decay heat from fuel for postulated transients and accidents and to keep the reactor in safe shutdown condition

NSSS-Differences between PWR-BWR

PWR: Design features: §  two coolant circutis:

primary: water secondary: steam-water

§  High primary operation pressure operation temperature

§  control rods moving top down gravity driven

BWR: Design features: •  single coolant circuit:

steam-water

•  Intermediate operation pressure operation temperature

•  control rods insertion from bottom up HP-water driven by gas cushion

NSSS-Differences between PWR-BWR PWR: §  control the power: o  reactor power control:

coolant boration control rods

o main coolant pumps o  pressurizer control o  steam generator valves

PORVs §  fast power control: o  reactor TRIP o RV/SV o  turbine bypass

BWR: •  control the power: o  reactor power control:

control rods o  coolant recirculation o  feedwater control o  PORVs

§  fast power control: o  reactor SCRAM o  borated water injection o  Standby Liquid Control S. o Automated depress. Syst. o  turbine bypass

NSSS-Differences between PWR-BWR PWR: cool the fuel: §  Core cooling options:

SGs MCP ECCS: o HPIS High Pressure

Injection System o ACCs Accumulators o  LPIS Low Pressure

Injection System o DHRS Decay Heat

Removal System

BWR: cool the fuel: •  Core cooling options:

MFPs/IRPs ECCS: o HPCI High Pressure

Coolant Injection o CS Core Spray System o RCIC Reactor Core

Isolation Cooling o  LPCI Low Pressure

Coolant Injection o RHR Residual Heat

Removal System

NSSS-Differences between PWR-BWR

PWR: retain radioactivity: §  Containment contains: o  reactor o  steam generators o  primary coolant loops o main coolant pumps

§  Containment structure: double wall concrete prestressed/reinforced

BWR: retain radioactivity: •  Containment contains: o  reactor o  dry-well (free volume) o wet-well (em. / heat sink) o  coolant recirculation

equipment

§  Containment structure: double steel wall/double wall concrete

ZNPP Site

BWR Layout

Containment & Internals

Functions: Barrier

Retention

Containment Pressure Control Containment Spray System

Containment Fan Coolers System Heat Removal – Heat Sink

Pressure Boundary Isolation Function Wet Well: Coolant Reservoir Heat Sink

Containment & Internals

BWR - ABWR Evolution 1

§  RPV

Fuel - Control Rod Assembly

To provide for power conversion

design, construct, operate and control the turbo-generator

Plant Cycle Scheme

The process to convert energy Its primary means are heat transfer to water to

transform it into steam in a cycle process it works similar to a Rankine cycle

In more detail, but still very simplified the cycle looks like that:

The process cycle

§  The NSSS – the reactor coolant system §  Superheater §  Turbogenerator Set §  Condenser §  Condensate Pumps §  Preheaters §  Feedwater Tank §  Feedwater Pumps

§ …and it works…

Boiling Water Reactor Control

§  control is done by adapting recirculation of the coolant in the reactor,

§  controls use the specifics of the boiling off of water to steam to control the power output

For Boiling Water Reactor Designs

Both control rod withdrawal and

flow increase are used to cool the fuel and control

the power

Control of the cycle §  Provides for a continuous energy conversion §  Allows to adapt conversion to demand §  Enables to cope with adverse conditions …to balance the multiple-stage conversion from thermal to gasdynamic to mechanic power

exemplary, control the pressure by adjusting the flow to the turbine...

BWR - ABWR Evolution

BWR - ABWR Evolution

Remarks – Questions and Comments?

ZNPP Layout for Comparison

Exemplary Practice Options

§  Structures, systems, components and materials important to safety

§  Management systems §  Operational activities §  Plant Monitoring §  Activities and Results with TSO, contractors and other

service providers §  Activities and Results augment Competence of staff §  Safety culture practical Exercises §  Liaison with organizations relevant for joint activities §  Checks on interactive processes in a close to reality

context … etc.

ZNPP Site Walkdown

Itinerary schematic

Thank you for your attention and please

follow us in the tour ...

ZNPP Emergency Cooling Systems

TH Residual Heat Removal Syst. 4 train RHR Nachkühlsystem 4 motor pump from SFP// Wet Well //Sump to 2 Wet// 2 Dry Well Spray// 4 MSLs

TM After Emergency FW System 1 train LPCS Nachspeisesystem pump - coolant from Wet Well to RPV (to cooler to Wet Well)

TJ Emergency FW System 1 train HPIS Einspeisesytem turbine driven pump - coolant from Wet Well to RPV

TK Flooding System 1 train LPCS Flutsystem motor pump - coolant from Wet Well to core spray nozzles

YT Fast Shutdown SCRAM 3 v 4 Notabschaltsystem 3 N2-

HP-ECCS

RCIC Reactor Core Isolation Cooling System

LP-ECCS

LPCI Low Pressure Coolant Injection System

Core Cooling Systems

Emergency Core Cooling Systems GE ZNPP

High-Pressure Coolant Injection System HPCI TJ Isolation Condenser Reactor Core Isolation Cooling System RCIC TG Automatic Depressurization System ADS yes Low-Pressure Core Spray System LPCS TM Low-Pressure Coolant Injection System LPCI TK Depressurization Valve System DPVS yes Passive Containment Cooling System PCCS none Gravity-Driven Cooling System GDCS none