Investigation into the Viability of a Investigation into the Viability of a Passively Active Decay Heat Removal Passively Active Decay Heat Removal

System In System In ALLEGROALLEGRO

Laura Carroll, Graduate PhysicistPhysics & Licensing Team, AMEC

MSc Physics & Technology of Nuclear Reactors University of Birmingham

22

Countries we work in

Introduction: My Project at a GlanceIntroduction: My Project at a Glance

To assess a proposed modification of a safety feature of a new type of reactor

Use of RELAP5/MOD3

Steady State (normal operation)

Loss Of Forced Cooling (LOFC) transient (accident scenario)

ALLEGRO: experimental demonstration reactor for the Gas Cooled Fast Reactor

33

1 0f 6 designs chosen by Generation IV International Forum (GIF)

Fast spectrum

Helium coolant

High outlet temperature

High power density

The Gas Cooled Fast ReactorThe Gas Cooled Fast Reactor

44

ALLEGROALLEGRO

55

Residual Heat; the need for constant Residual Heat; the need for constant cooling post shutdowncooling post shutdown

Once a reactor is shut down, its power will fall to approximately 7% of full power and then reduces exponentially thereafter.

The Decay Heat Removal (DHR) system exists to remove this residual heat from the reactor core.

It is currently activated after a reactor trip by a valve sequence

66

Loss of Forced Cooling Transient: Existing Loss of Forced Cooling Transient: Existing DesignDesign

After 10s Blower begins to run

down The reactor is shut down When mass flow rate reaches 3% of

its original flow, main loop valve closes

Simultaneously, DHR loop valves open

7

Modification: Direct connection and Modification: Direct connection and Stratification of Upper PlenumStratification of Upper Plenum

8

Stratification of the Upper PlenumStratification of the Upper Plenum

9

Stratification of the Upper Plenum: LOFCStratification of the Upper Plenum: LOFC

Core outlet temperature as a function of time

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Time (s)

Tem

per

atu

re (

K)

original

New

strat

Maximum clad temperature in hot channel as a function of time

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Time (s)

Te

mp

era

ture

(K

)strat

original

New

10

ConclusionsConclusions

Results are not ideal

Clad temperatures not as terrible as initially feared

Stratification of Upper Plenum showed great improvement on previous modifications

Substantial Potential for future Research and Development in this area

11

Further InvestigationsFurther Investigations

Develop a removable Decay Heat Removal system heat sink

Add a fluidic diode

12

For more information…For more information…

A Technology Roadmap for Generation IV Nuclear Energy Systems Dec 2002 U.S DOE Nuclear Energy Research Advisory

Committee

http://www.world-nuclear.org/info/inf77.html

Vortex Diode Pumps: No Moving Part Pumping Systems, NuVision Engineering

http://www.nuvisioneng.com/uploads/VortexDiodeProfile.pdf

Thank you…Thank you…

Any Questions?Any Questions?

1313

Parameter Original Stratificationcore power (MW) 50.00 50

Total mass system (Kg) 11126.67 11055.25pressure lower plenum (Pa) 7090038.00 7090040.00pressure upper plenum (Pa) 7029872.00 7025060.00

core inlet temp (K) 535.76 494.80core outlet temp (K) 835.39 769.83

Mass flow out of average channel (Kg/s) 27.52 29.95Max clad temperature hot channel (K) 893.16 823.94Max fuel temperature hot channel (K) 1320.55 1255.54

DHR hot leg mass flow rate (Kg/s) 0.07 7.38DHR hot leg temperature (K) 835.38 769.82DHR cold leg temperature (K) 363.78 622.93

Mass flow rate main heat exchanger (Kg/s) 32.00 34.84Total main heat exchanger flux -50365542.00 -33683116.00Total DHR heat exchanger flux 0.13 -4668545.40

14

Mass Flow rate through DHR hot leg and main heat exchanger (hx) as a function of time

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Time (s)

Ma

ss

flo

w r

ate

(kg

/s)

DHR

Main HX

Mass Flow rate through core as a function of time

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Time (s)

Mas

s fl

ow

rat

e (k

g/s

)

Maximum fuel temperature in hot channel as a function of time

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Time (s)

Tem

per

atu

re (

K) fuel

clad

1. Region of Blower run down

2. Establishment of Natural Convection

3. Natural Convection

LOFCLOFC resultsresults