Systems Modeling for IFE Power PlantsSystems Modeling for IFE Power Plants

Rob Schmitt, Wayne MeierLLNL

High Average Power Laser Program MeetingLos Angeles, CA

June 2, 2004Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

RCS—6/2/04

IntroductionIntroduction

Update on lithium-cooled blanket model– W/FS interface ΔT constraint not yet included; waiting for

resolution of discrepancies in W surface temperature calculated by different codes

– Costing for FW and blanket now included (need to add shield/reflector)

Progress on the helium-cooled solid breeder concept– 1-D heat transfer calculations and temperature constraints for first

wall have been added– Breeding blanket details to be added next– Modular Rankine cycle unit efficiency scaling as function of He

outlet temp included

RCS—6/2/04

Systems code of Li-cooled blanket is based Systems code of Li-cooled blanket is based upon ARIES designupon ARIES design

• Material masses needed for cost scaling are roughly based on an ARIES-type blanket.

• First wall unit includes first wall (W/FS), Li coolant, and coolant channel outer wall (FS/SiC/W). (See detail on far right)

• Remainder is considered as the breeding blanket, mostly Li (~98%) with FS structures (2%).

• Shield has not yet been included (requirements likely different for IFE since no superconducting magnets to protect).

RCS—6/2/04

Costing for Li-cooled blanket is based on Costing for Li-cooled blanket is based on ARIES unit costs (escalated to 2004) ARIES unit costs (escalated to 2004)

Material Mass (Mg) Unit costs($/kg) (2004$)

Approximate cost ($M)

Tungsten 48 111 5.3

Ferritic steel 152 91 13.8

SiC 3.2 544 1.7Liquid lithium 337 67 22.6

Based on estimates the first wall/blanket will cost ~ $43 M

Example: Y = 300 MJ, p = 10 mtorr, Rwall = 8.9 m

FW unit = 1.5 mm W / 3.5 mm FS / 2 cm Li / 3 mm FS / 1 mm SiC / 1 mm W

Blanket = 60 cm thick, 98 vol% Li, 2 vol% FS

•Will use updated unit costs from Les Waganer (ARIES) when they are available.

RCS—6/2/04

He-cooled first wall has been modeledHe-cooled first wall has been modeled

Temperature Constraints– Tungsten Wall ≤ 2400 oC– Ferritic Steel ≤ 800 oC

Steady-state heat flux

–

– Includes 3.5% heating from neutrons

Heat transfer coefficient is an important parameter to understand. (needs to remove heat from system)

24335.0

"w

f

RP

q

distance

temp

W FS Forced He

q”

2400 oC (max)

800 oC (max)

THe

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Radius of first wall depends on target Radius of first wall depends on target yield and chamber gas pressureyield and chamber gas pressure

0 100 200 300 400 5002

4

6

8

10

12

10 mtorr20 mtorr

Target Yield, MJ

Cha

mbe

r rad

ius,

m

Rep-Rate = 10 Hz

Given a specific target yield, we can find the allowable

chamber radius

•Chamber radius determined by using W temperature constraint (2400 C) for single pulse ΔT.

300 MJ

154 MJ

RCS—6/2/04

A heat transfer code was used to find the A heat transfer code was used to find the convective heat transfer coefficientconvective heat transfer coefficient

Dr. Shahram Sharafat (UCLA) has provided us with a heat transfer code which calculates the convective heat transfer coefficient for helium based upon a variety of parameters.– Heat transfer dependent on pressure, velocity, temperatures, pipe diameter

and roughness.– Using a fixed velocity (v = 50 m/s) and fractional roughness (10% of pipe

diameter) a parameter study was done in Mathcad to find a curve-fit for the heat transfer coefficient.

348.0

,

668.0

,

804.001.0

50773

89100

2

mh

m

KHe

K

MPa

He

KmW DT

Ph

2 MPa < P < 30 MPa 350 K < T < 1100 K

2.5 mm < D < 2 cmCurve fit within 10% for:

RCS—6/2/04

The heat transfer coefficient needed is within The heat transfer coefficient needed is within reasonable limits of engineering designreasonable limits of engineering design

Need adequate cooling of the steady-state fluence using convection of the helium along the ferritic steel surface.

Constants: 10 mtorr Xe, Dpipe= 1.7 cm, P = 8 MPa, V = 50 m/s

• At fixed He pressure, HT coefficient decreases with increasing temperature

• 154 MJ case allows Tmax = 860K HT coeff ~ 8200 W/m2K

• 300MJ case allows Tmax = 830K HT coeff ~ 8400 W/m2k

700 750 800 850 900 950 10006000

7000

8000

9000

1 104

Heat transfer coefficient154 MJ, 10 Hz300 MJ, 10 Hz

Helium Temperature (K)

Hea

t Tra

nsfe

r Coe

ffic

ient

(W/m

2-K

)

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The max allowable FS temp is the limiting The max allowable FS temp is the limiting constraint and sets the max He outlet tempconstraint and sets the max He outlet temp

6 7 8 9 10600

800

1000

1200

Helium OutletFS/He InterfaceW/FS InterfaceW/FS constraint

Chamber Wall Radius (m)

Tem

pera

ture

(K)

•The FS temp (1073 K at the W/FS interface) is the most constraining temp, therefore helium temperature is set for given yield and rep-rate.

•As shown on graph, the He outlet temp is given for a specific yield and radius.

Yield = 300 MJ

Rwall = 8.9 m

RCS—6/2/04

A modular Rankine cycle model is being A modular Rankine cycle model is being developed to couple with the blanket designsdeveloped to couple with the blanket designs

Curve fits have been created to model the efficiency of the steam cycle based upon chamber outlet helium temperature, as this is the most important parameter.

Cycle efficiencies range from 38-42% for 154 MJ and 300 MJ examples. (assuming chamber outlet = FW outlet temp)

If blanket materials can operate at higher temps, He from FW could be channeled through blanket to achieve higher chamber outlet temp and efficiency.

Thanks to R. Raffray for providing tabular Rankine cycle efficiency data.

600 700 800 900 1000 11000.2

0.3

0.4

0.5

Helium Outlet Temp. from Chamber (K)

Ran

kine

Cyc

le E

ffic

ienc

y @

573

K In

let

RCS—6/2/04

Summary / next stepsSummary / next steps

Work on the lithium-cooled blanket design is essentially complete

Helium-cooled first wall scaling complete Rankine cycle efficiency scaling now included Next steps

– Add solid breeder blanket information.– Include blanket cooling approach – coupled or separate from FW

cooling?– Add costing for solid breeder blanket.– Possibly start on molten salt coolant/breeder option.