Modeling SNS Availability Using BlockSimGeoffrey Milanovich

Spallation Neutron Source

2 Managed by UT-Battellefor the U.S. Department of Energy

Contributors

• G. Dodson for providing initial reliability study and discussion

• Vivian Chang (summer student from Carnegie Mellon) for building much of the accelerator reliability block diagram

3 Managed by UT-Battellefor the U.S. Department of Energy

Outline

• SNS Availability Numbers

• Modeling an Entire Accelerator in BlockSim

• Modeling Klystron End of Life Behavior

4 Managed by UT-Battellefor the U.S. Department of Energy

Availability for Last 2 Runs8/

8/20

118/

22/2

011

9/5/

2011

9/19

/201

110

/3/2

011

10/1

7/20

1110

/31/

2011

11/1

4/20

1111

/28/

2011

12/1

2/20

1112

/26/

2011

1/9/

2012

1/23

/201

22/

6/20

122/

20/2

012

3/5/

2012

3/19

/201

24/

2/20

124/

16/2

012

4/30

/201

25/

14/2

012

5/28

/201

26/

11/2

012

6/25

/201

2

40%45%50%55%60%65%70%75%80%85%90%95%

100%

Neutron Beam % Available

Run Running Avg.

Commitment

FY running Avg.

% a

vaila

ble

FY12 Availability – 93.6%

5 Managed by UT-Battellefor the U.S. Department of Energy

FY 12 Downtime by Group

RF

E-HVCM

Ion S

ource

E-othe

r

E-Mag

PS

Contro

ls

Physic

sCryo

Beam In

st.

Prot.

Sys.

Vacuu

m

CM/SRF

Coolin

g

RS/ESH

E-Cho

p...

Mech.

Ops

Targe

t0

10

20

30

40

50

60

70

80

90

100FY12-2FY12-1

Hou

rs d

own

6 Managed by UT-Battellefor the U.S. Department of Energy

Neutron Production Hrs, MWhrs, & Downtime by Year

FY07 FY08 FY09 FY10 FY11 FY120

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

60

65

70

75

80

85

90

95

100

Hrs. delivered

MWh delivered to target

Downtime

Availability

Hou

rs D

eliv

ered A

vailability %

7 Managed by UT-Battellefor the U.S. Department of Energy

Presentation_name

Downtime by Fiscal Year (07-12) ComparisonE-

HVCM

Ion

Sour

ce RFTa

rget

E-M

agPS

E-ch

oppe

rCo

ntro

lsVa

cuum

Co

olin

g E-

othe

rCr

yo APPr

ot. S

ys.

Mis

c./M

ag/R

S/ES

H BIFa

c./M

ech.

Sys

.Op

sNe

ut. I

nst.

0

50

100

150

200

250

300

350

400

450

FY07

FY08

FY09

FY10

FY11

FY12

System

Hour

s of

dow

ntim

e

8 Managed by UT-Battellefor the U.S. Department of Energy

Reliability Estimates, in the Beginning

• “the spreadsheet” – numbers from industry, design specs, LANL, JLab, experts, and guesses

• Exponential distributions only (constant failure rate)

• For 160 hours mission time, availability:– Source – 87%– Linac – 80%– Modulators – 99%– Overall - ??

9 Managed by UT-Battellefor the U.S. Department of Energy

RBD/BlockSim Advantages

• Reliability Block Diagram (RBD) – “graphical representation of the components of the system and how they are reliability-wise related”

• Many failure distributions allowed

• Standby, load share, failure of switching to standby

• Analytical solution of very complex diagrams (but not an accelerator)

• Monte Carlo simulation – maintenance phases, spares, crews

10 Managed by UT-Battellefor the U.S. Department of Energy

BlockSim 7/8 Model

11 Managed by UT-Battellefor the U.S. Department of Energy

Ion Source

12 Managed by UT-Battellefor the U.S. Department of Energy

RF Systems

13 Managed by UT-Battellefor the U.S. Department of Energy

Standby Containers

14 Managed by UT-Battellefor the U.S. Department of Energy

Full Accelerator Simulation Results

• Used exponential distributions (random failures)

• 86% - corrector power supplies, circulators, PPS modules, water valves, JT valves, etc.

• Change values for PS controllers and circulators from 50k to 100k

• 89% - RF feedthroughs, JT valves, etc.

• Change RF feedthrough from 100k to 4m (1 every 7 years), JT valves from 87k to 400k (1 every 5 years), etc

• 92% - Finally! But only for 1 seed

15 Managed by UT-Battellefor the U.S. Department of Energy

Klystron Spares Study

• 805 MHz, 550 (700) kW peak, 50 kW average power, 1.5 ms pulse length, 9% duty cycle

• M type cathode, 0.6-0.7 A/cm2 density, manufacturer predicted lifetime > 100,000 hours

• 81 in service, 70 with ~40000 hours on filament

• How many spares to order and how quickly?

16 Managed by UT-Battellefor the U.S. Department of Energy

Klystron High Voltage Hours

0

10000

20000

30000

40000

50000

0 10 20 30 40 50 60 70 80 90 100

Klystron Position

Ope

ratin

g H

ours

17 Managed by UT-Battellefor the U.S. Department of Energy

Weibull Distribution Parameters

Beta – “Shape” Parameter Eta – “Scale” Parameter

18 Managed by UT-Battellefor the U.S. Department of Energy

Klystron failures, different values of β

19 Managed by UT-Battellefor the U.S. Department of Energy

Klystron failures, different values of η

20 Managed by UT-Battellefor the U.S. Department of Energy

Cathode Life Time

• Dispenser Cathodes: The Current State of the Technology– L. R. Falce, Hughs Aircraft Company, Electron Dynamics Division, IEDM 83

1.00E+03

1.00E+04

1.00E+05

1.00E+06

0.1 1 10 100

Current Density (Amps/square cm)

Life

(Hou

rs) B,S

M,CD (Alloy) MM, SCANDATE

21 Managed by UT-Battellefor the U.S. Department of Energy

Conclusions

• SNS is middle aged - how long will it last?

• We still can not predict the wear-out curve – until it begins! But we can model maintenance plans

• Cathode lifetime may not be a major concern

• Klystron spares can be ordered at a steady rate