1 Draft Discussion Materials for Session 10: Device Availability Factor and Plasma Duty Factor in FNF Discussion on: 1.What availability goals are required

1

Draft Discussion Materials for Session 10: Device Availability Factor and Plasma Duty

Factor in FNF

Discussion on:1. What availability goals are required for FNF? What

are the corresponding MTBF and MTTR for various components and for base blanket?

2. What are the requirements on periods of continuous operations (test campaigns)? What are the requirements on the plasma duty cycle during these test campaigns?

3. What is the minimum achievable plasma dwell time? Maximum burn time during a pulse? Maximum plasma duty cycle?

4. What is needed to realize the above goals for the device availability factor and plasma duty factor?

Discussion Facilitator: Burgess Summary Preparer: Ying

2

Some RAMSome RAM terminologyterminology Availability (Due to Unscheduled Events)= AAvailability (Due to Unscheduled Events)= AUU

i

Risk Outage1

1

MTBF = mean time between failures = 1/failure rate

MTTR = mean time to repair

AU = represents a componenti

(Outage Risk) = (failure rate) • (mean time to repair) = i

i

MTBF

MTTRii i

Device Duty Factor= AS x AU

Plasma Duty Factor = time)Dwell (Burn time

Burn time

Fluence (integrated neutron wall load) = Neutron wall load x Calendar years x (Device Duty Factor x Plasma Duty Factor)

(Plasma duty factor = 1 for steady state operation)

Availability (Due to Scheduled Outage) = AAvailability (Due to Scheduled Outage) = ASS

3

LowerDiverter

Test Module

Upper Breeding Blanket

Lower Breeding Blanket

Shielding

Blanket Test Section

UpperDiverter

TFC Center

Leg Plasma

R0=1.2A=1.5к=3.2δ=0.4Ip = 12

TFC Return Leg / Vacuum Vessel

Support Platform

Inboard FW (10cm)

OutboardFW

(3cm)

Access Hatch

(VV/TFC Return)

Diverter/SOL Shaping Coil

Sliding Joint

Inlet Piping

Outlet Piping

Vacuum Seals

Neutral Beam Duct

Poloidal Field Coils

ST Component Test ST Component Test Facility (CTF)Facility (CTF)

Provides fusion nuclear technology test environment in support of Demo development

ITER-Era

Wall load: ~ 1 MW/m2

Fluence,~ 3 MW-yr/m2, (6 MW-yr/m2 later phase)

High Plasma Duty Factor Goal (30%),steady state, no dwell

User Facility maximizing test ports

Builds on ITER RH approach and technology

4

Disconnect upper pipingRemove sliding electrical jointRemove top hatch

Remove upper PF coilRemove upper diverterRemove lower diverterRemove lower PF coil

Extract NBI linerExtract test modulesRemove upper blanket assemblyRemove lower blanket assembly

Remove centerstack assembly

Remove shield assembly

Upper PipingElectrical JointTop Hatch

Upper PF coilUpper DiverterLower DiverterLower PF coil

Upper Blanket Assy

Lower Blanket Assy

CenterstackAssembly

ShieldAssembly

NBI Liner

Test Modules

• Similar to fission power plants, large vertical top access with large component modules with simple vertical motion expedites remote handling, minimizes MTTR and maintenance outages

• All welds are external to shield boundary are hands-on accessible• Parallel mid-plane/vertical RH operation

ST CTF has High Maintainability, Low MTTR, Using ST CTF has High Maintainability, Low MTTR, Using Large Integrated In-Vessel ModulesLarge Integrated In-Vessel Modules

5

Component RH Class

Expected Frequency

RH Operation Time Estimate* (very preliminary, improvable by practicing)

Divertor Module

1 ~ At least annually ~ Parallel operation

Upper module: ~ 4 weeks

Upper and lower: ~ 6 weeks (assuming center stack not removed)

Mid-plane Port Assemblies ~ 3 weeks per port assembly

Neutral Beam Ion Source ~ 1 week per NBI

In-vessel Inspection (viewing/metrology probe)

1 Frequent deployment

Single shift (8-hr) time target (deployed between plasma shots, at vacuum & temp.)

Upper and Lower Breeder Blanket (to approach tritium self-sufficiency)

2

~ Several times in life of machine ~ In parallel with mid-plane operation

Upper: ~ 6 weeks

Upper and Lower: ~ 9 weeks (need to retract mid-plane modules)

Center Stack ~ 6 weeks Neutral Beam Internal Components ~ 2 to 4 weeks

Vacuum Vessel Sector / TF Coil Return Conductor

3 Replacement not expected

Replacement must be possible and would require extended shutdown period

Shield

ST CTF Preliminary Component RH Time EstimatesST CTF Preliminary Component RH Time Estimates

6

ST CTF Very Preliminary RH Class 1 Annual ST CTF Very Preliminary RH Class 1 Annual Maintenance Time Estimate = ~ 1/4 YearMaintenance Time Estimate = ~ 1/4 Year

• A typical annual RH Class 1 remote maintenance campaign might replace:– 2 divertor modules (6 weeks*)– 6 midplane port assemblies (3 weeks ea.*)– NBI ion sources (1 week ea.*)

* Two 8 hr shifts per day, 6 work days per week during shutdown

• Each uses a different RH system, parallel operations are possible, and the midplane port changeouts are limiting provided at least 2 are being changed (6 weeks serial time)

• Assuming 3 midplane port RH casks are available for parallel operations, it is estimated to take ~ 8 weeks to complete the above tasks provided spare units are available.

• Add shutdown and machine pump down / conditioning time of 1 month, and the total outage from plasma burn to plasma burn is ~3 month or 0.25 of the year

• One unplanned port assembly failure (TBM, RF heating or diagnostics) that shuts the machine down, and that can't be delayed until the scheduled maintenance time, will consume ~ 6 weeks of maintenance time and 1 month of shutdown / startup time, or ~ 0.25 of the remaining year.

• Every shutdown requiring opening and venting of the vessel will require in excess of a month to recover, hence in-vessel maintenance should be planned and grouped together

• If components are operated to failure, 1 divertor + 1 midplane port failure not occurring at the same time frame could consume ~ 5 to 6 months of the year.

7

Current Baseline Requirements for In-vessel/ex-vessel RH InterventionsCurrent Baseline Requirements for In-vessel/ex-vessel RH Interventions

• The ITER remote handling equipment design and procurement is based on a maintenance requirement plan.

COMPONENTS MAINTENANCE REQUIREMENTS PLAN

1

4

7

10

13

16

19

Div

ert

or

TB

MN

B fi

lam

ent/

oven

Port

Lim

iter

All

Bla

nke

tS

om

e B

lanke

tsC

ryopum

pEC

H/IC

HEq/U

p d

iagn

ost

ics

NB

sourc

e c

lean

NB

valv

e0

20

40

60

80

100

120

WEEKS

YEARS

CLASS 1 & 2 COMBINED MAINTENANCE OPERATIONS(for multiple component's systems, operations are done in parallel)

8

Initial comments on burn and dwell time(B. Nelson, W. T. Reiersen, L. Cadwallader)

• The 400 seconds burn time in ITER is an inductive limit, i.e. they don't assume they can get much current drive.

• On ITER (with S/C coils), the operable limit seems to be the cryogenic system due to an economic limitation, not a technical limit.

• S/C coils can also be limiting if the helium transit time is long relative to the burn time - this could reduce the temperature headroom because the helium entering the high field region keeps getting hotter over time because equilibrium is not yet reached.

• The NBI system could be the limiting factor for CTF, since the cryo-pumps will not pump indefinitely and they don't seem to be able to have two sets working alternately for NB systems.

9

Reliability/Availability/MaintainabilityCritical Development Issues for DEMO and Fusion Power

Availability is determined by: a) reliability of components (unscheduled maintenance) b) life time of components (scheduled maintenance)

c) time required for replacement (down time)

• High availability is essential if fusion is to be economically competitive

10

11

DIII-D Tokamak Systems

Sys

tem

Fai

lure

Rat

e (/

hr) Preliminary system

failure rate goal for a fusion power plant

Preliminary system failure rate goal for ITER

λ > 1E-0110-1

10-2

10-5

10-3

10-4

Lee CadwalladerFusion Safety Program

ARIES-Pathways Project Meeting, GIT, Atlanta, GA, December 12-13, 2007

• Fusion experiments track “mission availability” which is actual operating hours compared to funded operating hours in the calendar year. Tokamaks are 60-80% mission available over 8 or 10 hour days of perhaps ~20 weeks/year. This is ~11% calendar availability. Such availabilities are early in a technology development path.

12

Example MTBF and MTTR of various major components of a Demo

13

Example MTBF and MTTR from Existing Tokamak Systems to Apply to an FNF

System Failure rate,/h MTBF, years

MTTR, major failure, h

MTTR, minor failure, h

Fraction of failures that are major failures

Outage Risk (OR), MTTR/MTBF

System Availaibility

TF coil set 1.0E-03 0.114 26280.0 24.0 0.01 0.2866 0.7773PF coil set 1.0E-04 1.142 350.0 24.0 0.10 0.0057 0.9944Magnet power Sup. 1.0E-02 0.011 100.0 5.0 0.01 0.0595 0.9438Water cooling system 1.0E-04 1.142 100.0 8.0 0.10 0.0017 0.9983Blanket 1.0E-04 1.142 1512.0 672.0 0.10 0.0756 0.9297Divertor 1.0E-04 1.142 1008.0 24.0 0.10 0.0122 0.9879RF Plasma Heating 1.0E-03 0.114 504.0 24.0 0.10 0.0720 0.9328TBM 2.0E-04 0.571 504.0 24.0 0.10 0.0144 0.9858Diagnostics 2.0E-04 0.571 504.0 24.0 0.10 0.0144 0.9858NBI 2.0E-04 0.571 672.0 168.0 0.10 0.0437 0.9581Fueling (PI) 1.0E-03 0.114 10.0 2.0 0.10 0.0028 0.9972Tritium plant 1.0E-05 11.416 200.0 8.0 0.10 0.0003 0.9997

Vacuum system 1.0E-03 0.114 250.0 8.0 0.10 0.0322 0.96880.050 0.9524

0.7 0.5984Conventional facilities SI&C, service water, ventilation, electric distribution, etc.

TOTAL FACILITY due to Unscheduled Events (maintenance only)

Total Facility AU (with 4 weeks pre and post conditioning) = 0.5984 *(48/52)= 0.552

14

What FNF availability needed to achieve 3 MW-y/m2 in 10 years for 1 MW/m2 neutron wall load

Mean

As 0.750 0.750 Au 0.500 0.800 Plasma duty factor 0.800 0.500

Year 1-2 Year 3-4 Year 5-6 Year 7-10

MW-y/m2 0.1 0.2 0.3 0.45Accumulated fluence 0.2 0.6 1.2 3.00

As 0.75 0.75 0.75 0.75Au 0.53 0.53 0.53 0.75Plasma duty factor 0.25 0.50 0.75 0.80

1 MW/m2 to achive 3 MW-y/m2 in 10 calendar years

15

Example MTBF and MTTR from Existing Tokamak Systems to Apply to an FNF (ST-

CTF)







TF coil set 1.0E-03 0.114 26280.0 24.0 0.01 0.2866 0.7773PF coil set 1.0E-04 1.142 350.0 24.0 0.10 0.0057 0.9944Magnet power Sup. 1.0E-02 0.011 100.0 5.0 0.01 0.0595 0.9438Water cooling system 1.0E-04 1.142 100.0 8.0 0.10 0.0017 0.9983Blanket 1.0E-04 1.142 2184.0 672.0 0.10 0.0823 0.9239Divertor 1.0E-04 1.142 1680.0 24.0 0.10 0.0190 0.9814RF Plasma Heating 1.0E-03 0.114 1176.0 24.0 0.10 0.1392 0.8778TBM 2.0E-04 0.571 1176.0 24.0 0.10 0.0278 0.9729Diagnostics 2.0E-04 0.571 1176.0 24.0 0.10 0.0278 0.9729NBI 2.0E-04 0.571 1344.0 168.0 0.10 0.0571 0.9460Fueling (PI) 1.0E-03 0.114 10.0 2.0 0.10 0.0028 0.9972Tritium plant 1.0E-05 11.416 200.0 8.0 0.10 0.0003 0.9997

Vacuum system 1.0E-03 0.114 250.0 8.0 0.10 0.0322 0.96880.050 0.9524



16

Example MTBF and MTTR from Existing Tokamak Systems to Apply to an FNF (ST-

CTF)







TF coil set 1.0E-03 0.114 26280.0 24.0 0.01 0.2866 0.7773PF coil set 1.0E-04 1.142 350.0 24.0 0.10 0.0057 0.9944Magnet power Sup. 1.0E-02 0.011 100.0 5.0 0.01 0.0595 0.9438Water cooling system 1.0E-04 1.142 100.0 8.0 0.10 0.0017 0.9983Blanket (4) 4.0E-04 0.285 2184.0 672.0 0.10 0.3293 0.7523Divertor 1.0E-04 1.142 1680.0 24.0 0.10 0.0190 0.9814RF Plasma Heating 1.0E-03 0.114 1176.0 24.0 0.10 0.1392 0.8778TBM (8) 1.6E-03 0.071 1176.0 24.0 0.10 0.2227 0.8178Diagnostics 2.0E-04 0.571 1176.0 24.0 0.10 0.0278 0.9729NBI 2.0E-04 0.571 1344.0 168.0 0.10 0.0571 0.9460Fueling (PI) 1.0E-03 0.114 10.0 2.0 0.10 0.0028 0.9972Tritium plant 1.0E-05 11.416 200.0 8.0 0.10 0.0003 0.9997

Vacuum system 1.0E-03 0.114 250.0 8.0 0.10 0.0322 0.96880.050 0.9524



8 TBMs; each has a MTBF of 0.57 FPY4 Blankets; each has a MTBF of 1.14 FPY

17

Draft Discussion Materials for Session 10: Device Availability Factor and Plasma Duty

Factor in FNF

Discussion on:1. What availability goals are required for FNF? What

are the corresponding MTBF and MTTR for various components and for base blanket?

2. What are the requirements on periods of continuous operations (test campaigns)? What are the requirements on the plasma duty cycle during these test campaigns?

3. What is the minimum achievable plasma dwell time? Maximum burn time during a pulse? Maximum plasma duty cycle?

4. What is needed to realize the above goals for the device availability factor and plasma duty factor?

Discussion Facilitator: Burgess Summary Preparer: Ying

18

• Back up slides

19

Session 10 Summary (to be revised during the discussion)

• Fusion system has many major components located inside the vacuum vessel.– Failures such as coolant leaks require shutdown (and redundancy in

the PFC/blanket is not feasible)– Repair/replacement takes long time

• The reliability requirements on Divertor/FW/Blanket are challenging due to a large surface area, long MTTR, and harsh environment, and must be

seriously addressed in FNF/CTF. – Predicting achievable MTBF requires real data from integrated tests in

the fusion environment. • One of the missions of FNF/CTF is to learn how to achieve a high device

availability under DEMO prototypical conditions, which include high heat load and surface heat flux, and moderate neutron fluence (i.e. 6 MW-y/m2.)

• This mission fills the RAM Gap that was identified in the FESAC Greenward Panel.

• A PRA-like approach that defines a RAM goal for each major fusion component can guide fusion energy development in a cost effective manner.

20

Example MTBFs & MTTRs from Existing Tokamak Systems with in-vessel RH MTTRs to Apply to an FNF

System Failure rate, /h

MTBF, years

MTTR, major

failure, h

MTTR, minor

failure, h



System Availability

TF Coil Set 1E-03 0.11 26,280 168 0.1 2.796 0.2634 PF Coil Set 1E-04 1.14 350 24 0.1 0.0059 0.9941 Magnet Power Sup.

1E-02 0.01 100 5 0.01 0.060 0.9434

Water Cooling Sys

1E-04 1.14 100 8 0.1 0.0018 0.9982

Blanket 1E-04 1.14 2940 1350 0.1 0.1644 0.8588 Divertor 1E-04 1.14 1680 1350 0.1 0.1518 0.8682 RF Plasma Heating

1E-02 0.01 1176 4 0.3 3.568 0.2189

Fueling (PI) 1E-03 0.11 10 2 0.1 0.003 0.9970 Tritium Plant

1E-05 11.4 200 8 0.1 2.8E-04 0.9997

Vacuum System

1E-03 0.11 250 8 0.1 0.033 0.9681

Conventional Facilities: I&C, service water, ventilation, electric distribution, etc ~ 0.05 0.9524 TOTAL FACILITY Availability = 1/(1+ Outage Risk) OR = 6.834 0.1276

21

Example MTBF and MTTR from Existing Tokamak Systems to Apply to an FNF

System Failure rate, /h

MTBF, years

MTTR, major

failure, h

MTTR, minor

failure, h



System Availability

TF coil set 1E-03 0.11 4400 24 0.1 0.464 0.6831 PF coil set 1E-04 1.14 350 24 0.1 0.0059 0.9941 Magnet Power Sup.

1E-02 0.01 100 5 0.01 0.060 0.9434

Water cooling Sys

1E-04 1.14 100 8 0.1 0.0018 0.9982

Blanket 1E-04 1.14 1350 670 0.1 0.0805 0.9255 Divertor 1E-04 1.14 1350 24 0.1 0.016 0.9843 RF Plasma Heating

1E-02 0.01 50 4 0.3 0.190 0.8403

Fueling (PI) 1E-03 0.11 10 2 0.1 0.003 0.9970 Tritium plant

1E-05 11.4 200 8 0.1 2.8E-04 0.9997

Vacuum system

1E-03 0.11 250 8 0.1 0.033 0.9681

Conventional facilities Š I&C, service water, ventilation, electric distribution, etc ~ 0.05 0.9524 TOTAL FACILITY Availability=1/(1+ Outage Risk) OR = 0.9045 0.5251

22

For Blanket Component Availability resulting from unscheduled maintenance requirements is more demanding than

lifetime requirements

MTTR = mean time to replace n = number of blanket segments = 80 (assuming 16 coils/sectors, 5 inboard + outboard blanket segments per sector) = failure rate per blanket segment MTBF = 1/ (Mean Time Between Failure) Note: a blanket segment has a full poloidal length in height and 1/48th toroidal circumference in width)

)(1

1

1

1

nMTTRoutageriskA dunschedule

Structural MaterialLifetime

MTTR MTBF per blanketsegment*

150 –200 dpa15- 20 MW.yr/m2

1 month (a minimumrequirement accountfor tight space andcomplexity)

42.7 years

For a neutron wallload of 2 MW/m2Lifetime ofstructure = 7.5 to10 years

2 weeks (Sectorreplacement schemecompensated withhigher capital costdue to larger vesseland coils)

21.35 years

*for achieving blanket availability of 86.5% and Demoavailability of 30%

23

Reliability Growth Testing is Key to Ensuring High FNT Component Reliability

A key objective of reliability growth testing in CTF will be to reduce the failure rate to an acceptable level

Beginning of life (BOL) failure mechanisms are easiest to address, because the failure rate is higher.

Improvements during the constant failure rate regime are sometimes elusive because the failure rate may be very small. These failures will be difficult to see in reasonable test times.

A Reliability growth testing program involves an iterative design/test/fix sequence aimed at improving component reliability.

Without such a program in a simulated nuclear fusion nuclear environment, FNT components intended for the first fusion facilities will represent new design applications without engineering precedence and will suffer from a lack of confidence in their estimated reliability.

Component failures are generally described by a “bathtub” curve.

24

Reliability Analysis Method for Component Testing Reliability Growth Model

A model allows the designer to estimate the amount of development effort needed to ensure that a reliability target is reached

Failure Models, Effect and Criticality AnalysisAn analysis process enables the test planner to identify the most critical constituents which must be addressed at the early stages of testing

Statistical methods are available to estimate:1. Cumulative test time required for MTBF demonstration tests at some

confidence level2. the required sample size and the

test time per test article for achieving goal MTBF

Bayesian ApproachAn approach taking into accountthe data (if available) from similar technology experiences which would

result in test time saving

NAVAIR reliability growth improvement model

An aggressive program of reliability development implies a higher growth rate and lesser testing times required for achieving the target MTBF

25

An Example CTF Device Duty Factor ScenarioA detailed assessment should be done during the CTF design exploration study

1. Group CTF into three major component categories

2. Perform best estimate of scheduled/unscheduled availability for each major component category

Engineering Components (coils, heating, current drive, tritium system, vacuum vessel)

Divertor (and Breeding Blanket Modules for tritium breeding) - Database from fission reactor testing- Reliability oriented (low T & p)

Test Modules for Demo Blankets and Divertors

Reliability growth

Ava

ilab

ilit

y

Time

10%

30%

Duty cycle increases; while approaching steady state operation

Insertion of test modules for Demo blankets and divertors

2035

• Initial availability with which has a low plasma duty factor?

• Insert test modules as the plasma duty factor grows to 80%?

• Availability drops to 9% as a result of test module insertion

3. Availability grows as reliability growth proceeds

26WG1 Presentation at JET 24/09/07

Ensuring the reliability of ITER systems - Ensuring the reliability of ITER systems - engineering practices, configuration control, engineering practices, configuration control,

and QA to support the procurementsand QA to support the procurements

• The achievement of the specified reliability and availability by ITER is challenging and requires careful attention to the Design, Quality Assurance, Testing, Maintenance and control of operation at every stage in the construction and operation of the facility.

• The appointment of a RAM officer and setting up of contracts with the EU and US to provide support are important initial steps, but more manpower must be found to avoid delay to the procurement.

• Better definition of the design and approval processes is required.

• Significant delays and design changes must be anticipated to arise from the detailed RAM analysis.

27

Major components of an ST-CTF

28

Example Port Assembly Replacement Tasks and Example Port Assembly Replacement Tasks and Time Estimates (from ITER and FIRE)Time Estimates (from ITER and FIRE)

Conditions and Assumptions

• Midplane port assembly is removed as an integrated assembly that is lip-seal welded to port, structurally attached at end of port (bolts and/or wedges) and is removed or installed in a single cask docking.

• Port assembly is transferred to hot cell and is replaced with a new or spare unit. If the removed assembly is to be reinstalled, the hot cell processing time must be added.

• If a port assembly is removed for other than a short period of time, the open port may be shielded to allow personnel access in the ex-vessel region of the machine. The time to install a shielded enclosure at the port is not included in the following estimate and would add days to the estimate.

• Operations are conducted in two 8-hour shifts per day (16 hrs total), 6 days per week.

• Time to leak check welded lip-seals and pipes not included. Could add a few days to campaign.

• Time to detritiate and vent the vessel after shutdown, and pump down and clean the vessel after maintenance are not included. Could add ~ 1 month to shutdown period.

29

Example Port Assembly Replacement Tasks and Example Port Assembly Replacement Tasks and Time Estimates (cont’d)Time Estimates (cont’d)

Task and Time Summary (assuming 16-hr days, 6 work days per week)

1) Hands-on prepare port for cask docking and 60 hrs 3.75 days

port assembly removal

2) Remotely remove port assembly and transfer to hot cell (remote) 28 hrs1.75 days

3) Remotely exchange port assembly at hot cell and return to port 20 hrs 1.25 days

4) Remotely replace port assembly in port 25 hrs 1.5 days

5) Hands-on port assembly recovery tasks 56 hrs 3.5 days

189 hrs11.8 days

Subtotal = 11.8 days + 2 days for leak tests, misc items = 13.8 days = 2.3 weeks (6 work days/week)

With 27.5% contingency = 17.6 days = ~ 3 weeks (6 work days/week, 16 hrs per day)

Assuming 24/7 continuous work weeks = [189 hrs + (2 x 16 hrs)] 1.275 = 282 hrs = 12 days or ~ 2 weeks

Documents

1 Draft Discussion Materials for Session 10: Device Availability Factor and Plasma Duty Factor in FNF Discussion on: 1.What availability goals are required