Nuclear Power Plant Risk Informed Life Management ver 9

Nuclear Power Plant Life Management

1 www.visisuite.net Phone: (719) 264-9991

The Challenges The first three sections of this write-up are

quoted from the IAEA June 2006 "Nuclear

Power Plant Life Management Processes".

"The design life of a nuclear power plant

(NPP) does not necessarily equate with the

physical or technological end-of-life (EOL) in

terms of its ability to fulfill safety and

electricity production requirements.

Operating equipment, generically called

critical systems, structures and components

(CSSCs) in a NPP is subjected to a variety of

chemical, mechanical and physical conditions

during operation. Such stressors lead to

changes with time in the CSSC material

properties, which are caused and driven by

the effects of corrosion, varying loads, flow

conditions, temperature and neutron

irradiation."

Life Extension Strategies

"Even allowing for significant ageing effects

in CSSCs, it is quite feasible that many NPPs

will be able to operate for times in excess of

their nominal design lives, provided

appropriate and proven ageing management

measures are implemented in a timely

manner. This aspect has been recognized by

operators and regulators alike, as seen in the

number of license renewal applications and

approvals, respectively, in the USA, and,

elsewhere, by extending licensing procedures,

primarily based on periodic evaluation of

safety, i.e. periodic safety reviews (PSR)."

Critical Systems Structures and Components (CSSCs)

"Key attributes of an effective plant life

management program include a focus on

important CSSCs (see Figure 1) which are

susceptible to ageing degradation, a balance

of proactive and reactive ageing management

programs, and a team approach that ensures

the coordination of and communication

between all relevant NPP and external

programs."

Figure 1. Pyramid of Plant Life Management CSSCs – IAEA June 2006 report on Nuclear Power Plant Life Management Processes.



"Continued plant operation, including

operation beyond design life (usually called

long term operation), depends, among other

things, on the physical condition of the

plant."

It comes down to assessing a number of life

extending strategies for CSSCs such as Fuel

Channels, Pressure Vessels, Feeders, and

Steam Generators. Each of these strategies

carries accompanying risks of success.

Multi-Unit Stations

Some station operators also deal with

implementing these strategies over multiple

reactor units which have different ageing

rates and mechanisms. Risk informed

scenario analysis is required to fully evaluate

the possible impacts of implementing the

various strategies across multiple CSSCs,

units and stations.

Commercial Considerations

Market pricing structures, electricity demand

and operational cost uncertainties

significantly impact operation, maintenance

and outage strategies. These commercial

considerations are subject to environmental

issues and the expanding demand for

alternate energy sources. Commercial

uncertainties contribute to the large number

of complex scenarios to be assessed. In

addition, the information, both technical and

commercial is dynamic and uncertain.

Figure 2, published in the Chockie Group

International Oct 2006 Ageing Management

and Life Extension in US Nuclear Power

Industry report, also recommends a scenario

approach to Life Cycle Management (LCM).

Here is a quote from their report.

"All potential LCM enhancements should be

identified, such that a concise list of new or

Figure 2. Life Cycle Management Flowchart - Technical and Economic Evaluation



modified maintenance activities can be

compiled, along with their costs and timing of

implementation. Each goal can be met by

a number of different options, called

Alternatives in the LCM process."

Scenario Charting Support

Scenario Charting Process Enablement

The above described challenges can be

effectively approached with a software

enabled scenario analysis process that

supports the LCM assessment steps shown in

Figure 2. Each scenario model consists of

alternate actions and mitigation plans that are

integrated with a unit base plan. Scenario

Charting software calculates and reports the

predicted impacts on unit maintenance and

refurbishment outage schedules and costs,

operational earnings and long term net profits

for each scenario.

Scenario Charting Process

VisiSuite LLC has developed the Scenario

Charting process to support the Nuclear

Power Industries efforts to more effectively

manage plant life sustainability and

implement effective CSSC life extension

strategies. Scenario Charting with our

VisiSuite software application enables and

enhances a highly successful visual planning

process. VisiSuite provides a seamlessly

integrated visual system for strategic, tactical,

scenario planning, scheduling, estimating and

analysis.

Visually Structured Planning Process

The Visually Structured Planning process

shown in Figure 3 is a consistently successful

work group planning technique that utilizes

clear meaningful pictures to focus program

planning. Its effectiveness is directly

dependent on the quality of the pictures and

Figure 3. Visually Structured Planning Process – Planning pictures are as important to planning as design diagrams are to system development.



facilitation techniques employed. Clear,

professional-quality visuals help a team cut

through the complexity of ideas being

presented, negotiate agreement and remain on

the same page during program execution.

Supporting Life Cycle Management

Predictive Life Cycle Analysis

At the heart of the Scenario Charting process

is a data repository containing a unit base

plan as well as additional or alternate actions,

designed to address uncertainties and mitigate

risks. These Scenario Charting elements are

configured into a set of scenarios that

implement various life extension strategies

and provide critical contingency plans as

shown in Figure 4.

Notional Power Plant Life Cycle Model

The remaining figures in this write-up are

snapshots from a notional "CANDU"

Scenario Charting program that helps

describes the predictive modeling, process,

analysis and capabilities of Scenario

Charting.

The Base Plan

This notional Canadian station unit plan

covers a six year period. For demonstration

purposes, the plan shows 329 day operational

periods followed by 36 day maintenance

outages each year. This hypothetical unit is

near the end of its normal operational life.

Therefore the last two years include a major

refurbishment followed by one operational

period. (A real plan base plan should exceed

its design lifetime.)

Figure 4. Scenario Charting Process – Scenario Charting actions are configured into a set of scenario - schedule/cost/profit projections.



Drivers

The process of planning scenarios begins

with the identification of environmental and

technological "drivers" from which various

life extension strategies, risks and

commercial uncertainties are derived.

Drivers are critical factors that influence

whether or not the key objectives will be

achieved.

Multiple Complex Scenarios

The base plan represents normal unit

operation and maintenance outages that

historically have proven to be effective. It

represents the current situation that will serve

as the common departure point of each of the

scenarios. Environmental uncertainties and

potentially effective life extension strategies

are then defined as scenarios. Additional

actions, alternative actions, and contingency

plans can be considered in the development

of the scenarios.

Additional and Alternate Actions

Additional or alternate actions to be

implemented in conjunction with the base

plan are specified for the defined scenarios.

Additional actions (such as preventive

mitigation activities) will be added to the base

plan when a corresponding scenario is

activated.

Alternate actions may be necessary instead

of, or in addition to, additional actions.

Alternate actions will replace corresponding

base plan efforts when a scenario is activated.

(These actions are the gray bars shown in

Figure 5.)

Contingency Plans

High risk life extending actions may require

contingency actions that will be required

should the life extension strategy fail.

Contingency plans are modeled as separate

Figure 5. Scenario Charting Process – A visually constructed plan integrates the actions of various scenarios with a unit's base plan to provide schedule/cost/profit projections.



scenarios from the scenarios whose failure

may necessitate their activation.

Critical Dependencies Integrate Actions

VisiSuite charts focus on the critical

dependencies between base plan actions and

scenario actions. The top-down Visually

Structured Planning process ensures that

these integrating elements are correctly

identified and agreed to during construction

of the plant’s scenario models. Figure 5 also

shows how the CANDU notional model

incorporates these key inter-action

dependencies that determine the start and

finish dates for the planned maintenance or

refurbishment outages. As the various

scenarios are activated these essential

linkages forecast the corresponding outage

schedules, costs, earnings and profits.

Analyze each Scenario's Schedule, Cost and Net Earnings

A simple to operate VisiSuite dialog allows

the user to activate a different scenario (or the

base plan) by simply selecting it from a pull-

down and clicking the "Change Scenario"

button shown in Figure 6.

In seconds, VisiSuite collects, integrates and

analyzes the appropriate actions, then updates

the charts (target and schedule dates) and

provides the "Scenario Summary" that is also

Figure 6. Scenario Charting Process – Activate scenarios using this dialog. A new integrated program plan/schedule is created, the chart dates are updated and results displayed



shown in Figure 6. All scenario values are

maintained in the VisiSuite database, so that

an up-to-date Scenario Register spreadsheet

can be generated by clicking a command

button on the bottom of the dialog.

Rapid What-if Scenario Modifications

Using the Find Adjust function, scenario

charting with VisiSuite allows rapid

adjustment to scenarios to answer "what-if"

questions.

Figure 7 illustrates this process. First it

presents each of the scenarios actions and

allows you to enter a "Desired Duration" or

"Desired Finish" date before clicking the

"Update this Work Effort" command button.

You can make several adjustments before

deciding whether you wish to make the

adjusted scenario permanent or discard it and

re-activate the original version.

Dynamic Commercial and Technical Environment

The Scenario Charting process is easily

extendable and dynamic. Scenario models

can be modified or extended quickly. The

Visually Structured Planning charts can then

be reviewed with your team to ensure the

intended extensions and revisions have been

properly incorporated.

Figure 7. Scenario Charting Process – Use this dialog to modify scenarios. A new integrated program plan/schedule is created, the chart dates are updated and results displayed



Risk Management Analyzing CSSC life extending strategies

requires assessing the accompanying risks of

success. These are "speculative risks" that

provide the potential for gain as well as loss.

Traditional risk management addresses

"hazard type" risks which only provide the

potential for loss. This tactical bottom-up

type of risk management, works best in

environments with low uncertainty.

The newer strategic methods for managing

speculative risks, in uncertain environments,

analyze "mission risks" top-down using a

systemic focus. The Software Engineering

Institute (SEI) calls their approach Mission

Oriented Success Analysis and Improvement

Criteria (Mosaic).

VisiSuite comprehensively supports both

tactical and strategic risk analysis methods.

Because the Nuclear Power Plant Life

Management environment contains

speculative risks and uncertainties. It can

derive considerable value from a top-down

strategic methodology.

Scenario Planning begins with identifying

Scenario Drivers for meeting the specific

objectives of life extension strategies (called

Mission Objective Drivers). These are also

the Mission Risk Drivers that assess a

program's potential for success or failure as

shown in Figure 8.

By assigning probability-of-success and

impact values to each Mission Objective

Driver, the team is simultaneously identifying

the Mission Risk Exposures. (Each driver

becomes a separate category of risk.)

Figure 8. Life Extension Risk Profile – The VisiSuite “Mission Risk Profile – Driver Framework View” presents Risk Exposure values in relation to a Risk Driver framework.



Figure 9 shows the “Mission Driver Profile"

graph provided by VisiSuite. This graphic

displays the same set of Mission Drivers

along with their respective probability-of-

success and impact values.

Extendable Risk Management

The above described scenario and risk driver

profiles are excellent presentations for

executives and stakeholders. There is very

little extra effort required to implement this

level of Mission Oriented Success Analysis

and Improvement along with Scenario

Charting.

VisiSuite also provides the following

program risk management capabilities:

Program scheduling with risks and

uncertainties

Risk register threats opportunities and

status

Risk probability vs. impact Matrix

Risk mitigation decision events

Risk mitigation costs

Scheduled risk mitigation tasks

showing risk level changes at decision

events

Enterprise risk breakdown structures

Program and enterprise risk registers

Enterprise risk driver structures

Risk multiplier tools that quickly

adjust mitigation durations and costs.

Risk cost and schedule variances for

the base plan and each configured

scenario.

Therefore, extensive tactical or strategic risk

management can be incorporated into your

software enabled Nuclear Power Plant Life

Management process.

In addition, the new "Event Chain

Methodology" can be implemented by using

scenarios as contingency actions that can be

triggered anywhere along a chain of risk

decision events. Event chain methodology is

an uncertainty modeling and program

analysis technique that focuses on identifying

and managing events and event chains in

order to easily model uncertainties and

mitigate the impact of risks. VisiSuite

supports Event Chain Methodology.

Figure 9. Driver Profile – The VisiSuite “Mission Driver Profile” supports the Mission Oriented Success Analysis and Improvement Criteria (Mosaic) methodology.

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Nuclear Power Plant Risk Informed Life Management ver 9