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DISCLAIMERNUCLEAR INSTALLATION SAFETY TRAINING SUPPORT GROUP

Lectures L.3.1 and L.3.5

Leadership and Management for Safety in an Operating

Organization

Joseph C. Braun ANL

IAEA/ANL Regional Workshop on Establishing a Nuclear Safety Infrastructure for a National Nuclear

Power Programme

Argonne, Illinois, USA

2 December 2010

OBJECTIVES

•To identify some of the safety-related characteristics of Nuclear Reactors.

•To present the fundamentals of Safety Management and examine how the basic safety elements are implemented in a working organization.

•To examine how the daily activities of every group in an organization can enhance or degrade plant safety.

BACKGROUND AND FUNDAMENTALS

• The objective of reactor safety is that reactors will be built and operated to pose no undue risk to public health and safety.

Reactor safety, therefore, is an essential prerequisite of reactor operation..

•It is important that nuclear safety experts continue to improve their understanding of the risks from nuclear reactors and communicate that information to plant operators and to the public.

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Safety-Related Character istics of Nuclear Reactors

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Safety-related Characteristics of Nuclear Reactors

Unique Characteristics:– A very large quantity of

radioactive material is present in the core of a nuclear reactor after any significant period of power operation;

– Significant energy release continues for a long time after shutdown;

– A reactor has no ‘natural’ or ‘intrinsic’ power level, and rapid power excursions are possible.

Basic Safety Functions:– Confinement of radioactive

materials, control of operational discharges, and limitation of accidental releases;

– Removal of residual heat from the core;

– Maintaining coolant inventory in Reactor Vessel

– Control of the reactivity.

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Radioactive Materials Inventory

The radioactive inventory in a reactor comes from:• Fission products;

– Activation products; and – Transuranics -- long lived heavy isotopes.

Fission products are the largest radioactive component. Most fission products are retained in the fuel. Decay of fission products is the principal source of radiation hazard for times of several hundred years, and decay heat from reactor fuel for times up to about 60 years.

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Radioactive Materials Inventory

Some fission products emit delayed neutrons, which are extremely important in reactor kinetics and control.Activation products arise from neutron absorption

in structural materials or in fission products.– Activation products such as N-16, H-3, Ar-41, Na-24,

and Co-60 must be considered in design for radiation protection.

– Neutron absorption in fission products is important in reactor operations due to large cross sections of Xe-135 (2E+6 barns) and Sm-149 (6E+4 barns).

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Radioactive Materials Inventory

Transuranics arise from non-fissile capture of neutrons in fuel and fertile materials, primarily U-235 and U-238. Plutonium, Americium and Curium are the elements of principal interest.

Most transuranics are alpha-emitters with long half-lives. They are a significant contributor to the radioactive hazard at times longer than a few hundred years and to the decay heat at times longer than about 60 years.

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Radioactive Materials Inventory

The radioactive material inventory depends on:– Reactor power and operating history;– Neutron flux and energy distribution;– Fission product yields and decay schemes;– Neutron cross-sections for important nuclides and

reactions.

The concentration of various fission products will reach saturation in a few half-lives of operation.

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Fission Product Decay Heat

Radioactive fission products release energy in decay to a stable state.

The decay heat depends on:– The fuel and fertile materials;– The time of irradiation and the power density;– The time after shutdown;

Since fission products are retained within the cladding, cooling must be sufficient to guard against cladding degradation or failure.

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Fission Product Decay Heat Long Time Operation, LWR, Uranium Fuel

Time after reactor shutdown:1 second1 minute1 hour1 day1 week1 month1 year10 years

Fraction of operating power:17%5 %1.5 %0.5%0.3%0.15%0.03%0.003%

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Fission Product Decay Heat

A standard for calculation of decay heat is available:– ANSI/ANS-5.1 – 2005, “Decay Heat Power in Light Water Reactors.”– Supersedes ANSI/ANS-5.1 – 1994.

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Fission Product Decay HeatFuel Cooling Considerations

Adequate cooling must be maintained at all times to remove decay heat and prevent cladding failure in the reactor or in spent fuel storage.

Decay heat is the thermal driving force in most accidents in LWRs.

Water is an excellent heat sink. However, water quality must be maintained to guard against corrosion.

Energy Released from the Fission of One U-235 Atom

Form Emitted energy, MeV Recoverable energy, MeV

Fission fragments 168 168

Fission product decay

β-rays 8 8

γ-rays 7 7

neutrinos 12 -

Prompt γ-rays 7 7

Fission neutrons (kinetic energy) 5 5

Capture γ-rays - 3-12

Total 207 198-207

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Reactivity Control Requirements

Control the reactor power level in operation and provide for shutdown under normal and off-normal conditions.

Compensate for reactivity changes due to core configuration, burnup, or temperature changes.

Compensate for transient poisoning effects, primarily from Xe and Sm.

Provide for rapid shutdown if necessary, and maintain the reactor subcritical, including in accident conditions.

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Reactivity Control

Some typical reactivity control mechanisms include:– Moveable control rods or blades.– Chemical means, such as boric acid in coolant.– Burnable poisons, such as Gadolinium.– Removable poison plates or curtains.

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Reactivity Control

Some typical reactivity feedback mechanisms include:– Fuel temperature – a prompt effect, which must be

negative;– Doppler broadening of resonance absorption in U-238 or

other materials – a prompt effect; – Moderator temperature – normally subject to heat

transfer delay;– Coolant void formation – can be positive or negative.

Historical Development� In the early years the primary focus was on development of basic physics and engineering principles, safety system design features, codes and standards, and general design criteria governing such matters as redundancy and diversity of safety systems.

� Actual operating experience has shown the importance of human performance aspects of safety, including operator qualifications and training, emergency operating procedures, accident mitigation measures, and emergency planning.

� In recent years, the importance of operational safety culture has come into clear focus. A strong safety culture is important to ensure the integrity of the multiple barriers of the entire defense-in-depth safety concept. That is, the basic safety values, norms and attitudes of an entire operating organization are just as important as the basic design and construction of the reactor.

DEFENSE-IN-DEPTHVery early thinking - Physical barriers

Fuel Fuel Primary Containment Site

Pellet CladdingSystem Structure Boundary

Boundary (if present)

DEFENSE-IN-DEPTH

Later thinking: A series of physical barriers and multiple levels of action to avoid or reduce damage and minimize impact on public health and safety.

- Achieved through design/construction/operation/maintenance

Levels of Action:

Preventive Mitigative Containment EmergencyActions Actions Actions Response

Actions

SAFETY CULTUREDEFINITION:

“Safety Culture is that assembly of characteristics and attitudes in organizations and individuals which establishes that, as an overriding priority, nuclear plant safety issues receive the attention warranted by their significance. IAEA - INSAG-4

Involves all aspects of organization

Attention/effort proportional to potential consequences

Implies a process of continuing vigilance, improvement

No room for complacency

For professionals – a lifelong learning process.

BASIC SAFETY ELEMENTS

#1. A solid foundation of knowledge of the basic physics, chemistry andengineering of nuclear reactor technology.

#2. A robust and proven design using established codes and standards that embody design margins, qualified materials, and redundant and diverse safety systems.

#3. Adherence to a defense-in-depth safety philosophy that rigorously maintains multiple barriers, both physical and procedural, to protect the public and workers from harm.

#4. A program for ensuring that the reactors are constructed and tested in accordance with the design specifications and safety analyses.

#5. Highly qualified and trained personnel who operate the reactor,maintain the equipment and conduct the radiation protection program.

BASIC SAFETY ELEMENTS (cont’d)#6. An operating staff that has a profound respect for the reactor core

and radioactive materials, keeping them under absolute control at all times

#7. Technical specifications that define and control the safety operating envelope of the reactor.

#8. A strong engineering function that maintains plant, systems and equipment in accordance with the plant design basis, analyzes technical issues as they arise, and provides support to operations and maintenance.

#9. A safety culture that has been instilled throughout the operating organization based on the highest safety values and that fosters an attitude toward conservative operation.

#10. Effective Quality Assurance, Self-Assessment and CorrectiveAction programs.

BASIC SAFETY ELEMENTS (cont’d)#11. Emergency plans, which have been thoroughly reviewed and tested, to enable operators to take actions to protect both onsite workers and offsite populations in the event of a nuclear accident.

#12. A program of operating experience analysis and feedback to operations.

#13. Access to a continuing program of nuclear safety research that is designed to add to our basic knowledge of safety fundamentals.

#14. A strong management organization that maintains all these activities and makes available adequate financial resources, and

#15. A safety regulatory authority that is responsible for independently assuring that nuclear reactors are designed, built and operated safely.

TYPICAL OPERATING ORGANIZATIONOF A NUCLEAR FACILITY� Company or Concern (Overall Operating Entity) Management

� Oversight and financial management of all facilities, e.g., plants/e.g., plants/ transmission lines/ local distribution networks.

- At each Site -possibly several different types of facilities

�� General Site Director or Manager�� Radiation Protection Management�� Quality Management and Records Management�� Safety Management/ Experience Analysis�� Site Emergency Management

� Engineering/ Configuration/ Licensing Management

TYPICAL OPERATING ORGANIZATIONOF A NUCLEAR FACILITY (cont’d)

� Plant Maintenance/Outage Management � Operations Management

� Licensed Operators (Control Room and Facility)� Non-Licensed Operators, e.g. certain site equipment

operators (certified, but not formally licensed)� Fuel and Fuel related management

Security ManagementGeneral Site Maintenance and Management

Waste Management

CorporateManagement

Site or Complex AdvisoryManagement Board(s)

Administrative

Site Safety Plant(s) Engineering Dept. RadiationSecurity Mgt. Mgr.(s) - Configuration Mgt. Protection- Licensing (“HealthQuality, Q/A, Site Emergency- Plant Modifications Physics”)Records, etc. Mgt.

Fuel and Fuel SitePlant Manager Related Waste Training

(Simulator(s))

Plant Radiation Plant Operations Plant WasteProtection Maintenance Manager(s) Chemistry Processing

- Lab(s) - Outage Planning - Crew Supervision - Labs - Facilities- Equipment - Preventive Maint. - Licensed Operators - Records - Operators- Records - Corrective Maint. - Non-licensed Operators - Records

- Records - Training- Records

OPERATING ORGANIZATION EXERCISE

� Draw the operating organization for your facility or a research or power reactor that you know about.

� Show where you fit onto the organization chart.•Assign the 15 basic safety elements to the different positions on the chart of this organization.•Are there any blocks on the chart that do not have a safety element attached to them?•Are there any safety elements that have not been assigned to a block on the chart?

14 1,3,4,9Corporate

ManagementRegulator 15 14 1,2,3,4,5,9,10,11, 1,2,3,9,10,13,14

Site or Complex 12, AdvisoryManagement 13 Board(s)

6,7,10 Administrative3,4,5,

9,12 13,11 1,2,9, 1,2,3,7,8,9,10,12,13 1,3,5,6,7,9,10,Site Safety Other Engineering Dept. Radiation 12Security Mgt. Plant(s) - Configuration Mgt. Protection

Mgr.(s) - Licensing 15 (“Health3,2,4,9,10 1,2,12,11,9 13,- Plant Modifications Physics”) 12,Quality, Q/A, Site Emergency

10,Records, etc. Mgt.1,3,6, 12,13 1,2,3,5,6, 7,9,

Fuel and Fuel Site1,2,3,4,5,6,7,9,10,Plant Manager 11, Related Waste Training

13 (Simulator(s))

1,3,5,6,7,9,12 1,3,4,5,7,9, 1,2,3,4,5,6,7,9,10, 1,3,4,5,6,7,9, 1,5,7,9,1212, 11, 10,Plant Radiation Plant Operations Plant Waste10 12 12,Protection Maintenance Manager(s) Chemistry Processing

13- Lab(s) - Outage Planning - Crew Supervision - Labs - Facilities- Equipment - Preventive Maint. - Licensed Operators - Records - Operators- Records - Corrective Maint. - Non-licensed Operators - Records

- Records - Training- Records

OPERATING ORGANIZATION

� � ITEMS FOR DISCUSSION

� Select any division, department or working group on organization charts shown in the lecture.

� What basic safety elements is this group involved with?

� How could plant safety be affected if this group did not perform these functions? Give an example of how a plant or component failure could occur if this group did not do its job.

OPERATING ORGANIZATION (cont’d)

� ITEMS FOR DISCUSSION: (cont’d)

� Consider the effect of the following items on the ability of a work group to perform the basic safety elements assigned to it:

✦ Group workload✦ Group attendance

✦

✦ Group compensation and morale

✦ Group professionalism✦ Animosity between individuals in a group

✦ Group financial resources, budget and staffing level

✦ An employee in the group who shows up unfit for work

OPERATING ORGANIZATION (cont’d)

� ITEMS FOR DISCUSSION: (cont’d)

What things can be done to help a group perform its safety functions more thoroughly and reliably?

Consider: ✦ Attitude of group leader

✦✦ Examples set by managers and group leaders✦✦ Daily decisions of managers and group leaders✦✦ Example set by individuals in a group✦✦ How the group responds to difficult situations

OPERATING ORGANIZATION (cont’d)

ITEMS FOR DISCUSSION: (cont’d)

� Imagine that you worked for the national regulatory agency in your country and were newly assigned to a facility in your country.

•What kinds of things would you look for in the operating organization of that facility?

•Who would you talk to?

•What questions would you ask?

OPERATING ORGANIZATION (cont’d)

ITEMS FOR DISCUSSION: (cont’d)� Imagine that an electrician was nearly electrocuted while working on a breaker cabinet in your facility.

•The plant manager asks you to conduct an “independent” investigation. He says: “How could we have let such a thing happen?”

•How would you approach your investigation?

Examples of Questions for Assessing Personal Contributions to the Enhancement of Safety Culture

A 2002 Publication of the IAEA - INSAG-15, entitled:“Key Practical Issues in Strengthening Safety Culture”

provides lists of questions that persons at all levels of an organization can ask themselves about their personal contributions to the improvement of safety culture.

THE END