safety culture

ENHANCE OF NATIONAL NUCLEAR SAFETY CULTURE AND PREDICTION OF POSSIBLE CORE ACCIDENTS IN AKKUYU NPP

Yusuf KavunCelal Bayar University & Akdeniz University

Department of Physics

Content:

Light Water Reactors (LWRs) Akkuyu NPP The Main Major Accidents Safety Culture Principles for Nuclear Safety Culture Discussions Conclusion

Yusuf KAVUN, NSP 2015

Light Water Reactors (LWRs)

The light water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator – furthermore a solid form of fissile elements is used as fuel. Thermal-neutron reactors are the most common type of nuclear reactor, and light water reactors are the most common type of thermal-neutron reactor The Pressurized Water Reactors

(PWRs) The Boiling Water Reactors (BWRs) Super Critical Reactors (SCWRs)

Diagram of a NPP (Utku, H., 2011)


A VVER (Voda-Vodyanoi Energetichesky Reaktor) or WWER (Water-cooled Water Moderated Power Reactor) is the Soviet/Russian version of Western Pressurized (Light) Water Reactors (PWRs).

VVER generations and corresponding Western-designed reactors


THE PRIMARY CIRCUIT IS:

RADIOACTIVE A REACTOR FOUR REACTOR COOLANT LOOPS

FOUR REACTOR COOLANT PUMPS HEATING PARTS OF FOUR STEAM GENERATORS STEAM PRESSURIZER

THE SECONDARY CIRCUIT IS: STEAM GENERATING PART OF STEAM

GENERATORS

FRESH STEAM CONDUITS

ONE TURBINE UNIT COMPRISING OF A TURBINE PLANT

A TURBINE GENERATOR

CONDENSATE PUMPS

Diagram of the power circuit and safety systems(akkuyunpp.com)

Akkuyu NPP


If the SGs are dry and hot, injection cold liquid into the SGs creates a thermal shock and may result in rupture of the SG tubes / or the Shell. The threat of SG Shell or tube failure posed by thermal shock arises only when the SG secondary side is dry and hot. Otherwise, thermal shock is not a problem.

STEAM GENERATOR

Schematic of a vertical PWR steam generator(www.intechopen.com)Yusuf KAVUN, NSP 2015

At Akkuyu NPP

• horizontal steam generators The horizontal design means that during SG phenomenon dry out will be reached earlier than the vertical design leading the creep-rupture of the tubes and core meltdown earlier. • has better seismic strength do not face such problems as primary water stress-corrosion cracking, fouling and denting which are the known problems for the vertical design that leads to SGs degradation earlier than the horizontal steam generators.

Three-dimensional view of primary circuit of the WWER440 reactor


On March 28, 1979, Three Mile Island ,Like an automobile engine with a hole in its radiator, the Unit 2 reactor overheated when an emergency release valve opened, then failed to close. The mechanical problem was made worse when a control room operator failed to identify the problem and correct it. The result was a partial meltdown of the reactor’s core. (Nuclear Regulatory Commission, Report of the President’s Commission on the Accident at Three Mile Island)

THE ACCIDENT AT THREE MILE ISLAND


The Chernobyl AccidentChernobyl NPP on 25-26 April 1986 were the main reasons of the Chernobyl accident. These identified violations were as follows:

• operation of the reactor at a very low operative reactivity surplus (ORS)

• conducting of the experiment by the power below the level provided for test

• blocking of the protection system relaying on water level and steam pressure in

• steam-separators• blocking of the protection system

relaying on shutdown signal from two turbogenerators

• connection of all the main circulating pumps to the reactor

• switching off the emergency core cooling systemChernobyl NPP after the Accident

(http://thayer.dartmouth.edu/~cushman/courses/engs43/Chernobyl.pdf)Yusuf KAVUN, NSP 2015

The Fukushima Accident(s)

The Fukushima accident occurred following the 9.0 magnitude Tōhoku earthquake and resultant tsunami on 11 March 2011 in Ohkuma, Japan (IAEA 2011; Teeghman).

This event is caused a power failure in the entire energy loss due to occurring in the reactor and the fuel battery damage caused overheating (World Nuclear Association, 2011).

General Layout of Fukushima Daiichi NPP(www.iaea.org/newscenter/focus/fukushima/japan-report/cover.pdf)

YUSUF KAVUN, NSP 2015

Safety Culture

An organization’s values and behaviors—modeled by its leaders and internalized by its members—that serve to make nuclear safety the overriding priority (INPO,2004).


Systems of Safety Culture

Safety culture has own values and behavior according to the organization, which keeps on it over people. It ensures the continuity of the organization and structure of the purposes of the proceeding in accordance with human.


In this process, awareness in the society that transform to culture by taking lessons from past events and prediction of future events will play a very important role for keeping alive.


Principles for Nuclear Safety Culture

The following principles are described (INPO, 2004): 1. Everyone is personally responsible for nuclear safety. 2. Leaders demonstrate commitment to safety. 3. Trust permeates the organization. 4. Decision-making reflects safety first. 5. Nuclear technology is recognized as special and unique. 6. A questioning attitude is cultivated. 7. Organizational learning is embraced. 8. Nuclear safety undergoes constant examination.


1. Everyone is personally responsible for nuclear safety

Responsibility and authority for nuclear safety are well defined and clearly understood. Reporting relationships, positional authority, staffing, and financial resources support nuclear safety responsibilities.


2. Leaders demonstrate commitment to safety

Executive and senior managers are the leading advocates of nuclear safety and demonstrate their commitment both in word and action. The nuclear safety message is communicated frequently and consistently, occasionally as a stand-alone theme.


3. Trust permeates the organization

A high level of trust is established in the organization, fostered, in part, through timely and accurate communication. There is a free flow of information in which issues are raised and addressed.


4. Decision-making reflects safety first

Personnel are systematic and rigorous in making decisions that support safe, reliable plant operation. Operators are vested with the authority and understand the expectation, when faced with unexpected or uncertain conditions, to place the plant in a safe condition. Senior


5. Nuclear technology is recognized as special and unique

The special characteristics of nuclear technology are taken into account in all decisions and actions. Reactivity control, continuity of core cooling, and integrity of fission product barriers are valued as essential, distinguishing attributes of the nuclear station work environment.


6. A questioning attitude is cultivated

Individuals demonstrate a questioning attitude by challenging assumptions, investigating anomalies, and considering potential adverse consequences of planned actions. This attitude is shaped by an understanding that accidents often result from a series of decisions and actions that reflect flaws in the shared assumptions, values, and beliefs of the organization.


7. Organizational learning is embraced

Operating experience is highly valued, and the capacity to learn from experience is well developed. Training, self-assessments, corrective actions, and benchmarking are used to stimulate learning and improve performance.


8. Nuclear safety undergoes constant examination

Oversight is used to strengthen safety and improve performance. Nuclear safety is kept under constant scrutiny through a variety of monitoring techniques, some of which provide an independent “fresh look.”


Discussions

Operating experience is a very significant parameter as well as the safety culture of the host nation. The concerns is not just a lack of experience with industry with the new comers, but also the infrastructure and established institutions who will be dealing with the Emergencies. Lack of trained operators and educated Emergency Response Organizations (ERO) is a major concern. The culture on simple fire drills even makes the difference when a severe condition occurs in the industry.



Conclusion

We assume that Russians will assign their best operators to operate the Akkuyu plant. Turkey is planning to build the required manpower during the transition period. In general, for the host countries the most important issue found was the build up their qualified operating personnel and develop a nuclear safety culture equivalent to the world standards.

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