Nuclear Safety

Chronic vs. Acute

What are chronic and acute hazardswith respect to radiation in nuclear power plants?

Chronic Radiation Hazard

Naturally OccurringCosmic rays, atoms in earth, building materials202 mrem /year

Man MadeMedical -- 110 mrem/yearWeapons fallout -- 2 mrem/yearOccupational -- 4mremConsumer products -- 2 mrem/yearNuclear power -- 0.3 mrem /year

Beta

Alpha

Gamma

Typical Dose

Operating staff 400 mrem/year (average)Office staff 20 mrem/year (some people)Person at station exclusion fence .3 mrem/year (maximum)Residential Area 1 kilometer from station .1 mrem/ year (maximum)

Accident Pyramid

600Incidents with no visible injury or damage

300Property damage accidents

10Minor injuries

1SeriousInjury

Self-Checking

Review Intended ActionReview Expected ResponseAcronym STAR

StopThinkActReview

ALARA

As Low As Reasonably Achievable

13 February 2004

REACTOR SAFETY PHILOSOPHYControl

CoolContain

RegulationBoundaries

Cool

ing

NormalAlarm

Coarse Control Action

ECINPC

SDS

Assumptions for Defense in Depth

There will be errors in designEquipment will occasionally failPeople will occasionally make mistakes

How can we minimize the risk?

Protecting the Public

Defense in Depth

MultipleBarriers

ReliableProcess Systems

ReliableSafetySystems

CompetentOperating&MaintenanceStaff

DetectandCorrectFailures

What are the five barriers between the radioactive nasties and the public?

Ceramic FuelFuel SheathPressure TubeContainmentExclusion Zone

Reliability Concepts

Reliabilitythe probability a device works for the period it is intended under the operating conditions encountered

Availabilitythe fraction of time that a device is available to work if called upon to do

Reliability

RedundancyIndependenceDiversityPeriodic Testing

Fail SafeOperational SurveillancePreventive MaintenancePredictive Maintenance

Redundant Diverse Diverse andIndependent

Documentation

Canadian Nuclear Safety Commission (CNSC) is our regulator

Formerly the Atomic Energy Control Board (AECB)

Hierarchy of documentationSafety ReportStation Operating LicenseOP&POperating and Maintenance ProceduresCertificates of Approval (Ontario)

Work Processes

Change Control ProcessWork Authorization Process

Authorized Positions

Authorized PositionsShift ManagerControl Room Shift SupervisorAuthorized Nuclear Operator

Protect the publicManage Work and Station ConfigurationKeep Within the Confines of the Operating License