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VN/RA/01 Task 1&2 Workshop Hanoi, October 2012 Confidential Ilari Aro STUK - PowerPoint PPT Presentation

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Siting of NPPs - External man made hazards and screening criteria for site suitability - Finnish experience. VN/RA/01 Task 1&2 Workshop Hanoi, October 2012 Confidential Ilari Aro STUK. What is siting.

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Vn ra 01 task 1 2 workshop hanoi october 2012 confidential ilari aro stuk

Siting of NPPs - External man made hazards and screening criteria for site suitability - Finnish experience

VN/RA/01 Task 1&2 Workshop

Hanoi, October 2012


Ilari Aro


What is siting
What is siting

  • Siting is the process of selecting a suitable site for a facility, including appropriate assessment and definition of the related design bases. (IAEA Safety Guide NS-R-3, 2003)

  • Existing sites

    • site characterization is updated for new units

    • site related design requirements are determined according to current regulatory requirements

  • New sites

    • an extensive siting process

  • Environmental Impact Assessment (EIA) is part of the siting process

    • role of EIA depends on national legislation

Vn ra 01 task 1 2 workshop hanoi october 2012 confidential ilari aro stuk

Nuclear power plants in Finland

  • Olkiluoto NPP (TVO)

  • 2 operating units - ABB BWRs

  • OL3 EPR under construction

  • EIA and DiP completed for a new unit

  • Loviisa NPP (Fortum)

  • 2 operating units - VVERs

  • EIA completed for a new unit

  • Fennovoima Ltd

  • EIA and DiP completed for a new plant

Stuk yvl 1 0 requirement external events man made hazards
STUK YVL 1.0 requirement: Externalevents (man made hazards)

  • … Othereventsexternal to the plantare at leastelectromagneticdisturbances, oilleaks, crashingaeroplanes, explosions, releases of poisonousgases and unauthorisedplantsiteentry.

  • In the plant'svicinity, no activitiesmaybecarried out thatcouldpose an externalthreat to the plant.

  • The applicant for a licenceshalllistthoseexternaleventsthatcouldpose a threat to safety at the site in question and shallalsoassess the risksarisingfromtheseevents. Effects on the supply of coolingwater and on electricpowergridconnectionsshallalsobeconsidered.

  • Hazardousindustry, trafficshallbeconsidered.

    • takingoil transport accidents into account in the design (coolingwaterintake)

  • The risksarisingfromexternaleventsareassessedbyanalysesconducted in accordancewith Guide YVL 2.8. Guide YVL 2.8 dealswithprobabilisticsafetyanalyses (PSA) for nuclearpowerplants.

  • Screening criteria for man made hazards
    Screening criteria for man made hazards

    • Screeningcriteriahaverelationshipwith PRA in Finland - PRA basisscreening is carried out and eventsarestudied and analysed

    • IAEA SafetyStandardsSeries No. NS-G-3.1 ”External Human InducedEvents in Site Evaluation for NPP’s” presentstwostepapproach for screening (no numericalvaluespresented)

      • Distance

      • Probability

    • Hazardousindustries and installationsneed to beconsidered

      • explosions

      • poisonous and / orflammablegasclouds, fluids

    • Transport routes: roads, railway, waterway, airway, includingpipelines and transportsneed to beconsidered as above

      • Design orregulatorycriterianeed to beestablished for distance and / orprobability: examplese.g. U.S. Regulatory Guide 1.91 (1978)

    Protection against external threats in finland
    Protection against external threats in Finland

    After September 11, 2001: political and public will was expressed to improve protection against terrorist actions

    • Reconsideration of aircraft crash design basis

      • consider large passenger and military aircrafts

      • no immediate release of significant amount of radioactive substances

      • initiation and maintenance of key safety functions in spite of the direct consequences of the event (penetration of structures by impacting parts, vibration, explosion, fire)

    • Microwave and biologic weapon consideration

    Effects of external events in the plant
    Effects of externalevents in the plant

    • Externaleventscancause

      • loss of externalelectricalnet (fire, stormeffects)

      • loss of watercoolingchannels (ice, algae, mud, oil)

      • loss of intactness of building (pressurewave), e.g. wall / roof

      • loss of systems and componentsbecause of vibrations

      • loss of ventilation and coolinge.g. of diesel generator (snow, sandetc)

      • floodingin the buildings

      • missiles to causedamage (e.g. turbine and tornado causedmissiles, airplaneengines)

      • fire in the buildings

      • poisonousgases, smoke to threatoperators’ health

      • loss of computersorelectricalsystems (electromagnetic)

    Site characterization man made hazards
    Sitecharacterization – man made hazards

    • Transport routes (sea, land and air routes, pipelines)

      • oil and hazardous substances

      • airports

  • Industrial activities

    • production, storage

  • Agriculture

  • Population

  • Information on the following topics is required for assessing site suitability and for determining plant design values for external events

    Stuk assessment result industrial and transport activities close to sites
    STUK assessmentresult: Industrial and transport activitiesclose to sites

    • No hazardous production plants or storage facilities or pipelines in the vicinity of Olkiluoto site

    • Shipping lines are not in the immediate vicinity of Olkiluoto site

    • Sea transport of oil near Loviisa/Ruotsinpyhtää

      • 30 % of Russian oil exports are transported through the Gulf of Finland

        • main fairway 40 km from the Loviisa site

        • a few supertankers and several small tankers per day

        • transports are increasing rapidly

      • the possibility of a major oil spill must be considered

      • risks of oil spills is a common topic in the media

    • Fennovoima sites

      • Kemi harbour and industrial area 6 - 8 km from the Simo site

      • some transports and use of dangerous materials

    Ol3 risk profile cdf 1 8e 06 a
    OL3 Risk Profile, CDF  1.8E-06 /a

    • Transients 45%

    • Loss of feed water

    • Component cooling system failures

    • Loss of Coolant Accidents 24%

    • Small LOCA being the most important

    • Loss of off-site power supply 5%

    • Internal Fires 2%

    • Internal Floods 2%

    • External events 16%

    • Frazil ize

    • Organic material in sea water

    • Wind&Snow

      Low power and shutdown 6% (internal)

    Non seismic external events screening study
    Non-seismic External Events - Screening study

    • Screening study done by an external consultant

    • Based on the report Knochenhauer and Louko, Guidance for External Events Analysis, SKI Research Report 02:27

    • Screening starts with ~ 50 phenomena

      • high/low air temperature, wind, lightning, snow, frost ...

      • high/low seawater level, high seawater temperature, frazil ice

      • oil and chemical spills, organic material in water (algae)

      • explosion pressure wave, EM pulses

    Non seismic external events screening criteria for single events
    Non-seismic External Events - Screening criteria for single events

    Source: Areva, Relcon Scandpower: OL3 PSA Ch. 6.2.1, External Events Screening Analysis

    Non seismic external events screening criteria for multiple events
    Non-seismic External Events - Screening criteria for multiple events

    Source: Areva, Relcon Scandpower: OL3 PSA Ch. 6.2.1, External Events Screening Analysis

    Regulatory issues on external events design values
    Regulatory issues on external events design values

    • No detailed quantitative requirements in current YVL guides (except seismic)

    • Quantitative risk targets provide some guidance

      • core damage frequency < 1E-5/a

      • large release frequency < 5E-7/a

      • no single factor shall dominate

    • Intensity-frequency distributions have been determined based on available observations

      • reliable observations for ~ 100 years

      • return periods of interest up to 10 000 - 1 000 000 years

      • uncertainties are very large at high return periods

    • Combinations of correlated events are potentially important

      • snow and wind: potential for loss of offsite power and simultaneous failure of diesel generators due to combustion air intake blockage

    Stuk statement man made hazards
    STUK statement: man made hazards

    • There are no industrial plants, storage facilities, traffic routes or gas pipes near site that could pose a risks to NPP as a result of accidents.

    • Oil transport routes do not run near the Olkiluoto site. The probability of oil spill affecting the supply of seawater is considered low.

    • Needed strengthening of national electric grid belongs to Grid Company. A new high voltage line to the site will be constructed. Own emergency generators will be constructed to the site to supply safety systems with the needed power. New lines are taken into account in the land use planning.

    Conclusions on finnish projects
    Conclusions on Finnish projects

    • Site specific external events have been considered extensively in the design and licensing of OL3

    Some findings on varans regulation on external human induced events
    Somefindings on VARANS regulation on externalhumaninducedevents

    • On the basis of headings VARANS regulationsfollows IAEA No. NS-G-3.1 ”External Human InducedEvents in Site Evaluation for NPP’s”

    • Whencomparingtext, copying is extensive. In manyplaces, copiedtext is notrepresentativeregulatorystyle. Someexampleshavebeenfoundwithconflictinginformation and verypoorformat.

    • Itwouldbewiser to refer to the IAEA No. NS-G-3.1 in VARANS regulation for sitingthancopyingitdirectlybecause IAEA is notregulatoryorganizationwithregulatorywritingstyle. Itproducesguidance for allinterestedparties and often IAEA style is moretrainingstylewithexplanatoryexpressions to enhanceunderstandingthansuitableregulatorystyle.

    • Regulatorybodycanselectsuitableregulatoryrequirementsfrom the IAEA requirementdocumentswith ”shall” formulation for itspurposesbutdirectcopying of safetyguideswith ”should” formulation is not a good idea.

    Aircraft crashes

    • 5.2.1 With regard to aircraft crashes, a study should be made of airports and their takeoff, landing and holding patterns, flight frequencies and types of aircraft. Air traffic corridors should also be taken into account.

    • 5.5.2 Air traffic

    • The information collected on air traffic should include the locations of airports and air traffic corridors in the region, the airports’ takeoff, landing and holding patterns, the types of warning and control devices available, the types and characteristics of aircraft and their flight frequencies. Information on aircraft accidents for the region and for similar types of airport and air traffic should be collected. Information should be collected for both civil and military air traffic. Of particular interest are military aircraft training areas which may show a comparatively high frequency of crashes in their vicinity and areas where low flying is practised.

    • The probability of occurrence and the severity of the events associated with air traffic should be determined.

    Screening spl
    Screening (SPL)

    • 6.1 is notregulatorytext, norutilityusesthis

      • E.g. “Initiating events with a probability of occurrence lower than this screening probability level should not be given further consideration, regardless of their consequences.”

      • IAEA asks regulatory body to define screening value. It is not defined in the VARANS guide.

    • 6.2

      • ”Relatively simple procedures may be used in a preliminary screening of source and interacting events.” is notregulatorytext.

      • “Events associated with major, possibly catastrophic, hazards should not be screened out unless their probability is shown to be significantly below the SPL.” There is a conflict with 6.1.

    Screening spl1
    Screening (SPL)

    • 7.2.2 (end) “For Type 3 events, the probability of crashes of civil aircraft near air traffic control corridors should be carefully examined, but in general for areas outside air traffic control corridors this probability decreases markedly and it is usually smaller than the specified SPL (for example, 10-7/a). This is not necessarily true for military aircraft which may not follow programmed flight plans or flight regulations.” How VARANS no this? This is not regulatory text.