seminario safety in nuclear fusion plant 24 aprile 2015 t. pinna safety report for a nuclear fusion...
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SEMINARIOSAFETY IN NUCLEAR FUSION PLANT
24 Aprile 2015
T. Pinna
Safety report for a nuclear fusion plant: generalities
2Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Pericoli e rischi nella fusione nucleare
Un pericolo è qualsiasi fonte di danno potenziale o di danno per qualcosa o di effetti
negativi sulla salute di qualcuno in determinate condizioni di lavoro.
In sostanza, un pericolo è qualsiasi cosa od evento in grado di provocare danni o effetti
negativi ad individui e/o ad attrezzature e/o ambiente.
Talvolta viene definito come pericolo il danno reale o l'effetto sanitario causato piuttosto
che l’entità che è in grado di generare il danno. Per esempio, la tubercolosi (TBC)
potrebbe essere definita un pericolo, ma, in generale, dovrebbe essere definito come
pericolo il battere od i batteri che causano la tubercolosi
It is a physical situation with potential for human injury, damage to property, damage to
the environment or any combination of these
HAZARD:PERICOLO
3Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Pericoli e rischi nella fusione nucleare
Rilascio incontrollato di energia
un oggetto che potrebbe cadere da un'altezza (energia potenziale o
gravitazionale),
una reazione chimica (energia chimica),
il rilascio di gas compresso o vapore (pressione, temperatura
elevata),
apparecchiature rotanti (energia cinetica), o
scariche elettriche (energia elettrica),
sostanze radioattive (radiattività).
HAZARD:PERICOLO
4Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Pericoli e rischi nella fusione nucleare
Si identifica con il termine rischio la possibilità o la probabilità che un
evento indesiderato avvenga in un tempo specificato e/o in specificate
circostanze. Ad esempio, che una persona sia danneggiata in caso di esposizione a un pericolo, che proprietà subiscano dei danni o attrezzature vadano perse.
Un modo di definire il rischio è ad esempio:
tra un numero di persone "N", esposte ad un pericolo (hazard), un certo
numero, "Y", di persone subisce un danno – > Rischio = Y/N
It is the likelihood of undesirable events (hazard) to occur within specified
time and/or specified circumstances
RISK:RISCHIO
5Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Pericoli e rischi nella fusione nucleare
Identificazione dei pericoli
Analizzare e valutare i rischi associati a ciascun pericolo
Identificare dei modi appropriati per eliminare o ridurre i
pericoli
In caso non sia possibile eliminare o ridurre i pericoli,
identificare i modi appropriati per eliminare o ridurre i
rischi associati
Cosa è un’analisi di rischio?
6Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Pericoli e rischi nella fusione nucleare
Generazione di malattie
Ferite sul corpo
Cambiamenti delle funzioni corporali
Cambiamenti nella normale crescita e sviluppo degli individui
Effetti sulla crescita dei feti e modificazioni genetiche
Effetti sui bambini e sugli anziani
Diminuzione delle aspettative di vita
Stress e traumi mentali
Effetti sulle capacità di affrontare in futuro nuovi stress o situazioni di
pericolo
Tra i pericoli che si analizzano, al primo posto: Pericolo per la salute dell’uomo
7Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Fundamental safety and environmental characteristics of fusion
• No climate-changing emissions
• Power excursions self-limited by inherent processes
• Products of fusion reaction are not radioactive
• Structures are activated by neutrons but:
– Low power density (“decay heat”) after termination of burn
– Short decay of radiotoxicity
• No fissile or fertile material, no actinides or fission-products
A Demonstration Power Plant should demonstrate that these characteristics lead to excellent Safety and
Environmental performance.
8Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Mobilizable Radioactive Inventory in ITER and in DEMO
Radiological source terms are
• Tritium: in VV, PFCs, fuel cycle and Hot Cell and Radwaste. Main relevant
contribution in term of safety is the tritium inventory in the VV, tritium
building and Hot Cell
• ACPs: the activation of the corrosion products present in in the primary
cooling loops
• Activation products:
• in-vessel components activation
• in-vessel dust from FW-plasma interaction
• liquid metal activation products
9Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Realizing the potential safety and environmental benefits of fusion
Design choices can help to make the most of the S&E potential benefits
• Materials selection
– “low activation” materials for components that experience significant neutron fluence
– combinations of coolant and in-vessel materials to be considered (e.g. avoid water + beryllium)
• Passive rejection of decay heat after loss-of-coolant
• Minimise dependence on active safety systems, or operator actions(passive safety)
• Extensive use of Remote Maintenance to avoid personnel doses
10Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Safety Approach for ITER and DEMO
• To protect workers, the public and the environment from harm;
• To ensure in normal operation that exposure to hazards within the facility and due to
release of hazardous material from the facility is controlled, kept below prescribed limits
and minimized to be as low as reasonably achievable;
• To ensure that the likelihood of accidents is minimized and that their consequences are
bounded;
• To ensure that the consequences of more frequent incidents, if any, are minor;
• To apply a safety approach that limits the hazards from accidents such that in any event
there is no need for public evacuation on technical grounds;
• To minimize radioactive waste hazards and volumes and ensure that they are as low as
reasonably achievable.
ALARADefence in depth Passive safety
Top-level safety objectives
Employ established safety principles
Mitigation of consequences of significant releases of radioactive material
Off-site emergency response (e.g. evacuation) – should not be necessary for fusion
11Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
“Defence in Depth” approach to safety
Main safety function is confinement of radioactivity,achieved by multiple layers of protection:
Prevention of accident progression, mitigation of consequences
Control of accidents within design basis
Control of abnormal operation and detection of failures
Prevention of abnormal operation and failures
• Multiple barriers
• Natural shutdown
• Filtering and detritiation systems
• Small inventories
• Conservative design
• Safety systems
• High quality construction
• Use of passive means wherever possible
Safety Approach for ITER and DEMO
12Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
A Nuclear Fusion Plant needs to be licensed
• The unlicensed operation of a nuclear installation is prohibited in any country.
• The risk associated to Fusion Plants are different from those of NPP– presence of huge amount of tritium and dust– Easy end of the fusion reaction, no risk of excursion (self-limited by
inherent processes)– Products of fusion reaction are not radioactive– Structures are activated by neutrons but:
• Low power density (“decay heat”) after termination of burn• rapid decay of radiotoxicity
– No fissile or fertile material, no actinides or fission-products
• The licensing is focused on Structure, Systems and Components (SSE) Safety Important Classified (SIC) performing a safety function necessary to bring and maintain the plant into a safe state in any circumstance (normal and accidental)
13Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Safety Functions in ITER
1. Confinement of radioactivity– Static barriers (mainly process barriers and some building walls)– Systems for maintaining depression and filtering/detritiation
2. Limitation of exposure– Shielding – Access control
3. Protection of systems for confinement and limiting exposure
– Management of pressure– Management of chemical energy– Management of magnetic energy– Management of heat removal and long term temperatures– Fire detection/mitigation – Mechanical impact (including seismic, load drop, etc.)
4. Support of systems for confinement and limiting exposure
– Services supporting systems implementing safety functions such as instrumentation and control, electrical power
– Provide transport/lifting of radioactive components/materials– Monitoring of safety functions
Main functions
Supporting functions
14Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Confinement: in-vessel inventoryConfinement strategy:
• Two confinement systems
• each with one or more static barriers and/or dynamic systemsTritium
(adsorbed in plasma-facing surfaces, in dust)
Active dust(tungsten eroded from plasma-facing surfaces)
Activated corrosion products
(in accidents with in-vessel loss of water coolant)
First confinement systemVacuum vessel and its extensions
Second confinement systemBuilding walls and slabs surrounding tokamak, rooms served by ventilation with filtering and detritiation systems.Other boundaries (e.g. cryostat under discussion)
Safety Functions in ITER
15Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Main safety functionConfinement concept – Glove box
1st Static barriersLeaktight process
Dynamic systems- filtration- detritiation
2nd Static barriers- filtration - detritiation
1st confinement system – closest to radioactive material, protects the worker
2nd confinement system– protection of population and environment in case of failure of first system
3H
Building - Filtration- Isolation
P
P
worker
16Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Safety analysis in ITER
Metodologia applicata ad ITER per l’analisi di sicurezza
PIE Postulated Initiating EventsFMEA Failure Mode and Effect AnalysisPST Process Source TermEST Environmental Source TermDCF Dose Conversion Factor
SOURCE
TERMS ASSESSMENT
Normal working conditions Occupational dose
IEAS
Thermodynamic transients Aerosols and H3 transport
Containments Release from the plant DCF
Overall Plant AnalysisFFMEA
Radioactive waste Operational&Decomm waste
Identification&classification
Management•On-site•Recycling•Final disosal
Effluents
PST
PST EST
DCF
man*Sv/y
dose/sequence to MEI
frequency*dose
Quantity and waste categories
mSv/y
SOURCE
TERMS
Normal working conditions Occupational dose
PIE Thermodynamic transients Aerosols and H3 transport
Confinements Release from the plant DCF
Overall Plant Safety AnalysisFMEA
Radioactive waste Operational&Decomm waste
Identification&classification
Management•On-site•Recycling• Final disposal
Effluents
PST
PST EST
DCF
man*Sv/y
dose/sequence to Public
frequency*dose
Quantity and waste categories
mSv/y
(Courtesy of S. Ciattaglia)
17Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
ITER Safety objectives
Objective for ORE: 500 mSv person/year
General safety objectives
For personnel For the public and environment
Situations in design basis
Normalsituations
As low as reasonably achievable, and in any case less than:Maximum individual dose
≤ 10 mSv/yrAverage individual dose
≤ 2.5 mSv/yr
Releases less than the limits authorised for the installation,Impact as low as reasonably achievable and in any case less than:
≤ 0.1 mSv/yr
Incidental situations
As low as reasonably achievable and in any case less than:
10 mSv per incident
Release per incident less than the annual limits authorised for the installation.
[i.e. 0.1 mSv per incident]
Accidental situations
Take into account the constraints related to the management of the accident and post-accident situation
No immediate or deferred counter-measures (confinement, evacuation)
< 10 mSvNo restriction of consumption of animal or vegetable products
Situations beyond design basis
Hypothetical accidents
No cliff-edge effect; possible counter-measures limited in time and space
18Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
The licensing procedure: the application• Early examination of the project
– Safety options (not compulsory)Presentation by the operator of safety objectives and main characteristicsReview by the ASN’s relevant advisory committee of expertsInformation of the operator on issues to be addressed in its applicationFor ITER: Safety options report consulted by the committee of technical experts in 2002
– National Public debate : compulsory when dealing with a new nuclear electricity generating site or a new site
not generating electricity but costing more than 300 million euros FOR ITER : debate closed in May 2006
• Application file– Content Description of the installation and of the operations to be carried out Report on the consequences on the environment Preliminary safety analysis report (hazards presented by the installation and steps
taken to prevent them ; measures capable of reducing the probability and the consequences of an accident)
Decommissioning plan
19Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
ITER Licensing process
• ITER is to be licensed in France as a Basic Nuclear Installation (Installation Nucléaire de Base, INB)according to the law on transparency and security in the nuclear field (Loi
Relative à la Transparence et à la Sécurité en Matière Nucléaire, TSN)• In order to obtain the decree to authorise ITER, at this stage, ITER has
submitted to the French nuclear safety authorities(Autorité de Sûreté Nucléaire, ASN):
The DAC files(Demande d’Autorisation de Création)
Request for authorisation, comprising 14 files including
Preliminary Safety Report (Rapport Préliminaire de Sûreté, RPrS)
Impact Study (Etude d’Impact)
20Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Preliminary Safety Report • At the end of this stage, construction authorization is given• Needed information : studies and calculations• Need to assess loads on buildings and structural confinement
barriers : – internal loads (normal operation, incidents and accidents) and
external loads (site and environmental loads) to be applied, combination of loads for: all that allow to set-up the design
• Studies and associated calculations of all “plausible” conservative internal and external hazards to consider for the design of rooms, buildings and non reversible components in order to demonstrate the adequacy of safety systems vs workers and public protection (e.g. in order to assess confinement systems, pre-requites of potential contamination level)
21Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Preliminary Safety Report
• Calculation of the worst “plausible” scenario and to assess potential impact on the construction
• Accident approach in particular fire risk (in order to assess whether static or dynamic confinement could be used, assessment of escape routes for workers)
• List of components and structures with safety requirements• Radiation protection approach in order to assess zones and
biological• Shields, radiological monitoring in rooms and stacks
22Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Preliminary Safety Report • All “plausible” conservative internal hazards = Postulated initiating events
Similar as in nuclear power plants such as Loss of flow accident (LOFA),
Loss of offsite-power (SBO), Leaks (VV, Primary System, …), Fire & explosion Fusion specific events: loss of cryogenic system, arcing , magnet system faults affecting
barriers
23Seminario Fusione 2015 – Safety report for a nuclear fusion plant: generalities
Safety report for a nuclear fusion plant: generalities
Grazie per l’attenzione
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