Hazardous Material Transportation through tunnels – A risk assessment framework
Eftihia Nathanail
Transportation engineer Assistant professor University of Thessaly, Greece
UH Honolulu, August 2012 The Mont Blanc Tunnel
• major trans-Alpine transport route • borders of France and Italy • length 11,611 m • single gallery with a two-lane dual direction road • 35% freight transport to north Europe • 1.1 million vehicles per year
2 The accident March 24 1999
10:46 am - ignition in a tractor refrigerated trailer carrying 9 tons of margarine and 12 tons of flour 10:52 am first signs of smoke 10:53 am explosion
3 The tunnel interior after the incident
4 The cost
• 41 persons dead • structural & mechanical damages • tunnel closed for three years
5 The Tauern Tunnel
• part of A10 Tauern Autobahn (Austria) • important north-south route through the Alps • connects Germany, Italy, and Slovenia • length 6,400 m • single bidirectional tube • ADT 14300 veh, 20% trucks
6 The accident
May 29 1999, 5:00 am
7 The tunnel interior after the incident
8 The cost
• tunnel closed for 3 months • remedial works cost USD 6.5 million • lost toll fees USD 19.5 million
9 More accidents
10 Tunnels in Hawaii
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15 What are hazardous materials • Class 1: explosives • Class 2: gases • Class 3: flammable liquids • Class 4: flammable solids, combustion-liable, flammable gases-liable, self-reactive • Class 5: oxidizing and organic • Class 6: toxic and infectious • Class 7: radioactive • Class 8: corrosive • Class 9: miscellaneous 16
17 Legal framework • International regulations – Accord Dangereux Routier (ADR) since 1957 • Classification • Vehicle • Securing • Packaging • Drivers • National regulations / restrictions • European directive 2004/54/ΕU
18 Scope
Planning the transportation of hazardous material (hazmat) to minimize the associated risk due to incidents and material releases Long term sustainability requires risk minimization in any infrastructure system
19 Objectives
. Estimation of the risk associated to the transportation of hazmat through tunnels . Identification of alternative routes . Comparison of risk on alternative routes . Examination of the impact of measures for minimizing risk along tunnels 20 Methodology Step 1
Tunnel analysis
Step 2 Tunnel is open to Step 3 yes Negligible hazmat zone Identify alternative transportation routes
Step 4 yes no Tunnel restriction Intolerable Tunnel route analysis advised zone Alternative routes analysis
Step 5 Identify alternative Step 6 routes Are there yes alternative routes with a Alternative lower risk than routes analysis the tunnel route?
Step 7 no Specify measures for tunnel and that Promote alternative route of lower risk minimize risk index 21 Risk assessment • For the quantification of risks, 4 stages are implemented – Stage 1: identification of possible scenaria and estimation of the probability of their occurrence – Stage 2: estimation of the impact area of the exposure – Stage 3: estimation of the impacted population – Stage 4: estimation of the number of fatalities and their frequencies
22 The procedural model
Risk source Population exposure model Consequence release model model Release Vapor Liquefied vapor Liquid
Dispersion Fatality index Pool Accident Dispersion of vapor cloud Minor Dense vapor Major Pool probability dispersion dispersion dispersion vaporization
Inflation yes yes yes yes yes Risk index Release Vapor cloud Pool of Fire Major fire frequency inflation fire model
Explosion Vapor cloud BLEVE explosion Release Individual risk (IR) probability Dose
Major Thermal Hyper- Particles poisoning radiation pressure Societal risk (SR)
23 Risk source release model
• Estimated figures: – The probability of involvement in a road accident – The possibilities of each impact scenario, based on the size of the release (event tree)
24 Road accident index
Ftdg = Faccid * xtdg * L * N
Ftdg = frequency of accidents of the specific type (per year)
Faccid = frequency of road accidents (per year/veh- km)
Xtdg = proportion of vehicles of specific type L = length (km) N = volume of vehicles (per year=ADT*365)
25 Scenarios
• Hot BLEVE (Hot Boiling Liquid Expandable Vapor Explosion) • Cold BLEVE (Vapor cloud explosion) or flash fire • Toxic gas leakage • Pool fire
26 BLEVE
27 FLASH FIRE
28 POOL FIRE
29 Event tree assumptions
30 Event tree
31 The procedural model
Risk source Population exposure model Consequence release model model Release Vapor Liquefied vapor Liquid
Dispersion Fatality index Pool Accident Dispersion of vapor cloud Minor Dense vapor Major Pool probability dispersion dispersion dispersion vaporization
Inflation yes yes yes yes yes Risk index Release Vapor cloud Pool of Fire Major fire frequency inflation fire model
Explosion Vapor cloud BLEVE explosion Release Individual risk (IR) probability Dose
Major Thermal Hyper- Particles poisoning radiation pressure Societal risk (SR)
32 Population exposure model • Dose reaching the population, depending on the distance from the source – Thermal radiation (q΄΄) – Hyper-pressure (po) (in case of BLEVE) – Toxic vapor as concentration (c) of CO – High temperature (T)
33 Thermal radiation (q΄΄)
may be created from a pool fire, or flash fire or BLEVE that is the consequence of the explosion of a boiling liquefied expandable vapor
q″ = f (Ff, mh′, ΔHc, x) where: q″ = thermal radiation (W/m2) Ff = percentage of thermal radiation that comes from the flame (%) mh′ = burning rate (kg/s) ΔHc = burning energy (J/kg) X = distance from the center of the fire (m)
34 Hyper-pressure (po) (in case of BLEVE) .. created during the BLEVE
where: Ps = hyper pressure (Pascal) z = relative distance (m/kg1/3)
35 Hyper-pressure (po) (in case of BLEVE)
where: z = relative distance (m/kg1/3) x = distance from source (m) W = ΤΝΤ equivalent (kg)
n.m.E W c EcTNT and m = mass (kg) n = explosion performance indicator (in %, the empirical value of 0,03 is being used) Ec = burning energy of the material (J/kg) EcTNT = burning energy for ΤΝΤ (J/kg, the value of 4,6 ∙ 106 J/kg is being used) 36
Smoke temperature
h P x T (x,t) T T ( ) T e o u A Cp g o g, o o where: Tg(x,t) = Average smoke temperature at point x and time t (Κ) Tg,o(τ) = Average smoke temperature in the middle of the pool fire (x=0) at time t τ = Time required for the heat transfer from the center of the pool fire in distance x (s) (τ= t – (x/u)) Το = Initial air temperature (K) h = Heat transfer component (W/m2∙K) P = Average perimeter of area (case of tunnel) (m) X = Distance from the center of the pool fire (m) T = Time from the start of the fire (sec) Ρo = Air concentration (=1,2 kg/m3) U = Average air speed (m/s) A = Average surface (case of tunnel (m2)) Cp = Air thermal capacity (kJ/(kg∙K))
37 Gases concentration
Ma Q( ) C YG MG maH c where:
ΥG = Amount of the gas that is produced per amount of material burned (kg/kg) Mα = Air molecular weight (g/mol) Q(τ) = Thermal energy rate (W) MG = Gas molecular weight (g/mol) ma = Gas mass flow rate (kg/s) Hc = Burning energy (J/kg)
38 Smoke
texp dt F heat (5, 2 0, 027 T ) 0 60 e where: Fheat = Dose of thermal radiation (%) texp = Exposure time (s) T = Smoke temperature (oC))
t exp C F dt toxicity 90 0 where: Ftoxicity = Toxicity dose of CO (%) texp = Exposure time (s) C = CO concentration (%)
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The procedural model
Risk source Population exposure model Consequence release model model Release Vapor Liquefied vapor Liquid
Dispersion Fatality index Pool Accident Dispersion of vapor cloud Minor Dense vapor Major Pool probability dispersion dispersion dispersion vaporization
Inflation yes yes yes yes yes Risk index Release Vapor cloud Pool of Fire Major fire frequency inflation fire model
Explosion Vapor cloud BLEVE explosion Release Individual risk (IR) probability Dose
Major Thermal Hyper- Particles poisoning radiation pressure Societal risk (SR)
40 Consequence model
Number of fatalities (N)
N = DP * [0,95*A90+0,7*(A50-A90)+0,3*(A10-A50)]
where DP: population density
41 Population risk contours
42 The procedural model
Risk source Population exposure model Consequence release model model Release Vapor Liquefied vapor Liquid
Dispersion Fatality index Pool Accident Dispersion of vapor cloud Minor Dense vapor Major Pool probability dispersion dispersion dispersion vaporization
Inflation yes yes yes yes yes Risk index Release Vapor cloud Pool of Fire Major fire frequency inflation fire model
Explosion Vapor cloud BLEVE explosion Release Individual risk (IR) probability Dose
Major Thermal Hyper- Particles poisoning radiation pressure Societal risk (SR)
43 44 Risk index model
45 The case of Attica Motorway
46 Restrictions applying
• Restricted traffic of road tankers through the tunnels of Mavri Ora, Zefiri, Vrilissia and ring road of Imitos • Restricted traffic of other HazMat (excluding road tankers) through the tunnels of Liossia and Aharnes • No restrictions for the tunnels of Elefsina, Metamorfosi and Iraklio
47 The assumptions
• Vehicle capacity 35m3 • Type of release: – Small 500 lt – Large (all 6 compartments) 5541 lt
48 The results
49 50 51 52 After the analysis tunnels regulation result actions 6 tunnels No Negligible risk None Elefsina No ALARP Measures Mavri ora Total restriction ALARP Measures Liosia Only road ALARP Measures tankers
Zefiri Total restriction ALARP Measures Aharnes Only road ALARP Measures tankers Metamorfosis No ALARP Measures Iraklio No ALARP Measures Vrilissia Total restriction Intolerable risk None Imitos Total restriction Intolerable risk None 53 54 Measures
Design, maintenance: geometry, alignment, illumination, equipment, materials, purpose-built drainage system for HazMat Motorist mitigation: emergency exits Traffic management: speed/time regulation, control, enforcement, traffic diversion plans Emergency management system: monitoring, communication
55 56 Summing up
Road accidents involving hazmat are rare but have a high impact Community and road safety sustainability requires a low risk Risk methodology for impact assessment Implementation in a case study Six tunnels in negligible, seven in ALARP, two in intolerable zones Mitigation measures for tunnels to minimize risk
57 Eftihia Nathanail (PhD, MSc), Transportation Engineer – Ass. Professor tel.: +3024210 74164 – fax: +3024210 74131 - e-mail: [email protected], este.civ.uth.gr
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