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Nuclear Engineering and Design 57 (1980) 207- 214 © North-Holland Publishing Company EVALUATION OF HAZARDS FROM INDUSTRIAL ACTIVITIES NEAR NUCLEAR POWER PLANTS - DETERMINISTIC AND PROBABILISTIC STUDIES * A. LANNOY Electricit~ de France, Direction des Etudes et Recherches, F-93206 Saint Denis Cedex 1, France and T. GOBERT Electricit~ de France, Direction de L 'Equipement, F-92080 Paris-La Defense, France Received 30 July 1979 Among the potential hazards which could arise from industrial activity near nuclear power plants, fires and explosions of dangerous products are of particular concern. Indeed, thermal radiation from an adjacent f'tre could endanger the resistance of a plant's structures. Likewise, an accidental explosion would induce an overpressure wave which could affect buildings' integrity. This paper presents the methodology developed by Electricit~ de France to evaluate the consequences of accidents affecting: - Industrial facilities: refineries, chemical and petrochemical plants, storage areas, pipelines of gaseous, liquid and liquefied materials. - Transportation routes (roads, railways, inland waterways) used to carry dangerous substances (solid explosives, liquid, gaseous or liquefied hydrocarbons). Probabilistic methods have been developed by analysis of actual accident statistics (e.g. risks induced by transportation routes) and realistic and representative accident scenarios have been set up. Five sequences have been identified: - Formation of a fluid jet at a breach. - Evaporation and possible formation of a liquid layer. - Atmospheric dispersion and drift of a gaseous cloud. - Heat radiation from fire. - Unconfined explosion of a gaseous cloud. This paper gives an overview of the methods and the main assumptions used to deal with each sequence. Those meth- ods, presently applied by Electricit~ de France, provide a coherent and realistic approach for the evaluation of the risks at nuclear power plants induced by industrial activity. 1. I n t r o d u c t i o n In the analysis of the safety of nuclear power plants, a special importance is attached to the assess- ment of dangers which could arise from nearby industrial activity. Among the potential hazards, fires and explosions of dangerous substances are * Invited Paper J10/1', presented at the 5th International Conference on Structural Mechanics in Reactor Tech- nology, Berlin (West), 13-17 August, 1979. of particular concern. A nearby fire could cause structural damage to a plant (heat radiation) or involve the important safety systems malfunction (air-heating, smoke fall-out). Similarly, an accidental explosion could induce an overpressure wave affecting the buildings in which safety equipment is installed. The possible causes of fires or explosions are: - Industrial facilities: refineries, chemical and petrochemical plants, storage areas, and pipelines carrying gas, liquids or liquefied substances. - transportation routes (roads, railways, inland 207

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Page 1: Evaluation of hazards from industrial activities near nuclear power plants — deterministic and probabilistic studies

Nuclear Engineering and Design 57 (1980) 207- 214 © North-Holland Publishing Company

EVALUATION OF HAZARDS FROM INDUSTRIAL ACTIVITIES NEAR NUCLEAR POWER

PLANTS - DETERMINISTIC AND PROBABILISTIC STUDIES *

A. LANNOY Electricit~ de France, Direction des Etudes et Recherches, F-93206 Saint Denis Cedex 1, France

and

T. GOBERT Electricit~ de France, Direction de L 'Equipement, F-92080 Paris-La Defense, France

Received 30 July 1979

Among the potential hazards which could arise from industrial activity near nuclear power plants, fires and explosions of dangerous products are of particular concern. Indeed, thermal radiation from an adjacent f'tre could endanger the resistance of a plant's structures. Likewise, an accidental explosion would induce an overpressure wave which could affect buildings' integrity.

This paper presents the methodology developed by Electricit~ de France to evaluate the consequences of accidents affecting:

- Industrial facilities: refineries, chemical and petrochemical plants, storage areas, pipelines of gaseous, liquid and liquefied materials.

- Transportation routes (roads, railways, inland waterways) used to carry dangerous substances (solid explosives, liquid, gaseous or liquefied hydrocarbons).

Probabilistic methods have been developed by analysis of actual accident statistics (e.g. risks induced by transportation routes) and realistic and representative accident scenarios have been set up. Five sequences have been identified:

- Formation of a fluid jet at a breach. - Evaporation and possible formation of a liquid layer. - Atmospheric dispersion and drift of a gaseous cloud. - Heat radiation from fire. - Unconfined explosion of a gaseous cloud. This paper gives an overview of the methods and the main assumptions used to deal with each sequence. Those meth-

ods, presently applied by Electricit~ de France, provide a coherent and realistic approach for the evaluation of the risks at nuclear power plants induced by industrial activity.

1 . I n t r o d u c t i o n

In the analysis of the safety of nuclear power plants, a special impor tance is at tached to the assess- men t of dangers which could arise from nearby industr ial activity. Among the potent ia l hazards, fires and explosions of dangerous substances are

* Invited Paper J10/1' , presented at the 5th International Conference on Structural Mechanics in Reactor Tech- nology, Berlin (West), 13-17 August, 1979.

of particular concern. A nearby fire could cause

structural damage to a plant (heat radiat ion) or involve the impor tan t safety systems mal func t ion (air-heating, smoke fall-out). Similarly, an accidental explosion could induce an overpressure wave affecting the

buildings in which safety equ ipment is installed.

The possible causes of fires or explosions are: - Industr ia l facilities: refineries, chemical and

petrochemical plants, storage areas, and pipelines carrying gas, liquids or l iquefied substances.

- t ranspor ta t ion routes (roads, railways, inland

207

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208 A. Lannoy, T. Gobert / Hazards from &dustrial activities near nuclear power plants

waterways) used to transfer dangerous materials, such as solid explosives and liquid, gaseous or lique- fied hydrocarbons.

A major research programme has been undertaken by Electricit6 de France (EDF) in the past few years to develop methods for assessing each of the risks mentioned above.

The dangers are generally evaluated on the basis of probabilistic considerations [ 1 ], and this has led t oa substantial volume of analysis of actual accident statistics from which findings of the two following types can be derived:

- Assessment of the probability of accidents whose consequences could affect the safety of a nuclear power station.

- Conclusions regarding the possible sequences involved in accidents, making it possible to define realistic and representative "accident scenarios" and "typical accidents".

The purpose of the present note is to describe the status of the work which has been undertaken up to now by EDF, and, in particular, to outline the approach followed for the analysis and appraisal of the risks engendered by industrial activity and the presence of communication routes near nuclear power stations.

2. S ta t i s t i ca l a n a l y s i s a n d m e t h o d s o f p r o b a b i l i s t i c e v a l u a t i o n

The analysis of accident statistics, already carried out or under way at EDF, covers each of the possible causes of fires and explosions mentioned above.

2.1. Communication routes

The statistical data used to determine methods of assessment were kindly provided by the Ministry of Equipment for the road traffic, by the National Railway Corporation (SNCF) for the railways, and by the National Navigation Office for the river transport. The most general relation expressing the annual probability/)/(year-1) of an accident involv- ing possible structural damage to a plant for a given substance i and mode of transport is:

Pi=PE X E X S X F i X L i , (1)

in which

PE is the probability of explosion of the danger- ous substance per vehicle-kilometer,

E is a meteorological (wind direction, diffusion conditions) and topographical factor, which only exists in the case of propagation of a gaseous cloud,

S is an adjustment factor depending on the type of transport or the location of the route consideredl

F i is the frequency of passage of vehicles carry- ing substance i (vehicles × year - l ) and is expressed as

Ti is the total annual quantity of substance i carried (kg),

j3j is the percentage of total traffic accounted for by substance i carried on the route considered in a vehicle of type j,

Mj is the total weight of products transported in vehicles of type j (kg),

Li is the length (km) of the section of route to be considered = 2x/D~ - D 2 (fig. 1), where Do is the shortest distance from the power plant to the route and Di is the distance beyond which the consequences of an explosion have no effect on safety; this distance depends both on the typical accident taken into account and on the buildings resistance to overpressure waves.

The present estimated values of the parameters in formula (1) are as shown in table 1.

The method used to determine the distance D depends on the typical accident taken into account. It may be taken as a first approach that the whole cargo explodes or is instantaneously released. This overall approach has the advantage of being simple to use, but it leads to an overestimate of the risks: But, taken as a whole, the resulting couple: estimated fre- quency/typical accident, is not homogeneous. Actual accidents are generally on a much smaller scale than the typical accident thus defined. For a more refined approach, studies, such as those discussed in section 3, are indispensable.

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A. Lannoy, T. Gobert / Hazards from industrial activities near nuclear power plants 209

k I I

Fig. 1.

2.2. Permanen t industrial facilities

A previous report [2] presents in detail the main findings so far drawn from the analysis of real acci- dents. These findings are the basis of the methods outlined in section 3.

The following points should be emphasized: - In practice, fires may consume large quantities

of the substances involved, and, in general, last several hours.

- Accident scenarios involving gaseous products or materials liquefied under pressure or at a low temperature can be divided schematically as follows:

• opening of a breach with formation of a f luid jet ;

Table 1

Road River Rail

PE 5.0 × 10 -9 2.6 × 10 -9 S Motorway : 0,7 Broad

canal : 1.3 Ordinary Small Roads : 0.9 canal : 0.3

/ 1 1

M/ 20 t Very variable

8.5 X 10 -1° 1

Train normally loaded : 0.44 Full : 0.56 Normally loaded : 60 t Full : 1200 t

• evaporation of the escaping substance accom- panied, in some case, by the formation of a liquid sheet covering the adjacent water or ground; • drift and atmospheric dispersion of the resulting gaseous cloud; • explosion of this cloud in contact with the

potential ignition sources found in an industrial location. - The explosions that occur, mainly deflagrations,

have a low yield in relation to the ene:gy potential ly contained in the total amount of substance released•

2.3. Gas and oil pipelines

Only studies relating to natural gas pipelines will be dealt with here. These studies have been undertaken in collaboration with the Gaz de France (GDF) Transport Service.

The annual probabil i ty of a pipeline accident capable of causing structural damage to a plant is written:

P=Pr XPi XPEXS X E X L (2)

with

PF

Pi

BE

= annual probabil i ty of occurrence of a leak (leak year -1 km-1) ;

= probabil i ty of ignition provided that there has been a leak;

= probabil i ty of occurrence of an explosion provided that the gas has been ignited

Page 4: Evaluation of hazards from industrial activities near nuclear power plants — deterministic and probabilistic studies

210 A. Lannoy, T. Gobert / Hazards from industrial activities near nuclear power plants

(Pi and PE are conditional probabilities); E, S and L are defined as before. The present estimates of the values of the param-

eters of formula (2) are as follows: PF = 7.9 × 10 -4, P~ = 0.065, Pi = 0.062, S = within the range of 0.84 to 4.39, according to the diameter and the location of the pipe.

Using formula (2) requires an estimate of the distance D, i.e., a realistic assessment of the rate of discharge and the volume of gas released and the extent of the cloud thus formed. The approach followed is described in section 3. It is nevertheless important to observe that the explosions which have occurred, consecutive to a leakage, had less serious effects than the consequences resulting from the typical accident defined (double sided pipe break, "guillotine" rupture). Therefore, assigning to the typical accident a probability value deduced from accidents that have actually occurred, leads to an overestimation of the risk.

3. Deterministic approach to evaluate the consequences of accidents

The analysis of accident statistics can contribute to define typical accidents which are as realistic as possible, or conservative when required.

Rough or overvalued estimates of the consequences of an accident are sometimes sufficient to determine whether the risk can be disregarded as a contributive factor in the plant design. As far as the initial anal- ysis shows that the risk must be taken into account, more refined estimates are often indispensable to define the optimal specifications for the necessary protective means.

This section presents the methods developed or in process of development at EDF, related to realistic estimates of risks. It deals successively with the different steps identified in section 2.2: and which may be generalized to all kinds of accidents. This approach is analogous to the one proposed by the Dutch Institute TNO in [8].

It should first be observed that a rigorous evalua- tion of these events, which involve very complex physical phenomena (two-phgse flows, chemical kinetics, turbulence, atmospheric diffusion) is difficult and may even be an illusion. Hence, realistic assump-

tions, or, if these cannot be formulated, pessimistic assumptions, are needed.

3.1. A ceidental release

It is first necessary to calculate the flow rate at the breach, as a function of time. The flow depends on the nature of the substance involved, on trans- port or storage conditions (geometry of the container, pressure and temperature) and on the breach charac- teristics (location, area). The two dominant param- eters are the pressure in the tank and the area of the breach. For this reason, studies are undertaken to determine realistic breach sizes.

In the case of gas liquefied under pressure, the flow is actually two-phased; the pessimistic assump- tion is made that it is liquid, what increases the estimated value of the mass of the outflow.

One of the two following assumptions regarding the calculation of the outflow is taken as appropriate:

- Isothermal flow: the pressure of the gaseous phase is constant; the calculated outflow is there- fore an overestimate.

- Adiabatic flow: the pressure and temperature of the gaseous phase vary simultaneously; the calculated value of the flow is closer to reality.

In the case of a gas pipeline, the typical accident taken into consideration is a sudden rupture of the pipe. A calculation model worked out by GDF takes into account the configuration of the transport network and gives a realistic estimate of the gaseous outflow. In general, the maximal amount discharged corresponds to the volume contained between two section cutoff valves.

3.2. Vaporization

Two phenomena may occur:

3.2.1. Flash vaporization (case o f pressurised lique- f ied gas)

Liquefied gas is transported and stored under pressure at the ambient temperature. In case of breakage, the internal pressure of the tank falls down to the atmospheric pressure, and the liquid cools down. It is assumed that the expansion is adiabatic, without any heat exchange with the

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A. Lannoy, T. Gobert / Hazards from industrial activities near nuclear power plants 211

environment. This enables the percentage of the mass of the gas which evaporates to be calculated.

The greater the initial storage pressure is, the stronger the instantaneous vaporization is. The flash vaporization rate at the surrounding tempera- ture (20°C) can be calculated for several typical substances as shown in table 2.

3.2.2. Normal vaporization (case of pressurised liquefied gas after expansion and case of cryogeni- cally liquefied hydrocarbons)

The liquid spreads on the ground, generally at a low temperature.

The quantity of evaporation depends on the heat supplied by the ground, the air and the sun. Heat from the ground is the main source which induces boiling, which will be more intense at the edges than at the centre of the sheet, for the ground is warmer at the edges. The lower the boiling temperature of the substance concerned is, and the larger the area of the layer is, the greater the heat transfer between the liquid and the ground is.

Experience [3] and calculation show that the rate of vaporization q as a function of time t is

q = K A T e - To

4t

with A Te

= area of the liquid layer, = boiling temperature of the hydrocarbon

considered, To = initial temperature of the ground, K = a constant, which depends on the prop-

erties of the ground and the hydrocarbon considered.

The area A is a dominant parameter which should be defined realistically, taking account of the existence of collecting tanks, the configuration of the ground and the physical aspects of the flow

(roughness, progression velocity, etc.). For instance, a breach of 1 m 2 in a propane tank

under an 8 bar pressure involves an overall vaporization of 32% of the tank's contents within one minute after the breakage, a maximal evaporation rate of approximately 250 kg/s, and a maximal radius of the liquid sheet of 240 m, in the case of the possibil- ity of an illimited extension.

3.3. Formation and drift of an explosive cloud

Several different models may be used for the study of the drift and the atmospheric dispersion of the cloud thus formed. A gaussian model, which deals with variable source areas and flow rates as a function of time, has been formulated by EDF to evaluate isoconcentrations in the cloud and the mass of gas contained within the flammability limits for each category of atmospheric stability.

The various calculations showed that the explosive mass in the cloud is approximately 20% of the total mass of gas composing it [7].

Experimental results obtained by GDF [3] are also used to calculate the greatest distance from the accident location at which concentration is equal to the lower flammability limit.

3.4. Thermal radiation

This risk arises essentially from fires in storages of liquid hydrocarbons held in normal atmospheric conditions: gasoline, kerosene, fuel oil, crude oil, etc.

There are several steps when evaluating the thermal radiation effects:

- Determination of the average radiant heat of the flames on the basis of experimental results found in the literature (the selected value is 29730 W m-2), the temperature of flames ranging from approximately 1100°C (at the basis of the flames) to 450°C (at a height of 15 m).

Table 2

Substance Propane Butane Propylene Methylchloride Ethyloxide

Rate of instantaneous 33% 9% 38% 17% 5% vaporization

Page 6: Evaluation of hazards from industrial activities near nuclear power plants — deterministic and probabilistic studies

212 A. Lannoy, T. Gobert / Hazards from industrial activities near nuclear power plants

- Evaluation of the combustion speed of substances (from 0.5 mm/min for the heavy components to 3.4 mm/min for the more volatile components);

- Calculation of the fire size and then of the heat flux reaching the power plant structure, provided that a part of the flux is absorbed by the surround- ing atmosphere (for instance, with a humidity ratio of 6 g/kg of dry air, approximately 30% of the initial flux is absorbed within 500 m),

- Calculation of the structures heating-up using a thermal model, taking into account the nature of the facing wall and the flux reflected. An example of the results obtained is given in fig. 2 for a concrete facing wall (emissivity factor = 0.93).

Protective measures consisting in the implementa- tion of devices for spraying water on the wall surfaces exposed to radiation have also been studied. In particular, imperfect spraying of the surface has been simulated using a Monte-Carlo method.

3.5. Explosion

3. 5.1. Approach selected The measure universally adopted to depict the

effects of an accidental explosion - [2], [4] is the "TNT equivalent of this explosion": from inspection of the damage, the mass of TNT whose explosion

would have engendered the same damage at the same distance can be deduced.

To translate the effects of an explosion into terms of "TNT equivalent" needs the assessing of the energy yield of this explosion. This yield is defined as the ratio of the combustion energy of the equivalent mass of TNT to the potential combustion energy contained in the mass of the substance involved in the explosion.

For instance, for most of the hydrocarbons in common use (propane, ethylene . . . . ) a yield of 1 involves a TNT equivalent mass 10 times greater than the mass of hydrocarbon involved (the theore- tical TNT equivalent).

It should be stressed that this notion of "TNT equivalent" is scientifically inadequate. Only very seldom, observation of damage enables to derive a unique yield of a unique mass of TNT which describes the effects of the real explosion. This translates the likelihood that the overpressure waves generation and propagation laws are not entirely similar, and that local confinement effects can change the conditions of the cloud combustion, e.g., by accelerating the flames.

It should nevertheless be observed that the trans- lation of an accidental explosion (slow or rapid deflagration or even detonation, local or generalised)

Temperalure of the face exposed to flames ('C)

(Ep : 0.93)

700 "-J~/......~...~ lh O.Sh

= - - 15 mn 600 I

500 1 ~ 5 mn / / / / / / / / Determination of

400 r E / / / / / temperature o, the face

o- ooo; zoo'= 3doo ,o;oo so;oo ;ooo w= -2 Fig. 2.

Page 7: Evaluation of hazards from industrial activities near nuclear power plants — deterministic and probabilistic studies

A. Lannoy, T. Gobert / Hazards from industrial activities near nuclear power plants 213

in terms of a TNT detonation can be carried out independently of the type of explosion which actually occurred.

As a result, to assess the effects of a possible explosion, occurring after an accident involving dangerous substances, EDF has adopted the TNT equivalent concept, thus aligning itself with the universal approach to describe the effects of the accidents that practically occurred.

3.5.2. Evaluation principles (a) Whatever the process of the explosion observed

may be, it is assumed that it can be expressed as a TNT explosion, and the estimate of the frontal shock wave characteristics is made by means of a pre- established TNT chart. The chart selected is taken from the report TM 5-1300 [5]. It gives the over- pressure relations (duration of the positive phase and impulse) as a function of the scaled distance (actual distance/cubic root of the exploding mass). This chart has been extrapolated by EDF for low overpressure values, with the use of least squares polynomials.

(b) It is assumed that the total yield of the explo- sion is 10% (a pessimistic value whose justification is stated in [2]): 1 kg of hydrocarbon released is therefore equal to 1 kg of TNT. This value is consistent with the two following hypotheses:

- The TNT equivalent of a hydrocarbon is 5 kg of TNT/kg of hydrocarbon,

- The maximal mass of hydrocarbon that may explode is estimated at 20% of the total mass of the substance released (see section 3.3).

It is then possible to write: equivalent mass of TNT = 1 × total mass of hydrocarbon = 5 × 20% × total mass of hydrocarbon.

(c) It is assumed that ignition occurs one minute after the breakage; the mass of the cloud is there- fore the mass vaporized in this time. This is verified statistically in 56% of real accidents (the delay is less than 5 minutes in 76% of accidents).

(d) Statistically, ignition occurs generally at the point of breakage or very close to it (61% of cases; numerous ignition sources exist in an industrial complex); nevertheless, ignition of the gaseous cloud at its edge occurs relatively frequently (39% of cases). If the point of ignition cannot be easily determined, it is supposed to be the point of the cloud which is the closest to the point at which concentration is equal to the lower flammability limit.

(e) In the case of solid explosives, the overpressure is estimated by using the TNT chart referred to above, and the TNT equivalent of the explosive involved (if unknown, 1), the origin of the explosion being taken to coincide with the accident location.

A P(bar) 10

AIR-ETHYLENE

MfKTURE

(8%) 1

0,1

0,01

~ Points collected in literature - - by J. LEE and (iUIRAQ

TESTS 3 ~ ] k | Exper,mental ~ ~ ~ results

1st test 215n 3 | 2nd test Z15n 3 x J

.=r TNT equivalent : S

• - KOGARGO results

\ ~ , . - - Statistical fitting \ ~ " ~ \ i~ on tests

X - ' ~ ; ~ • - - piston model

\ ~ , • - - Bfinkley - Kirk wood \ ~ ~ theory (J LEE)

N , ,

10 100 Y RIRo

~g. 3.

Page 8: Evaluation of hazards from industrial activities near nuclear power plants — deterministic and probabilistic studies

214 A. Lannoy, T. Gobert /Hazards from industrial activities near nuclear power plants

(f) In the case of an empty storage or an empty tank, initially filled with a hydrocarbon substance (often a hydrocarbon with a high boiling point: crude oil, gasoline), it is supposed that the hydro- carbon vapors (generally the lightest and most volatile C8 (octene) components) are in stoichiometric proportion with air; the previously described method is used, the point of ignition being taken unambigu- ously as the storage location or t~e accident location.

3.5.3. Comments

The unscientific character of the "TNT equiva- lent" concept has been pointed out above. This is why, when undertaking more refined studies, the more the physical properties of the phenomena should be considered, the more adequate models of gaseous explosions have to be developed.

Therefore, EDF, in collaboration with the Atomic Energy Commissariat, the University of Poitiers and GDF, has undertaken a series of experimental and theoretical studies [6]. Tests have been carried out on air-hydrocarbon mixtures contained in thin-walled spherical, hemispherical or polyhedric balloons whose volume varies from 1 m 3 to 215 m 3, with ignition at the centre of symmetry• These tests have concerned air-methane, air-acetylene, air-ethylene and air-propane mixtures (see example in fig. 3). Furthermore, small scale laboratory tests are carried out for the study of deflagration phenomena and the influence of various parameters (concentration gradients, presence of obs tac le s . . . ) on the kinetic properties of the reac- tions•

7. C o n c l u s i o n

The methodology briefly described above is presently used by EDF. It provides an evaluation of the external hazards arising from nearby industrial activity (fires and explosions), which can then be taken into account in the design of nuclear power plants structures.

This method is based on realistic assumptions,

or, when the physical phenomenon is not well known, pessimistic ones• It has the advantage of being general and consistent, but it is not yet com- plete.

Consequently, further study is required, with, as an expected outcome:

- extension of statistical inquiries and probabilistic evaluations (e.g. tank breakage).

- A better approach of physical phenomena in the description of the accident scenario, in order to come closer to reality (e.g., the study of the atmos- pheric dispersion of heavy gases).

- Follow-up of theoretical and experimental studies on the explosion phenomena.

• Characterisation of detonation waves and study of ground effects.

• Evaluation of overpressures due to deflagrations and of the possibility of a deflagration to detonation transition.

• Effect of turbulence on the kinetic properties of explosions•

R e f e r e n c e s

[1] H. Procaccia and T. Gobert, ANS Topical Meeting on the probabilistic analysis of nuclear reactor safety, Los Angeles (May 1978).

[2] A. Lannoy and T. Gobert, SMiRT 4 (Aug. 1977) San Francisco.

[3] R. Humbert-Basset and A. Montet, Congres GNL 3, Washington (1972).

[4] R.A. Strehlow, 14th Symposium on Combustion, Pitts- burgh (1973).

[5] Departments of the Army, the Navy and the Air Force, Technical Manual, TM 5-1300/NAFVAC-P 397/AFM 8-22.

[6] Brossard, Duco, Gobert, Lannoy and Perrot, Conference given at the ENS/ANS Topical Meeting on Nuclear Reac- tor Safety (Oct. 16-19 1978), Brussels.

[7] J.P. Granier and A.G. Saab, EDF Internal Report by Research Department.

[8 ] TNO Institute, "Methoden voor het berekenen van de de gevolgen van het vrijkomen van gevaarlijke stoffen (vloeistoffen en gassen)".