Lecture 5: External Safety

Question 1

What is external safety policy?

Answer 1

External safety policy aims to control risks fro civilians related to the production, storage and use of hazardous materials as well as transport by road, rail or water and through pipelines

Question 2

Explain the risk contours

Answer 2

Risk contour in law: PR contour. There is a chance that one in 10 to the power of 5, 6, 7, 8 person dies in one year, if that person stands within the respective contour. That person would basically need to stay there unprotected for the whole year in this scenario.

In the Netherlands the government determined that nobody may run the area bounded risk than 1 on the 1 milion per year (PR 10 6).

Question 2

What are the three focus areas of external safety policy in NL?

Answer 2

fire focus area (brandaandachtsgebied)
explosion focus area (explosieaandachtsgebied)
toxic cloud area (gifwolkaandachtsgebied)

Question 3

Why is external safety important in the Netherlands?

Answer 3

Because we have strong ties with transport, a lot of main ports.
* distribution to hinterland
* we produce and use a lot of hazardous material
* dense countries with real estate developments in city centres.
–> all location based.

Question 4

What is a BLEVE?

Answer 4

Boiling liquid expanding vapour explosion. The heat of the fire with this is so high, that it becomes lethal immediately.

Question 5

What is risk?

Answer 5

the likelihood (probability) that people may be harmed or suffer adverse health effects if exposed to a hazard (effect).

So Risk = probability x effect.

Risk is often seen as the probability that human actions or events lead to
consequences that harm aspects of things that humans value.

Also interchangeable with:
* likely consequence of a hazard
* porbability multiplied by the effect of a negative event.

Question 6

What is a hazard?

Answer 6

A potential source of harm or adverse health effect on a person or perons.

Question 7

Explain the key concepts of risk analysis, assessment and management.

Answer 7

Risk analysis: identification of hazards, affected parties, frequency of occurence, level of exposure, potential consequences

Risk assessment: evaluate risks, estimation and reference to acceptance criteria (standards).

Risk management: controlling risks by mitigating probability and/or effect of hazards.

Question 8

Explain forms of risk analysis: Fault tree analysis / swiss cheese model.

Answer 8

Fault tree analysis starts with the top event, which is the specified undesired event. The possible causes for this event such as human error or system or component failure are investigated in depth to find their underpinning causes. This process is repeated until the required level of detail is reached. The fault tree describes a combination of system states that can lead to the top event.

Swiss cheese model:
One system in place: first, third and fourth one is not functioning  incident.

Question 9

How does quantitative risk analysis work?

Answer 9

1. Quantifcy risks into numerical levels
2. expected harm estimation and best knowledge about damage that is logically or empirically linked with each possible action

Based on available statsitics/knowledge at that moment

method to test risks against a norm

Question 10

Name the four different strategies of risk mitigation.

Answer 10

• Avoid risks (remove the hazards from a place of impact)
• Reduce risks (lower the probability or the effect)
• Risk insurance (insure against adverse effects)
• Risk retention (acceptance)

Question 11

Explain risk policies with ships.

Answer 11

› 1 cone: 10 meter distance of another ship, 100 meter of residential areas,
and “ kunstwerken ” like sluices, bridges, fuel storage facilities,

› 2 cones: 50 meters of other ship, 100 meter of “ kunstwerken ”, 300 meter of
residential areas

› 3 cones: 100 meter of other ship, 500 meter of residential areas and
kunstwerken

Question 12

Explain what ALARP is?

Answer 12

the region where risk must be reduced if ‘reasonably practical’. Above it is unacceptable region of risk and below is the acceptable risk.

Question 13

What is the area-bounded risk or individual risk?

Answer 13

This is the annual probability that an unprotected person will die as a result
of an accident involving hazardous materials at a certain spot if that person
resides there for a full year, visualized by risk contours on a map
(standard: IR 10 6 contour)

Question 14

What is the group risk?

Answer 14

This is the cumulative probability for each year that at least 10, 100 or 1000 people die as a direct result of their presence in the influence area of an establishment or transport route if an incident happens with hazardous materials. This is visualized on a logarithmic scale by using the fN curve , where f represents the frequency of an accident and N the
number of people expected to die as a result of that accident.

Question 15

Is the group risk a hard norm or not? Explain how

Answer 15

It is not connected to a strict norm. governments can choose to accept a certain risk if it is higher than the orientation value for example. It should be strongly motivated why the risk is accepted in that case. This also has to do with the aspect of zelfredzaamheid (evacuation). Children in a daycare for example are not self-relient.

Question 16

Name the three categories of vulnerable spatial functions.

Answer 16

• limitedly vulnerable locations
• vulnerable locations
• very vulnerable locations (buildings in which groups of people live that are unlikely or unable in case of unexpected accident to take care of their own safety)

Question 17

What are examples of vulnerable locations and very vulnerable locations?

Answer 17

Vulnerable: accommodations where more than 50 people stay overnight; Sport, game, or leisure accommodation (during the day) with under normal conditions a large number of persons attending during a significant part of
the day;

› Open air festivals with at least 5.000 visitors.

• houses

Very vulnerable:
a. 24 7 care provided residential unit
b.
1. Child care
2. Day care for persons with disabilities
c. A prison
d. A health care facility with beds
e. An education function
1. primary schools
2. persons under age with disabilities

Question 18

Explain the basic network

Answer 18

The basic network categorises transport routes and assigens a maximum volume of transport of hazardous materials by rail to these categories.

Three main categories:
* primary routes: unlimited transport of hazardous materials. Urban development has major limitations due to safety zoning.
* secondary routes: transport of hazardous materials as well as urban development have their limitations
* tertiary routes on which transport of hazardous materials is limited and next to which urban development should not be hindered at all.

Question 19

Name advantages and disadvantages of the Basic network (rail).

Answer 19

Two main advantages:
 The first advantage is that it reflects a new approach to risk policy, facilitating solutions to bottlenecks in the rail network regarding urban
development in the vicinity of those routes
 The second advantage lies in the fact that the memorandum also strongly
underlines that the Dutch government should strive to continuously
improve safety

Two main disadvantages:
 The first is that at several places in the network the number of permitted
transports is higher than it is at this moment
 The second disadvantage is a possible problem concerning the
enforcement of these ceilings.

Question 20

What characterizes the causes of an incident or disaster?

Answer 20

Often not just one cause but a chain of events.

Question 21

Explain what criteria could be taken into consideration with a decision to accept the group risk.

Answer 21

+ fire focus area (brandaandachtsgebied)
+ explosion focus area (explosieaandachtsgebied
+ toxic cloud area (gifwolkaandachtsgebied)
+ target groups
+ alternatives to evacuate
+ money