The generalized risk scale a scalar integrated [631723]

The generalized risk scale – a scalar integrated
tool for developing risk criteria by consensus,
in the field of explosives for civil uses

Camelia Lavinia Unguras1*, Doru Anghelache1, Victor Gabriel Vasilescu1, Florian Stoian1,
and Gabriel Ioan Ilcea2
1 University of Petrosani , Doctoral School , 20 University St., Petrosani, Romania
2 University of Petrosani, Research Depa rtment, 20 University St., Petrosani, Romania .
Abstract: The paper highlights the result of the critical analysis upon
criteria regardi ng the safety of explosives based on the quantification of
risks specific for handling explosive materials, for the proper criteria
selection and for defining the integrated concept “how safe is safe
enough?”, applicable to complex work system s whose activ ity object
involves the use of hazardous substances such as explosives for civil use.
In this regard are conceptual and applicative presented judicial precedents
and standards which are used for establishing risk acceptance criteria.
These dat a and informa tion are represented graphically along a series of
logarithmic scales which ensure an objective manner for risk quantification
based on scientific reasoning, real information derived from a data base
which is specific for a deep knowledge of m orbidity indi cators recorded
over an a statistically acceptable .
1 Introduction
In 1999, the DoD (Depart ment of Defen se) sponsored the initial development of risk
criteria for use in risk -based management of explosive materials. Initially, these criteria
were to be used on a trial basis for decisions assoc iated with siting of explosives facilities.
To support the development of these criteria, various d ata relating to ri sk-acceptability were
gathered from a variety of sources. To be compared, th is data needed to be accumu lated in
a common format. This need led to the development of the Universal Risk Scale 1.
The U niversal Risk Scale proved to be a valuable tool in reaching consensus within the
Risk Based Explosives Safety Criteria Team (RBESCT) on th e risk criteria used for siting
explosives facilities. The scales have also been used to compare relevant data to assist
policy makers in s electing appropriate risk related criteria in other areas. As the use of risk –
based techniques expands within the are a of explosives safe ty, and into ot her areas where
hazards to the public reside, further research is needed to support the development of r isk
criteria applicable to these areas 15.
This paper provides an update on the RBESCT’s continuing research into the
fundamental ques tion – “How safe is safe enough?”
2 Material and method
The logarithmic scale is preferred for risk analysis because (Fig.1,2):
– Range of interest for risk spans many orders of magnitude;

1Corresponding author: camelialaviniaungu [anonimizat]

– Proportional logic – Multiplying the risk by a cons tant factor gives a constant
separation;
– In widesp read use for quantitative risk assessment .

Fig.1 Number scales with logarithmic values represented in engineering notation

Fractio n Scientific
notation Engineering
notation
Fraction 2/3 6.67×10-1 6.67E -01
1/10 1.00x 10-1 1.00E -01
Small fraction 1/3,000 3.33×10-4 3.33E -04
7/100 ,000 7.00×10-5 7.00E -05
Extremely small
fracti on 1/100,000,000 1.00×10-8 1.00E-08
5/10,000,000,000 5.00×10-10 5.00E -10

Fig.2 Number scales using the Log Scale
2.1 Pascalian Methods
Accord ing to th e Pascalian Methods (Fig.3) , 10: Concept of risk : Risk = Likelihood x
Consequence ; Proportionality : Consistency in risk space ; Systematic devolution :
Description of contributing elements ; Preciseness: Quantitative .

Mishap
Probab ility
Level s Mishap Severity Categori es
(1) Catastrophic (2) Critical (3) Marginal (4) Negligib le
(A) Frequent High High Serious Medium
(B) Probable High High Serious Medium
(C) Occasional High Serious Medium Low
(D) Remote Serious Medium Medium Low
(E) Improba ble Medium Medium Medium Low

Fig.3 Example Risk Assessment Matrix as viewed by Pascal s Proportional Concept

According to th e Risk Assessment Methods (Fig. 4), 10:
– Qualitative : Risk assessment are often subjective and based on judgments
– Quantitative : Ri sk assessment are based on t he best available information
including accident history, physical science, test results, expert judg ment and
statistics.

Fig.4 Risk Assessment Matrix

Basic risk equation:
Risk = Probability x Consequence (1)

Basic risk equation to person (s):

Risk = Probability x (Consequence level x Human Exposure) (2)

Equation of risk to person(s) from explosives events – Annual risk:

Pf = Pe x Pf/e x E p (3)

Where : Pf -Probability of fatality ; Pe-Probability of event; Pf/e -Probability of fa tality given an event
and a person ; Ep-Exposure hours per year
Expansion of P f/e term: Pressure/Impulse, Glass and Building Failure, Debris, T emperature

2.2 Criteria Basis
Basis of Criteria for Safe Enough  is showing in Fig.5.

Fig.5 Criteria Basis

3 Results and Discussion
3.1 The U niversal Risk Scale Format
The answer to this question, “How safe is safe enough?” is an essential ingr edient in
establishing any risk criterion. Though the question is fundamental to achievi ng the
practical goal of esta blishing risk criter ia, it is also a somewhat philosophica l question, in
that it requires individuals to make subjective interpretations of legal precedents, societal
values and past risk experiences 10.
Opinions vary widely as to what t ypes of information sh ould be considered when
making these judgments, and these differences of opinion become all the more pronounced
when the relative importanc e of individual data points is considered. For this reason,
consensus decisions re garding risk criteria are particula rly difficult to ac hieve. To facilitate
decisions of this type, the U niversal Risk Scale was developed to display on a single scale a
wide variety of inform ation for the purpose of comparison. The intent is to display as much
information as practical, with the hope that th e individual partic ipants in the decision will
find among the data, information they consider relevant.
There are two primary types of info rmation shown on the U niversal Risk Scale. The
first, is various risk-related legal precedents and governmental standards which may be
considered releva nt to the case at hand, the second is r eal-world statistical data derived
from documented accident experience (Fig.6).

Fig.6 Universal Risk Scale Format

Figure 6 shows the format of t he U niversal Risk Scale. The loga rithmic scale was
chosen beca use it can display a wide variety of di sparate data and allows t he aggregate
weight of the individual data points to be viewed at once. This scale also enables large
difference s in the amount of actual risk to be displaye d in a small numerical space.
For instance, the difference between the val ues of zero and one on a linear scale is
small; in fact, most people think of this numerical space in linear terms of percent. The
linea r paradigm, however, does not provide the nec essary perspective for a useful
understanding of the concept of risk. Measu red risk is better viewe d logarithmically; as
orders of magnitude, to allow comparisons of relative risk.
The U niversal Risk Scale form at attempts to achieve this perspective so that the concept
of relativ e risk can be more properly understood.
3.2 The Two Universal Risk Scales
In the figures that follow, all data are shown in terms of annual risk. The surroun ding data
points are the prod uct of re search for relevant supporting data. Many d ata points are shown
because indivi duals may ascribe more or less relevance to each data point 14.
3.2.1 Risk to Any One Worker
The scale supporting the criterion for protection of any one worker is sho wn in Figure 7.
This scale is labeled “indiv idual volunta ry” because the risk to the individ ual is accepted
voluntarily as a condition of employme nt. Figure 7 plots the data on a U niversal Risk Scale
and the following paragraphs describe each data point 1-9, 11-13.
The reactions still continue in the Taylor rarefaction wave, b etween the so nic line and
end of reaction zone, and they cannot contribute to the shock fron t but they can
signi ficantly contribute to the blast.

Fig.7 Scale – Individual Voluntary
3.2.2 Risk to Any One Person
The scale supporting the protection c riterion for any one person is shown in Figure 8. This
scale is labeled “individual involuntary” because the risk is not accepted as a voluntary
action taken by an individual. For example, victims of homicide, stroke or tornado
generally do n ot die as the resul t of a voluntary decision to accept risk. Figure 8 plots the
data on a U niversal Risk Scale and t he following paragraphs describe each data point 1-9,
11-13.

Fig.8 Scale – Individual Involuntary

Conclusions
The RBESCT (Risk Based Explosives Safety Criteria Tea m) has b een conducting research
for data to s upport the criteria cho sen for personnel protection.
Accident data, regulations, and legal precedents have been reviewed to identify data
relevant to the level of personnel protection. These data have been plot ted on th e Universal
Risk Scales.
A foundati on has been laid that c an benefit the international explosives safety community,
as well as other safet y communities who are using risk -based a nalyses and numerical risk
criteria.
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