Technical Seminar:Progress with societal risk aroundonshore, non-nuclear major hazardsPresenting societal risk information

Ian Lines 30 April 2009

Overview

• Definition of societal risk

• Objectives of societal risk framework

• Options considered for presenting societal risk

• Approaches currently being taken forward

• Examples

• Possible criteria/guidelines

Definition of societal risk

The relationship between the frequency and number of people in a given population suffering a specified level

of harm from the realisation of specific hazards

• Societal concern – a wider issue

• Level of harm – fatality

• Population – off-site/on-site

ObjectivesThe UK Framework for the assessment of societal risk must:

1. Be effective in controlling societal risk (including incremental, large, multiple use, unusual, new installations, etc), ideally promoting a reduction in societal risk over time.

2. Be technically robust and not likely to be subject to significant challenge.

3. Provide clear and useful guidance to land use planning decision makers (LPA) – in context of local development plans, specific case developments (and perhaps hazardous substances consents).

4. Be broadly consistent with COMAH assessments in terms of approach and assumptions

5. Be simple and easily understood.

6. Be capable of dealing with case, local and perhaps national societal risk.

7. Be practicable and implementable by HSE (i.e. can be embedded within HSE systems as supplemental to PADHI).

Options considered

• Nmax

• fN points

• fN histograms

• FN curves

• EV/PLL

Measures for presenting societal risk:

• Other risk integrals (e.g. RI, ARI, SRI, ESRI)

• Risk indices (e.g. MSRI, (FN)max)

• Location specific societal risk (LSSR) (i.e. hotspot map or EV Density map)

• Area specific societal risk (ASSR)

Criteria for societal risk

• Nmax values

• Anchor points

• FN criteria/comparison/guideline lines

• Comparison values for EV and RI

• Risk index values (e.g. for MSRI)

Approaches being taken forward

1. Classical approach• FN curve, EV, Nmax• No scale aversion in calculations

2. Scale averse approach• FN curve, RIs• Explicit scale aversion

3. Map based approach• EV density, area specific societal risk• Various map based approaches

Examples

Classical approach• FN curve (illustrates EV and Nmax)

Scale averse approach• FN curve

Map based approaches• Expectation Value Density (EVD) plot• Area specific societal risk: e.g. Total EV plot

Classical approach

Examples of FN comparison guidelines

Scale averse approach

Examples of FN comparison guidelines

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1E-009 fat/km²/y3E-009 fat/km²/y1E-008 fat/km²/y3E-008 fat/km²/y1E-007 fat/km²/y3E-007 fat/km²/y1E-006 fat/km²/y3E-006 fat/km²/y1E-005 fat/km²/y3E-005 fat/km²/y0.0001 fat/km²/y0.0003 fat/km²/y0.001 fat/km²/y

Expectation Value = 0.0019 fat/y

Map based approach:

Example of Expectation Value Density

(EVD) plot

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1E-008 fat/y3E-008 fat/y1E-007 fat/y3E-007 fat/y1E-006 fat/y3E-006 fat/y1E-005 fat/y3E-005 fat/y0.0001 fat/y0.0003 fat/y0.001 fat/y

Map based approach:

Example of Total Expectation Value

(TEV) plot

Individual Risk Criteria (fatality)

10-6 per year10-6 per yearBroadly acceptable

10-4 per year10-3 per yearMaximum tolerable

Members of PublicWorkers

Reasonably well established and accepted

Societal risk guidelines

1000.001 fat/km2/yr0.0001 fat/year0.001 fat/yearLower

10000.01 fat/km2/yr0.001 fat/year0.01 fat/yearMiddle

100000.1 fat/km2/yr0.01 fat/year0.1 fat/yearUpper

Truncation value (Nmax)

Expectation Value Density

Increment to EV from a

single development

Total EV for a major hazard installation

Comparison value

Indication of possible guidelines

SummaryPresenting societal risk information• Definition of societal risk

• Objectives of societal risk framework

• Options considered for presenting societal risk

• Approaches being taken forward

• Examples

• Possible criteria/guidelines