United Kingdom

THIS ANNUAL SCIENCE Review showcases the high quality of science evidence and analysis that underpins HSE’s risk-based regulatory regime. To be an effective regulator HSE has to balance its approaches to informing directing advising and enforcing through a variety of activities. For this we need capacity to advance knowledge; to develop and use robust evidence and analysis; to challenge thinking; and to review effectiveness.<br/>In simple terms policy provides the route map to tackling issues. HSE is particularly well placed in terms of the three components of effective policy - “politics” “evidence” and “delivery”. Unlike most regulators and arms-length bodies HSE leads on policy development which draws directly on front line delivery expertise and intelligence; and we are also unusual in having our own world class science and insight capabilities.<br/>The challenge is to ensure we bring these components together to best effect to respond to new risk management and regulatory issues with effective innovative and proportionate approaches.<br/>Many of the articles in this Review relate to new and emerging technologies and the changing world of work and it is important to understand the risks these may pose and how they can be effectively controlled or how they themselves can contribute to improved health and safety in the workplace. Good policy development can support approaches to change that are proportionate relevant persuasive and effective. For example work described in these pages is: to help understand changing workplace exposures; to provide robust evidence to those negotiating alternatives to unduly prescriptive standards; to understand how best to influence duty<br/>holder behaviors in the changing world of work; to inform possible legislative changes to allow different modes of safe gas transmission; to change administrative processes for Appointed Doctors; and to support our position as a model modern regulator by further focusing our inspection activity where it matters most.<br/>The vital interface between HSE science and policy understand how best to influence duty holder behaviors in the changing world of work; to inform possible legislative changes to allow different modes of safe gas transmission; to change administrative processes for Appointed Doctors; and to support our position as a model modern regulator by further focusing our inspection activity where it matters most.<br/>We work well together and it is important we maintain this engagement as a conscious collaboration.

It is well-known that deflagration to detonation transition (DDT) may be a significant threat for hydrogen explosions. This paper presents a summary of the work carried out for the development of models in order to enable the industrial computational fluid dynamic (CFD) tool FLACS to provide indications about the possibility of a deflagration-to-detonation transition (DDT). The likelihood of DDT has been expressed in terms of spatial pressure gradients across the flame front. This parameter is able to visualize when the flame front captures the pressure front which is the case in situations when fast deflagrations transition to detonation. Reasonable agreement was obtained with experimental observations in terms of explosion pressures transition times and flame speeds for several practical geometries. The DDT model has also been extended to develop a more meaningful criterion for estimating the likelihood of DDT by comparison of the geometric dimensions with the detonation cell size. The conclusion from simulating these experiments is that the FLACS DPDX criterion seems robust and will generally predict the onset DDTs with reasonable precision including the exact location where DDT may happen. The standard version of FLACS can however not predict the consequences if there is DDT as only deflagration flames are modelled. Based on the methodology described above an approach for predicting detonation flames and explosion loads has been developed. The second part of the paper covers new paradigms associated with risk assessment of a hydrogen infrastructure such as a refueling station. In particular approaches involving one-to-one coupling between CFD and FEA modelling are summarized. The advantages of using such approaches are illustrated. This can have wide-ranging implications on the design of things like protection walls against hydrogen explosions.

This discussion session interrogated the current understanding of hydrogen embrittlement mechanisms in steels. This article is a transcription of the recorded discussion of ‘Hydrogen in steels’ at the Royal Society Scientific Discussion Meeting ‘The challenges of hydrogen and metals’ 16–18 January 2017.

The text is approved by the contributors. E.L.S. transcribed the session. M.P. assisted in the preparation of the manuscript

Link to document download on Royal Society Website 

With government legislating for net-zero by 2050 what does this mean for UK energy markets and business models?<br/>Getting to net-zero will require economy-wide changes that extend well beyond the energy system leading to rapid and unprecedented change in all aspects of society.<br/>This report shines a light on the level of disruption that could be required by some sectors to meet net-zero targets. With many businesses making strong commitments to a net-zero carbon future the report highlights the stark future facing specific sectors. Some will need to make fundamental change to their business models and operating practices whilst others could be required to phase out core assets. Government may need to play a role in purposefully disrupting specific sectors to ensure the move away from high carbon business models facilitating the transition a zero-carbon economy. Sector specific impactsThe in-depth analysis presented in ‘Disrupting the UK energy systems: causes impacts and policy implications’ focuses on four key areas of the economy highlighting how they may need to change to remain competitive and meet future carbon targets.<br/>Heat: All approaches for heat decarbonisation are potentially disruptive with policymakers favouring those that are less disruptive to consumers. Since it is unlikely that rapid deployment of low carbon heating will be driven by consumers or the energy industry significant policy and governance interventions will be needed to drive the sustainable heat transformation.<br/>Transport: Following the ‘Road to Zero’ pathway for road transport is unlikely to be disruptive but it is not enough to meet our climate change targets. The stricter targets for phasing out conventional vehicles that will be required will lead to some disruption. Vehicle manufacturers the maintenance and repair sector and the Treasury may all feel the strain.<br/>Electricity: Strategies of the Big 6 energy companies have changed considerably in recent years with varying degrees of disruption to their traditional business model. It remains to be seen whether they will be able to continue to adapt to rapid change – or be overtaken by new entrants.<br/>Construction: To deliver low-carbon building performance will require disruptive changes to the way the construction sector operates. With new-build accounting for less than 1% of the total stock major reductions in energy demand will need to come through retrofit of existing buildings.<br/>The report identifies how policy makers plan for disruptions to existing systems. With the right tools and with a flexible and adaptive approach to policy implementation decision makers can better respond to unexpected consequences and ensure delivery of key policy objectives.

Having a robust evidence base enables us to tackle real issues causing pain and suffering in the workplace. Critically it enables us to better understand developing issues and ways of working to ensure that we support innovation rather than stifle it through lack of knowledge. For example the work on the use of 3D printers in schools demonstrates HSE’s bility to engage and understand the risks to encourage safe innovation in a developing area (see p47).<br/>Other examples in this report show just a selection of the excellent work carried out by our staff often collaborating with others which contributes to improving how we regulate health and safety risks proportionately and effectively.<br/>One of HSEs key priorities is to prevent future cases of occupational lung disease by improving the management and control of hazardous substances. The case study on measuring Respirable Crystalline Silica exposure contributes to this and to recognise developing and future issues such as the work on diacetyl in the coffee industry (see p24 and p39). This type of scientific investigation gives our regulators good trusted information enabling critical decisions on the actions needed to protect workers.<br/>The case study on publishing new guidance on the use of Metalworking Fluids (MWF) demonstrates the important contribution of collaborative science to improving regulation. If used inappropriately exposure to MWF mist can cause serious long-term lung disease and it was recognised that users needed help to control this risk. HSE scientists and regulators worked with industry stakeholders to produce new free guidance which reflects changes in scientific understanding in a practical easy to use guide. As well as enabling users to better manage the risks and as a bonus likely save money it has assisted regulation by providing clear benchmarks for all to judge control against. An excellent example of science contributing to controlling serious health risks (see p22).<br/>These case studies are excellent examples of how science contributes to reducing risk. Hopefully they will inspire you to think about how risk in your workplace could be improved and where further work might be needed.

The Sixth Carbon Budget report is based on an extensive programme of analysis consultation and consideration by the Committee and its staff building on the evidence published last year for our Net Zero advice. In support of the advice in this report we have also produced:

• A Methodology Report setting out the evidence and methodology behind the scenarios.
• A Policy Report setting out the changes to policy that could drive the changes necessary particularly over the 2020s.
• All the charts and data behind the report as well as a separate dataset for the Sixth Carbon Budget scenarios which sets out more details and data on the pathways than can be included in this report.
• A public Call for Evidence several new research projects three expert advisory groups and deep dives into the roles of local authorities and businesses.

Our recommended pathway requires a 78% reduction in UK territorial emissions between 1990 and 2035. In effect bringing forward the UK’s previous 80% target by nearly 15 years.

To develop safety strategies for the use of hydrogen indoors the HyIndoor project is studying the behaviour of a hydrogen release deflagration or non-premixed flame in an enclosed space such as a fuel cell or its cabinet a room or a warehouse. The paper proposes a safety approach based on safety objectives that can be used to take various scenarios of hydrogen leaks into account for the safe design of Hydrogen and Fuel Cell (HFC) early market applications. Knowledge gaps on current engineering models and unknown influence of specific parameters were identified and prioritized thereby re-focusing the objectives of the project test campaign and numerical simulations. This approach will enable the improvement of the specification of openings and use of hydrogen sensors for enclosed spaces. The results will be disseminated to all stakeholders including hydrogen industry and RCS bodies.

A possible consequence of pressurized hydrogen release is an under-expanded jet fire. Knowledge of the flame length radiative heat flux and fraction as well as the effects of variations in ground reflectance is important for safety assessment. The present study applies an open source CFD code FireFOAM to study the radiation characteristics of hydrogen and hydrogen/methane jet fires. For combustion the eddy dissipation concept for multi-component fuels recently developed by the authors in the large eddy simulation (LES) framework is used. The radiative heat is computed with the finite volume discrete ordinates model in conjunction with the weighted-sum-of-gray-gases model for the absorption/emission coefficient. The pseudo-diameter approach is used in which the corresponding parameters are calculated using the correlations of Birch et al. [22]. The predicted flame length and radiant fraction are in good agreement with the measurements of Schefer et al. [2] Studer et al. [3] and Ekoto et al. [6]. In order to account for the effects of variation in ground surface reflectance the emissivity of hydrogen flames was modified following Ekoto et al. [6]. Four cases with different ground reflectance are computed. The predictions show that the ground surface reflectance only has minor effect on the surface emissive power of the hydrogen jet fire. The radiant fractions fluctuate from 0.168 to 0.176 close to the suggested value of 0.16 by Ekoto et al.[6] based on the analysis of their measurements.

The introduction of hydrogen into the UK natural gas main has been reviewed in terms of how materials within the gas distribution network may be affected by contact with up to 80% Natural Gas : 20 mol% hydrogen blend at up to 2 barg. A range of metallic polymeric and elastomeric materials in the gas distribution network (GDN) were assessed via a combination of literature review and targeted practical test programmes.

The work considered:

• The effect of hydrogen on metallic materials identified in the network
• The effect of hydrogen on polymeric materials identified in the network
• The effect of hydrogen exposure on polyethylene pipeline techniques (squeeze off and collar electrofusion)

The trials concluded that the majority of metallic materials showed no significant deterioration in mechanical (tensile) properties when stored in hydrogen environments compared to those stored in analogous methane or blended gas atmospheres up to 2barg. Polymeric materials showed no deterioration to efficiency of squeeze-off nor collar electrofusion in socket or shoulder orientations following soaking in hydrogen methane or hydrogen blends.

The paper describes CFD modelling of lean hydrogen mixture deflagrations. Large eddy simulation (LES) premixed combustion model developed at the University of Ulster to account phenomena related to large-scale deflagrations was adjusted specifically for lean hydrogen-air flames. Experiments by Kumar (2006) on lean hydrogen-air mixture deflagrations in a 120 m3  vessel at initially quiescent conditions were simulated. 10% by volume hydrogen-air mixture was chosen for simulation to provide stable downward flame propagation; experiments with the smallest vent area 0.55 m2  were used as having the least apparent flame instabilities affecting the pressure dynamics. Deflagrations with igniter located centrally near vent and at far from the vent wall were simulated. Analysis of simulation results and experimental pressure dynamics demonstrated that flame instabilities developing after vent opening made the significant contribution to maximum overpressure in the considered experiments. Potential causes of flame instabilities are discussed and their comparative role for different igniter locations is demonstrated.