Research and analysis

Nuclear power station cooling waters: protecting biota - summary

Published 9 April 2020

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1. Chief Scientist’s Group research summary

1.1 Introduction

This study reviewed the recent published literature on the effectiveness and UK applicability of technologies which can protect animal and plant life (biota) from large scale cooling water systems at nuclear power stations.

We will use the information from this study when permitting and regulating the cooling water systems of new nuclear power stations or other large scale water infrastructure projects. This review updates an earlier report from 2010 (SC070001/SR3) on the cooling water options available at the time.

1.2 Method

The study built on previous Environment Agency work and reviewed literature from the UK and abroad. The subjects covered were:

  1. Fish behavioural deterrent systems
  2. Decisions on cooling water systems of other/international environmental regulators
  3. Fisheries and other biota impact assessment methods
  4. Cooling water intake siting
  5. Intake head designs
  6. Approach/escape velocity
  7. Cooling water system tunnels: pressure changes
  8. Forebay and screenwell designs
  9. Entrainment – downstream of fine screens
  10. Onshore screening including fish recovery facilities
  11. Fish return launders and discharge head design
  12. Fish lift pumps
  13. Biofouling control
  14. Monitoring and assessment protocols for fish recovery and return facilities
  15. Monitoring and assessment protocols for fish deterrent effectiveness.

This review compiled the recent science and technology on each specific subject. We looked at the strength of evidence in each area and applicability to the UK situation. This gave us an assessment of the confidence we can place in the information available for each subject reviewed.

1.3 Main results

The specific siting of the intake on a plant (where water is channelled from the sea or estuary to the cooling water system) can influence the impact on biota. Low velocity side intake designs may reduce the number of fish being trapped on the intake screens (impingement), but not the number which pass through the cooling water system (entrainment).

For those fish passing through the station, rapid pressure changes caused injuries (barotrauma), but there were few studies of fish species found in UK waters. Shear stress was also found to cause damage in some species and conditions studied.

Some fish-friendly systems (for example those with smooth surfaces or steady water flow) are available for fish screening, recovery and return systems. Most of the information obtained on these systems was for non-UK fish species. The applicability of the results for UK species is not certain.

Biocides are required for control of algae at some points in cooling water systems. The impacts of biocides on fish have been studied in laboratory settings, but there is little evidence on the effects of biocides on fish in combination with the other stressors in a large cooling water system.

1.4 Conclusions

The detailed information provided in this review will help in the future regulation of large-scale cooling water systems in the UK, reducing the impact on biota. The effectiveness of the methods and technologies reviewed will vary depending on individual locations and site designs.

We recommend further study into those areas with limited available information, particularly with reference to the impact on UK marine species.

1.5 Publishing details

This summary relates to information from project SC180004, reported in detail in the following output:

Report:

SC180004/R

Title:

Nuclear power station cooling waters: protecting biota

April 2020

Project manager:

Louise Paul, Research, Analysis and Evaluation

Research Contractor:

Pisces Conservation Ltd, IRC House, The Square, Pennington, Lymington, Hants, SO41 8GN. Tel: +44 (0) 1590 674000

This project was funded by the Environment Agency’s Research, Analysis and Evaluation group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk

© Environment Agency

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