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Underwater acoustics

UXO Clearance Technologies

Controlled Underwater Acoustic Testing Opportunity

Defra, together with the National Physical Laboratory (NPL), is seeking candidate technologies for clearance of Unexploded Ordnance (UXO) to participate in a funded acoustic testing programme in a controlled facility to determine their acoustic performance.  This is a key aspect of Defra’s efforts to reduce the environmental impacts of UXO clearance in the marine environment.  

The tests are planned to be carried out during March-June 2024 in an inland quarry in Scotland (subject to availability). The project will be designed and managed by scientists in the National Physical Laboratory, with support from Loughborough University.

Suppliers with novel technologies for disposal of UXOs are invited to apply for the tests.


The location and scale of industrial development at sea means there is a high potential to encounter UXO during construction: a legacy of the World Wars, military training areas and munitions disposal sites. As part of development planning, detailed surveys are undertaken to identify possible UXO and confirm what action is needed to reduce health and safety risks to a tolerable level. When UXO cannot be avoided or safely removed, clearance of the UXO may be necessary.

A common method used for the disposal of UXO is deliberate detonation initiated by a small donor charge placed on the munition to initiate an explosion of the main charge (commonly referred to as a high-order detonation). This can produce some of the highest sound levels of all anthropogenic sound sources with the potential to cause fatal injury to marine mammals and other marine fauna near the blast, but also auditory damage and behavioural responses at much longer ranges. 

Alternate clearance technologies are becoming available to the market that can neutralise the UXO in a better, safer way than current methods achieve, leading to a reduced acoustic output and reducing impacts on marine fauna.

Defra encourages the development of such novel technologies; however, it is important they are proven safe and effective during controlled-environment experiments before being consented for use at sea.

This funded trial will therefore provide novel clearance technologies equal opportunity to acquire controlled environment data. NPL will lead the acoustic test programme on behalf of DEFRA. 

Innovative, novel technologies are encouraged to apply to be selected for the tests. All technologies that fit the testing criteria will be considered.

National Physical Laboratory

The acoustic characterisation will be undertaken by the National Physical Laboratory with support from Loughborough University. They conducted all 5 phases of controlled environment testing of low noise technologies for UXO clearance during the OESEA trials.

NPL is the national metrology institute of the United Kingdom. It is responsible for developing and maintaining standards for measurement within the UK, and support regulators and UK industries through scientific research.

NPL has been providing world-leading metrology for ocean acoustics to support offshore energy, defence applications and the marine technology industry for over 30 years.  NPL's capability enables provision and dissemination of traceable acoustic standards. The accurate measurement of anthropogenic, or man-made pollution, noise is key to the assessment of its effect on marine life.

For consideration prior to applying

Candidate technologies should consider the following:

  • Solutions should aim to significantly reduce offshore campaign time while reducing environmental, health and safety risks. Time restrictions on campaigns are often imposed for the protection of marine mammals, primarily cetaceans (whales and dolphins). In the Southern North Sea, harbour porpoise populations are of particular concern, while in the Northern North Sea and to the west of Britain, porpoises and various dolphin and whale species are of concern.
    • As an example, in the Southern North Sea, it could take approximately 1 day to neutralise a single UXO using current methods, not including mobilisation and demobilisation time. In this region, the time restrictions are predominantly to minimise sound exposure levels to the harbour porpoise population, for which a Special Area of Conservation has been designated.
  • Underwater noise is the main issue for marine mammals from UXO clearance, rather than blast injuries. A solution needs to avoid a temporary or permanent shift in hearing ability or fatality/injury of marine life.
  • Typically, UXO removal contractors place a donor charge on a UXO to destroy the whole shell, no matter how degraded it is. UXOs are typically steel casings that contain explosives, the steel casing can corrode over time, exposing the explosive compounds to seawater. Through this process, often the explosive may have significantly reduced in volume and may not need to be detonated. A solution that took the state of degradation into account may increase the speed at which UXOs can be cleared.
  • Low order techniques such as plasma injection, high-pressure water jet and shockwave treatment have previously been trialled, but improvements on the current status quo in these areas would be of interest.

Technical requirements

Candidate technologies should meet the following criteria:

Candidate technologies should be ready for use in the following project conditions:

  • Significantly reduce the sound output of UXO clearance, when compared to a high order detonation.
  • Reduce harm to the environment through the release of chemicals or materials (e.g. toxic) as a result of clearance of the UXO. All solutions must be consistent with the OSPAR convention. 
  • Abide by established subsea and marine standards.
  • North, Atlantic and Baltic Seas 
  • A minimum design temperature of -15 ºC
  • A maximum water depth of 250m

Benefits to candidates

Successful candidate technologies will be given an opportunity to participate a funded field trial at a licensed, fully instrumented facility for shock testing, to conduct a controlled experiment to characterise the acoustic performance of their product. This needs to be obtained before a technology can be used at sea.

The candidates will also receive copies of technical reports, documenting the underwater sound characteristics of the solution demonstrated.

No payment will be made to candidates for the participation of the tests.

IP and confidentiality

Where necessary, a non-disclosure agreement (NDA) may be signed to uphold confidentiality in the engagement between the Candidate Technology Provider(s) and Defra and the NPL.

Eligibility and assessment criteria

Entrants must be:

  • Established businesses, startups, SMEs or individual entrepreneurs
  • UK based

Applications from universities are welcome but there must be a clear route to commercialisation and meeting the required timeframes.

Applications will be assessed on:

  • Maturity and readiness of solution
  • Track record of offshore explosive ordnance disposal projects if applicable
  • Innovative and development potential
  • Feasibility/ economic viability
  • Ability to launch project timely/Ease of implementation. Fully deployable for prototype testing and fully deployable commercially within 1.5-2 years.
  • Suitability for the UK and European work

Your application

Please send an email to Sei-Him Cheong and Jas Kainth expressing your interest in taking part in the trials by 25 January 2024.

Then, please submit a Word Document to Sei-Him Cheong and Jas Kainth before 15 February 2024 outlining your suitability for the trial:

A brief description of the technology (up to three A4 pages), this should include:

  • Overview of the technology/solutions
  • Application to UXO disposal
  • Deployment method and requirement


  • Launch of the Competition: 15 January 24
  • Deadline for expression of interest: 25 January 24
  • Deadline for applications: 28 March 2024
  • Notification of shortlist for interview: March / April 2024
  • Anticipated interview dates: 2 - 12 April 2024
  • Notification of successful candidate technology for testing: Mid April 2024
  • Date of Testing: 13 - 24 May

Contacts for queries

NPL: Sei-Him Cheong or Jas Kainth

Defra: Natasha Hill or Louise Treacy

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