EDF Energy Nuclear Generation Limited Hunterston B site aqueous discharge variation application

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Closes 22 Apr 2025

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Application details

We received an application from EDF for the Hunterston B site, on 31 January 2024 for a variation to permit EAS/P/1173596, made under EASR for the management of radioactive substances. EDF have requested their permit be varied to allow the following:

radioactive aqueous discharges to no longer be concurrent with a flow of cooling water at seven cubic metres per second (7m3/s;

radioactive aqueous discharges to be independent of tide times; and 

radioactive aqueous discharges to be made at the end of the cooling water culvert at National Grid Reference NS 1773 5176.

EDF have submitted a number of documents in support of their application. The documents include the application form as submitted by the applicant, along with technical and non-technical supporting documents. These documents, listed below, can be downloaded below or are available on request from SEPA.

After reviewing the submitted documents, we requested further information regarding short-term releases. The following documents were provided in response to that request:

The following documents were submitted in support of the application. However, in the interests of managing the number of documents on the website, these have not been placed on-line. These documents are available on request from SEPA.

  • EASR radioactive substances activities permit for Hunterston A EAS/P/1173609
  • Water Environment (Controlled Activities)(Scotland) Regulations 2005 registration for Hunterston B CAR/R/1012347 (water abstraction)
  • Notice of Non or Reduced Availability, dated 20/09/2022
  • Water Environment (Controlled Activities)(Scotland) Regulation 2005 licence for Hunterston B CAR/L/1000649 (main cooling water)
  • Hunterston A Site Engineering Design Calculation Sheet, dated April 2019
  • Active Effluent Discharge flow considerations HPS/ENG/DR2729
  • Water Environment (Controlled Activities)(Scotland) Regulations 2005 licence for Hunterston B CAR/L/1010509 (sewage)
  • Public Radiation Dose in the Vicinity of EDF Energy Nuclear Power Stations 2018 ERO/REP/0232/GEN
  • Public Radiation Dose in the Vicinity of EDF Energy Nuclear Power Stations 2020 ERO/REP/0259/GEN
  • Public Radiation Dose in the Vicinity of EDF Energy Nuclear Power Stations 2022 ERO/REP/0291/GEN
  • Life-cycle Assessment Management Plan: Hunterston B Power Station, G31 Circulating Water Plant HNB/REP/LAMP2/G31/001

SEPA shared the application with the Office for Nuclear Regulation and Food Standards Scotland in accordance with our Memoranda of Understanding with these organisations as well as with Scottish Ministers in accordance with our working arrangements. No comments were made.

Background to the consultation

During the generating and defueling phases of the power station, Hunterston B uses a significant volume of sea water as a tertiary cooling water system. The EASR permit for the management of radioactive substances specifies a large volume flowrate of water (7 m3/s) to make radioactive discharges to sea, which can only be achieved using the Main Cooling Water system.

Following removal of all nuclear fuel from the site, EDF states there will be no justification for the continued use of the Main Cooling Water system, which requires significant electrical power and maintenance resource to operate. Consequently, EDF has reviewed the credible options with a view to establishing the most appropriate, sustainable options for future radioactive effluent discharges. 

EDF appointed a contractor to undertake dispersion modelling of the effluent discharges from both Hunterston A and Hunterston B and has carried out a number of internal optioneering sessions. Following an option elimination process, EDF established that there were three main options available, and these have been reviewed as part of the Best Practicable Means assessment. EDF came to the conclusion that the option to thread a small bore pipe through the existing large cooling water culvert represented the best value for money and the least environmental risk. This option requires a variation to the EASR permit for the management of radioactive substances due to the removal of nominal cooling water flowrates for discharges. 

In addition, the dispersion modelling indicated that a tidal window provides little benefit to dilution and dispersion of the radioactive discharges in the Clyde Estuary at the existing discharge point. EDF has deemed that a tidal window constraint within the permit is therefore disproportionate to the risk and has requested its removal. The existing permit condition requires that radioactive aqueous discharges are only made during the interval of one hour after high tide and one hour before low tide.

The application does not seek to change the existing authorised radioactive aqueous discharge radionuclides or activities or the authorised location of the discharge point.

The Hunterston A site, operated by Nuclear Restoration Service Limited (NRS), uses the same discharge arrangements as Hunterston B. Consequently, NRS has applied to vary the Hunterston A EASR permit in the same manner. SEPA is carrying out a simultaneous consultation on the NRS Hunterston A EASR application.
 

1. Do you have any information to provide us in relation to the removal of the minimum flowrate of 7m3/s that EDF have applied for that we should consider?
2. Do you have any information to provide us in relation to the removal of the tidal window for radioactive aqueous discharges that we should consider?