Preventive cleaning of steam generators is carried out by injecting various chemicals including EDTA (ethylene diamine tetra acetic complexing agent), EDA (ethylene diamine complexing agent) and a corrosion inhibitor. As these compounds are not part of the plant’s discharges during normal operation, they must be specifically analysed before discharge.
For two days, rinsing effluent from preventive cleaning of the steam generators at a nuclear power plant was discharged into the River Rhône without first being exhaustively subjected to chemical analysis. These tests are a prerequisite for the direct discharge of this effluent with low chemical content. The operator pledged to conduct them in the licence application approved by France’s nuclear safety authority. Further discharging of effluent was halted. The remaining effluent was tested. The analysis results were well below the authorised discharge limits. A total of 22 m³ was discharged without first being subject to chemical analysis.
Organisational issue
The operator’s analysis of the event revealed a weakness in the management and monitoring of the requirements of an operational protocol. Various entities are involved in the many stages of these operations, complicating their management. The following causes led to the event:
- A lack of buy-in of the protocol by the parties involved:
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The plant’s technicians used a projected calculation made by central services to analyse the chemical content of effluent before discharge.
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Central services considered that it was the site’s responsibility to follow the protocol and therefore check the concentrations using specific analyses.
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The site’s chemicals and environment division determined that the radiation levels of the effluent were within normal limits; this was interpreted as a validation of all the parameters.
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The environmental engineer was not asked to validate the discharge of effluent into the natural environment because he did not draw up an action follow-up sheet reminding this validation.
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None of the parties re-read the protocol’s requirements governing these operations; they considered that everyone knew this.
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- Responsibilities were not clearly defined: no department felt responsible for storing this effluent and no manager was designated.
- There was no organisational structure for monitoring the requirements of a validated protocol.
Corrective actions
The operator instituted a more robust and comprehensive monitoring process. He defined the responsibilities of the various departments and appointed a manager of effluent disposal operations. A process for establishing protocols on changes to the facility or its operation was defined. The conclusions drawn from this event were shared with the various departments.
