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Incident Reports

Sellafield Ltd is committed to keeping the public informed about operations on our site.

Below you will find details of operational issues and events.

Some of these are graded using the International Nuclear and Radiological Event Scale (INES).

Level 1 represents the lowest severity, known as ‘anomaly’, rising to Level 7: ‘major incident’.

ONR improvement on HALES cooling towers 

Update: June 2017

In September 2016 we were issued with an improvement notice by the Office for Nuclear Regulation in relation to the condition and cleanliness of cooling towers supporting one of our facilities at Sellafield. 

We have now complied with this improvement notice, and continue to progress improvement work in this area to ensure that our cooling towers meet the requirements not only now, but also in the future.

Personnel contamination event

Date: 05/02/2017

INES Rating: 2

In February 2017, an employee was contaminated during operations in one of the product finishing lines at Sellafield.

While carrying out routine work in a glove box wearing protective clothing i.e. latex gloves, the operator felt a pain in his hand and immediately called the Health Physics team for assistance.

The individual attended the site surgery where the wound was monitored and dressed. A follow up monitoring assessment by Health Physics a few weeks after the initial injury identified a small point of contamination which required further medical intervention to remove the contamination.

An investigation is underway to determine how the incident happened.

A provisional dose estimate indicates that the dose received is greater than the statutory annual dose limits. For this reason an INES level 2 rating has been assigned.

Electrical fault in calibration centre

Date: 28/02/2017

INES Rating: 1

During the routine calibration of monitoring equipment in one of our buildings, an electrical fault occurred which caused the system to stop working.

This caused a radioactive source to be exposed inside a shielded cell, and elevated levels of radiation were detected, triggering an alarm.

Trained operators closed the system down, and the source lowered back into a shielded enclosure.

No-one was in the area where the elevated levels were detected, and there were no safety implications for employees.

An investigation confirmed that an electrical fault caused the error.

The event carries an International Nuclear International Event Scale (INES) Level 1 rating (an anomaly) based on the safety system failure and the exposure of a radioactive source.

Personnel contamination event

Date: 08/01/2017

INES Rating: 2

In early January this year, a Sellafield Ltd employee was contaminated during highly active sampling operations in one of our plants.

The contamination was detected on the worker’s hand during exit checks from the facility. The employee was referred to the Sellafield site surgery where the contamination was successfully removed via chemical washing. Although the dose was well below the level at which it would be expected to impact on wellbeing, an assessment has been undertaken which indicates that the dose received is greater than the relevant statutory limit.

The safety of our workforce and the community remains our number one priority. A full investigation has been carried out and findings will be used to inform ongoing improvements to safety procedures.


ONR improvement on HALES cooling towers – Update : 27th January 2016

In September 2016 we were issued with an Improvement Notice by the Office for Nuclear Regulation (ONR) in relation to the condition and cleanliness of cooling towers supporting one of our facilities.

The ONR has agreed an extension to the deadline, so that the works can be completed appropriately to ensure the cooling towers meet our requirements now and in the future.

We remain committed to providing a robust series of improvements against the improvement notice. This is recognised and supported by ONR.

The cooling tower refurbishment works have proved more challenging than anticipated, but the above commitment remains.

Triggering of personal alarm during digital imaging

Date: 15.08.2016

INES Rating: 2

Two operators were carrying out digital imaging of legacy crates, using x-ray equipment to identify the contents, when their electronic personal dosimeters (EPD) alarmed during screening operations. The incident took place in a redundant reprocessing facility at Sellafield during August 2016.

Neither of the operators received a significant radiation exposure; however a management investigation was convened to look into aspects such as adherence to safety procedures.

The investigation concluded that radiation measured on the electronic personal dosimeter was due to the X-ray generator, rather than from ambient radiation levels in the cell, or originating from the crates in storage.

Sellafield Ltd gave the event an INES (International Nuclear and Radiological Event Scale) Level 2 rating, which has been confirmed by the UK INES National Officer. Although no one received a significant radiation exposure and there was no release of radiation to the environment, this was assessed as a Level 2 rating due to shortfalls in adherence to safety procedures and the potential for an operator to receive a significant radiation exposure.

Learning from experience is being shared to ensure that the appropriate improvements will be made to prevent a reoccurrence.


Disruption to electricity

Date: 12.12.2016

INES Rating: 0

Disruptions to the electricity network in Cumbria led to a number of power dips on the Sellafield site on 10 December 2016.

Well-established procedures for dealing with power supply issues were followed and disruption to site operations was minimal. There were no nuclear safety implications.

An investigation later found cabling equipment on a pylon in an electricity substations had sustained damage during the incident, leading some dispersal of debris in a nearby compound. The compound is fenced off and was unoccupied at the time. No one was injured.


Sewage Treatment Works

Date 15.12.2016

INES Rating:

A small release of treated effluent has entered the site’s drainage network and subsequently the river Ehen, from one of the site’s settlement tanks.

The tank was immediately isolated, before being returned to service on reduced flow.

Samples show no environmental impact and investigations are ongoing into the cause.


Contamination on floor

Date 13.10.2016

INES Rating : 0

During routine operations in a waste metals recycling facility, a small area of contamination, measuring roughly 2mm in diameter, was found on the floor.

Operations were immediately halted while the facility was decontaminated.

There was no contamination of personnel or material. Investigations are ongoing into the cause.


Mobile platform fall – First Generation Reprocessing Plant

Date : 3/11/2016

INES Rating : 0

During operations to move a mobile elevating work platform (MEWP) through a door frame for maintenance works to be undertaken, the platform fell to the ground.

There was no injury to any personnel and no radiological implications. Some minor damage occurred to the platform.

Investigations into the cause are being undertaken. Early indications suggest the incident occurred due to a failsafe measure not being activated.


Disposal of post analysis chemical samples

Date 16/09/2016

INES Rating – 0

Disposal of post analysis chemical samples

Cooling towers at Sellafield are regularly inspected for legionella bacteria, in line with standard industry practice.

As part of this process, chemicals are added to samples of cooling tower effluent for analysis purposes. These chemicals are not radioactive and do not contain legionella.

It has been identified that a small volume of post-analysis samples have been disposed of via Sellafield’s surface water drainage system. The volume is estimated to be less than 12 litres per week and the environmental impact has been assessed as negligible.

However, this was done before the samples were assessed to determine their correct disposal route, contrary to established Sellafield Ltd procedures. These samples are now being retained while the correct disposal route is identified and relevant permissions secured.


Grout washings

Date: 26/09/2016

INES Rating – 0

Following routine wash down of grout preparation area in one of the encapsulation plants on the Sellafield site, a small amount of non-radioactive grout washings entered a surface water drain which outfalls to the River Calder.

This outfall is listed within Sellafield Ltd’s non radiological environmental permit for the discharge of storm water only.

The environmental impact from the grout washings was assessed using methods agreed with the Environment Agency and was determined to be insignificant.


Conformance paperwork

DATE: 01/09/2016

INES: Level 0

It has been identified that a chemical used for decontamination purposes has not been included in our non-radiological discharge conformance paperwork.

When a chemical previously used to decontaminate nuclear flasks became unavailable, a replacement chemical (synthetic foam concentrate) was then used. This change of product was not updated in our paperwork.

We have stopped using this product until investigations have been completed. The Environment Agency has been informed. 


ONR improvement on HALES cooling towers

The ONR improvement notice in relation to the condition and cleanliness of cooling towers supporting one of our facilities formalises an improvement programme we had already identified.

In this instance our cleaning regime wasn’t as robust as it should have been and we have already started work on an improvement plan.

The age and nature of the Sellafield site means that some of our facilities are more difficult to maintain than they might be elsewhere, but that is not an excuse; we will learn from this and implement our improvement plan promptly.

The Legionella bacteria found in the towers during routine tests does NOT cause Legionnaires’ disease.


Non-irradiated nuclear fuel assembly

Date of incident: 17/08/2016

During  a routine transfer of an un-irradiated fuel assembly to a storage canister, operators witnessed the lifting adaptor becoming lodged on to the shield plug metal framework. This caused the fuel assembly to be inadvertently  lifted out with the plug.

As work to return the shield plug to the correct position was being carried out, the adaptor and fuel assembly dislodged and the fuel assembly fell a short distance of around one foot into the canister. We fully anticipated this and had confirmed beforehand as part of our assessments that this would cause no damage or safety issues.

An investigation is being carried out into the incident and we have been keeping our regulators updated.

There was no harm to our employees and no radiological or environmental consequences.


Laboratory spillage

Date of incident: 11/08/2016

Area: Analytical laboratories

INES rating – Level 0

Whilst carrying out routine work in our analytical laboratories, a bottle containing uranium and nitric acid was knocked over causing a small spillage onto the work bench and the floor. As a result there was a small area of contamination. Work to clean and decontaminate the area was carried out using approved processes.

There was no harm to the employees and no radiological or environmental consequences.


Shield doors gamma testing

Date of incident: 28/03/2016

Area: First Generation Magnox Storage Pond

INES rating – Level 1: Anomaly

During a procedure to check that the shield doors on the newly installed export cell facility cannot be opened while there is a source of gamma radiation in the cell, a Sellafield Ltd operator was exposed to a higher than planned level of gamma radiation.

While the dose received (26uSv) was still well within safe limits, it did show an anomaly in the testing procedure. The export cell itself successfully shielded operators from the gamma source, but while it was being transferred into the cell there is a brief moment when it is passes through an unshielded delivery tube to enter the cell. As the operator was positioned too close to that delivery tube, he was very briefly exposed to a gamma source of 42mSv/hr.

Sellafield Ltd has reviewed its operating procedures for this test to ensure operators remain at a safe distance and have the necessary monitoring equipment to allow them to reapproach the test area and check that the gamma source is safely contained.  These lessons on this new piece of equipment are being shared across the organisation as part of our learning from experience best practice.


Compressor omitted from register

DATE: 15/07/2016

INES: INES level 0

It was recently discovered the emissions of a portable diesel powered compressor installed in the Waste Encapsulation Plant were not reported as part of the site’s Greenhouse Gas Emission Permit.

The compressor was omitted from the annual reporting figure as it was understood that, due to the equipment initially being installed and operated by a supplier, it would fall out of the scope of reporting.

The regulators have been informed. The total emissions from the unit are a very small percentage of the annual discharge and will have negligible environmental impact.


Non-irradiated nuclear fuel assembly

Date: 29/07/2016

INES: INES level 0

An incident occurred earlier this year in one of the plants on the Sellafield site involving a fall of an non-irradiated nuclear fuel assembly. An investigation is ongoing and our regulators have been informed and recently updated. There was no harm to employees or the general public and no radiological or environmental consequences.


Loss of hydrogen analysis

Date: 06/01/2016

Area: Magnox Swarf Storage Silo

INES rating – Level 1: Anomaly (11/05/2016)

A temporary power failure on 30 December 2015 resulted in a loss of power to certain hydrogen analysers in the Magnox Swarf Storage Silo.

Following reinstatement of power, the engineered design configuration of the hydrogen monitoring system indicated that it had been successfully reset and was “healthy” when in fact the sample pumps required to feed the analysers had not restarted automatically.

This meant that one of the 22 compartments in the silo was not having its hydrogen levels monitored for eight days. The other 21 other compartments continued to have hydrogen monitored throughout either through the main or back-up systems.

When the pump was restarted, and hydrogen analysis carried out, no hydrogen was detectable as per normal operating conditions. Other safety controls remained in operation throughout including resilience passive ventilation and there was no release of radioactivity or increased dose to individuals.

An investigation has been carried out and lessons learned are being shared across the organisation – focusing on equipment checks and risk mitigation measures.


Loss of active ventilation

Date: 09/03/2016

Area: Magnox Swarf Storage Silo

INES rating – Level 1: Anomaly (11/05/2016)

The Magnox Swarf Storage Silo has a forced ventilation system for hydrogen management which draws air via electrically powered fans through all compartments and then through a cleaning system before discharge to atmosphere through a chimney stack. It also has an alternative ‘passive’ ventilation system installed as a safety measure in 2013 to mitigate against a prolonged loss of power.

During routine maintenance work, it is normal practice to switch from the “fan-based” to the “passive” system in the original silo building, with a requirement to re-establish the fan-based ventilation within 33 hours.

On 05/03/2016 the extract fans were switched off for 16 hours in order to undertake some improvements to the ventilation system, but when it was restarted the system indicated zero flow. Manual checks and readings of substitute instrumentation suggested that there was an air flow and therefore it was assumed the flow instrumentation was faulty. Work was put in place to repair/replace the instrument.

Further checks on instrumentation and ductwork over the subsequent days confirmed on 09/03 that clean water (steam condensate) had collected in the ventilation ducting and was preventing airflow. The water was subsequently drained out of the ductwork and full ventilation restored, however the plant had exceeded its 33-hour requirement for using passive ventilation only.

Throughout this period of low ventilation flow, hydrogen levels were monitored throughout. There was no increase in hydrogen concentration and no increase in levels of airborne activity within the facility.

An investigation has been carried out and lessons learned are being shared across the organisation – focusing on equipment checks and challenging assumption