Fires in the Drigg Nuclear Waste Dump Trenches

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Freedom of Information Request sent today

11 July 2016

Dear Environment Agency,

In a Technical Review of 2015 for the Low Level Nuclear Waste Repository at Drigg you say that “there is evidence of a number of waste fires during operations of the trenches”.

We request sight of all the evidence of a number of waste fires at the LLWR

Yours faithfully,

Marianne Birkby

 

Environment Agency Technical Review http://llwrsite.com/wp-content/uploads/2…

Statement of Technical Query

Status

Date

Description

Raised

03/01/2013

Acknowledged

03/01/2013

LLWR Response

11/02/2013

Response Assessed

25/07/2013

Transferred

24/01/2014

Closed

14/11/2014

The Guidance on Requirements for Authorisation of Near Surface Disposal Facilities (GRA) asks for all reasonable scenarios which could result in discharges of radioactivity to the environment to be considered as part of the Environmental Safety Case (ESC). We have identified that the presented ESC does not carry out an assessment of the radiological consequences of a fire occurring in disposed combustible wastes after the period of authorisation.

We believe any fire scenario would most likely be restricted to the trench wastes. A waste fire occurring in the grouted and containerised vault wastes is considered unlikely and does not require an assessment. However, a fire in the trench waste after the period of authorisation is considered a credible, if a low probability event, and could result in a discharge of radioactivity to the environment.

During the post authorisation period we consider that a realistic cause of fire in the trench wastes could include the introduction of oxygen into the waste mass. A possible cause of this would be the exposure of the waste during coastal erosion. The introduction of oxygen into the waste mass could result in exothermic or pyrophoric reactions in individual waste components such as thorium or reactive metals. Such a fire is likely to be shallow seated, with the possibility of direct release of radioactivity to the environment.

Page 1 of 4 Last updated 18/06/2015

Technical Review of the 2011 ESC for the LLWR near Drigg

Issue Resolution Form

ESC-TQ-SUE-030

TECHNICAL QUERY

Technical Query Actions

ESC-TQ-SUE-030.A1

Please identify the potential presence of waste streams or items within the trenches which could exhibit pyrophoric or exothermic properties when exposed to air or water. Consideration should be given to the presence of sealed vessels containing volatile materials.

ESC-TQ-SUE-030.A2

For the post authorisation period please identify and present reasonable fire scenarios taking account of the disruption and exposure of the waste during coastal erosion, or any other credible mechanism which could cause the introduction of oxygen into the waste mass or initiate waste fires.

Please provide a short qualitative assessment of any reasonable fire scenarios which could occur in the trench wastes during the post authorisation period.

LLW Repository Ltd Acknowledgement

LLW Repository Ltd Response

Provided by:

Assessment of LLW Repository Ltd Response

By: Environment Agency

ESC-TQ-SUE-030.A1

In response to this action, LLW Repository Ltd has presented a comprehensive review of available trench waste records. The flammability of each waste type is assessed. The company concluded that the materials and conditions in the trenches at any time after the period of authorisation are very unlikely to support combustion, and that any fire events that might occur would be confined to very small volumes of waste with little or no potential for release of radionuclides.

We note that contemporary disposal practices during trench disposals did not seek to fully characterise the chemical composition of wastes and as such the records of past disposals are not as comprehensive as they are today. We are therefore not convinced with LLW Repository Ltd’s assumption that the waste acceptance criteria used in the past would have

LLW Repository Ltd

ESC Project Manager

03/01/2013

Comment: The assessment requested will be provided.

LLW Repository Ltd

ESC Project Manager

11/02/2013

Please see the attached memo: LLWR/ESC/Mem(13)194
Please see the attached spreadsheet: LLWR_ESC_Mem(13)194_App1.xls

Owner: Environment Agency

Date: 25/07/2013

Approved by: Environment Agency

Date: 14/11/2014

Page 2 of 4 Last updated 18/06/2015

Technical Review of the 2011 ESC for the LLWR near Drigg

Issue Resolution Form

ESC-TQ-SUE-030

TECHNICAL QUERY

always prevented the disposal of pyrophoric or flammable material, as there is evidence of a number of waste fires during operations of the trenches.

While we accept the findings of the presented trench inventory information, it is subject to a significant level of uncertainty with regards to the non-radiological composition of the waste. Due to the nature of a number of processes that may have resulted in waste being consigned to the LLWR in the past, we consider it likely that other wastes susceptible to pyrophoric or exothermic reactions have been consigned. However, due to the age of the disposals, it is also likely that much of this material may now have been rendered inert, although there remains a low risk of reactive material remaining contained within larger (still intact) containers.

ESC-TQ-SUE-030.A2

In response to this action, LLW Repository Ltd identified two scenarios which we consider credible for potential fires in trench wastes; the first associated with the exposure of waste during coastal erosion and the second associated with the introduction of oxygen into the anaerobic trench waste during construction of geotechnical boreholes into the waste after the period of authorisation.

With respect to the first scenario, LLW Repository Ltd concluded that the materials and conditions in the trenches at any time after the period of authorisation are very unlikely to support combustion, and that any fire events that might occur would be confined to very small volumes of waste with little or no potential for release of radionuclides. As a result LLW Repository Ltd did not undertake a radiological assessment of the consequences of ignition and subsequent fire during the erosion of the trench wastes. We accept that the likelihood of a fire event at any scale would be low, but because of the long period of waste exposure during the erosion sequence (potentially 100s years), the uncertainty over deliberate human interventions and the uncertainties associated with the exposed waste during the erosion period we consider that such a scenario should be considered as a ‘what if’ scenario.

We have raised a Forward Issue (ESC-FI-028) which identifies the need for a more comprehensive understanding and conceptualisation of the behaviour of the repository wastes during the predicted repository erosion sequence. Within the resulting forward programme we recommend the potential nature, extent and consequence of waste fires resulting from human actions are further investigated, considering appropriate ‘what if’ scenarios for waste fires (Recommendation ASS26 of Environment Agency 2015, Review of LLW Repository Ltd’s 2011 Environmental Safety Case: Assessments).

LLW Repository also identified a human intrusion scenario associated with the construction of a geotechnical borehole into the waste mass which could give rise to a deep seated waste fire. The company assumed that any fire in a borehole would be short lived and not requiring the involvement of the fire service, with dose only being received by the drillers. The dose to a drilling engineer was calculated at about five times that received by the driller in the absence of the fire event and two orders of magnitude below the dose guidance value that applies to exposures of short duration from human intrusion events.

We disagree with the assumption that a borehole fire will always be short lived and extinguished in 1-2 days with dose only being received by the drillers. Experience from the contemporary landfill sector indicates that deep seated waste fires can be difficult to extinguish and can burn for extended periods (Environment Agency 2007). Assuming the fire

Page 3 of 4 Last updated 18/06/2015

Technical Review of the 2011 ESC for the LLWR near Drigg

Issue Resolution Form

ESC-TQ-SUE-030

TECHNICAL QUERY

is significant then there would be a need for fire service involvement in order to extinguish the fire. Extinguishing of deep seated fires may involve the disturbance of wastes.

Although we continue to consider the likelihood of such fires to be very low, we believe that for completeness LLW Repository Ltd should either provide further justification for the limited duration of such a fire, or undertake further work to extend the scenario in time and those who may be affected (for example, fire service personnel). We have therefore requested that LLW Repository Ltd undertakes a further assessment to take account of an extended duration fire and the involvement of fire personnel as a ‘what if’ scenario (via Forward Issue ESC-FI-003).

Conclusion

We consider that the further information on the nature of the trench wastes which could give rise to spontaneous combustion provided by LLW Repository Ltd meets our requirements. We accept that the likelihood of a waste fire in the trench disposal remains very low. We consider that LLW Repository Ltd has presented sufficient information to allow this Technical Query to be closed. However, we consider that there is scope for further investigation and conceptualisation of the borehole fire scenario and the potential for fires during the repository erosion sequence in order to better inform future updates of the ESC, as detailed in ESC-FI- 003 and ESC-FI-028.

Reference

Environment Agency, 2007. Science Report – Review and Investigation of Deep-Seated Landfill Fires. Environment Agency, March 2007.

Actions completed, Technical Query resolved and Form closed

Owner: Environment Agency

Date: 21/01/2014

Approved by: Environment Agency

Date: 14/11/2014

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