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7.5 MILLION PLANT SETS NEW STANDARDS IN ENVIRONMENTAL PROTECTION

A  new  and  modern facility for the treatment of radioactive effluent from decommissioning is set to come into service at Dounreay.

Built  at  a  cost of 7.5 million, the Low Level Liquid Effluent Treatment Plant  will  set  new  standards  for  the  management of effluent from the clean-up of the former experimental reactor establishment.

Site  operator  UKAEA  today welcomed confirmation that it has been granted formal  consent  by  the  Scottish  Environment  Protection Agency to begin active  commissioning.  The  new plant will be phased into service over the coming months.

Site  director  Peter  Welsh  said:  "The  development of this new facility underlines  the  commitment  we have given to decommission Dounreay to high standards  of  environmental  protection. I'm pleased that SEPA has granted consent to bring this new plant into service."

The  new plant, which took three years to build, will collect effluent from a variety of facilities now being decommissioned at Dounreay as well as the neighbouring  Vulcan  test site. The effluent will pass through a series of treatment tanks and checks before being disposed.

"Our  existing effluent plant was designed in the 1950s and is out of date, so  its  replacement  with  this  new  facility  built  to modern standards represents   a   major   improvement   in   how  we  manage  effluent  from decommissioning,"  explained  Mark  Raffle,  waste  operations manager with
UKAEA Dounreay.

"We  will  gradually  phase in the new plant and build up experience of its operation   during  a  period  of  commissioning.  Once  it  becomes  fully operational,  it will set new standards for how we manage effluent from the decommissioning of the site."

MAJOR CHANGES TO DOUNREAY AUTHORISATION

The Scottish Environment Protection Agency (SEPA) has made significant changes to the authorisation covering UKAEA Dounreay's discharges of gaseous radioactive waste. The changes mean a cut of 59% in the quantity of tritium that the site is allowed to release to the environment and will come into effect on Friday 18 July.

The change also permits the operation of UKAEA's new facility for collecting and disposing of liquid waste to sea. This facility, known as the Low Level Liquid Effluent Treatment Plant (LLLETP), will replace the old sea discharge tanks that were the subject of a SEPA enforcement notice in January 2002.

UKAEA is required by SEPA to improve the discharge system for gaseous waste from the main facilities in the fuel cycle area (FCA). It will also have to produce a strategy which will set out

 principles for radioactive waste management
 how it will manage gaseous waste discharges, and
 how it will comply with the government's international environmental commitments.

SEPA is also finalising a similar downward change in the limits controlling liquid waste from Dounreay, where there is greater scope for reduction. This has been brought about by UKAEA's move away from reprocessing, to a mission of restoring the environment. 

There may be scope for further reductions in the authorised limits for the disposal of gaseous and liquid waste. These will be explored and detailed by UKAEA in a new application for the disposal of radioactive waste from Dounreay. The application will be made to SEPA during 2003 and will be subject to full public consultation.

The changes now being made and those being finalised by SEPA  are considered to be interim measures while UKAEA finalises its application for a new authorisation. This application will be supported by UKAEA's plan for the environmental restoration of the Dounreay site. SEPA will consult the public about the application and expects that the new authorisation may be in place by 2005.

Tom Inglis of SEPA said: "The point of the changes is to help ensure that there is efficient and robust regulation of the site. They will continue the downward pressure on the disposal of radioactive waste to the environment and will ensure that our authorisation is appropriate to the new focus on decommissioning."

 Under the international OSPAR agreement, the government is committed to reducing radioactive discharges to the environment.

 In 1999 SEPA issued an authorisation to UKAEA for the disposal of gaseous waste. UKAEA applied for a variation to this authorisation so it could operate its new sea discharge tanks (the facility produces a small quantity of gas also).

 While considering this application, SEPA decided to reduce the limits in the authorisation. SEPA also made other, minor, changes:

        o strengthening a condition that requires UKAEA to maintain its waste disposal system o requiring UKAEA to provide information to enable SEPA to review the adequacy of
           the authorisation at any time.

This process began in August 2000 when SEPA and UKAEA discussed the operation of its proposed new sea discharge tanks. Public consultation on the changes took place from May - July 2001. Additional consultation and discussion has taken place with the Nuclear Installations Inspectorate, the Food Standards Agency and the Scottish Executive.

Full details of the changes and the process are available in SEPA's decision document which will be
    available on
www.sepa.org.uk/dounreay from Thursday 17 July.

More About LLEPT
Control of the plant systems is carried out by microprocessor based controllers. A Distributed
Control System (DCS) allows operating staff to control the plant remotely using keyboards and
VDUs. These systems are linked to the D1208 Control Room via telemetry. Plant operators also
take routine readings of the ventilation system and other systems.


Typical process pipework
Control and
Instrumentation
Restoring our Environment
What is LLLETP ?
The Low Level Liquid Effluent Treatment Plant is used for the collection, treatment and disposal of
Low Level liquid effluent from the Dounreay and Vulcan Sites. The facility, built between 1998 and
2001 at a cost of 7.5m replaces the D1211 Effluent Plant constructed in the 1950s.

The Process
The gravity receipt solvent separator tank is sized to separate solvent from the incoming effluent. This is
done by reducing the velocity of the effluent thereby allowing the solvent to rise to the surface.  Suspended solids within the incoming effluent lines will settle in this tank due to the low velocity. The solvent will be removed periodically from the top of the effluent by gravity into a solvent collection section. The solids/sludge collected at the bottom of the tank can be removed as determined by readings from a sludge concentration-detecting instrument in the bottom of the tank. Flushing water is supplied to the tanks in order to facilitate sludge removal. It is estimated there is 10 years sludge storage space in these tanks and one option for the future treatment of this sludge is to cement it and release it as Low Level Waste. 

From the Gravity Receipt Tank (GRT) the Effluent is transferred to the buffer tank which has a capacity 3 of 300 m . It is then passed through a two stage neutralisation plant in order to control the pH of the effluent which is to be discharged to sea (the effluent enters the plant with a discharge between 2 to 12 and leaves the neutralisation plant with a pH between 5 and 9). Adjusting the pH of the effluent, reduces the impact on the environment and meets the latest discharge criteria.

Sea Discharge Tanks
Neutralised effluent overflows out of the second stage neutralisation tank by gravity into either of the two sea discharge tanks. These tanks each have a working 3 capacity of 550 m and operate on a batch basis.  Effluent will normally be discharged continuously from the neutralisation system into one of the sea discharge tanks.  During filling of the tank a representative bulk sample is taken, this is the A sample. The sampled sea discharge tank is allowed to stand for at least two hours to enable  settling of any solids before discharge.  Analysis is carried out on the A Sample and authorisation is required by the Shift Manager prior to discharge to sea. During discharge to sea a further B sample is taken as
required by the regulatory authorities.

How Does it Work ?
Effluent from the Low Active Drain system flows into the gravity receipt/solvent separator tank.  The tank is below ground level to allow effluent to flow continuously from the drain lines by gravity.  Effluent arrives periodically from PFR, Vulcan, Fuel Cycle Area and other sources.


Process Flow Diagram Low Level Liquid Effluent
Treatment Plant & Sludge Handling Facility