Chapelcross nuclear power station is a former

Magnox Magnox is a type of nuclear power/production reactor that was designed to run on natural uranium with graphite as the moderator and carbon dioxide gas as the heat exchange coolant. It belongs to the wider class of gas-cooled reactors. The n ...

nuclear power station A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces ele ...

undergoing decommissioning. It is located in Annan in Dumfries and Galloway in southwest Scotland, and was in operation from 1959 to 2004. It was the sister plant to the

Calder Hall nuclear power station Calder Hall Nuclear Power Station is a former Magnox nuclear power station at Sellafield in Cumbria in North West England. Calder Hall was the world's first full-scale commercial nuclear power station to enter operation, and was the sister plant t ...

plant in

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. C ...

, England; both were commissioned and originally operated by the

United Kingdom Atomic Energy Authority The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of fusion energy. It is an executive non-departmental public body of the Department for Business, Energy and Industrial Strategy ...

. The primary purpose of both plants was to produce

weapons-grade Weapons-grade nuclear material is any fissionable nuclear material that is pure enough to make a nuclear weapon or has properties that make it particularly suitable for nuclear weapons use. Plutonium and uranium in grades normally used in nucle ...

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...

for the UK's nuclear weapons programme, but they also generated electrical power for the National Grid. Later in the reactors' lifecycle, as the UK slowed the development of the nuclear deterrent as the cold war came to a close, power production became the primary goal of reactor operation. The site is being decommissioned by Nuclear Decommissioning Authority subsidiary Magnox Ltd. The station's four cooling towers were demolished in 2007. The reactors are spent-fuel free and are currently undergoing dismantlement of primary loop equipment such as heat exchangers and hot gas ducts. Once complete, the reactors will enter a care and maintenance stage to allow radiation levels to decline before the reactors themselves are demolished.

Location

Chapelcross occupies a site on the location of former World War II training airfield, RAF Annan, located north east of the town of Annan in the Annandale and Eskdale district within the Dumfries and Galloway region of south west Scotland. The nearest hamlet is Creca.

History

Chapelcross was the sister plant to

Calder Hall Sellafield is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nucl ...

, England. Construction was carried out by Mitchell Construction and was completed in 1959. The primary purpose was to produce

for the UK's nuclear weapons programme, for weapons including the

WE.177 The WE.177, originally styled as WE 177, and sometimes simply as WE177, was a series of tactical and strategic nuclear weapons with which the Royal Navy (RN) and the Royal Air Force (RAF) were equipped. It was the primary air-dropped nuclear we ...

series. Electricity was always considered to be a by-product. Both Chapelcross and Calderhall were the only nuclear power stations built as part of the UK's gas reactor fleet to use cooling towers as a heat sink as opposed to using the sea. The Chapelcross Works was officially opened on 2 May 1959 by the Lord Lieutenant of Dumfriesshire, Sir John Crabbe. It was initially owned and operated by the Production Group of the

(UKAEA) until the creation of British Nuclear Fuels Limited ( BNFL) in 1971 by an act of Parliament. The site then operated in conjunction with Calder Hall under the banner of BNFL's Electricity Generation Business (EGB) until rebranding, relicensing and restructuring of the various nuclear businesses operated by HM Government under the umbrella legal entity of BNFL took place in April 2005. Chapelcross had four

reactors capable of generating 60

MWe The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt ...

of power each. The reactors were supplied by the UKAEA and the turbines by C.A. Parsons & Company. Ownership of all of the site's assets and liabilities was transferred to the Nuclear Decommissioning Authority (NDA), a new regulatory body created by the

Energy Act 2004 The Energy Act 2004 (c 20) is an Act of the Parliament of the United Kingdom concerned with nuclear power, renewable and sustainable energy and energy regulation. Royal assent was granted on 22 July 2004. Part 1 Chapter 1 Section 10 Section 10 ...

. The site was then operated under the two-tier Site Management Company/Site License Company (SMC/SLC) model, with British Nuclear Group's Reactor Sites business as SMC and Magnox Electric Ltd as the SLC. In June 2007, EnergySolutions LLC bought the Reactor Sites Management Company Ltd (RSML, consisting of two operational divisions, Magnox North and Magnox South) from British Nuclear Group. RSML subsequently became Magnox Ltd and is now a wholly-owned subsidiary of the NDA. Several significant events in 2001 persuaded BNFL to upgrade the fuel routes of both Calder Hall and Chapelcross to near modern standards at a cost of tens of millions of pounds, to guarantee that a License Instrument would be granted by the

Nuclear Installations Inspectorate Nuclear may refer to: Physics Relating to the nucleus of the atom: * Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics *Nuclear space *Nuclear ...

(NII) to permit final defuelling: the engineering work was carried out by BNS Nuclear Services (formally Alstec). Generation ceased in June 2004.

Decommissioning and the cooling towers

The Health and Safety Executive (HSE) granted consent to carry out decommissioning projects at Chapelcross under the regulations to Magnox Electric Ltd on 26 September 2005. The first visible sign of

decommissioning Decommissioning is a general term for a formal process to remove something from an active status, and may refer to: Infrastructure * Decommissioned offshore * Decommissioned highway * Greenfield status of former industrial sites * Nuclear decommi ...

was controlled demolition at 09:00 BST on 20 May 2007 of the four natural-draught concrete

cooling tower A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat an ...

s, which were of the same hyperboloid design as conventional inland

power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many ...

s such as

Didcot Didcot ( ) is a railway town and Civil parishes in England, civil parish in the Ceremonial counties of England, ceremonial county of Oxfordshire and the Historic counties of England, historic county of Berkshire. Didcot is south of Oxford, eas ...

, Drax,

Ferrybridge Ferrybridge is a village in West Yorkshire, England. Ferrybridge lies at a historically important crossing of the River Aire which borders the North Yorkshire village of Brotherton. It is linked to other communities by the A1, which follows t ...

and Fiddlers Ferry. The explosions were designed to remove a section of the towers' shells. Approximately two-thirds of the circumference and two-thirds of the shell legs were removed by the blasts, causing a controlled collapse of each tower. The charges were fired sequentially, reducing the high towers to an estimated 25,000tons of rubble in less than 10seconds. Those at Calder Hall were demolished on 29 September 2007. Some local people (including site employees) were opposed to the obliteration of a symbol of the region's industrial heritage. The towers were considered a local landmark that could be seen from a distance of up to in good weather conditions. British Nuclear Group and the NDA prioritised conventional demolition over deplanting and post-operational clean-out (POCO) of the nuclear facilities on the site. A large part of the shell of tower 1 managed to resist the explosives despite having a visible bulge that resulted from a construction anomaly. By December 2012, three of the four reactors had been defuelled. Defuelling was completed in February 2013. Removal of most buildings is expected to take until 2023-2024, followed by a care and maintenance phase from 2024 to 2089. Demolition of reactor buildings and final site clearance is planned for 2089 to 2095.

Plant design

The plant design was essentially the same as

, comprising four 180MWth

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

moderated Moderation is the process of eliminating or lessening extremes. It is used to ensure normality throughout the medium on which it is being conducted. Common uses of moderation include: *Ensuring consistency and accuracy in the marking of stud ...

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

cooled

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...

s fuelled by natural abundance

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

(0.71% ²³⁵U) enclosed in

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

cans, the principal difference being in plant layout. Since Chapelcross was commissioned from the outset as a four-reactor site (the option for a further four reactors was not exercised) rather than separate two-reactor sites as at Calder 'A' and 'B' stations, the site layout was more compact. There is a single turbine hall housing all eight turbines, which were originally rated at 23MWe but progressively uprated to 30MWe as the reactor thermal output was uprated to nominally 265MWth. Reactor 1 had the same

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...

design as Calder Hall (i.e. unsleeved), but the fuel channels of reactors 2, 3 and 4 were fitted with graphite sleeves to allow the bulk moderator to run 80°C hotter, to limit the effects of in-service graphite damage due to

irradiation Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve ...

. Two of the reactors were used to produce

tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of ...

for the UK's nuclear weapons and required

enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U ...

fuel to offset the

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

absorbing effect of the

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

target material.

Layout and facilities

The south part of the site consists of a modular administration building, four reactor buildings, turbine hall, maintenance workshops, stores, fuel element cooling pond building,

processing plant (CXPP) and new flask handling facility (FHB). The part of the site referred to as north site consists of legacy buildings including

aircraft hangar A hangar is a building or structure designed to hold aircraft or spacecraft. Hangars are built of metal, wood, or concrete. The word ''hangar'' comes from Middle French ''hanghart'' ("enclosure near a house"), of Germanic origin, from Frankish ...

s, a graphite handling laboratory and a large building that originally housed some 10,000drums of yellow depleted uranium trioxide arising from reprocessing at Sellafield. In the mid 2010s, the NDA removed and shipped all of the depleted uranium drums from Chapelcross to Sellafield. Liquid effluent is disposed of via a long pipeline to the

Solway Firth The Solway Firth ( gd, Tràchd Romhra) is a firth that forms part of the border between England and Scotland, between Cumbria (including the Solway Plain) and Dumfries and Galloway. It stretches from St Bees Head, just south of Whitehaven ...

. All environmental discharges are subject to an annual discharge authorisation which is regulated by the

Scottish Environment Protection Agency The Scottish Environment Protection Agency (SEPA; gd, Buidheann Dìon Àrainneachd na h-Alba) is Scotland's environmental regulator and national flood forecasting, flood warning and strategic flood risk management authority. Chapelcross produced tritium for the Polaris and

Trident A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other mari ...

strategic nuclear weapon systems from about 1980 until 2005. This was achieved by

bombardment of

target material, with the tritium gas extracted in the Chapelcross Processing Plant (CXPP). This facility was managed by BNFL on behalf of the Ministry of Defence (MoD). The material was transferred to

Atomic Weapons Establishment The Atomic Weapons Establishment (AWE) is a United Kingdom Ministry of Defence research facility responsible for the design, manufacture and support of warheads for the UK's nuclear weapons. It is the successor to the Atomic Weapons Research ...

at Aldermaston via secure road convoys. Because of its involvement in the nuclear weapons programme, the site was not subject to international safeguards until 1998.

Operating experience and incidents

Single channel fuel clad melt (May 1967)

Fuel in a single channel in Reactor 2 that was loaded with fuel elements under evaluation for the commercial reactor programme experienced a partial blockage, attributed to the presence of graphite debris (see

fuel element failure A fuel element failure is a rupture in a nuclear reactor's fuel cladding that allows the nuclear fuel or fission products, either in the form of dissolved radioisotopes or hot particles, to enter the reactor coolant or storage water. The ' ...

). The fuel overheated and the Magnox

cladding Cladding is an outer layer of material covering another. It may refer to the following: *Cladding (boiler), the layer of insulation and outer wrapping around a boiler shell *Cladding (construction), materials applied to the exterior of buildings ...

failed, causing contamination to be deposited in one region of the core. The reactor was restarted in 1969 after successful clean-out operations and was the final reactor to cease operation in February 2004.

Fatal accident (ca. 1978)

Response reference 120714 in House of Commons Hansard written answers for 5 May 2000 (pt 5) shows that BNFL was fined £200 in 1978 for a fatal accident at Chapelcross.

Boiler shell defect (June 1997)

Cracks associated with brackets in Heat Exchanger 6 on Reactor 2 were discovered during routine

ultrasonic testing Ultrasonic testing (UT) is a family of non-destructive testing techniques based on the propagation of ultrasonic waves in the object or material tested. In most common UT applications, very short ultrasonic pulse-waves with center frequencies ...

. Metallurgical examination of samples of the defect showed that: * It originated during fabrication in the workshop and prior to an over-pressure test of 2.35 times the design pressure (a loading significantly in excess of a modern pressure vessel code requirement). * There was no evidence of in-service

fatigue crack In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of ...

growth. * The material in which the crack was located was different from that specified in the design. Similar material was also identified in other heat exchangers, and no additional cracks of structural significance were revealed during comprehensive inspections. The NII considered the material to be adequate and within the bounds of the heat exchanger safety case.

Exposure of workers to an irradiated fuel element (first quarter 2001)

During refuelling operations on Reactor 2, an irradiated fuel element failed to release from the grab which holds an element while it is withdrawn from a reactor. Routine methods were used to release the grab. However, the irradiated fuel element snagged during the operation and was lifted out of its shielding, resulting in the operators on the pile cap being exposed to the intense radiation being emitted from the irradiated fuel element. Personnel responded quickly, and the radiological dose they received was small. The event revealed shortfalls in the safety of the refuelling operation and the licensee took the immediate step of halting all refuelling while it investigated the event and reviewed the safety of the equipment. The NII investigated the event and judged that it was due to inadequate design and operation of the equipment. The incident was classified as Level 1 (anomaly) on the

International Nuclear Event Scale The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 by the International Atomic Energy Agency (IAEA) in order to enable prompt communication of safety significant information in case of nuclear accidents. The ...

(INES).

Leak of Magnox depleted uranium trioxide (July 2001)

A small amount of Magnox depleted uranium leaked from some corroded mild steel drums due to rainwater ingress and leaching. MDU is a dense yellow powder that is less radiologically toxic than naturally occurring uranium but chemotoxic in a similar manner to lead. Owing to its high density and low solubility, it does not tend to disperse far and dry spills are easy to clean up. This material was stored at the larger sites, including Capenhurst in mild steel drums. BNFL upgraded the fabric of the building and the original drums were overpacked into stainless steel drums and dispatched to Capenhurst for long-term storage.

Dropped basket of irradiated fuel elements (July 2001)

During routine defuelling activities on Reactor 3, a basket containing 24 low-rated irradiated Magnox fuel elements fell a few feet within the discharge machine onto the door at the top of the fuel discharge well. Remote TV camera inspections revealed that twelve of the elements had fallen just over down the discharge well into a water-filled transport flask at the bottom. The NII initiated an investigation because dropping irradiated fuel elements is a serious issue even when, as in this event, BNFL had advised NII that there had been no release of radiological activity.

Charge pan movement relative to the core (September 2001)

Because of known shrinkage of the

moderator bricks in the core due to in-service irradiation effects, some of the steel charge pans on top of them had become dislocated from their design position in the interstitial channel and were suspended from the Burst Can Detection (BCD) pipework. This was most prevalent in Reactor 1 because of the different core design to Reactors 2, 3 and 4. BNFL were unable to make an adequate safety case or effect an economic repair and therefore, Reactor 1 did not return to power from its annual outage in August 2001. The core of Reactor 4 was repaired but this reactor did not return to power after the repair.

Interim storage facility

An interim storage facility for storing intermediate level

radioactive waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons r ...

from Chapelcross came into operation in 2021. Construction began in 2014 of the facility, which can store 700 waste packages for 120 years.

References

External links

Official website
archived in February 2008 {{Authority control 1959 establishments in Scotland 2004 disestablishments in Scotland Buildings and structures in Dumfries and Galloway Civilian nuclear power accidents Former nuclear power stations in Scotland Nuclear weapons infrastructure of the United Kingdom Scottish coast Annandale and Eskdale Military nuclear reactors Energy infrastructure completed in 1959