CASTOR : A High-Tech Product Made of Ductile Cast Iron ® Casting of a CASTOR ® specified by the authorities ensures that the CASTOR conforms with all applicable conditions. These include extensive tests on the material and structure plus integrity verifications by ultra-sound, for example. In the assembly process in the GNS (Gesellschaft für Nuklear-Service mbH) building in Mülheim the cask body, assembly basket, moderator rods, trunnions, lids and a diversity of other small parts are put together to form the total product . In the overload test the diverse screw fittings and load impact points are tested with 1.5 times the load of the maximum permissible cask weight. In the leakage test all the cask's seal barriers are fully tested. Adding together all the stages involved in production (including the preparation time for the mold production, molding etc.), the total time required for each project is about 1 year or even longer. This excludes the time involved for permissions, reports and safety tests, which can be particularly time consuming where new types of casks are introduced or major design modifications made. When the caskl is finally put into use at the nuclear power station a lengthy project path with many highly complex individual stages comes to an end. The precondition for trouble-free production - and this should be mentioned here too - is not only a high level of technical competence on the part of all the institutions involved but a committed and responsible team effort between them all. ® Loading a CASTOR with spent fuel rods ® in the NPP Assembly work for the CASTOR ® Contact Christian Jurianz Phone.: +49 (0) 2151-894-481 Fax: +49 (0) 2151-894-488 Email: [email protected]Siempelkamp Nukleartechnik GmbH · Siempelkampstrasse 45 · 47803 Krefeld, Germany Phone +49(0)2151- 894-0 · Fax +49(0)2151- 894-488 · [email protected]www.siempelkamp.com Our Know-how - Your Benefit CASTOR: A Hight-Tech Product_01/06_GB
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CASTOR : A High-Tech Product
Made of Ductile Cast Iron
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Casting of a CASTOR®
specified by the authorities ensures that the CASTORconforms with all applicable conditions. These includeextensive tests on the material and structure plusintegrity verifications by ultra-sound, for example.
In the assembly process in the GNS (Gesellschaft fürNuklear-Service mbH) building in Mülheim the caskbody, assembly basket, moderator rods, trunnions, lidsand a diversity of other small parts are put together toform the total product .In the overload test the diverse screw fittings and loadimpact points are tested with 1.5 times the load of themaximum permissible cask weight.In the leakage test all the cask's seal barriers are fullytested.
Adding together all the stages involved in production(including the preparation time for the mold production,molding etc.), the total time required for each project isabout 1 year or even longer. This excludes the timeinvolved for permissions, reports and safety tests, whichcan be particularly time consuming where new types ofcasks are introduced or major design modificationsmade.
When the caskl is finally put into use at the nuclear powerstation a lengthy project path with many highly complexindividual stages comes to an end. The precondition fortrouble-free production - and this should be mentionedhere too - is not only a high level of technical competenceon the part of all the institutions involved but a committedand responsible team effort between them all.
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Loading a CASTOR with spent fuel rods® in the NPPAssembly work for the CASTOR
he CASTOR is the most widely usedtransport and storage container for spentfuel rods in the world and provides anecessary and at the same time safemeans of disposal. Not only is theproduction process for making the caskextremely complex, it also involves anextensive network of quality assurancemeasures.
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In connection with the disposal of waste from Germannuclear power stations a total of some 900 CASTOR( ask for torage and ransport f adioactivematerial) transport and storage containers have beendeveloped, tested, certified and manufactured since theearly 1980s. Nearly all of the containers in this serieshave a cask body made of ductile cast iron. A double lidsystem seals the inside and the contents are sealedlong-term by metal seals.
In accordance with the latest requirements and wishes ofthe German utilities operating nuclear power stations,the following versions of this model of cask are currentlyused for interim storage at the power stations or in thecask storage facilities:The CASTOR V cask was developed to hold spentpressurized water reactor or boiling-water reactor fuelrods from German power stations with a decay time afterloading of the cask of approx. five years (Roman: V). Thedesign is based on the international regulations of theIAEA (International Atomic Energy Agency) inaccordance with predefined requirements, such that thecasks conform with all international standards andregulations for public transportation by road, rail or sea.The CASTOR® V/19 cask is designed to hold 19 spentfuel rods from pressurized water reactors, and theCASTOR® V/52 cask for holding 52 fuel rods fromboiling-water reactors. Both casks are almost 6 m inlength, have external diameters of approx. 2.5 m andwall thicknesses of approx. 50 cm. The proper weight ofeach cask
For returning HAW glass canisters (HAW = igh ctiveaste) with vitrified, highly radioactive waste from the
reprocessing of spent fuel rods in France and GreatBritain, the CASTOR HAW 20/28 CG cask, which holdseither 20 or 28 canisters, was developed and givenapproval.
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is approx. 105 Mg; when loaded the totalweight is approx. 125 Mg.
3. The production process
Extensive experience has been gathered in planning,production and operational use. Nevertheless, theCASTOR is not actually a serial product in the normalsense of the word. Each cask is a high-tech systemwhich is manufactured in small piece numbers for eachorder with all the rigour required to achieve assuredquality.With its 160 Mg or thereabouts of molten iron in thepouring process required as a consequence of thenecessarily thick shield wall, the cask body is also one ofthe largest cast parts to be produced in the world, onlycapable of being
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made to high quality standards by handmold casting by just a few manufacturers such asSiempelkamp.The production process begins with the raw cast of thecask body at a casting temperature of approx. 1320° Cat the Siempelkamp foundry in Krefeld.Some 2 days after casting the molds are stripped as theouter cast structure, and after a further week in the pit forfurther cooling the cast part is then brought to theblasting shop.In mechanical machining on the large lathe, which takesplace in the Siempelkamp Nuclear Technologyproduction center in Mülheim), approx. 50 mm of the wallof the cask bodies is then turned off to ensure that anyunavoidable surface defects caused during the castingprocess are removed. The cooling fins are thenmachined in a later phase of work.In deep hole machining, up to 100 lengthwise holes aremade in the cask wall to a depth of approx. 5,500 mm forfitting the neutron moderator rods.A large boring machine is used mainly for the holes forthe screw fittings for the lids and the trunnions.The main purpose of the galvanized nickel plating on theinside of the cavity and the lid holders is to provideprotection against corrosion during later loadingunderwater in the nuclear power station.Acomprehensive and stringently regulated handling andverification system involving predefined test instructions
2. The material
The CASTOR is a cask which has to meetrequirements in respect of both transportation andstorage. The material used must therefore conform withspecial qualification characteristics, all of which can bemet by nodular cast iron.A key advantage for the CASTOR as a system as awhole is the monolithic structure of the cask body, whichunder the principle of "all from a single cast" meets therequirements for completely safe and reliable enclosureand the shielding function without any additional seams.The suitability of the material must be proved in a seriesof highly involved tests and the specifications for thedesign include the transportation accident conditions setout by the IAEA (e.g. a drop from 9 m onto an inflexibleground surface, a 1 m drop onto a spike and asubsequent heating test).
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Mechanical machining on the large lathe
Structural design of theCASTOR using HAW as an example
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In addition to these standard versions a range of specialmodels were also developed to meet the specificrequirements of the diverse reactor types in the EastEuropean market.
The protection plate is only used during storage andprovides protection against external mechanical stressand loads and the influence of the weather.During transportation the cask is fitted with shockabsorbers at both ends to reduce the impact of anypossible impacts. These are made of wood covered withsheet metal.The lids are made of stainless steel. All the lids arescrew-fitted and sealed with long-term resistant metalseals, and a complex cask monitoring system ensuresthat the condition of the seals is permanently monitoredduring storage.
What is the structural design of the CASTOR ?The main elements - taking the HAW 20/28 CG as anexample - are a thick-walled cylindrical cask body madeof ductile cast iron and a double lid system, whichtogether form a sealed enclosure and provide the shieldagainst radiation. To provide a shield against theneutrons which are also generated in nuclear fission,holes distributed evenly along the wall of the cask arefitted with so-called moderator rods made ofpolyethylene, and panels of the same material are alsofitted to the floor and underside of the secondary lid. Inaddition, the shell of the container has a pair of trunnionsfitted on both the floor and lid side to enable handlingequipment to be attached.The so-called assembly basket for holding the fuel rodsis a welded structure. The cylinder surface is augmentedwith cooling fins which provide for the efficientdissipation of heat to the surroundings.
