In-Pile Measurements of Diffusion of Fission Products Through Impregnated Graphite Shells of Fuel Elements
Creators
- 1. Brown Boveri/Krupp Reaktorbau G.M.B.H., Duesseldorf, Federal Republic of Germany (Germany)
- 2. Societe d'Etudes de Recherches et d'Applications pour l'Industrie, Brussels (Belgium)
Description
The high-temperature reactor, presently built in Juelich by Brown-Boveri/Krupp ReaktorbauG.m.b.H., is designed for the use of spherical fuel elements. These consist of a fuel insert containing the fissile material and of a graphite shell which must be as tight as possible and which serves simultaneously as moderator and as canning. The purpose of the investigation was to determine the influence of various impermeability treatments of the graphite shells upon the release of fission products from the fuel elements. The tested fuel elements have been manufactured by NUKEM (Nuklear-Chemie und -Metallurgie G.m.b.H., Wolfgang bei Hanau/Main, Federal Republic of Germany). Each fuel element was irradiated during a period of 11 days in a neutron flux of 4 x 1010 n/cm2s and under simultaneous heating to a temperature of 1000oC in the reactor BR-1 of the Centre d'etudes nucleaires in Mol. During irradiation, the fuel elements were either free in circulating helium or embedded in granulated graphite within closed steel capsules. The free fuel elements allowed the measurement of the build-up in the circulating gas of the activities of Kr87, Kr88, Kr85m, Xe135 and Xe133 during irradiation. Puncturing of the steel capsules after irradiation gave the total of Kr85m, Xe135 and Xe133 released from the encapsulated fuel elements. The distribution o f the concentration o f the fission products I131, I133, Te132, Sr89, Ba140 and Ce141 in the graphite shells of the fuel elements as well as their activities in the granulated graphite were determined after irradiation. The experiments have shown that the isotopes Sr89, Ba140 and Ce141 do not diffuse appreciably in the graphite shells, but are formed in situ through disintegration of the diffusing rare gas precursors. The distribution curves of these isotopes were therefore proportional to the stationary distribution of the rare gas isotopes Kr89, Xe140 and Xe141 and it was possible to determine the diffusion constants and the stay periods of the rare gases in the graphite shells. The investigations have shown that the rare gases diffuse within a few seconds through an unimpregnated graphite shell about 2 cm thick. The impermeability of the shells achieves stay periods for the rare gases up to about 50 min, so that the short-lived rare gas isotopes up to Kr89 (T1/2 = 3.2 min) were largely retained, while rare gas isotopes with longer half-lives from Kr87 upwards (T1/2 = 78 min) were released without significant attenuation. The isotopes I131, I133 and Te132 were retained by the unimpregnated as well as by the impregnated graphite so that only less than 0.1% o f the total amount formed within the fuel pellet was released. (author)
Abstract (French)
Le reacteur a haute temperature construit a Juliers par la societe Brown-Boveri/Krupp Reaktorbau GmbH, est concu pour utiliser des elements spheriques,. Ces derniers consistent en un noyau, contenant la matiere fissile, enrobe d'une sphere en graphite qui doit etre aussi etanche que possible et sert a la fois de ralentisseur et de gaine. L'etude qui fait l'objet du memoire avait pour objet de determiner l'influence des divers traitements d'etancheite des spheres en graphite sur le degagement des produits de fission. Les elements de combustible soumis aux essais ont ete fabriques par NUKEM (Nuklear-Chemie und -Metallurgie GmbH, Wolfgang bei Hanau/Main, R. F. d'Allemagne). Chaque element combustible a ete irradie pendant une periode de 11 jours dans un flux de neutrons de 4 x 1010n/cm2s et chauffe simultanement jusqu' a 1000oC dans le reacteur BR 1 du Centre d'etudes nucleaires a Mol. Au cours de l'irradiation, les elements combustibles etaient soit libres dans un courant d'helium, soit noyes dans de la grenaille de graphite a l'interieur de capsules hermetiques en acier. Les elements libres ont permis de mesurer l'accumulation de 87Kr, 88Kr 85mKr, 135Xe et 133Xe dans l'helium en cours d'irradiation. La perforation des capsules en acier, apres irradiation, a permis de mesurer la totalite de 85mKr, 135Xe et 133Xe degages par les elements combustibles sous capsule. La distribution de la concentration des produits de fission 131I, 133I, 139Te , 89Sr, 140Ba et 141Ce dans le graphite des elements combustibles, de meme que leur activite dans la grenaille de graphite ont ete determinees apres irradiation. Les experiences ont montre que les radioisotopes 89Sr, 140Ba et 141Ce ne se diffusent pas d'une maniere appreciable dans le graphite des elements, mais se forment in situ par desintegration des gaz rares precurseurs qui eux penetrent dans le graphite par diffusion. Les courbes de distribution de ces radioelements sont de ce fait proportionnelles a la distribution stationnaire de 89Kr, l40Xe et 141Xe, et l'on a pu determiner les constantes de diffusion et les temps de sejour des gaz rares dans le graphite des elements. Les recherches ont montre que les gaz rares penetrent en quelques secondes dans une epaisseur de graphite non impregne d'environ 2 cm. Le traitement d'etancheite des spheres en graphite permet de prolonger jusqu'a 50 minutes les temps de sejour des gaz rares, de telle sorte que les gaz rares radioactifs a courte periode, jusqu'a 89Kr (3,2 min), sont en grande partie retenus, tandis que les gaz rares a plus longue periode, a partir de 87Kg (78 min) et au-dessus s'echappent sans avoir perdu beaucoup de leur activite. 131I, 133I et 132Te sont retenus par le graphite, impregne ou non, de telle sorte qu'il se degage moins de 0,1% de la quantite totale formee dans la pastille combustible. (author)Abstract (Spanish)
Los experimentos han demostrado que los isotopos 89Sr, 140Ba y 140Ce no se difunden en cantidad apreciable en las envolturas de grafito, sino que se forman in situ por desintegracion de los respectivos gases nobles precursores en proceso de difusion. Las curvas de distribucion de dichos isotopos son, por lo tanto, proporcionales a la distribucion en regimen estacionario de los isotopos de los gases nobles 89Kr, 140Xe y 141Xe ; asi se pudieron determinar las constantes de difusion y los periodos de permanencia de los gases raros en las envolturas de grafito. Se comprobo, durante la investigacion, que los gases nobles se difunden en pocos segundos a traves de una envoltura de grafito sin impregnar de unos 2 cm de espesor. Gracias a la impermeabilizacion de las envolturas, el periodo de permanencia de los gases nobles se prolonga hasta unos 50 min, de manera que los isotopos de los gases raros de periodo breve hasta el 89Kr (T1/2 = 3,2 min) son retenidos en su mayor parte, mientras que los isotopos de los gases nobles de periodo mas largo, a partir del 87Kr (T1/2 = 78 min), se desprenden sin atenuacion apreciable. Los isotopos 131I, 133I y 132Te quedan retenidos tanto por el grafito sin impregnar como por el impregnado, de modo que solamente se desprende menos de 0,1% de la cantidad total formada en el interior de la pastilla de combustible. (author)Abstract (Russian)
Vysokotemperaturnyj reaktor, postroennyj ''Obshchestvom stroitel'stva reaktorov Braun-Boveri/Krupp''v Yulikhe, prednaznachen dlya ispol'zovaniya sfericheskikh teplovydelyayushchikh ehlementov. Poslednie sostoyat iz toplivnoj serdtseviny, soderzhashchej delyashcheesya veshchestvo, i grafitovoj obolochki, kotoraya dolzhna imet' naibol'shuyu plotnost' i odnovremenno sluzhit' kak zamedlitelem, tak i pokrytiem. Tsel'yu issledovaniya yavlyalos' opredelenie vliyaniya razlichnykh vidov propitki grafitovykh obolochek, povyshayushchikh ikh nepronitsaemost', na vydelenie produktov deleniya iz toplivnykh ehlementov. Ehlementy, podvergavshiesya ispytaniyu, byli izgotovleny Obshchestvom yadernoj khimii i metallurgii, Khanau-na-Majne, FRG. Kazhdyj iz teplovydelyayushchikh ehlementov podvergalsya oblucheniyu v techenii 11 dnej nejtronnym potokom moshchnost'yu 4 x 1010 n/cm2sek i odnovremennomu nagrevaniyu do temperatury v 1000oC v reaktore yadernogo tsentra v Mole. Teplovydelyayushchie ehlementy vo vremya oblucheniya nakhodilis' libo svobodnymi v tsirkuliruyushchem gelii, libo byli zadelany v granulirovannyj grafit i zaklyucheny v stal'nye kapsuly. Svobodnye teplovydelyayushchie ehlementy pozvolyali izmeryat' vo vremya oblucheniya nakoplenie aktivnostej Kg87, Kg88, Kr85m, Xe135 i Xe133 v tsirkuliruyushchem gaze. Sdelav v kapsulakh otverstiya posle oblucheniya, opredelili polnoe vydelenie Kr85m, Xe135 i Xe133 iz teplovydelyayushchikh ehlementov, zaklyuchennykh v kapsuly. Raspredelenie kontsentratsii produktov deleniya I131 I133, Te132, Sr89, Ba140 i Ce141 v grafitovykh obolochkakh teplovydelyayushchikh ehlementov, a takzhe ikh aktivnosti v granulirovannom grafite byli opredeleny posle oblucheniya. Opyty pokazali, chto izotopy Sr89, Ba140 i Ce141 ne diffundiruyut v zametnoj mere v grafitovye obolochki, a obrazuyutsya v nikh vsledstvie raspada diffundiruyushchikh inertnykh gazov-predshestven- nikov. Poehtomu krivye raspredeleniya ehtikh izotopov byli proportsional'ny statsionarnomu raspredeleniyu izotopov inertnykh gazov Kr89, Xe140 i Xe141, chto davalo vozmozhnost' opredelit' konstanty diffuzii i periody zaderzhki inertnykh gazov v grafitovykh obolochkakh. Issledovaniya pokazali, chto inertnye gazy v techenie neskol'kikh sekund diffundiruyut skvoz' nepropitannuyu grafitovuyu obolochku, imeyushchuyu tolshchinu okolo 2 cm. Povysheniem nepronitsaemosti obolochek dostigayutsya periody zaderzhki inertnykh gazov priblizitel'no do 50 minut, tak chto korotkozhivushchie izotopy inertnykh gazov do Kr89 (T1/2 - 3,2 min) v znachitel'noj stepeni uderzhivayutsya, v to vremya kak zametnogo umen'sheniya vykhoda izotopov inertnykh gazov, imeyushchikh bolee dlitel'nye periody poluraspada, nachinaya s Kr87 T = 78 min) i vyshe, ne proiskhodit. Izotopy I131, I133 i Te132 uderzhivalis' kak nepropitannym tak i propitannym grafitom, i ikh vydelenie sostavlyalo men'she 0,1% obshchego kolichestva, obrazovavshegosya v tabletke goryuchego. (author)Additional details
Additional titles
- Original title (English)
- Mesures, en pile, de la diffusion des produits de fission a travers le graphite impregne enrobant le combustible dans des elements spheriques; Vnutrireaktornye izmereniya diffuzii produktov deleniya skvoz' propitannye grafitovye obolochki teplovydelyayushchikh ehlementov; Mediciones en reactor de la difusion de los productos de flsionta traves de las envolturas de grafito impregnadas de los elementos combustibles
Publishing Information
- Publisher
- IAEA
- Imprint Place
- Vienna (International Atomic Energy Agency (IAEA))
- Imprint Title
- New Nuclear Materials Including Non Metallic Fuel Elements. Vol. II. Proceedings of the Conference on New Nuclear Materials Technology, Including Non Metallic Fuel Elements
- Imprint Pagination
- 586 p.
- Series
- Proceedings Series
- Journal Page Range
- p. 347-365
- ISSN
- 0074-1884
Conference
- Title
- Conference on New Nuclear Materials Technology, Including Non Metallic Fuel Elements
- Dates
- 1-5 Jul 1963
- Place
- Prague (Czech Republic)
INIS
- Country of Publication
- International Atomic Energy Agency (IAEA)
- Country of Input or Organization
- International Atomic Energy Agency (IAEA)
- INIS RN
- 44098348
- Subject category
- S22: GENERAL STUDIES OF NUCLEAR REACTORS; S11: NUCLEAR FUEL CYCLE AND FUEL MATERIALS;
- Resource subtype / Literary indicator
- Conference
- Descriptors DEI
- BARIUM 140; CERIUM 141; EVALUATION; FISSION PRODUCT RELEASE; FISSION PRODUCTS; FUEL ELEMENTS; IODINE 131; IODINE 133; IRRADIATION; KRYPTON 85; KRYPTON 87; KRYPTON 88; KRYPTON 89; NEUTRON FLUX; STRONTIUM 89; TELLURIUM 132; TEMPERATURE RANGE 0400-1000 K; XENON 133; XENON 135; XENON 140; XENON 141
- Descriptors DEC
- ALKALINE EARTH ISOTOPES; BARIUM ISOTOPES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CERIUM ISOTOPES; DAYS LIVING RADIOISOTOPES; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; HOURS LIVING RADIOISOTOPES; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE ISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; KRYPTON ISOTOPES; MATERIALS; MICROSECONDS LIVING RADIOISOTOPES; MINUTES LIVING RADIOISOTOPES; NUCLEI; ODD-EVEN NUCLEI; RADIATION FLUX; RADIOACTIVE MATERIALS; RADIOISOTOPES; RARE EARTH NUCLEI; REACTOR COMPONENTS; SECONDS LIVING RADIOISOTOPES; STRONTIUM ISOTOPES; TELLURIUM ISOTOPES; TEMPERATURE RANGE; XENON ISOTOPES; YEARS LIVING RADIOISOTOPES
Optional Information
- Notes
- 8 figs., 3 tabs., 7 refs.
- Secondary number(s)
- STI/PUB--77(v.2)