Designing a system to detect leaking in fuel elements in Brazilian Triga research reactor

Rodrigues, Rogerio Rivail; Mesquita, Amir Zacarías; Palma, Daniel Artur Pinheiro

doi:10.1504/ijnest.2018.095691

Cited by 4 publications

(1 citation statement)

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“…Após a irradiação, o pH das amostras sofreu um pequeno aumento, já a condutividade teve mudanças pouco significativas. A avaliação desses parâmetros é importante na caracterização da qualidade da água e no controle de impurezas de reatores refrigerados à água leve (Rodrigues et al, 2018) (IAEA, 2010, 2011.…”

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Avaliação experimental da eficiência do boro no controle da reatividade dos reatores nucleares refrigerados a água

Oliveira

Gonçalves

Mesquita

2022

RSD

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Reatores nucleares são dispositivos em que reações de fissão em cadeia são obtidas de modo controlado. A grandeza que representa este controle é a reatividade. Através da inserção ou remoção de barras absorvedoras de nêutrons controla-se o fluxo de nêutrons, determinando deste modo os níveis de potência. Já para o controle de longo prazo, substâncias químicas com alta seção de choque de absorção, são dissolvidas na água de refrigeração dos reatores à água pressurizada (PWR). O ácido bórico é utilizado para este propósito, devido ao isótopo B-10. O propósito deste trabalho foi mostrar a efetividade do boro no controle da reatividade dos reatores nucleares refrigerados a água leve. Foram inseridas amostras, com concentrações diferentes de ácido bórico no núcleo do reator nuclear de pesquisa Triga IPR-R1, do Centro de Desenvolvimento da Tecnologia Nuclear - CDTN. As variações de reatividades foram avaliadas utilizando o Método Estático da Reatividade Nula. Medidas do pH e da condutividade elétrica foram realizadas nas soluções para caracterizá-las. Os resultados encontrados possibilitaram simular o consumo de B-10 durante a operação do reator e seu efeito na reatividade com o aumento da concentração de ácido bórico. Os valores de pH tiveram um aumento muito pequeno após a irradiação. Já as condutividades das amostras tiverem alterações pouco significativas. Como resultado desta pesquisa, foi levantada uma correlação entre várias concentrações de ácido bórico e a reatividade do reator.

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Section: Conclusãounclassified

Avaliação experimental da eficiência do boro no controle da reatividade dos reatores nucleares refrigerados a água

Oliveira

Gonçalves

Mesquita

2022

RSD

Self Cite

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Defected fuel rods identification in TRIGA Reactors: The experience at the ENEA Casaccia TRIGA RC-1 reactor

Lepore,

Falconi,

Fabrizio

et al. 2023

EPJ Web Conf.

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Experience in running TRIGA reactors all around the world has shown that fuel cladding failures can occur. Fission products, especially in gaseous physical form, can exit the defected fuel rods being dispersed within the water primary coolant. Suspects of a cladding failure event can be confirmed by detection of short-lived fission products, i.e., Krypton, Xenon, and even Iodine isotopes in primary water, or within the ionic-exchange resins tank installed for the purification of the primary coolant loop. The magnitude of the release of those ‘key-indicators’ from the defected fuel element(s) is the driving method by which the defected rod(s) can be identified. ‘Significant’ releases can be detected with a direct online sampling of the water from the top of the suspected fuel rod with reactor at power, leading this water to an online high-resolution gamma spectrometry analysis system. By considering delays due to the water velocity in tubes and decay time of radionuclides identified within the gamma spectrum, it is possible to calculate the concentration of those radionuclides just emerging from the inspected fuel rod. Releases lower than the minimum detection capabilities of the previous online experimental configuration push to modify the detection method with an indirect identification of the release. This is the case when the ‘normal’ radioactive background of the activated water, when reactor is on power, is the dominant component in the gamma spectrum of the sampled water, and fission gases (even produced) are not identified promptly, i.e. a relationship to a specific fuel rod by the sampling circuit before could not be identified. The paper describes the experience carried out at the Italian ENEA TRIGA RC-1 reactor, deepening the technical aspects and solutions applied to solve the issue. In particular, a ‘significant’ release has been found in the instrumented fuel rod within ring B, i.e. the inner fuel ring, exposed to the maximum neutron flux of the reactor. The leaking element was found within a week, in two days of operation, being the sampling system designed on detection of minutes-shortlived fission gases (no need to ‘cool’ down the primary loop by waiting decay of hours-lived radionuclides). After the removal of the instrumented fuel rod in ring B, further days in searching other ‘significant’ release with the sampling circuit before have reported nothing detected. But in samples of water taken after reactor shutdown, some iodine emerged after decaying of ‘normal’ radioactive background of the activated water. This was sufficient evidence of another defected fuel rod in the pool. Identification of the latter defected fuel element is still ongoing, being based on: 1) selective removal of rod(s) from the reactor core, 2) run power of the reactor, 3) take samples of water after shutdown and measure iodine after decaying of ‘normal’ radioactive-background of the activated water, 4) identify the rod responsible of the remaining leakage when no further iodine is detected.

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Identification of a defected fuel rod in the TRIGA R.C.-1 facility of the ENEA Casaccia Research Center: radiation protection aspects

Sperandio,

Lepore,

Borra

et al. 2023

Eur. Phys. J. Plus

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The nuclear facility TRIGA RC-1 is located at the ENEA Casaccia Research Center in Rome. It is a thermal spectrum research reactor with a thermal power of 1 MW and a Mark III containment. The failure of the fuel cladding of the General Atomic TRIGA is a well-known phenomenon in the literature and is normally expected during its lifetime. Depending on the severity of the cracking, this results in the transfer of radioactivity from inside the fuel rods to the demineralized moderation and cooling water of the primary circuit. This occurs especially when the fuel is heated, as the temperature rise leads to an increase in the internal pressure inside the rods, causing fission products, especially gaseous ones, to be released through the cracks. The sustained release of these fission products over time causes impurities with longer half-lives (e.g., Cs-137) to accumulate in the primary water purification system and, in particular, in the ion exchange resin tank. Therefore, the detection of Cs-137 in the ion exchange resins of the primary water purification system of the reactor is a sufficiently clear indication of the occurrence of such disturbances. Indeed, Cs-137 is not only a direct fission product of U-235, but is also produced by the decay of Xe-137 (one of the major fission noble gasses), which, because of its physical nature, readily escapes through the rod cladding. To ensure worker protection from ionizing radiation during the identification and replacement of defective fuel rods, a special program of physical, environmental, and personal radiation protection monitoring was conducted. In addition to a brief description of the work performed, this report presents the results of radiometric measurements and associated individual dose assessment performed before, during, and after the identification and replacement of the defected fuel elements.

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Designing a system to detect leaking in fuel elements in Brazilian Triga research reactor

Cited by 4 publications

References 0 publications

Avaliação experimental da eficiência do boro no controle da reatividade dos reatores nucleares refrigerados a água

Avaliação experimental da eficiência do boro no controle da reatividade dos reatores nucleares refrigerados a água

Defected fuel rods identification in TRIGA Reactors: The experience at the ENEA Casaccia TRIGA RC-1 reactor

Identification of a defected fuel rod in the TRIGA R.C.-1 facility of the ENEA Casaccia Research Center: radiation protection aspects

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