MODÜLER HELYUM REAKTÖRÜNÜN KAZA DURUMUNUN ZAMANA BAĞLI ISIL AKIŞ ANALİZİ

Modüler Helyum Reaktörü (MHR)’nün en önemli özelliği kaza durumunda aktif soğutma sistemi çalışmadığı zaman kendiliğinden soğuyabilmesidir. Bu çalışmanın ilk amacı; kaza durumunda MHR’nin atık ısı uzaklaştırma yeteneğini incelemek için sayısal bir model geliştirmek ve oluşan tepe sıcaklığı hesaplamaktır. İkinci amacı; grafit iletimi, atık ısı gibi parametrelerdeki değişiminin maksimum aktif kor sıcaklığına etkisini belirlemek için duyarlılık analizleri yapmaktır. Bu çalışmada, aktif soğutmanın çalışmadığı kaza durumunda, atık ısının pasif olarak reaktörden atılmasını simule etmek için bir sayısal model oluşturulmuştur. Zamana bağlı ısıl-akış simülasyonları sayısal akışkanlar dinamiği yazılımı Ansys Fluent kullanılarak yapılmıştır. Simule edilen geometri Eşdeğer Silindir Modeli olarak seçilmiştir. Korun içindeki kompleks yapıyı modellemek için gözenekli ortam yaklaşımı kullanılmıştır. Hesaplamalar basınçsız kaza durumu için yapılmıştır. Basınçsız kaza durumunda pasif soğuma 100 saat için nümerik olarak çözülmüştür. Nümerik metodun güvenirliği diğer çalışmalar ile karşılaştırılarak doğrulanmıştır. Kaza durumunda meydana gelen maksimum sıcaklığın 1492°C olduğu bulunmuştur. Duyarlılık analizlerinin sonuçları kaza durumunda oluşan maksimum sıcaklığa en çok grafit ısı iletim katsayısı ve atık ısı değişiminin etkisi olduğunu göstermektedir.

Anahtar Kelimeler:

Modüler helyum reaktörü, kaza, SAD, zamana bağlı, Isıl-akış

TRANSIENT THERMAL HYDRAULIC ANALYSIS OF MODULAR HELIUM REACTOR UNDER ACCIDENT CONDITION

The main characteristic of MHR is that it can automatically cool down when the active cooling system does not work under accident condition. The first purpose of the study is to develop a numerical model to analyze the decay heat removal capabilities and evaluate peak temperature in the MHR under accident condition. The second purpose of the study is to perform some sensitivity analyses to evaluate the effect of varying the parameters, i.e. graphite conductivity, decay heat, etc., on the maximum active core temperature. In this study, a numerical model has been constructed to simulate the passive decay heat removal under a loss of active cooling accident. Thermal-hydraulic transient simulations were carried out by using Computational Fluid Dynamics software Ansys Fluent. The simulated geometry was chosen as an Equivalent Cylinder Model. The porous media approach has been applied to model the complex structure in the core. Calculations were performed for loss of forced cooling without pressurization condition. Passive cooldown under depressurized accident is solved numerically for 100 hours. The reliability of the numerical method was validated by comparing with the published data. It was found that the maximum temperature was 1492°C under accident condition. The results of sensitivity analyses show that the graphite thermal conductivity and decay power has a strong effect on the maximum temperature under accident condition.

Keywords:

Modular helium reactor, Accident, CFD, Transient, Thermal–hydraulic,

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