Flow Blockage Accident Analysis of Tehran Research Reactor Fuel Assembly

نوع مقاله: مقاله پژوهشی

نویسندگان

Reactors and Accelerators R & D School, Nuclear Science and Technology Research Institute, P.O. Box: 1439951113, Teheran- Iran

چکیده

Tehran Research Reactor (T.R.R.) is a pool-type, 5 MW thermal research reactor. One probable event is that if some external objects or debris fall down into the reactor core and cause obstruction of the coolant flow through one of the fuel assemblies, decreasing the surface flow area, ceases the coolant flow, and also raises the fuel and sheaths temperature. Thermal hydraulic analysis of this event has been studied using RELAP5 system code. This report is related to the partial and total obstruction of a single Fuel Element (F.E.) and cooling channel of 27 F.E. equilibrium core of the T.R.R. Such event may lead to severe accident for such type of research reactors, since it may cause a local dry out and eventually loss of the F.E. integrity. Two scenarios are analysed in order to emphasize the severity of the mentioned accident. The first is a partial blockage of hot F.E. which is considered for four different obstruction levels of the nominal flow area: 25%, 50%, 75% and 93%. The second is related to an extreme case which consists of the total blockage of the same F.E. The reactor power is derived through the kinetic point calculation in the RELAP5 code. The point kinetic feedbacks including the fuel temperature (Doppler coefficient) and the coolant density coefficient have been considered through the applied model. The main results obtained from the RELAP5 calculations are as follows: 1. In case when the flow blockage is under 93% of the nominal flow area of an average F.E., only the increase of the coolant and clad temperatures are observed with no integrity of the F.E. consequences. The mass flow rate remains sufficient enough and cools the clad safely 2. In the case of a total obstruction in the nominal flow area, it is seen that the severe accident is due to dryout conditions and reaches promptly, while melting of the cladding occurs.
 

کلیدواژه‌ها


عنوان مقاله [English]

Flow Blockage Accident Analysis of Tehran Research Reactor Fuel Assembly

نویسندگان [English]

  • J Jafari
  • S Khakshournia
چکیده [English]

Tehran Research Reactor (T.R.R.) is a pool-type, 5 MW thermal research reactor. One probable event is that if some external objects or debris fall down into the reactor core and cause obstruction of the coolant flow through one of the fuel assemblies, decreasing the surface flow area, ceases the coolant flow, and also raises the fuel and sheaths temperature. Thermal hydraulic analysis of this event has been studied using RELAP5 system code. This report is related to the partial and total obstruction of a single Fuel Element (F.E.) and cooling channel of 27 F.E. equilibrium core of the T.R.R. Such event may lead to severe accident for such type of research reactors, since it may cause a local dry out and eventually loss of the F.E. integrity. Two scenarios are analysed in order to emphasize the severity of the mentioned accident. The first is a partial blockage of hot F.E. which is considered for four different obstruction levels of the nominal flow area: 25%, 50%, 75% and 93%. The second is related to an extreme case which consists of the total blockage of the same F.E. The reactor power is derived through the kinetic point calculation in the RELAP5 code. The point kinetic feedbacks including the fuel temperature (Doppler coefficient) and the coolant density coefficient have been considered through the applied model. The main results obtained from the RELAP5 calculations are as follows: 1. In case when the flow blockage is under 93% of the nominal flow area of an average F.E., only the increase of the coolant and clad temperatures are observed with no integrity of the F.E. consequences. The mass flow rate remains sufficient enough and cools the clad safely 2. In the case of a total obstruction in the nominal flow area, it is seen that the severe accident is due to dryout conditions and reaches promptly, while melting of the cladding occurs.
 

 

  1. 1.      W.L. Woodroff, N.A. Hanan, R. Smith, J.E. Matos, “A  comparison of the PARET/ANL and RELAP5/Mod3.3 codes for the analysis of IAEA Benchmark transient,” Proceeding of the International Meeting on Reduced Enrichment for Research and Test Reactors, Oct. 7-10, Seol, South Korea (1996).

 

  1. 2.      B. Di Maro, F. Pierro, M. Adorni, A. Bousbia Salah, F. D’Auria, “Safety analysis of loss of flow transients in a typical research reactor by Relap5/Mod3.3,” Nuclear Energy for New Europe, Portoroz, Slovenia, Sept. 8-11 (2003).

 

  1. 3.      T. Hamidouche, Anis Bousbia-Salah, Martina Adorni, Franscesco D’Auria, “Dynamic calculations of the IAEA safety MTR research reactor Benchmark problem using Relap5/3.2 code,” Annals of Nuclear Energy 31, 1385-1402 (2004).

 

  1. 4.      Ch.S.Y. Suresh, G. Sateesh, S.K. Das, S.P. Venkateshan, M. Rajan, “Heat transfer from a totally blocked fuel subassembly of a liquid metal fast breeder reactor: Part I. Experimental investigation and Part II Numerical Simulation,” Nuc. Eng. Des. 235, 885-912 (2005).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. 5.      M. Adorni, T. Hamidouche, A. Bousbia-Salah, B. Di Maro, F. Pierro, F. D’Auria, “Analysis of partial and total flow blockage of a single fuel assembly of an MTR research reactor core,” Annals of Nuclear Energy, Vol. 31, 1679-1692 (2005).

 

  1. 6.      Safety Analysis Report of Tehran Research Reactor, Nuclear Research Center, Atomic Energy Organization of Iran (September 2006).

 

  1. 7.      RELAP5 Code Manuals, NUREG/CR-5535 (June 1999).

 

  1. 8.      F. D’Auria, M. Frogheri, W. Giannoti, “RELAP5/MOD3.2 Post Test Analysis and Accuracy Quantification of Lobi Test BL-44,” NUREG/IA-Reactors, Oct. 7-10, Seol, South Korea (1996).