Proceedings of the 12th International Conference of the Croatian Nuclear Society Zadar, Croatia, 3-6 June 2018
Paper No. 140
Implementation of Sodium Single Phase Thermodynamic and Transport Properties plus Heat Transfer Correlation in RELAP/SCDAPSIM for SFR Applications A. K. TRIVEDI, M. PEREZ-FERRAGUT Innovative Systems Software 3585 Briar Creek Lane, Ammon, ID 83406, USA
[email protected],
[email protected] Z. FU, C. ALLISON Innovative Systems Software 3585 Briar Creek Lane, Ammon, ID 83406, USA
[email protected],
[email protected] ABSTRACT The current work involves the implementation of the thermodynamic and transport properties of single phase Sodium into the system thermal hydraulic code RELAP/SCDAPSIM/MOD4.1. These properties were selected from the open literature and are used by other thermal hydraulic codes such as TRACE, SAS-SFR and ASTEC-Na, RELAP5-3D and SIMMER-III for SFR applications. The focus of this study was to insert the correct set of the properties and critical constants for Sodium into the code and to verify them, a simple pipe (three components) problem is was used with typical SFR pressure and temperature conditions to confirm that the temperature dependent property correlations show the intended behaviour and were properly inserted into the code. This work also includes the implementation of Sodium heat transfer correlations into the code which are the Lyon’s correlation for tube flow and Mikityuk’s correlation for tube bundle flow. RELAP/SCDAPSIM/MOD4.1 is the first release of the code with Na-capabilities that will be used for future safety and severe accident analyses activities for SFRs. It was completely rewritten to FORTRAN 90/95/2000 standards and has a number of the unique options in previous versions of RELAP/SCDAPSIM which include advanced numerical techniques, integrated uncertainty analysis, advanced graphical user interfaces, a standardized interface for a user supplied 3D reactor kinetics package, and advanced models and correlations for water and alternative reactor coolants including LiPb, PbBi, and molten salts. The overall objective of this paper is to summarize the process and methodology adopted to modify RELAP/SCDAPSIM for advanced alternative fluids such as Sodium and the associated heat transfer correlations. The input modifications needed in the input deck are demonstrated using a simple pipe example for with Sodium as the fluid for the SFR thermal hydraulic calculations. The results from this phase were satisfactory as demonstrated by the simple pipe example, which showed that the code can now be successfully used to analyze design basis accidents in SFRs. The heat transfer correlations for tube and tube bundle flow conditions will be improved by inserting the flow regimes for two phase conditions in future versions. The next step is to assess the current RELAP5 capabilities for the Sodium system modelling using the EBR-II SHRT-17 benchmark problem. Keywords: RELAP5, thermal hydraulics, SFR, sodium, nuclear safety 140-1
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INTRODUCTION
Fast reactors are designed to utilize high energy neutrons in the fission of the fertile isotope of uranium or plutonium that come from the used Gen-II LWRs fuel without any moderation effect. It has been well established that fast reactors can efficiently use available uranium resources and significantly reduce the high-level waste and actinides which can then be easily stored in much smaller waste disposable facilities. These reactors have reduced size of the core due to the availability of enough high energy neutrons for fission. About 20% fuel enrichment leads to a high power density which requires the use of liquid metal coolants to successfully and quickly transport the generated heat to the steam (in the tertiary loop) for power generation. There were number of coolants [1] proposed for these reactors which belong to the liquid metals category. The most basic expectations from the coolants are minimum neutron moderation; to adequately remove heat from a high power density system (~ 4 times higher than for LWRs); and minimum parasitic absorption. These coolants are Na, NaK, Hg, Pb, FLiBe, Pb-Bi (LBE) which Na was considered as a potential candidate for the coolant in all the operating fast reactors based on the thermal properties reported in Table 1, mainly due to its high thermal conductivity and low density (crucial for pumping power) although it is highly inflammable with air/water. These reactors were termed as Sodium cooled fast reactors (SFR) and the dominant member of the six designs proposed for Gen-IV. The nuclear industry has immense experience in building and operating SFR demos throughout the world. Russia and France are the leaders in this technology. China, South Korea and India have been devoting lots of resources to develop this kind of technology for the past several years. India has already completed the construction of SFR demo called Prototype Fast Breeder Reactor [1] (PFBR) which is close to commissioning. There is a great need to use a standard system thermal hydraulic code like RELAP/SCDAPSIM [2] to understand a design basis accident in SFR systems. With this objective of providing a tool to the SFR community, Sodium fluid has been inserted into RELAP/SCDAPSIM which has a detailed plan for the improvement and assessment of the code for reliable future safety analysis activities for SFRs. The previous versions of RELAP/SCDAPSIM code contain both light water and heavy water as coolants. They were only capable of analysing Nuclear Power Plants (NPPs) cooled with light and heavy water. RELAP/SCDAPSIM [2] is designed to describe the overall reactor coolant system (RCS) thermal hydraulic response and core behaviour under normal operating conditions or under design basis or severe accident conditions. The overall RCS thermal hydraulic response, control system behaviour, reactor kinetics and behaviour of special reactor system components such as valves and pumps are calculated by the RELAP5 models. RELAP/SCDAPSIM uses the publicly available RELAP5/MOD3.3 and SCDAP/RELAP5/MOD3.2 models developed by the US Nuclear Regulatory Commission (US NRC) in combination with proprietary (a) advanced programming and numerical methods, (b) user options, and (c) models developed by Innovative Systems Software (ISS) and other members of the SCDAP development and training program (SDTP) administered by ISS. RELAP/SCDAPSIM/MOD3.2 was the first production version released under SDTP sponsorship. This version used standard RELAP5 and SCDAP/RELAP5 input but included enhanced output options such as integrated 3D and time history plotting options. RELAP/SCDAPSIM/MOD4.1 [3] is the first release of the code with Na-capabilities that can be used for future safety analyses activities for SFRs. It was completely rewritten to FORTRAN 90/95/2000 standards and it has a number of the unique options available in previous versions of RELAP/SCDAPSIM. These options include advanced numerical techniques, integrated uncertainty analysis, advanced graphical user interfaces, a standardized interface for a user supplied 3D reactor kinetics package, and advanced models and correlations for water and alternative reactor coolants including LiPb, PbBi, and molten salts. This version of the code also has an option of using the NIST subroutines (National Institute of Standards and Technology, Gaithersburg, Maryland) for the 140-2
steam and water property tables in addition to the ASTEM steam tables. These NIST subroutines reside in the “STEAM” subdirectory. Subroutine stgh2o.ff calls these subroutines and instructs the subroutine gentpf.ff to create thermodynamic property tables. Hence, the MOD4.1 version can calculate the thermodynamic properties of water based on two different equations of state. It allows the user to select either of the two tables. Subroutines astem.ff and tprslts.ff in the “envrl” subdirectory create a data base for the thermodynamic tables generated. Subroutines sth2x0.ff, sth2x1.ff, sth2x3.ff, sth2x6.ff are now called by “20” other subroutines. The present version of RELAP/SCDAPSIM/MOD4.1 contains following 9 fluids. • • • • • • • • •
1 ( h2o ) 2 ( d2o ) 8 ( Na ) 10 ( LiPb ) 12 (h2on, light water using p & U ) 15 (h2os, light water using NIST tables) 16 (h2osx, light water using NIST tables interpolating along the saturation line) 17 (pbbi) 18 (flibe)
The overall objective of this paper is to summarize the process and methodology adopted to modify RELAP/SCDAPSIM for advanced alternative fluids like Sodium and the associated the heat transfer correlations. The input modifications needed in the input deck are demonstrated using a simple pipe example with Sodium as the fluid for the SFR thermal hydraulic calculations. The results from this phase were satisfactory as demonstrated by the simple pipe example which showed that the code can now be used successfully for analyzing design basis accidents in SFRs. The heat transfer correlations for tube and tube bundle flow conditions will be improved by inserting the flow regimes for two phase conditions in future versions. The next step is to assess the current RELAP5 capabilities for the Sodium system modelling using the EBR-II SHRT-17 benchmark problem. Table 1: Comparison of Heat Transfer Data for Various Coolant Candidates [1] Properties
Coolant NaK 18 826 855 1.2 26 20000 0.93
Na Hg Tmelt (oC) 98 -38 o Tboil ( C) 880 357 Density (kg/m3) 880 13500 Cp (kJ/kg-K) 1.3 0.14 k (W/m-K) 75 12 2 h (W/m -K)* 36000 32000 Relative pumping 0.93 13.1 power (Water=1) *For 2.3 m/s velocity in a 25 mm duct 2
Pb 328 1743 10500 0.14 14 23000 11.5
Water 0 100 1000 4.2 0.7 17000 1.0
IMPLEMENTATION OF THE ALTERNATIVE FLUIDS IN RELAP/SCDAPSIM
This section summarizes the code structure [4] implemented for alternative fluid systems those proposed for Gen-IV. The user first chooses a number for the new fluid other than 1, 2, 8, 10, 11, 12, 15, 16, 17 or 18. This new fluid number should be declared in mxnfcd.ff and stgenr.ff to be considered as a fluid by the main program RELAP5. The user then writes a new module named stfluidname.ff containing 9 subroutines stfluid0 stfluid0d stfluid1 stfluid2 stfluid3 stfluid6
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stfluidb stfluidc1 and stfluidinit which contain the thermodynamic properties for the new fluid and perform functions as follows. 1) stfluid0- At given temperature (t), the subroutine returns the saturation pressure (press) 2) stfluid0d- calculates saturation pressure (press) and dpdt (presdt) for a given (t) if itype = 1 or the saturation temperature (t) and dpdt (presdt) for a given (press) if itype = 2 3) stfluid1- computes the fluid thermodynamic properties as a function of temperature and quality 4) stfluid2- computes the fluid thermodynamic properties as a function of pressure and quality 5) stfluid3- computes the fluid thermodynamic properties as a function of temperature and pressure 6) stfluid6- computes the fluid thermodynamic properties as a function of pressure and internal energy 7) stfluidb- computes fluid thermodynamic properties as a function of pressure and quality where the saturation pressure has been stored in s (a matrix in tprslts.ff) 8) stfluidc1- computes the remaining saturation values needed by subroutines stfluid1, stfluid2, and stfluidb 9) stfluidinit- Initializes the fluid thermodynamic property package by acquiring space and storing limit values This module (stfluid.ff) is then placed in the envrl directory. New equations for calculating the dynamic viscosity, thermal conductivity and surface tension for the lead bismuth eutectic, the lead lithium eutectic, sodium, and lithium beryllium fluoride have been inserted into the respective subroutines viscos.ff, surftn.ff, and thcond.ff. These three subroutines viscos.ff, surftn.ff, and thcond.ff should be placed in the relap directory of the code. Sodium was inserted into the code using the fluid number 8 and it can be activated by declaring the fluid as “na” on the 120 cards. Module stna.ff in envrl subdirectory of the code contains all thermodynamic properties such as saturation pressure, specific volume, the volume expansion coefficient, isothermal compressibility, specific heat, internal energy, entropy, sonic velocity, the melting point temperature, and the critical temperature. Table 1 reports all the important parameters of Sodium which have been inserted in to the stnainit subroutine of stna.ff. This work also includes the implementation into the code of Lyon’s heat correlation for tube flow and Mikityuk’s correlation for tube bundle flow. The user needs to create separate heat transfer correlation subroutine for each alternative fluid; the subroutine name has the convention of htrc(fluid number).ff. For example, Na has fluid number 8 in RELAP/SCDAPSIM/MOD4.1, so its heat transfer correlation subroutine is named htrc8.ff. These htrc(no.).ff subroutines contain all correlations for each alternative fluid and users can use existing subroutines, such as htrc8.ff, as a guideline when creating a new fluid heat transfer correlation subroutine. For the alternative fluid heat transfer correlation subroutines, option 63 is enabled for code testing. This change allows RELAP to recognize and implement this option without giving error messages. 2.1
Thermodynamic, Transport Properties and Critical Constants
These properties were selected from the open literature and are used by other thermal hydraulic codes such as TRACE, SAS-SFR, RELAP5-3D, SIMMER-III and ASTEC for SFR applications. 140-4
The critical parameters for Sodium are reported in Table 2. The required thermodynamic and transport properties are reported in Table 3 and the incorporated heat transfer correlations are presented in Table 4. The focus of this study was to insert the correct set of the properties and critical constants for Sodium into the code and verify them using a simple pipe (three components) problem with pressure and temperature conditions typical of those used for SFRs to confirm the temperature dependent property correlations show the intended behaviour and have been properly inserted into the code. Table 2: Important parameters of Sodium [5, 6, 7] Parameter Tc (K) Pc (MPa) Vc(m3) ρc(kg/m3) Zc TM (K) TB (K) M (kg/mol)
Sodium 2503.7 25.64 0.104499×10-3 220 0.129 371 1155 22.9898×10-3
Table 3: Correlations for thermodynamic & transport properties of liquid Sodium Parameter Density [5]
correlation ρl = 1011.8 − 0.22054 ∗ T − 1.9226 ∗ 10−5 T 2 + 5.6371 ∗ 10−9 T 3 kg/m3
Vapor pressure[6]
ln P = 11.9463 −
Specific volume Specific Heat [5] Thermal expansion coefficient [7] Sonic velocity [6] Isothermal compressibility Total Internal energy [5] Change in Entropy [5] Thermal conductivity [6] Dynamic viscosity [6] Surface tension [6] Heat of vaporization [7]
12633 .73 T
− 0.4672 ln T MPa
v = 1 [ρl ] cp = 1646.97 − 0.831587 ∗ T + 4.31182 ∗ 10−4 T 2 J/kg.K 1 β = 4316 −T K-1
Applicability 373
