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NEA-1746 ZZ-PBMR-400.

ZZ PBMR-400, OECD/NEA PBMR Coupled Neutronics/Thermal Hydraulics Transient Benchmark - The PBMR-400 Core Design

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Program name Package id Status Status date
ZZ-PBMR-400 NEA-1746/04 Tested 26-JUN-2009

Machines used:

Package ID Orig. computer Test computer
NEA-1746/04 Many Computers PC Windows
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This international benchmark, concerns Pebble-Bed Modular Reactor (PBMR) coupled neutronics/thermal hydraulics transients based on the PBMR-400MW design. The deterministic neutronics, thermal-hydraulics and transient analysis tools and methods available to design and analyse PBMRs lag, in many cases, behind the state of the art compared to other reactor technologies. This has motivated the testing of existing methods for HTGRs but also the development of more accurate and efficient tools to analyse the neutronics and thermal-hydraulic behaviour for the design and safety evaluations of the PBMR. In addition to the development of new methods, this includes defining appropriate benchmarks to verify and validate the new methods in computer codes.
The scope of the benchmark is to establish well-defined problems, based on a common given set of cross sections, to compare methods and tools in core simulation and thermal hydraulics analysis with a specific focus on transient events through a set of multi-dimensional computational test problems.
The benchmark exercise has the following objectives:
- Establish a standard benchmark for coupled codes (neutronics/thermal-hydraulics) for PBMR design
- Code-to-code comparison using a common cross section library
- Obtain a detailed understanding of the events and the processes
- Benefit from different approaches, understanding limitations and approximations
Major Design and Operating Characteristics of the PBMR:
PBMR Characteristic          Value
Installed thermal capacity   400 MW(t)
Installed electric capacity  165MW(e)
Load following capability    100-40-100%
Availability                 >= 95%
Core configuration           Vertical with fixed centre graphite reflector
Fuel                         TRISO ceramic coated U-235 in graphite spheres
Primary coolant              Helium
Primary coolant pressure     9MPa
Moderator                    Graphite
Core outlet temperature      900 C.
Core inlet temperature       500 C.
Cycle type                   Direct
Number of circuits           1
Cycle efficiency             >= 41%
Emergency planning zone      400 meters
The PBMR functions under a direct Brayton cycle with primary coolant helium flowing downward through the core and exiting at 900 C. The helium then enters the turbine relinquishing energy to drive the electric generator and compressors. After leaving the turbine, the helium then passes consecutively through the LP primary side of the recuperator, then the pre-cooler, the low pressure compressor, intercooler, high pressure compressor and then on to the HP secondary side of the recuperator before re-entering the reactor vessel at 500 C. Power is adjusted by regulating the mass flow rate of gas inside the primary circuit. This is achieved by a combination of compressor bypass and system pressure changes. Increasing the pressure results in an increase in mass flow rate, which results in an increase in the power removed from the core. Power reduction is achieved by removing gas from the circuit. A Helium Inventory Control System is used to provide an increase or decrease in system pressure.
The benchmark is divided into Phases and Exercises as follows:
PHASE I: Steady State Benchmark Calculational Cases
Exercise 1: Neutronics Solution with Fixed Cross Sections
Exercise 2: Thermal Hydraulic solution with given power / heat sources
Exercise 3: Combined neutronics thermal hydraulics calculation - starting condition for the transients
Phase II: Transient benchmark
Exercise 1: Depressurised Loss of Forced Cooling (DLOFC) without SCRAM
Exercise 2 : Depressurised Loss of Forced Cooling (DLOFC) with SCRAM
Exercise 3: Pressurised Loss of Forced Cooling (PLOFC) with SCRAM
Exercise 4 : 100-40-100 Load Follow
Exercise 5: Fast Reactivity Insertion - Control Rod Withdrawal (CRW) and Control Rod Ejection (CRE) scenarios at hot full power conditions
Exercise 6 : Cold Helium Inlet
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Package ID Status date Status
NEA-1746/04 26-JUN-2009 Tested restricted
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NEA-1746/04, included references:
- F.Reitsma, K.Ivanov, T.Downar, Haas, S.Sen, G.Strydom, R.Mphahlele,
B.Tyobeka, V.Seker, H.D.Gougar, H.C.Lee:
PBMR Coupled Neutronics/Thermal Hydraulics Transient Benchmark The PBMR-400
Core Design, Benchmark Definition, Draft V07, to be published by OECD
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No specified programming language
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Frederik Reitsma
Reactor Design and Fuel Management Group Leader
PBMR Pty Ltd
PO Box 9396
South Africa
This information is restricted to benchmark participants.
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Records of meetings
-Proceedings of the first workshop (PBMRT1)
-Summary of the First workshop, Paris, 16-17 June 2005 (PBMRT1)
-Proposed Agenda for Ad-hoc meeting, Avignon, 13 September 2005 (PBMRT1.5)
-Proposed Agenda for  Second workshop (PBMRT2) OECD/NEA Issy les Moulineaux,
France, 26-27 January 2006
-Update concerning the Benchmark (20 October 2006)
-Proceedings of the second workshop (PBMRT2)
-Summary of the Second Workshop, Issy les Moulineaux, France, 26-27 January 2006

-Proceedings of the third workshop (PBMRT3)
-Summary of the Third Workshop, Issy les Moulineaux, France , 1-2 February 2007

-Proceedings of the fourth workshop (PBMRT4)
-Summary of the Fourth Workshop, OECD/NEA Issy-les-Moulineaux, France, 21-25
January 2008
-Proceedings of the fifth workshop (PBMRT5)
-Summary of the Fifth Workshop, Kongresszentrum, Interlaken, Switzerland, 14
September 2008
Benchmark Specification
-Updated Benchmark specifications document Draft V07 (dated 20 June 2007)
-The Simplified Cross Section Set: 'OECD-PBMR400-Simplified.XS'
-Decay Heat Values (12 December 2006)
-The multi-dimensional interpolation routine 'lint5d.for'
-Sample Excel spreadsheets to report results for steady-states and transient
cases (21 June 2007)
Latest comparisons of results of the PBMR-400 benchmark (update: 14 September
-PBMR-400 Exercise 1 comparison sheets
-PBMR-400 Exercise 2 comparison sheets
-PBMR-400 Exercise 3 and Transient Cases comparison templates
-Updated library description (Section 7 from the specification)(14 November
-Cross section library OECD-PBMR400 (21 June 2007) - Only change is in 1/v data
of void areas - was zero - now a typical value is included
-Results used in the comparisons for the 3rd workshop (PBMRT3) held on 1-2 Feb.
2007 (6 June 2007)
Action List
-Update of actions and solutions on Task list / Outstanding issues - PBMRT5
meeting (14 September 2008)
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Keywords: computational benchmark, coolants, high temperature reactors, pebble-bed modular reactor, thermal hydraulics, transients.