Status of HTGR Research and

Development in South Africa Dr Vishnu Naicker

Snr. Lecturer, School of Mechanical and Nuclear Engineering

North-West University

Meeting of the Technical Working Group on

Gas Cooled Reactors (TWG-GCR)

25 – 27 February, 2015

IAEA

Vienna, Austria

Introduction

• PBMR

• Steenkampskraal Thorium Limited

• North-West University

PBMR: Background

• During the second half of the 1990s the South African

utility Eskom embarked on a feasibility study regarding

the possible development and demonstration of the

Pebble Bed Modular Reactor (PBMR)

• The design is a refinement of an earlier established high

temperature reactor technology.

Work Completed

• A detailed technical and economic feasibility study has been completed

• A business case, based on scenarios of local and international market

penetration, has been completed.

• Initial licensing studies have been performed by the National Nuclear

Regulator.

• A comprehensive environmental impact assessment (EIA) and public

participation process were undertaken for a PBMR demonstration plant

on the Koeberg site and a pilot fuel manufacturing plant at Pelindaba,

including the transport of imported low-enriched uranium from Durban

to Pelindaba and fresh fuel from Pelindaba to Koeberg.

• The company has documented the considerable intellectual property

and expertise developed in the project after termination of the funding

of the project by the South African government in 2010.

• The company has also developed strategies for the preservation of this

body of knowledge for use in the future.

Current Status of Project

• PBMR is currently in a state of Care and Maintenance.

• The mandate of PBMR is to: – Preserve PBMR as a legal entity,

– Preserve the PBMR Intellectual Property,

– Preserve certain licenses,

– Preservation and/or disposal of research assets in conjunction with the

Department of Public Enterprises,

– Ensure that PBMR remains a going concern given the available funding,

– Ensure compliance with relevant legislation,

– Ensure that PBMR is integrated into the Eskom Governance structures

and monitored, in accordance with agreements on this matter with

Eskom,

– Prepare PBMR to be in a defined state: this state and time to it being

achieved, being defined for the Company as per the guidance obtained

from the Minister of Public Enterprises.

Future of PBMR

• The future of PBMR remains unclear.

• A Cabinet decision on the future of PBMR post care and

maintenance is required.

• To that end, the Department of Public Enterprises has

been engaging with relevant South African Government

departments on the possible options for PBMR, the

outcome of which will be submitted to Cabinet for

approval

• The report “The status of Pebble Bed Modular Reactor

(SOC) LTD” is made available for those who wish more

information.

The HTGR (High Temperature Gas Reactor) Initiative in South Africa

by

HTGR Initiative in RSA by privately owned company STL

• STL has built up a technical team for Reactor Design, Fuel Development/Manufacture as well as Reactor and Fuel Plant Design and Construction.

• 3 Years of engineering done on a 25MWth as well as a

100MWth HTGR called High Temperature Modular Reactors (HTMR100 & HTMR25).

• Marketing is being preformed in various countries • Objective is cleaner, safer, sustainable nuclear power

HTMR100/25 Reactors

Power (Thermal) 100MW / 25MW

Pressure 40 bar

Reactor Outlet Temperature

750 °C

Power Conversion Steam Cycle

Product Heat and/or Electricity

• The HTMR100/25 is a pebble bed reactor • Once Through Then Out (OTTO) fuel cycle • Passive safety features • Helium cooled core • Power output HTMR25 – up to 30 MWth • Power output HTMR100 – up to 130 MWth • Different fuelling options from LEU to LEU/Th as well as Pu/Th

Application/ Status

Application 1. Electricity production (Rankine cycle) 2. Process heat applications (low and high temperature applications) 3. Co-generation 4. Buildings above/below ground for safety 5. Single/multi-units

Status 1. Conceptual design completed 2. Preliminary analysis (neutronics, Thermo-hydraulic) completed 3. All systems and interfaces defined 4. Plant layout(main components, positioning and zoning completed) 5. Costing completed 6. Plant description completed

Crane

Reflector rod drive

mechanisms

Reactor unit

Citadel

Steam generator Spent fuel cask

Core unloading

Machine (CUM)

Reactor Building

Plant Layout (Multi Module) ; Sub-ground level

North-West University

• Mainly driven by student projects

• International projects

– Archer Project

– Korean collaboration on HTRs

– IAEA CRP on UA analysis

• Specific fields of interest

– Pebble bed neutronics

– Pebble bed heat transfer

– Prismatic block heat transfer

M.Eng: K Sehoana

• Title: Simulation of natural circulation in an air-cooled Reactor Cavity

Cooling System using Flownex.

• Supervisor: Prof P.G. Rousseau

• Co-Supervisor: Prof C.G. du Toit

• Scope:

– Three Flownex® models of air-cooled RCCS system developed (i.e.

single, double and quad loop).

– Steady state simulation of RCCS system at (T_RPV = 250°C and

T_RPV = 350°).

– Used the Flownex® RCCS models to simulate selected operational

scenarios (i.e. Flow reversal, pipe breaks and pipe blockages) in the

RCCS.

Outcomes

• The major findings are:

– Radiation heat transfer dominates in the reactor

cavity.

– The RCCS carries with it enough heat to the ambient

such that the concrete wall temperature is maintained

below the benchmark value of 65°C.

– RCCS remain functional for very high blockage ratios

and pipe breaks. All riser pipes must have blockage

ratio of 95% for the temperature of the concrete wall

to reach 65°C

– Flow reversal can be experienced in the RCCS,

increasing the temperature of the concrete wall to

65°C in 17 hours.

M.Eng: M de Beer

• Title: Characterisation of thermal radiation in the near-wall region of a

packed pebble bed

• Supervisor: Prof P.G. Rousseau

• Co-Supervisor: Prof C.G. du Toit

• Scope:

– Development of a methodology that can be used to:

– Obtain experimental data of the heat transfer through the near-wall

region of a packed pebble bed at very high temperatures.

– Calculate the effective thermal conductivity from the experimental data

including a comprehensive uncertainty analysis.

– Development of a CFD model that can be calibrated with the

experimental data.

– Calculation of the effective thermal conductivity for the CFD simulations.

– Separate the radiation and conduction components of the effective

thermal conductivity with the use of the CFD model.

Methodology

• Use the newly constructed Near-wall Effect Thermal

Conductivity Test Facility (NWETCTF) to perform the

experimental tests and obtain the experimental data.

• Generate a numerically packed pebble bed with the

DEM model of STAR-CCM+.

• Setup of CFD heat transfer simulations done in STAR-

CCM+.

NWETCTF test section

NWETCTF vessel & test

section

NWETCTF packed pebble bed

(top view)

M.Eng: P.Sambureni

• Title: Thermal fluid network model for a prismatic block in a gas cooled

reactor

• Supervisor: Prof C.G. du Toit

• Co-Supervisor: Prof P.G. Rousseau

• Scope:

– Development of a methodology that can be used to:

• develop a thermal-fluid network model for a prismatic block in a gas

cooled reactor using Flownex.

• Model conduction and convection in the radial and tangential

directions as well as convection at the bypass gap.

• Model the steady state as well as transient states

– Validate models using a CFD code STAR-CCM+, which is used as the

experimental set up.

M.Eng: S.N. Khoza

• Title: Characteristic behaviour of Pebble Bed High

Temperature Gas-cooled Reactors during water ingress

events

• Supervisor: Dawid E. Serfontein

• Co-supervisor: Frederik Reitsma.

• Presented paper at 7th International Topical Meeting on

High Temperature Reactor Technology HTR2014,

Weihai, China, October 27-31, 2014, Paper nr.

HTR2014-51126

Research Aims

Posed as the following questions:

• How will the reactivity of each of the reactors be

influenced by water ingress into the fuel core and

reflectors?

• What are the mechanisms that drive these reactivity

changes?

• How can the designs of these reactors be modified to

eliminate undue risk from water ingress?

Model

PBMR 400MW VSOP model

0

250

500

750

1000

1250

1500

1750

0 50 100 150 200 250 300

Radius

Axia

l h

eig

ht

Void

Shutdown

System

Borings

Control Rod

Borings in the

Side Reflector

Annular Core (85 cm)

with Pebble flow

channels (1 - 5)Fixed

Central

Reflector /

Column

(100 cm)

Side Reflector

(90 cm)

Bottom Reflector

Top Reflector

1 2 3 4 5

Side Reflecor

Region with

He Inlet Riser Tubes

Bottom Conus

(3 Defuel chutes)

Conclusions

• The details of the mechanisms and effects of water

ingress on the reactivity of the PBMR-400 MW and

PBMR-200 MW reactors were investigated.

• The present simulation approach and results were partly

successfully validated and verified against simulations

results from the literature.

• Preliminary explanations of many unexpected results

were offered, but more detailed studies will be required

in order to obtain more accurate explanations.

M.Eng: G.A.Richards

• Title: The influence of thorium on the temperature

reactivity coefficient in a 400 MWth pebble bed high

temperature plutonium incinerating reactor

• Supervisor: Dr Dawid E. Serfontein

• Presented paper at the 7th International Topical Meeting

on High Temperature Reactor Technology HTR2014,

Weihai, China, October 27-31, 2014, Paper nr. HTR

2014-51384.

Aims

1. To further scientific research on the potential for high temperature reactor technology to contribute to satisfying increasing energy demand

2. To create a conceptual fuel design for the incineration of plutonium from the spent fuel of pressurised light water reactors for the PBMR DPP-400 that is potentially licensable

Results

Addition of Thorium

Causes Negative

UTC

Negative UTC

Achieved by more

Pu only

Results

High mass loading causes lower

thermal flux

Low thermal fluxes negate the

positive cross-sections of the Pu

isotopes

High mass loadings are safe

Conclusions

• A fuel design containing a mixture of thorium and plutonium was created that achieved a negative maximum UTC

• A fuel design containing 12 g Pu(PWR), without any Th, achieved a negative maximum UTC and met all the other PBMR safety limits.

• This fuel design produces double the burn-up of the proposed PBMR DPP-400 LEU fuel and may possibly be commercially viable.

• The mass of plutonium in the spent fuel is high possibly

raising proliferation resistance & waste disposal

concerns

Kaeri/NWU collaboration

• Kaeri/NWU research collaboration on the air-cooled RCCS

system analysis.

– GAMMA+ and Flownex codes are used in the analyses of the air-

cooled RCCS system.

– Presented joint paper at IHTC15, Kyoto, Japan, 8 – 12 August 2014.

– Submitted joint full-length paper to Nuclear Engineering and Design.

Kaeri/NWU collaboration

• Findings

– Radiation heat transfer comprises the bulk of the total rate of heat

transfer.

– It is possible to obtain a negative flow through the RCCS.

– The results show good comparison between the two codes.

– RCCS remain functional for very high blockage ratios supporting the

safety case.

IAEA CRP on UA

• Signed contract with IAEA for be part of the Coordinated

Research Project (CRP) I31020: "High Temperature Gas Cooled Reactor Physics, Thermal-Hydraulics and Depletion Uncertainty Analysis"

• Attended Second Research Coordination Meeting on

High Temperature Gas Cooled Reactor Physics,

Thermal-Hydraulics and Depletion Uncertainty Analysis,

2 to 5 December 2014, IAEA, Vienna

• Research Team

– Dr. V Naicker

– Prof CG du Toit

– Prof PG Rousseau (Advisory Capacity)

– D Maratele (M.Sc.)

– S Khoza (Ph.D)

– J S Matshobane (M.Sc.)

Work Schedule: 2015

Jan 2015 – Jun 2015 Jul 2015 – Dec 2015

Ex I - 1A, Ex I – 1b

Neutronic Pin Cell Calculations

D. Maratele / V. Naicker

XSDRN and NEWT Models

TSUNAMI or SUSE

Ex I – 2a, Ex I – 2b

Local neutronics on Fuel Assembly

V. Naicker

NEWT and possibly NEM

TSUNAMI or SUSE

Ex I – 3A, Ex I – 3b

Heat transfer and thermal fluid study

of unit cell

V Naicker / Prof CG du Toit

Flownex

Thermal and Heat Transfer Model of

Assembly Block

Ms. S. Khoza / Prof C.G. du Toit

Adaption of model by P. Sambureni to

fit benchmark parameters

Thank you for your attention.