THE REPLACEMENT RESEARCH REACTOR  DESCRIPTION AND PROGRESS REPORT  PABLO ABBATE and JUAN PAI3LO ORDONEZ  INVAP SE Moreno 1089

8400 Bariloche, Rio Negro, ARGENTINA

SUMMARY. A contract for the design, construction and commissioning of the Replacement Research Reactor  was signed in July 2000 between Australia authorities and INVAP fkom Argentina. Since then the detailed design  has been completed, an application for a construction license was made in May 200 1 and granted in April 2002. The  construction and manufacturing phase is presently underway, with full operation of the facility being scheduled for

2006.

This paper explains the safely phdosophy embedded into the design together with the approach taken for main  elements of the design and their relation to the proposed applications of the reactor. Also information is provided  on the suit of neutron beam facilities and irradiation facilities being constructed. Finally it is presented an outline  of the project management organisation, project planing, schedule, licensing and general project progress.

1. INTRODUCTION

The Australian Nuclear Science and Technology  Organisation (IlwSTO) has contracted a new high  performance Research Reactor -RRR-. The reactor is  being designed and built by INVAP (Argentina) in  the Lucas Heights Science and Technology Centre,  near Sydney.

The RRR is a pool-type reactor featuring a total  fission power of 20 MW. It has a compact core of  low-enriched uranium fuel surrounded by a heavy  water reflector vessel. The reactor will be at the

bottom of a light-water filled pool that provides both  cooling and shielding to the core.  The RRR has been optimised with high priority  for beam tube experiments, and at the same time is

provided with a large amount of diverse facilities for  irradiation experiments and isotope production.  The design incorporates state of the art technology,  high neutron fluxes per unit of power, low fuel costs,  two independent shutdown systems, a passive pool  for decay heat removal, a containment system for

extreme events, and is sensible to operation and  maintenance needs.  The paper first presents a key to the core and plant  design, with details on the neutron beam facilities and  irradiation facilities as well as information on safety  features, safety assessment and licensing. Finally

some aspects of project organisation, planing,  delivery process and present project status are  presented.

2. DESIGN ASPECTS

The RRR has been designed to deliver a high thermal  neutron flux in a large volume outside the reactor  core where it is accessible for experimental use. The  concept has been to physically isolate the core from  the utilisation facilities; thus neither beams nor  irradiation facilities are located inside the core itseE.  This feature permits a better optimisation of the  neutronic performance of the core as well as it  enhances the reactor safety by preventing that beam  or irradiation activities may jeopardise the conditions  in the core fuel or control elements.

Inside the heavy water reflector that surrounds the  core and coincident with the highest neutron flux  densities, there are several neutron beam tubes, a  Cold Neutron Source and positions for material  irradiation.

Maximisation of the neutronic performance of the  utilisation facilities is in inverse proportion to the  core volume. The limit on how small the core is has  been mandated by a number

of constraints, such as:

the use of plate type fuel assemblies, the use of low  enriched uranium fuel, the target cycle length  duration, the removal of decay heat by passive means  and the use of a non pressurised primary cooling  system.

The core. The core consists of sixteen fuel  assemblies of square shape having low-enriched  uranium silicide fuel plates with aluminium cladding.

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The fuel plates incorporate burnable poisons to help  minimise the core excess reactivity along the  operation cycle. The core is cooled and moderated by  light water and features a heavy water reflector.  Fission heat is removed by water circulating through

coolant channels between the fuel plates. The reactor  core volume is some seventy litres.  Five control rods are used to control core  reactivity. Four have neutron-absorber plates inserted  into the core in a cross-shaped array and the fifth has  a central cruciform shaped absorber plate. The core is  thus divided into four portions of four fuel assemblies  each. In Table 1 are provided main reactor data and  Figure 1 shows the core and reflector arrangement.

Shutdown systems. The reactor has two  independent, redundant and diverse shutdown  systems. The sole action of any of them is capable of  shutting down the reactor and keeping it in a safe  shutdown condition during the range of accident  events and other events of interest considered in the  design.

The First Shutdown System inserts five control  rods into the core by the combined action of gravity  and compressed air when requested by the First  Reactor Protection System. During normal operation  the central control rod is used for reactivity regulation

and the other four are used for coarse reactivity  compensation, commanded by the Reactor Control  and Monitoring System.  The Second Shutdown System partially empties  by gravity the heavy water from the Reflector Vessel

into a storage tank beneath the core when requested  by the Second Reactor Protection System.  Reactor Cooling. The reactor core is cooled by  forced circulation of light water in upwards direction,

thus no flow reversal occurs in the transition from  forced circulation to natural circulation cooling  regimes. In addition other cooling systems remove  heat from the reflector heavy water and from the

irradiation rig

TABLE 1. Main Reactor Data

Fuel assembly residence

Number of plates per fuel

190 full power

8.1 m/s

Figure 1: Arrangement of Reactor Core and Reflector Vessel

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The Reactor Pool Coolant Boundary ensures  availability of the water inventory required for core  cooling during all foreseeable conditions. If normal  electric power is lost the reactor core and the  irradiation rigs are cooled by natural circulation of  the pool water. The pool has a sufficiently large water  inventory to provide long-term cooling without  reliance on external systems or sources of power.

Buildings. The facility occupies some 13,000 square  meters, which includes the Reactor Building built in  reinforced concrete housing the reactor and service  systems, the Neutron Guide Hall where the neutron

guide systems and the research equipment are  located, and some other Auxiliary buildings, Ofices  and Cooling Towers.  The Reactor Containment System encloses the  Reactor and Service Pools, Reactor Hall, and areas  below the Reactor Pool that house Reactor Pool water

systems and Reflector Vessel heavy water systems.  The Reactor Containment System  is designed to  prevent the uncontrolled release of radioactive  materials to the environment.

The facility is divided in zones considering the  different tasks carried out within the plant, and taking  into account radiation protection, fire protection and  security issues. The layout aims at providing each of  the different groups acting in the facility, (beam  users, reactor operators, reactor maintenance  personnel, radioisotope operations and visitors), with  dedicated areas and appropriate circulation paths that

allow segregation of their activities. At the same time  some strategically placed zones favor “cross  breeding” between these groups to provide  integration.

3, SAFETY PHILOSOPHY

The overall safety objective for the RRR is to protect  individuals, society and the environment by  establishing and maintaining an effective defence  against radiological hazards.

Good design practice and construction, including  the use of appropriate codes and standards and a  quality assurance program, will ensure reactor safety  for normal operation and anticipated abnormal  events.

A thorough and comprehensive design together  with operating procedures for the reactor will ensure  that radioactive releases and the resultant radiation  doses are as low as reasonably achievable. The

defence in depth strategy has been followed in the  design of the RRR to compensate for potential human  and mechanical failure and unexpected occurrences.  Abnormal events are prevented, then mitigated, then

accommodated, in that order; and a series of barriers  will prevent, reduce or slow down releases of  radioactivity into the environment.  The facility meets the regulatory requirements of the  Australian Radiation Protection and Nuclear Safety

Agency (ARPANSA) and complies with applicable  International Atomic Energy Agency (IAEA)  guidelines and recommendations. Safety Concept. The safety concept of the RRR is  based on the provisions for shutting down the reactor

under all circumstances and the prevention of fission  product releases by means of successive physical  barriers, namely fuel matrix and cladding, pool water  and reactor building. Even in the highly improbable

failure of the fuel, the reactor pool water will retain a  large portion of the fission products and the rest will  be retained by the containment system.  Engineered Safety Features are provided which

are capable of maintaining the reactor in a safe  condition under all anticipated conditions. They  constitute the third level of “defence-in-depth’ and are  designed to prevent incidents from developing into

accidents. They comply with fail-safe and reliability  safety criteria.  The design incorporates many safety features and  inherent safety characteristics. These include:

a) The ability to cool the reactor by use of natural  circulation cooling in the event of loss of normal  cooling.  b) The lack of dependence on normal power supplies

to shutdown and cool the reactor.  c) The two diverse and independent shutdown  systems. Each employing its own triplicated  sensors, logic and actuators.  d) The large volume of low pressure and low

temperature water contained in the reactor pool  acts as  a heat sink for every relevant accident  scenario, this together with the core enclosure and  its dedicated Emergency Make Up Water System  (EMWS) render negligible the risk of “fuel  meltdown” due to exposure to air.  e) An energy management system that ensures that

the pressure in the containment remains negative  during accident scquences.  f )  The levels of protection against loss of coolant  accidents.

g) The ability to withstand a 1 in 10,000-year  seismic event and beyond and the grille protection  against aircraR crash.  h) The low generation of gaseous radioactive

emissions due to the use of water cooling of rigs,  nitrogen in the pneumatic systems, helium  systems in high dose beam areas and a hot water  layer at the reactor pool surface.

Safety Assessment. The analysis used both  deterministic methods and a level 1 probabilistic  safety assessment. A deterministic analysis of the  behavior of the reactor and associated systems  following a comprehensive range of identified Design  Basis Initiating Events was performed All cases

analysed have been conservatively assessed with an  assumed single failure of the protectiodshutdown

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systems. The failure of one shutdown system and the  need for a reactor shutdown by the second acting  signal have also been assessed. The numerical  calculations show that the reactor goes through a

series of safe states following the occurrence of a  Design Basis Initiating Event. No signficant core or  rig damage occurs in any of the assessed transients.  The assessment of individual safety systems was

done by means of Failure Mode Effect Analyses.  The core damage frequency of 4x  1 OW7 per year  fully complies with regulatory limits and the selected  bounding sequences are well below the frequency-

dose acceptance curve.

4. NEUTRON BEAM FACILITIES

Beams of neutrons, originated in a cold and a thermal  neutron source placed in the high-density neutron  areas of the Reflector Vessel, are guided to  experimental stations outside the reactor core, where  they are used as p o w e h l  probes of materials.  Neutron super mirror guides are used to transport in

efficient manner neutrons to the research instruments  located in the Reactor Beam Hall and the Neutron  Guide Hall.  ANSTO is looking forward to incorporate in the  RRR a suite of neutron instruments to provide  Australia with state of the art capabilities for research

in wide ranging fields of science and engineering.  The cold neutron source, which is a key element of  many facilities around the world, will open new fields  of research for Australian scientists.

The buildings that support these facilities  comprise:

a) The Reactor Beam Hall (RBH)-an area in the  reactor building that accommodates the neutron  beam instruments that need to be as close to the  reactor as practicable.  b) The Neutron Guide Hall (NGH) -An area

adjacent to the reactor building that

accommodates the majority of the neutron beam  instruments, workshops, laboratories, ofices and  a viewing gallery.  Cranes in the RBH and the NGH, air conditioning  and ventilation systems and other services support  these facilities.

Cold Neutron Source. The 1 iquid Deuterium type  Cold Neutron Source is located close to the peak  thermal flux in the Reflector Vessel. It has a  maximum neutron yield with energy less than 5 meV,

an operating temperature below 25 K, and serves two  neutron beam assemblies located on opposite sides of  the Reflector Vessel. The cold neutron flux at the  performance measurement locations at the reactor  face will be of the order of 1 .4x1Oio n cm-'s-' and at

the performance measurement locations in the NGH  will be of the order of 2 . 7 ~  1 O9 n cm-2s-',

The Cold Neutron Source cooling system

is a double-

wall liquid helium design that promotes reliable and  safe operations. Both the Cold Neutron Source  cooling system and the reactor are capable of  operation if the other is shut down. Postulated failures  of the cold source do not affect reactor safety. The  cold source is automatically monitored and controlled  by the Cold Neutron Source Control System.

Thermal Neutron Source. The thermal neutron  source comprises a heavy water zone located close to  the region of peak thermal flux in the Reflector  Vessel and serves two neutron beams located in

almost opposite directions and tangential to the core.  The nominal thermal neutron flux at the performance  measurement locations at the reactor face will be  higher than 1 . 6 ~ 1 0 ' ~  n cm.'s.' and at the performance  measurement locations in the NGH will be higher  than 1 .6x109 n cm.' s-'. The neutron spectrum has a  temperature in the range from 40Â°C to 60Â°C.

Not Neutron Source (future). On the centre of one  of the core faces a place has been reserved for the  future installation of a Hot Neutron Source FINS).  The envisaged IHNS design would be based on a

Graphite block heated by radiation coming from the  core. It is foreseen that the HNS will operate at a  temperature close to 1800 "C. One neutron beam,  tangential to the core, originates at the position  reserved for the HNS. While the HNS is not installed,

the beam will be used as an additional thermal beam.

Neutron Transport Systems. There are five neutron  beam assemblies leaving the reflector vessel in a  tangential arrangement with respect to the core. Two  neutron beams deliver neutrons towards the NGH

(one thermal and one cold beam) placed north with  respect to the Reactor Building. The neutron beam  serving the future HNS is directed into the RBH in  West direction. The remaining two neutron beams  (one thermal and one cold) leave the reactor in South  direction. The facility layout allows for the fbture  construction of a second Neutron Guide Hall on 'the  South of the Reactor Building. Except for the I-INS  beam that caters for two neutron guides, all the other  beams have capacity for three neutron guides each of  them.

The neutron beams leave the reflector vessel,  traverse the reactor pool liner and the shutters  embedded in the reactor block. The shutters contain  sections of neutron guides that penetrate the block for  maximising the neutron transport from the core to the  experiments.

Neutron supermirror guides are built by sputtering  multiple successive layers of titanium and nickel on  glass slabs. The guides feature a critical angle of two  and three times that of nickel. Guides are contained

inside a vacuum housing to ensure optimum  transmission and alignment stability.

5. IRRADIATION FACILITIES

Radioisotopes are produced by introducing targets  into dedicated irradiation positions in the reflector  vessel. Numerous irradiation positions are provided  in the reflector tank, some are water-cooled and other

are served by pneumatic transport systems. Facilities  for irradiation of Silicon ingots for NTD and several  hot cells are also provided.

General Purpose Irradiation Facilities. They  comprise f i  tubes that run from two pneumatic  transfer hot cells to locations in the reflector vessel  having neutron fluxes ranging from 2 . 4 ~ 1 0 ' ~  to 1 .0 x

1 O J 4  n cmT2 s-'

Target materials are loaded into aluminium or  titanium containers and are transferred to the  irradiation positions in the reflector by nitrogen.  There they can remain for period ranging from

seconds to weeks. The nitrogen gas is used both for  transport and cooling and consequently targets are  limited to those that can be adequately cooled by the  nitrogen gas.

Bulk Production Irradiation Facilities. They  comprise seventeen irradiation tubes running  vertically through the reflector vessel. They are  water-cooled. Irradiation rigs, which can be removed  with the reactor at power, will accommodate up to  five target cans and have a cooling capacity of

125KW. Thcy will be used primarily for the  irradiation of low enriched uranium for the  production of Mo-99, tellurium dioxide for the  production of 1-131 and iridium metal for the

production of Ir-192.

Large Volume Irradiation Facilities. They  comprise several irradiation tubes in the reflector  vessel that will be used to irradiate mineral and other  samples mainly for the minerals industry, and for the  neutron transmutation doping of single crystal silicon  ingots for the electronics industry. To ensure  irradiation homogeneity within the Silicon ingots,  they are provided with neutron flux flatteners and are  rotated by means of a hydraulic system.

Neutron Activation Laboratory. A laboratory has  been provided in the reactor building for the analysis  of samples that are irradiated in large pneumatic  conveyor irradiation tubes for only a few minutes.

They travel from the reactor to the laboratory in 3  seconds for immediate analysis of the very short  activation products.

Neutron Transmutation Doped Silicon  Laboratory. This laboratory is provided for the  post irradiation scanning, cleaning and packaging of  the silicon ingots.

Shielded Hot Cells. The facility is provided with  four shielded hot cells to allow safe and efficient  handling of the radioisotope targets and their delivery  to the ANSTOs adjacent radioisotope processing  facilities. The irradiated targets are handled as sealed

sources within the RRR. The total system is designed  for the minimum involvement of staff, and for the  minimum exposure of those staff that are involved to  radiation from the targets being transferred. The

design is particularly successful in this latter regard.  Two Pneumatic conveyor hot cells are provided  for the transfer of targets from the irradiation tubes to  the radioisotope production buildings. This is

achieved either via a further pneumatic conveyor  system or via the transfer of the targets to the  Loading hot cell in a lower level and hence via on  site transport containers.

An additional isotope Transfer hot cell is provided  for the unloading of the bulk irradiation rigs and for  the transfer of the targets removed to the Loading hot  cell.

6. PROJECT MANAGEMENT AND  ORGANIS ATION

The construction of the RRR represents an important  undertaking for INVAP and Australian private  companies. Expertise is drawn from INVAP seasoned  management and design teams and from strategic

associations with the PNPI (Russia) and

MIRROTRON (I-Iungary) for the Cold Neutron  Source and the Neutron Guides respectively. INVAP  is responsible for the overall delivery of the project  that involves the co-ordination of a team of some

twelve companies all around the world.  A Project Management Plan (PMP) establishes the  overall organisational grounds, responsibilities and  links between all the parties participating in the

project. The PMP is the key to other general and  phase specific plans that are the basis of the project  management effort. The project is run under an I S 0   9000 certzed system, covering design as well as

construction activities.  Communication and reporting to the client is done  on a regular basis allowing a close control of the  project progress and status.

Planning and Schedule. The project schedule for  the RRR has a duration of 66 Months. The project is  organised through a Work Breakdown Structure  (WBS) with more than 200 work packages that cover  the different phases: Launching, Preliminary  Engineering, Detail Engineering, Construction,  Manufacturing and Procurement, Installation, R e -

operational Testing and Commissioning.  The Project Master Schedule (PMS) shows the  time frame and precedence for the execution of the  different work packages and is an important tool in  the planning and control ofthe project.

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The contract for the design, construction and  commissioning of the Replacement Research Reactor  was signed in July 2000. This was followed by the  completion of the detailed design and an application  for a construction license was made in May 2001. In

Table 2 are indicated the main project milestones.

Milestone

Risk Management. A Risk Analysis and  Management Plan is run to control, have early  warning and allow development of contingency plans  to address any technical, organisational or  commercial issue that may threaten the project

schedule, budget or quality of the final product to be  delivered. Relevant actions are taken as to provide  early detection of any significant change in the risk  levels, detect new risks and ensure that tasks and  measures are in place to keep risks under control.

Time since project  start date

TABLE 2. RRR Project Milestones

Contract signature 0 month

Presentation of PSAR 10'" month

Construction starts 2 1 * month

Construction and 55 th month

installation complete  Nuclear commissioning 6 1 '" month  comnlete

Local Industry Participation. While INVAP has  the overall responsibility for the delivery of the  project more than fifty per cent of the RRR project  will be sourced from Australia. To this end INVAP  formed an alliance with John Holland and Downer  RML for the delivery of the project. These Australian

companies have participated in the project since the  tender and they are responsible for half of the project  work packages encompassing engineering,  construction, installation and preoperational testing

activities.

Client Participation. ANSTO is provided visibility  over all the project activities. During design it has  participated actively as part of the design teams and  in formal design review meetings, during

construction it will control the activities by mean of  witness and nominated hold points indicated in the  Construction Inspection Test Plans.

7. LICENSING

As usual with nuclear project, a careful planning and  preparation of the documentation for submitting to  the Regulator in order to obtain the required licences  is essential for ensuring the success of the project.

Supporting the request for a Licence to start the  construction of the facility, a comprehensive  Preliminary Safety Analysis Report (PSAR) was

prepared at the Preliminary Engineer stage.  The development of the PSAR involved

INVAps

multidisciplinary staff in addressing in a

comprehensive way the facility systems and their  safety analysis and evaluation. The PSAR was  prepared in accordance with the I M A  Safety Guide  SS 35-G 1 "Safety Assessment of Research Reactors

and Preparation of the Safety Analysis Report" 1994.  The PSAR was thoroughly reviewed by ANSTO,  before submitting it to the regulatory agency,  ARPANSA.

ARPANSA reviewed the document, using when  required the assistance of international experts, and  the Licence for Construction was granted in April  2002.

ARPANSA regulations, through Regulation 54,  also require the Detail Engineering of systems and  components signifcant for the safety of the  installation to be submitted to the Regulator before

starting the construction or manufacturing of such  items. This process has require a significant  dedication from all the parties involved, as it means  that ANSTO has had to submit more than eighty five  Request for Authorisation to ARPANSA. Each of  these requests involves a significant number of  documents, which have to be prepared and presented  to ANSTO by INVAP, while ANSTO has to review  and accept the documents and submit them to  ARPANSA with the documentation substantiating the  Request for Authorisation. ARPANSA has then to  review the presentation, and after making the relevant  comments and asking for clarifications, issue the  permit for manufacturing the corresponding item,  component or system once they have satisfied  themselves that the design complies with the safety  requirements.

The close co-operation between INVAP and  ANSTO has made  it possible for this complex  process to work. The quality of the original

documentation and the completeness of the  presentation, addressing every issue, have been  fundamental for achieving until now more than eighty  approvals from ARPANSA.

Presently ANSTO and INVAP are delineating the  process for the submission of the presentation  supporting the request for a Licence for Operation for  the facility.

8. PROJECT STATUS

We are now in month 39 after the signature of the  contract. The project has achieved more than 50%  progress. There have been three causes of significant  delays:

* The programme allowed for nine month between  the presentation of the PSAR and the issue of the  Licence for Construction; eleven months passed  between these milestones.

During the excavation, a fault was found that

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could not immediately be ruled as inactive; the  fault had to be dated, and it was shown to have  moved for the last time at least several millions  of years ago; dating the fault an proving the case  to the satisfaction of the Regulator cause a  further four months of delay.  The Reg 54 process has caused some delay in  the start of the manufacturing of some  components in the critical path of the project.

a

Although these delays mean that the original  contracted date is probably not achievable, the project  is moving forward at a very good step, and several  significant milestones have already been achieved.  First concrete was achieved the first of November of  2002, and one year later the progress in the  construction of the buildings is 60%, while the  manufacturing and procurement is 55%. The

construction and manufacturing phase will be

finishing by mid next year, most of the installation  phase will be finished by early  2005, commissioning  the facility will take up most of 2005 and the reactor

will fully be operational in 2006.

9. CONCLUSIONS

The reactor being constructed is a world class  neutron source of great flexibility, high productivity  and very high availability. It will sigdicantly  enhance the ability to supply industrial and medical  radioisotopes to satisfy the demand into the future.

This will be done with a reactor that has many  inherent safety features and very low levels of risk.  The project is on schedule and on budget, the  detail engineering of it is well underway and the  relevant information has been presented to the  Australian Regulator (ARPANSA) in an application  for a Construction permit.

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