P. Chakrov 1), F. Arinkin 1), Sh. Gizatulin 1), R. Schultz 2), N. Mote 3), K. Alldred 3)

Abstract:
The WWR-K is a tank-type, light water moderated and cooled multipurpose research reactor with a nominal power rating of 6 MW and a peak thermal neutron flux of over 1014 n/cm2s. The reactor is operated by the Institute of Nuclear Physics of the National Nuclear Center of the Republic of Kazakhstan (INP), and is located at Alatau, near Almaty, the largest city in Kazakhstan. The reactor was commissioned in 1967 with a power rating of 10 MW, then shut down between 1988 and 1998 while seismic safety upgrades were completed. Currently, INP is undertaking the planning and technical work to allow the reactor to be converted from HEU fuel with a U-235 content of 36% to LEU fuel with a U-235 content of 19.7%. The reactor has an important role in Kazakhstan, and is producing isotopes for medical and industrial uses, providing material testing services and neutron activation analysis.

Replacement of reactor control and protection system (CPS) is a part of the wider program of the reactor modifications related to its conversion from HEU to LEU fuel, supported by the US Department of Energy, the Nuclear Threat Initiative and the Kazakhstan government. The program includes development of a new LEU fuel assembly design and re-configuration of the reactor core, with change in number and positions of the control rods, which requires modification of the CPS. Furthermore, replacement of the existing instrumentation, some of which is 40 years old, will improve reactor safety, bring the CPS up to current international standards, and provide an upgraded control interface.

The existing CPS at the WWR-K relies to a large extent on old designs of detectors and electronic equipment that are no longer in production and the system as a whole does not meet the necessary standards for prolonged operation of the reactor. Consequently, the Kazakhstan Atomic Energy Committee (KAEC), the nuclear regulatory body of Kazakhstan has mandated that the project for conversion of the WWR-K to use LEU fuel must include replacement of the CPS. By using the support services available from the IAEA for procurement of the replacement CPS, INP will ensure that the new system meets current safety standards.

Organizationally, the project will take full advantage of the assistance available from the IAEA Technical Cooperation program for the procurement of equipment and services for the replacement of the CPS at the WWR-K reactor. As a first step, INP is developing a draft technical requirements document for the new system. IAEA technical and procurement staff will work closely with the team from INP, as will the reactor designer and the funding parties in reviewing the technical requirements document for completeness and compliance with applicable safety regulations and standards. The completed technical requirements document will be submitted to the KAEC, for approval. After approval by KAEC, it will be formally submitted to the IAEA along with a request for procurement, to initiate a standard tender procedure. The contract between IAEA and the selected supplier of the replacement CPS is expected to be signed in late 2008.

Replacement of the CPS includes the following activities:

1. Replacement of the reactor power monitoring, automatic control and emergency shutdown systems based on in-core neutron flux measurements;
2. Installation of a new module for collection and processing of data from instruments measuring non-nuclear parameters. The seismic detection instrumentation will be replaced, although the existing instrumentation will be retained for measurement of other non-nuclear parameters;
3. The existing control rod drive motors will be retained but the control rod position monitoring instruments will be replaced and a new control system will be installed. The control rod position indicators on the reactor control desk will also be replaced;
4. The control desk in the main control room and all reactor operations and emergency system displays will be replaced;
5. The control desk in the stand-by control room will be replaced (including all safety system equipment, neutron flux and rod position indicators and operational controls);
6. All audible and visual warning systems will be replaced;
7. A new data management system will be installed, to provide upgraded collection, storage and processing of information on operation of the reactor and ancillary equipment, plus improved control room data readouts;
8. Provision of an auto-diagnostic system to provide pre-startup testing of the relevant instrumentation and monitoring equipment and testing of the serviceability of operating equipment.

Both to ensure maximum reliability and to simplify maintenance, the replacement CPS will, to the extent possible, be based on standard industrial controllers. Performance of the power level and rate of power increase control systems and the emergency protection system will be tested under reactor operating conditions during commissioning of the new CPS.

Procurement and installation of the replacement CPS will include the following steps:

1. development of the technical requirements document for the new system compatible with other core modifications,
2. development of the system design for the new system,
3. equipment manufacturing and factory acceptance tests,
4. installation of the new CPS at the reactor,
5. commissioning of the new CPS and staff training.

These activities will meet the regulations, technical and safety norms and standards of Kazakhstan, IAEA, IEC and other relevant bodies that set safety standards for the operation of research reactors and replacement of research reactor control and protection systems.