Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

Project goals

The Halden Reactor Projects research programme is

defined as framework for 2012–2014 [1] and in the

detailed plan for 2012 [2].

The main goals of the R&D work in the fuels and

materials area are to provide data on:

fuel properties needed for design and licensing of

high burnup reactor fuel

fuel response to transients, in particular on phenomena

occurring during loss-of-coolant accidents

cladding creep, corrosion and hydriding to determine

mechanisms and operational conditions

that affect cladding performance, e.g. water

chemistry issues

stress corrosion cracking of reactor materials at

representative stress conditions and water chemistry

environments for plant lifetime assessments

The main goals of the R&D work in the MTO area

are to:

provide knowledge on how and why accidents

occur, with the aim to prevent them from happening

establish empirical knowledge about human potentials

and limitations as operators in a control

room setting based on experiments carried out in

HAMMLAB and the VR Centre

develop advanced information and support systems

for use in plant optimization, operation and

maintenance

develop methods and tools to improve the dependability

of software based systems

Work carried out and results

obtained

The results from the OECD Halden Reactor Project’s

research programme are in detail reported to the

members in two annual status reports [3, 4]. Important

activities are summarised below.

Fuels & materials research

The Halden Reactor was in planned operation accumulating

about 190 full power days in 2012.

Fourteen experiments were irradiated in the HBWR

at various times as part of the joint research programme

of the Halden Reactor Project, while seven

tests were in preparation and four underwent postirradiation

examinations. The experiments comprised

studies of UO 2 fuel, additive and gadolinia

doped fuel as well as cladding and in-core materials

with various fluence levels. Many of the experiments

are carried out using pre-irradiated test

specimens of fuels and materials taken from commercial

reactors and re-instrumented at Institute

of energy technology’s Kjeller hot laboratory. This

provides the necessary realistic starting point for

experiments where fuel temperature, rod pressure,

dimensional stability, corrosion and crack growth

are being measured under representative thermalhydraulic

and water chemistry conditions.

The integral fuel performance test with Gd-doped

fuel was unloaded after seven years of irradiation.

Post-irradiation examination of the six rods has

started and will be completed in 2012.

The long-term irradiation of VVER fuel continued.

The experiment contains VVER-1000 additive fuel

with enhanced grain size (25–30 µm) and standard

VVER fuel (11 µm grain size) as reference fuel.

The test also contains fuel with 5% gadolinium.

In 2012, the large grain and reference fuels were

operated at powers of 16–18 kW/m keeping the

fuel temperature low enough to avoid fission gas

release. The current burnup is about 53 MWd/

kg oxide. The Gd-doped fuel, which has lower

enrichment and power, has reached a burnup of

23 MWd/kg oxide. Irradiation will continue in 2013.

Athermal creep of UO 2 fuel under irradiation is

studied in a dedicated experiment aiming at generating

data for improved modelling of fuel periphery

behaviour during PCMI. The test comprises standard

UO 2 fuel and commercial Cr-doped pellets.

When fuel densification was finished, axial stresses

of 30, 45 and 60 MPa were applied at fuel temperatures

of 400, 600 and 800 °C at a burnup of

about 10 MWd/kg. In 2012, the temperature and

load sequence was repeated at 20 MWd/kg. The

estimated creep rates obtained in the second period

were slightly higher than those from the first

period, and the creep rates of Cr-doped fuels were

slightly higher than those of standard fuel. However,

the differences are within the scatter of the

measurements.

A fission gas release test containing standard UO 2

fuel, Cr-doped and BeO-doped fuel is continuing.

The six rods have been operated at heat rates of

30–35 kW/m and fuel temperatures in the range

1200–1300 °C. The BeO-doped fuel, which is expected

to have higher thermal conductivity than

UO 2 fuel, shows in fact the lowest temperatures.

No fission gas release has been observed so far, and

power will be gradually increased until the fission

gas release threshold is exceeded.

Another LOCA test with BWR fuel (IFA-650.13) was

conducted in October 2012. The BWR fuel had

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ENSI Erfahrungs- und Forschungsbericht 2012

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