Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

5% Gd rodlet, ramped with 12 h hold time, has

been examined in LOM and the results have been

compared with results from the father rod and to

the results from a rodlet, which was ramped without

hold time. The results were presented at the

November 2011 meeting, and have been reported.

Two additive rods, ramped and examined in 2003,

have been subjected to additional DE, and the

results were presented in the June 2012 meeting.

The results will be reported in 2013.

Two MOX rods, ramped and examined in 1993

have been presented in the meeting November

2012.

Old results from three so called Bump tests from

the 80’s and 90’s were presented in the meeting in

November 2009 and the reports have been issued.

Subtask 1:5 Modelling workshop

The modelling workshop planned to be held in year

five, was discussed in the June meeting year two,

in the November and June meetings in year three,

Subtask 1:6 Conclusions

No activity during year three.

Task 2: Pellet Cladding Interaction

(PCI)

Subtask 2.1 Chemical pellet properties

The main objective of this subtask is to map the

chemical differences between different pellet types

that may be of importance for the PCI behaviour as

a function of burn-up.

Subtask 1:2 Ramp testing of rods

The three rodlets within subtask 1:2 were tested

in December 2009 (year one). The results have

been presented at SCIP II meetings and they are

reported.

Subtask 1: 3 Ramp testing of rods

Subtask 1:3 includes five rods:

Standard and additive rods at two burnup levels

of about 50 and 58 MWd/kgU. The rods were

ramp tested in year two, and the PIE has been

performed in year three.

2% Gd rod with burnup around 53 MWd/kgU.

The rod was refabricated in year two, and it was

ramp tested in year three. The PIE will be performed

in year three and four.

PIE of the father rods has been performed earlier

in bi-lateral projects.

Subtask 1:4 Ramp testing of rods

Rods with high density pellets and with a burnup

of about 69 MWd/kgU were refabricated in year

two, and ramped in year three, one with a short

holding time and the other with long holding

time. PIE will be performed in year three and four.

PIE of the father rods has been performed earlier

in bi-lateral projects.

The last two rods in Task 1 are two segment rods

with Cr additives irradiated to a burnup of about

27 MWd/kgU. One rodlet will be ramped with

short hold time and the other with long hold time.

The ramp testing has been performed in December

2012, and the PIE will be performed in 2013

(year four). A sibling segment representing the fuel

before ramp will be examined in late 2012.

Subtask 2.1.1 Microscopic examination of

fuel pellets before and after ramp tests

During the second year, SEM-EPMA has been performed

on samples from rodlet WaH and WsH

after ramping. The SEM-EPMA results from the

WaH sample before ramping showed that Cs was

increasing towards the periphery and that the

(Al+Cr) agglomerations did not trap Cs.

The preparations for the TEM examinations to be

performed at NFD are ongoing. During the SCIP II

autumn meeting 2012, initial results from the precharacterization

and FIB sample preparation have

been presented.

Subtask 2.2 The effect of local stresses

The objective of this subtask is to compare the PCI

behaviour of cladding materials with uniformly distributed

stress versus locally enhanced stress. This

is achieved by performing mandrel testing using

different crack patterns (similar to the pattern in

the pellet) of the ceramic insert and by modelling

the local stresses created in the cladding during

testing by means of finite element modelling or

Electron Back-Scattered Diffraction (EBSD). The

modelling of the mandrel tests is mainly performed

by CEA.

In order to study the effects of different ceramic

geometry, test campaigns were performed using

identical test conditions but two different types

of ceramic inserts, 4-notch ceramics and 16-notch

ceramics. The two test campaigns were performed

on non-irradiated Zry-4 cold-worked stressrelieved

material at a temperature of 350 °C, and

constituted of mandrel tests interrupted a various

diametrical strains (0.6%, 1% and 2%).

ENSI Erfahrungs- und Forschungsbericht 2012 125

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