Analysis of void volume distribution of oxide fuel pins with high linear rod power

Technical Report · Fri Aug 10 04:00:00 EDT 1973

OSTI ID:4938202

Hoffmann, H

The aim of this work was to gain a quantitative knowledge of the void volume redistribution by measuring radial void volume profiles of irradiated fuel pins, such as porosity and crack volume, and by comparing these profiles with calculated ones. Short-term (He-Loop) and long-term irradiated pins (bundle irradiation Mol7A) were analyzed. The quantitative interpretation was done by comparison calculations with the fuel pin modeling computer code SATURN-1a. One of the features of SATURN-1a is the capability of calculating the porosity as well as the crack volume distributions as a function of time and variable irradiation conditions. The former was calculated by means of a balance of porosity migrating into and out of a ring element. The latter was computed on the basis of a multifractured fuel model. It was assumed that a multifractured fuel is formed if the thermal stresses are tensile stresses and exceed the fracture stress of the fuel. A critical literature survey confirmed that the evaporation-condensation mechanism is the main contribution to the total migrating velocity of pores larger than 10 mu m. Only this contribution was considered in the computer code and set independent of the pore radius. An additional porosity increase in the hot fuel region (T > 1700 deg C) due to fission gas swelling was computed for long-term irradiations. The comparison between predicted and measured radial porosity distributions gives the following results: the measured radial porosity distributions of the short-term irradiated fuel pins could be fitted with calculated ones, using suitable heat transfer coefficients: the measured crack volume distributions were verified by predicted profiles; the discrepancies between calculated and measured porosity distributions for high burn-ups were explained by axial material transports, prodaction or fission gas bubbles, and negative swelling rates simulating hot pressing of the outer fuel region. (auth)

• Research Organization: Kernforschungszentrum Karlsruhe (F.R. Germany). Inst. fuer Material- und Festkoerperforschung
• Sponsoring Organization: Sponsor not identified
• NSA Number: NSA-29-023505
• OSTI ID: 4938202
• Report Number(s): KFK--1863
• Country of Publication: Germany
• Language: German

Related Subjects

BURNUP
COMPARATIVE EVALUATIONS
CRACKS
FUEL PINS
LMFBR TYPE REACTORS
N77500* --Reactors--Power Reactors
Breeding
PHYSICAL RADIATION EFFECTS
PLUTONIUM OXIDES
POROSITY
POWER DENSITY
TEMPERATURE DEPENDENCE
URANIUM DIOXIDE
VOIDS