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IFPE/ROPE-II, PWR rod over pressure experiment from Studsvik

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Program name Package id Status Status date
IFPE/ROPE-II NEA-1723/01 Arrived 14-APR-2008

Machines used:

Package ID Orig. computer Test computer
NEA-1723/01 Many Computers
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The STUDSVIK ROPE II Project was an internationally sponsored research program, with the aim of studying the performance of PWR fuel rods with an end-of-life rod internal pressure exceeding the system pressure.


The project focused on clad creepout as a function of overpressure, time dependent changes in the fuel rod thermal conductance (in particular behaviour possibly indicating 'clad lift-off'), and general performance during extended operation with rod overpressure.


A Siemens-KWU segmented rod (14x14) from the Obrigheim reactor, with a burnup in excess of 40 MWd/kg U, was made available to the Project as one set of three test rodlets (K rods). The other set of three test rods (A rods) were refabricated from an ABB Atom 17x17 rod (Westinghouse type) irradiated to a similar burnup in the Ringhals 3 reactor.


Three rodlets were 'refabricated' from the ABB Atom rod. They were filled with a simulated fission gas. For two of the rodlets the fill pressure was chosen to give high and intermediate overpressure at power. For the third rodlet the fill pressure was low giving underpressure at power. One of the Siemens-KWU segments was used unchanged as test rod. Two other segments were "refabricated" and filled with the simulated fission gas mixture to give high and intermediate overpressures.


The six rodlets were irradiated in the R2 reactor for eight cycles under typical PWR conditions. The first and the last cycles were used for noise measurements. The six intermediate long term cycles were the main part of the experiment for studying possible changes in the fuel rodlets due to operation with high inner overpressure. The cladding diameter changes were monitored by profilometry in the shutdowns between the 18 day operating cycles.


After the irradiation nondestructive and destructive examinations were performed on the rodlets in order to see if the R2 irradiation had resulted in fuel or clad changes. The major results were:

  1. The experiment was successfully performed as planned in its entirety.

  2. There was no fuel rod failure.

  3. Good overall performance of fuel and cladding during extended overpressure operation was shown by detailed PIE.

  4. Clad creepout was measured corresponding to rod overpressure.

  5. Although the clad creepout exceeded the pellet diameter increase expected due to solid fission product swelling there was no indication of a decrease in the gap conductance in the overpressure rods.

  6. The clad creepout did not influence the fission gas release during the R2 irradiation.

  7. Mechanical contact between fuel and cladding was maintained during overpressure operation at a constant LHR of about 20 kW/m.

  8. Some hydride reorientation in the cladding of all the overpressure rods was observed - corresponding to overpressure.

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Package ID Status date Status
NEA-1723/01 14-APR-2008 Masterfiled restricted
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NEA-1723/01, included references:
- The ROPE II Project, Summary of Data for the K-Rods (STUDSVIK-ROPE II-1,
October 1991)
- D. Schrire: Summary of Data for the A-Rods (STUDSVIK-ROPE II-3, 1991)
- K. Malen: Refabrication of A-Rods (STUDSVIK-ROPE II-5, September 1992)
- Hans Tomani, Mikael Carlsson and Karl Malen: Final Report of the ROPE II
Project (STUDSVIK-ROPE II-20, September 1995)
- Hans Tomani and Mikael Carlsson: Complementary Report on Long-Term
Irradiation Data on Rod Surface Temperatures and Cladding Neutron Dose (ROPE
II-93/7, September 1993)
- Karl Malen: ROPE II. SKIROD and TD2 Calculations - Final Report
(STUDSVIK/N(H)-95/11, 1995)
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No specified programming language
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Studsvik Nuclear AB




Compilation: J.A. Turnbull

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Base history for rods A
Base history for rods K
R2A*.his    Single zone base irradiation histories for rods A1-A3
R2K*.his    Single zone base irradiation histories for rods K1-K3
R2RA*.his   Single zone R2 irradiation histories for rods A1-A3
R2RK*.his   Single zone R2 irradiation histories for rods K1-K3
Fast neutron exposure.doc   Numerical values of fast flux and fluence during
base & R2 irradiation
PIE Measurements.doc   Summary of important PIE extracted from the Final Report
Pre-Characterization.doc    Pre-characterization data
QA report for ROPE II.doc   QA report for compiling dataset
ROPE-II Summary.doc         File summarizing the dataset
README.doc Readme file
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Keywords: data, overpressure, pressurized water reactor.