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FIRE EXPOSURE TESTING OF ENCAPSULATED SIMULANT RADIOACTIVE WASTES.

Objective

IN ORDER TO ESTABLISH CRITERIA FOR THE SAFE STORAGE, TRANSPORT AND DISPOSAL OF INTERMEDIATE LEVEL WASTES A KNOWLEDGE OF THE RESPONSE OF WASTE PACKAGES TO FIRE ACCIDENT CONDITIONS IS REQUIRED.
IAEA REGULATIONS EXIST FOR TRANSPORT AND A TRANSPORT FLASK OR OVERPACK IS PROVIDED TO PROTECT THE PACKAGE FROM THE DAMAGING EFFECTS OF FIRE. THERE ARE, HOWEVER, NO SUCH REGULATIONS IN THE UK OR ELSEWHERE IN THE EC THAT DEAL SPECIFICALLY WITH SITUATIONS SUCH AS MAY OCCUR AT A REPOSITORY WHERE UNPROTECTED WASTE PACKAGES COULD BE EXPOSED DIRECTLY TO FIRES.
THIS PROGRAMME WILL PROVIDE DATA ON THE BEHAVIOUR OF TYPICAL WASTE PACKAGES IN SUCH FIRE ACCIDENTS USING FULL SCALE NON-RADIOACTIVE SIMULATED PACKAGED WASTEFORMS. INFORMATION ON THE BEHAVIOUR OF A RANGE OF WASTE TYPES WILL BE PROVIDED.
THE INITIAL OBJECTIVE IS TO IDENTIFY THE TEST CONDITIONS FOR PACKAGES, WHICH WILL ALLOW INTERPOLATION OF RESULTS RATHER THEN EXTRAPOLATION, FOR FIRES IN WHICH DRUMS OF WASTE ARE DIRECTLY EXPOSED TO A HYDROCARBON POOL FIRE, AND THOSE IN WHICH PACKAGES ARE IN THEIR TRANSPORT OVERPACKS LEADING TO SIGNIFICANTLY LOWER HEAT FLUXES.
A THEORETICAL MODEL ALREADY EXISTS IN ROUGH FORM WHICH PREDICTS WASTE FORM TEMPERATURE PROFILES AND STEAM RELEASE RATES FROM IMMOBILISED WASTE. THE RESULTS FROM THIS PROGRAMME OF WORK WILL ENABLE THE MODELLERS AT HARWELL TO DEVELOP AND VALIDATE THIS MODEL AND CONSEQUENTLY PREDICT BOTH THE GASEOUS AND PARTICULATE TRANSPORT AND RELEASE MECHANISMS FROM THE WASTE MATRIX WHICH MAY BE ENCOUNTERED IN FIRE ACCIDENT CONDITIONS.
THIS PROGRAMME IS BEING CONDUCTED IN PARALLEL AND CLOSE LIAISON WITH SMALL SCALE FULLY ACTIVE STUDIES AT AERE HARWELL UNDER CONTRACT NUMBER FI1W0176.
In order to establish storage fire accident criteria for intermediate level wastes (ILW) and develop test methods, it is pertinent to provide data on the behaviour of typical waste packages in severe fire accidents. This study seeks to provide information on the performance of a range of waste types using full scale nonradioactive simulated waste packages. The initial objective is to identify the test conditions for packages, which will allow interpolation of results rather than extrapolation, for fires in which drums of waste are directly exposed to a hydrocarbon pool fire, and those in which packages are in their transport overpacks leading to significantly lower heat fluxes. These conditions provide the experimental parameters for the execution of thermal tests to measure the performance of full scale packages.
THE PACKAGES TO BE TESTED ARE STAINLESS STEEL DRUMS OF NOMINAL 0.5 M3 VOLUME CONTAINING SIMULATED IMMOBILISED WASTE. THE DRUMS HAVE BEEN FULLY INSTRUMENTED WITH THERMOCOUPLES AND ARE VENTED, IN A CONTROLLED MANNER, IN ORDER TO STUDY ANY RELEASED MATERIAL. THE WASTES SELECTED FOR STUDY ARE:

- SHREDDED COMBUSTIBLE PCM IN PFA/OPC (RMA 11.1)
- OXIDE FUEL ELEMENT HULLS IN BFS/OPC (RMA 6).
- METAL HYDROXIDE SLUDGE IN BFS/OPC (RMA 8).
- ORGANIC/INORGANIC ION EXCHANGE RESIN IN VINYL ESTERS (RMA 4).

ONCE THE PACKAGES HAVE BEEN PREPARED THE CEMENT BASED PRODUCTS ARE ALLOWED TO CURE, UNDER AMBIENT CONDITIONS, FOR AT LEAST 90 DAYS, IN ORDER TO ACHIEVE OPTIMUM PRODUCT STABILITY. THE VINYL ESTER BASED PRODUCTS REQUIRE NO EXTENDED CURING PERIOD.

ONE OF EACH OF THESE PACKAGED WASTES WILL BE SUBJECTED TO A POOL FIRE TEST AS A REPOSITORY FIRE (BARE DRUM) AND ONE TO HEATING IN AN ELECTRIC FURNACE AS A TRANSPORT FIRE (DRUM IN A OVERPACK). MEASUREMENTS WILL BE MADE DURING ALL OF THE TESTS TO IDENTIFY THE ACTIVITY RELEASE MECHANISMS, THE ACTIVITY RELEASE FRACTION AND THE CONSEQUENCES FOR SUBSEQUENT PACKAGE DISPOSAL.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

United Kingdom Atomic Energy Authority (UKAEA)
Address
Winfrith Technology Centre
DT2 8DH Dorchester
United Kingdom