Measurement Value Logging and Data Analysis

During the impact of the test object, the mechanical stresses, to which the cask body is subjected, and the involved impact kinematics are investigated.

For high-level mechanical impact measurments the cask body is extensively instrumented with various miniature piezoelectric or piezoresistive accelerometers (in the left figure, using ENDEVCO and ENTRAN sensor types). Strain gauges (picture on the right) are used to determine the time dependent magnitude of any deformation as well as associated stresses.

Acceleration sensors (left) and strain gauges (right)

 

Mobile measuring station

 

Appropriate electronic devices concerning range of analogue bandwidth, sample rate, etc. are utilised to acquire, record and store data.

Additionally, the impact process is visually analysed using a high-speed camera in connection with an intensive lighting unit.

For example, BAM investigated the mechanical stresses resulting from the impact of a 4000 kg transport cask for radioactive materials, which was dropped from a height of 9 metres onto an unyielding target; measurement values were recorded at numerous individual measurement points along the cask body.

Figure above: 9 metres horizontal drop of a transport cask for radioactive materials, with a drop angle of 5 degrees (slap down) onto an unyielding target with an impact pad area made of mild steel plates.

In the shown example referred to, the interval between the initial impact onto the left side of the cask and the secondary impact was approx. 10 ms, whereby comparatively high stress maxima occurred during slap down.

Figure below: Deceleration-time history at the moment of impact during horizontal fall with 5 degrees drop angle, primary and secondary impact (horizontal fall, slap down).

Leakage Test

The following leakage test methods and measurement techniques are used for testing of leakage rates of enclosed radioactive substances:

Methods for leakage test (DIN 25426, T. 3)	Test equipment
Vacuum method (Helium)	Mass spectrometer leak detector
Sniff test method (Helium)	Mass spectrometer leak test with sniff probe
Vacuum bubble test	Vacuum pump, vacuum chamber
Bubble test after pressurisation	Pressure chamber, vacuum pump