- Email: [email protected]
Lost source starts six-day search
l
=|IrtTERIBRI ORRIL inllEU$ ]
Lost source starts six-day search A six-day search ended successfully last November when a crane hauled a gamma-radiation source from 12 m of water 800 m from the shore at the mouth of the Tees. The 14 Ci iridium192 source fell into the sea when a radiographer was winding it from its container for inspection work at Philips Petroleum at Seal Sands on Thursday 6th November. The Health and Safety Executive (HSE) has asked the National Radiological Protection Board (NRPB) to investigate the incident. The operator, who works for an out side ndt company, wound the cable out until there was no more cable. The source and 15 m of cable then broke away and fell from the steel construction undergoing radiography. I nvestigators believe that the exposure tube was not properly attached to the container. The usual procedure for such cases, the NAI R scheme, was then followed. This scheme, the national arrangements for incidents involving radiation, means the police and the HSE were called in. The HSE asked the NRPB Northern Centre at Leeds for help the day after the accident and the search began. It took six days of effort by scien-
tists, safety officers, policemen and oilmen to find and recover the lost source. The NRPB officers first visited the site of the loss at number 6 jetty next to a barge called Oyster Point (Fig.6). They asked their Leeds Centre to make an underwater radiation detector and searched for the source from the Beaver boat the next day with the detector which was a 45 mm Nal crystal in a plastic pipe at the end of 18 m of coaxial cable connected to the ratemeter. By evening they thought they had found it, after breaking the cable twice and changing from the boat to a platform hung from a crane. Searchers confirmed the position on Monday after the detector was repaired; the intervening day was spent trying to pick the cable up with a permanent magnet without success. The next day a meeting of all those involved, including police divers, decided to use divers to feel for the cable in the murky water with an underwater radiation detector of cadmium-sulphide able to measure 10-107 mJ kg "l to trace the source and to warn of its nearness. The divers would also carry radiation badges and the Nal detector which
would however saturate 1 m from the source. The divers were linked by telephone to the surface and searched for the source and its cable for the rest of that day and half the next. Finally, on Wednesday almost a week after the loss a crane with a grab was used and pulled the source and cable out first time. It was then put in a container by a man with a pair of long tongs. The NRPB report that the exercise needed and received the help of many different bodies. All worked well together and noone was hurt; the divers receive only 20 mrem. The NRPB also say it cost a lot of money.
Fig.6 The radiographer's platform stands empty as searcherslook for the radiation source under the jetty
d3EU EQUIIPPtEn3T US system h a n d l e s 3 2 c h a n n e l s of acoustic-emission data Signal processing and display in a single cabinet handles 32 channels for acoustic-emission data in an American system now available in Great Britain. The cabinet stands 1,220 m high on a 762 x 584 mm base and contains two cathode-ray displays, a simulator and loudspeaker, up to 32 signals processors and a time-difference processor to calculate time of flight between sensors (Fig.l). Acoustic Emission Consultants Ltd is to market the system in the UK for
the manufacturers Acoustic Emission Technology Corporation. Up to 32 sensors each with a preamplifier are magnetically held onto the test surface. Data from the sensors is processed by the signal processors. These maintain an automatic signal threshhold just above the noise level. The time-difference processor calculates locations from the differences in time of flight. It also reactivates the system when the signal drops below the signal threshhold. It can also provide ring-down counts and peak amplitudes from the sensor nearest the event and measures other
NON-DESTRUCTIVE TESTING . FEBRUARY 1976
parameter inputs such as temperature, load or pressure. The twin display can show the data in a wide number of combinations giving location, counts against time or load and so on, depending on programming. A Texas Instruments teleprinter prints data out and can play it back from tape cassettes. The system is transportable; the cabinet weighs about 113 kg. Acoustic Emission Techno-
logy Corporation, 1828A Tribute Road, Sacramento, California 95815, USA: British Agent: AECL, 9 Station Road, St Ives, Hunts, Cambs, UK.
49
=|IrtTERIBRI ORRIL inllEU$ ]
Lost source starts six-day search A six-day search ended successfully last November when a crane hauled a gamma-radiation source from 12 m of water 800 m from the shore at the mouth of the Tees. The 14 Ci iridium192 source fell into the sea when a radiographer was winding it from its container for inspection work at Philips Petroleum at Seal Sands on Thursday 6th November. The Health and Safety Executive (HSE) has asked the National Radiological Protection Board (NRPB) to investigate the incident. The operator, who works for an out side ndt company, wound the cable out until there was no more cable. The source and 15 m of cable then broke away and fell from the steel construction undergoing radiography. I nvestigators believe that the exposure tube was not properly attached to the container. The usual procedure for such cases, the NAI R scheme, was then followed. This scheme, the national arrangements for incidents involving radiation, means the police and the HSE were called in. The HSE asked the NRPB Northern Centre at Leeds for help the day after the accident and the search began. It took six days of effort by scien-
tists, safety officers, policemen and oilmen to find and recover the lost source. The NRPB officers first visited the site of the loss at number 6 jetty next to a barge called Oyster Point (Fig.6). They asked their Leeds Centre to make an underwater radiation detector and searched for the source from the Beaver boat the next day with the detector which was a 45 mm Nal crystal in a plastic pipe at the end of 18 m of coaxial cable connected to the ratemeter. By evening they thought they had found it, after breaking the cable twice and changing from the boat to a platform hung from a crane. Searchers confirmed the position on Monday after the detector was repaired; the intervening day was spent trying to pick the cable up with a permanent magnet without success. The next day a meeting of all those involved, including police divers, decided to use divers to feel for the cable in the murky water with an underwater radiation detector of cadmium-sulphide able to measure 10-107 mJ kg "l to trace the source and to warn of its nearness. The divers would also carry radiation badges and the Nal detector which
would however saturate 1 m from the source. The divers were linked by telephone to the surface and searched for the source and its cable for the rest of that day and half the next. Finally, on Wednesday almost a week after the loss a crane with a grab was used and pulled the source and cable out first time. It was then put in a container by a man with a pair of long tongs. The NRPB report that the exercise needed and received the help of many different bodies. All worked well together and noone was hurt; the divers receive only 20 mrem. The NRPB also say it cost a lot of money.
Fig.6 The radiographer's platform stands empty as searcherslook for the radiation source under the jetty
d3EU EQUIIPPtEn3T US system h a n d l e s 3 2 c h a n n e l s of acoustic-emission data Signal processing and display in a single cabinet handles 32 channels for acoustic-emission data in an American system now available in Great Britain. The cabinet stands 1,220 m high on a 762 x 584 mm base and contains two cathode-ray displays, a simulator and loudspeaker, up to 32 signals processors and a time-difference processor to calculate time of flight between sensors (Fig.l). Acoustic Emission Consultants Ltd is to market the system in the UK for
the manufacturers Acoustic Emission Technology Corporation. Up to 32 sensors each with a preamplifier are magnetically held onto the test surface. Data from the sensors is processed by the signal processors. These maintain an automatic signal threshhold just above the noise level. The time-difference processor calculates locations from the differences in time of flight. It also reactivates the system when the signal drops below the signal threshhold. It can also provide ring-down counts and peak amplitudes from the sensor nearest the event and measures other
NON-DESTRUCTIVE TESTING . FEBRUARY 1976
parameter inputs such as temperature, load or pressure. The twin display can show the data in a wide number of combinations giving location, counts against time or load and so on, depending on programming. A Texas Instruments teleprinter prints data out and can play it back from tape cassettes. The system is transportable; the cabinet weighs about 113 kg. Acoustic Emission Techno-
logy Corporation, 1828A Tribute Road, Sacramento, California 95815, USA: British Agent: AECL, 9 Station Road, St Ives, Hunts, Cambs, UK.
49