Following a tip-off of plans to scrap a very old but extremely accurate whole body radiation counter stored at the Rocky Flats facility, Marvin Goldman at the University of California, Davis, was able to launch a rescue project. This unique piece of equipment is now being sent to Russia where it will be used for a highly valuable human dose monitoring programme at the Mayak Production Complex, a weapons production facility very similar to Rocky Flats, in the South Urals.
The device, which includes heavy shielding and the electronics, will take part in the extensive studies being carried out on the populations around the Mayak plant which, coupled with comparisons with US nuclear worker data, may prove to be a key factor in future reassessments of radiation protection standards and regulations everywhere.
A LUCKY SAVE
The story started last year when Goldman was told that Rocky Flats was about to discard the monitor and was asked if he had any use for it. Thinking of the joint US/Russian radiation research programme being carried out at Mayak, Goldman, who had been involved in setting up the programme, contacted the US Department of Energy which has arranged to have it refurbished and shipped to Russia. At Mayak it will be used in support of the epidemiological and dosimetric studies related to the workers and near-by population exposed over decades from radiation released from the nuclear activities.
When the project was first publicly announced, the US press depicted it, quite wrongly, as a swap of a radiation monitor for valuable Russian health data. According to Goldman, there is no quid pro quo on this offer – “it is a simple and welcome add-on to an existing programme”. There is no connection between the two – it is a gift, pure and simple, from US scientists and workers to their counterparts at Mayak. Furthermore, he added, the notion that the Russians are trading their extensive data on the health effects of the nuclear activities at Mayak in return for some shielding and electronics, is considered quite insulting by them. The data are Russian property and are being evaluated in Russia by Russian scientists in a collaborative programme with US specialists.
MAYAK DOSE DATA
The Southern Urals’ data, according to Goldman, represents our only large data base on the effects in humans of plutonium exposures and also on chronic radionuclide exposures in the population, thus providing a unique opportunity to learn about lung and leukaemia risks from long-term exposures. The collective dose may be about as large as that due to the Hiroshima and Nagasaki atomic bomb explosions.
The data is expected to help answer critical questions on health impacts associated with long-term, low-level radiation exposure that have not been answered by previous health studies, particularly of atomic bomb survivors in Japan.
The Japanese group was exposed to a very short burst of external radiation, unlike the pattern of exposure normally encountered or expected in the nuclear industry (eg uranium mining, operating nuclear facilities, transport and disposal of radioactive materials, the testing and dismantling of nuclear weapons, radiation accidents, and grossly contaminated sites or facilities). The Southern Urals’ populations, on the other hand, experienced chronic exposures over a much longer period. This unique whole body monitoring equipment will help insure that past and future measurements of plutonium (and americium) uptake by Russian workers at Mayak can be compared and pooled with data from nuclear workers at US facilities.
The operation to transport the counter to Russia is not a simple crate and dispatch operation – the unit’s shield weighs approximately 63 t. The Lawrence Livermore National Laboratory (LLNL) has been given responsibility to refurbish and then ship the shield and associated germanium detectors and electronic equipment to the First Institute of Biophysics in Ozersk, as well as for the training of the Russian scientists in its use. The whole project is being sponsored by the DOE Office of International Health Programs.
The 63 t shield is unique because its 6-inch thick walls, ceiling and floor were manufactured from pre-World War II steel and are lined with lead, tin and zinc to minimise interference from extraterrestrial and terrestrial background radiation which can adversely affect the sensitive plutonium measurements. Pre-World War II steel is free of contamination from modern smelting and recycling processes and to a lesser extent radioactive fallout from above ground weapons testing. This unique capability would have been lost forever had the shield been demolished and melted as originally planned. As it was, the detectors and electronics were already in surplus and in some cases “squirrelled” away at various research locations, when scientists in Russia and the US hatched the plan to rescue the shield.
The shield was removed and hauled to Oklahoma at the beginning of this year to be disassembled and refurbished. LLNL scientists will translate manuals and train the scientists on the calibration and measurement protocols common to DOE laboratories.
The Mayak programme
Enormous amounts of radioactive materials were released into the environment after a series of accidents and poor management practices at Mayak from the time it went into operation in 1949, through to 1967. As a result, thousands of square kilometres have been contaminated and hundreds of thousands of people have received significant radiation exposures. Furthermore, because of limited and inadequate radiation protection measures and procedures, thousands of workers were seriously overexposed.
This joint multi-faceted programme will help Russian scientists preserve and analyse the very detailed records of personnel dosimetry and health outcomes that have been collected at Mayak.
Started in 1994, the collaborative programme now involves many US and Russian health and radiological scientists and is funded at about $3 million per year. The main thrust of the work is to perform retrospective dose reconstruction and epidemiology studies on worker and general populations. These include late effects (particularly cancer) risk studies as well as learning about acute and chronic radiation syndromes. Another project to help the Russians is to provide equipment and training to microfilm the mass of health records of workers and residents around Mayak, many hand written, for eventual conversion into computer databases.
Groundhog makes the day for surveying contaminated land
In the first half of this century Britain’s industries used many different radioactive materials, such as luminous paints and uranium-based ores in their processes and they were discarded with no thought of the contamination which would be left behind.
These processes have left Britain with a huge legacy of contaminated land with potentially hundreds of former industrial sites which are still contaminated with radioactivity. This is becoming a major problem as pressure to re-use brown field sites grows and a quick, auditable way of assessing this hazard is crucial.
Methods of assessing, surveying and remediating contaminated land have changed little in 40 years and are time consuming and inaccurate. Scientists at AEA Technology realised that a fast and effective way of surveying sites which could be contaminated with radioactivity was needed. They developed Groundhog.
Groundhog is a portable system which fits into a specially designed back pack or onto a vehicle. It is linked to a Global Positioning Satellite (GPS) providing accuracy which was previously impossible. The system can go anywhere a man can go and takes tens of thousands of readings on each side to build an accurate radiation picture of the site. It has already been used on around 20 sites since its launch last summer with a combined total of over three million radiation readings.
Using the pinpoint accuracy of the GPS system computer models can be created showing the site and exactly where the contamination is. For the first time customers are able to see proof that the site has been covered properly and exactly what their problem is. Remediation work can also be effectively targeted because of the accuracy of the readings, cutting down on the cost.
Among the areas surveyed by Groundhog was an old furnace site which was thought to be contaminated with radioactivity from ash. AEA Technology staff surveyed the site and neighbouring allotments and found the furnace area was contaminated as expected. But Groundhog also discovered that the allotment site was contaminated with mild amounts of radioactivity because ash from the furnace had been dug in to help the vegetables.
Another site surveyed using Groundhog had a known area of contamination. But Groundhog picked up an area of radiation beneath the surface running away from the main contaminated area. It was discovered that a drain was carrying the contamination further than was previously thought.
Groundhog uses an optimised detector for gamma radiation which AEA Techno-logy says is the best of its type. Detection equipment suitable for other types of chemical or radiological contamination will be offered as alternatives in future.
The system is already being used across the country by those involved in developing former industrial sites. It can be used to make initial checks of the site and to ensure remediation work has been carried out properly.
Neil Spurway, a Business Development Manager within Health Physics said: “A site we recently surveyed using Groundhog would have produced 9000 radiological readings if it had been surveyed using traditional techniques. Groundhog took 170 000 readings making the final analysis of the site much more complete.”
NRC ends environmental programmes with states
The US Nuclear Regulatory Commission has ended its contracts with 34 states to perform radiation monitoring around certain nuclear facilities which it says will not impact its ability to monitor and regulate safety at the facilities.
The decision followed a staff review which determined that the information received from the states appears to be of limited value from a safety perspective.
This programme began in the 1970s as a joint effort with the states to independently compare the results of environmental measurements with those performed by NRC licensees, who are still required to continue their own environmental monitoring activities to verify that radiation levels around their facilities are negligible. The programme was also intended to help states develop their own radiological health programmes, but not to fully fund them.
In making the decision, which followed its usual inquiry procedure, the NRC cited both the cost (over $1 million a year) and the excellent record of licensees in maintaining their own environmental monitoring programmes.
Radiological criteria for decommissioning
The NRC has been holding workshops on methods for demonstrating compliance with its recently issued regulation on radiological criteria for licence termination.
The workshops’ purpose is to receive suggestions from the public and licensees on the development of a regulatory guide on this subject. The meetings focus on methods for demonstrating compliance with the regulations, including those for unrestricted and restricted release of the site. For example, how will licensees demonstrate that radiation doses from contamination remaining on the property after licence termination and unrestricted release of the site will be as far below the required limits as reasonably achievable.
Dose on disc
The provision of dose reports on disc is a new service introduced by the UK’s National Radiological Protection Board (NRPB) to enable its customers to extract dose information and interpret trends by computer techniques. The disc service is an addition to the NRPB’s dose reporting service approved by the regulator, the Health & Safety Executive, and will simplify the monitoring of the radiological environment in which people work.
Discs are dispatched regularly (weekly, four weekly or quarterly) and contain records of all dose readings that were added to the NRPB database for the customer since the last disc was produced for that customer. The costs for these discs are included in the price quoted for the dosemeters.
The data are in the form of individual records for each dosemeter in the “comma delimitated” format used by many common spreadsheet and database programs so that they may be readily imported into the customer’s own data processing system. A separate pair of files are normally produced for each customer delivery address, but larger customers with several delivery addresses may have the data for all sites combined.
Hand scanning for neutrons
Harwell Instruments (part of AEA Technology plc), UK, has recently launched the N92 Neutron Scanning Monitor. This new monitor is a battery powered portable instrument that is ideally suited for neutron scanning measurements near fuel flasks, neutron sources and neutron generators. The N92 provides users with high neutron sensitivity and good measurement accuracy at low dose rates, and can therefore be used to identify potential weaknesses in radiological shields.
The monitor consists of a He 3 proportional counter inside a spherical polythene moderator along with an advanced signal processing & display unit. The membrane control pad allows the user to select the required measurement parameters, including the sample time, alarm levels and correction factors for particular neutron spectra.
Outputs from the display unit include RS232 which can be used to configure the monitor via a palm-top computer, TTL and a user selectable audio indication. The monitor can be supplied with an optional transportation case and palm-top computer.
Counting alphas on complex surfaces
Following the earlier release of the pipe contamination alpha monitor, BNFL Instruments has launched its large item alpha monitor, the IonSens 208, which is designed to measure alpha contamination on the varied surfaces of large complicated components.
The IonSens technique, developed by BNFL Instruments and the Los Alamos National Laboratory, measures alpha contamination on the exposed surfaces of metallic waste, providing the data needed to classify them as either low level waste (LLW) or suitable for free release. This enables reuse or their disposal by the most efficient and economical route.
The new large item monitor measures contamination on a much wider variety of items than the earlier system which was designed primarily for pipes, including complex items, such as process equipment, and bent pipes, in a large range of sizes. Solid objects such as ingots can also be measured.
Measurement time is only 100 seconds with a sensitivity lower than the UK and US alpha activity levels for free release and the IAEA limits for surface alpha contamination.
Existing alpha contamination measurement techniques rely on their sensitivity to the direct presence of alpha particles. This requires the detectors to be close to the contamination source in order to obtain accurate, consistent results. The detection technique of IonSens rather focuses on the ions produced by alpha particle interactions in the air surrounding the whole item. A single measurement effectively calculates the contamination of all exposed surfaces ensuring accurate and rapid results.
As a further option this monitor will provide beta/gamma measurement using scintillation detectors. And as an alternative to outright purchase, the IonSens 208 can be hired for short-term operations, using BNFL Instruments’ own personnel.
STREET-WISE Radwaste detector
If scrap or waste contain contaminated pieces or radioactive sources from medical or industrial facilities, they will be found only by chance. Random tests with hand held instruments are time consuming and not very reliable. The FHT 1388 Monitoring System by Eberline solves this problem. The basic version consists of the two detector boxes and the measuring electronics.
Applications include: checking of cargoes on trucks, rail cars and ships; prevention of smuggling and accidental transport; and waste monitoring with separate alarm thre-sholds for artificial and natural radiation.
The NBR (natural background reduction) process used allows the detection of even the smallest amounts of artificial gamma radiation in the presence of fluctuating natural radiation background fields. In the case of the process developed by Eberline, the average energy and the distribution of the gamma radiation are monitored continuously and irregularities detected in fractions of a second. This means: high statistical certainty and – even in the case of well shielded sources – extremely short measuring times.
A software program has been designed for fast, simple, and error free operation of the scrap monitor. This flexible program supervises routinely the function of the complete monitoring system.
Hands up for alpha monitoring
Mini Instruments Ltd has developed new line of portable alpha monitor to fill a market need following a competitor’s withdrawal from this application. Many features were incorporated after discussions with users covering several industrial applications.
The 1800 PAM has an analogue meter, rather than a digital display which was considered much more difficult to interpret. Simple one-handed operation was also a key requirement, met by using a single switch, large logarithmic scale and a very loud audible alarm.
Alpha particles are detected using ZnS scintillator and photo-multiplier technology. The grille is designed to protect the vulnerable foil during contamination measurements, while still allowing foil replacement to be both quick and straightforward.
Another key feature is the fast and consistent response across the whole detector face, making it particularly easy to detect contamination on large flat surfaces, hands and clothing.