ENVIRO Station Aerosol · Profectronics

Station

Construction of the station

The measurement cabin is part of the measuring instrument. Outside −30 to +50 °C, inside controlled 5 to 35 °C.

Measurement cabin ISO 10′, 2 991 × 2 438 × 2 591 mm
Mass approximately 2.6 t
Flow rate 6.0 m³/h nominal
Service life 60 days for each magazine

Photo · ENVIRO Station in the measurement cabin, door open

Continuous sampling A heated omnidirectional head on the roof, a conditioned sample line and a controlled blower. The blower holds 6.0 m³/h, also when the filter becomes clogged.
A new filter each day A magazine holds 60 round filters with a diameter of 47 mm. The advance follows a schedule that you set. The filters are single discs. There is no tape to thread.
Measurement during sampling The station counts alpha and beta at the filter while the air continues to flow. The gamma detector looks at the same filter from a lead chamber with 50 mm walls on all sides.
2 months for each magazine Air conditioning, weather station and a ring buffer for 3 years. At the visit, the personnel replace the magazine and take the loaded filters to the laboratory. Duration 20 minutes each 60 days.

Measurement chain

Measurement chain in 5 stages

From the outside air to the result in Bq/m³, the sample goes through 5 stages. The station counts at the filter.

Stage	Assembly	Design
01	Intake head	Omnidirectional, with louvres. The heater prevents ice on the head.
02	Sample line	Heated above the dew point, a condensate separator at the lowest point.
03	Filter	Round filter with a diameter of 47 mm from the magazine, with an NFC chip.
04	Blower	Controlled, holds 6.0 m³/h, also when the filter becomes clogged.
05	Gas meter	Volume referred to 0 °C and 1 013 hPa, collection efficiency 0.99.

Alpha and beta at the filter Silicon semiconductor detector with 1 700 mm², 55 keV alpha and 30 keV beta, spectrally separated.
Gamma spectrometry Scintillator or germanium in a lead chamber with 50 mm walls on all sides, with a lining of copper and tin.
Result Activity concentration for each nuclide in Bq/m³, with uncertainty, decision threshold and detection limit in accordance with ISO 11929.

The 2 detectors are at the filter, not behind it. The station counts alpha and beta while the air continues to flow. The gamma detector looks at the same filter from the lead chamber. Thus all 3 results apply to the same sample and the same time slice.

Magazine

The loaded filter goes into the laboratory dish as a full disc. On the way to the laboratory, a telephone reads the chip. Thus the sample identification stays correct.

Data on the chip

At ejection, the station writes the station identifier, start time, volume, flow rate and result to the chip. The full data set stays in the station.

Background

Iodine-131 next to lead-214

The radon background sets the limit of the gamma measurement at the filter, not the counting statistics. A sodium iodide detector shows iodine-131 and lead-214 as one peak. Most of this peak comes from radon.

The station subtracts the radon contribution with the lead-214 line at 295.2 keV. The ratio to the line at 351.9 keV is a constant of the decay scheme and does not drift.

The Environmental Solutions overview describes the physics, the resolution of the detectors and the compensation methods.

Versions

Version S and version G

The measurement cabin and the air path are the same in the 2 versions. This also applies to alpha and beta: the same silicon detector with 1 700 mm² as in the ENVIRO GO.

Version S · Scintillator

NaI(Tl) 3″ × 3″ with photomultiplier
Resolution approximately 7 % at 662 keV
No cooling, ready to measure immediately
Library with 10 to 15 nuclides
Lower connected load, easier maintenance

Version G · High-purity germanium

Coaxial HPGe, 50 % relative efficiency
1.90 keV at 1.33 MeV
Electric cooler, no liquid nitrogen
Library with more than 50 nuclides
Separates lines that a scintillator shows as one peak

Open design of the lead chamber

Each detector with a front face that covers the 47 mm filter is applicable: NaI(Tl), CsI(Tl), CeBr₃, LaBr₃ and coaxial HPGe. Profectronics examines each detector separately at procurement.

New detector with no modification

Profectronics calculates the efficiency for each detector and geometry with Geant4 and confirms it with check sources. The chamber, the shielding and the software stay the same.

Detection limits

Detection limits for each nuclide

In accordance with ISO 11929 at 95 %, at 6.0 m³/h and a radon level of 40 Bq/m³ in the air.

Nuclide	S · 1 h	G · 1 h	S · 24 h	G · 24 h
Cs-137	0.50 Bq/m³	0.10 Bq/m³	25 mBq/m³	5.0 mBq/m³
Cs-134	0.44 Bq/m³	0.085 Bq/m³	22 mBq/m³	4.2 mBq/m³
I-131 · on the filter	0.48 Bq/m³	0.092 Bq/m³	24 mBq/m³	4.6 mBq/m³
Co-60	0.52 Bq/m³	0.11 Bq/m³	26 mBq/m³	5.3 mBq/m³
Gross alpha	0.40 Bq/m³	0.40 Bq/m³	20 mBq/m³	20 mBq/m³
Gross beta	0.60 Bq/m³	0.60 Bq/m³	30 mBq/m³	30 mBq/m³

Alpha and beta are the same in the 2 versions. Here, I-131 is the particle-bound part on the filter. The ENVIRO Station Iodine measures gaseous iodine. The values are in the range of comparable stations in the field. No value is below the lowest published value.

Cycle

Cycle and integration time

A short cycle decreases the response time. A long integration time decreases the detection limit.

Cycle	Cs-137, one window	Use
2 minutes	3 to 15 Bq/m³	Plant status and early warning
5 minutes	1.7 to 6 Bq/m³	Plume tracking during an event
10 minutes	1.2 to 3 Bq/m³	Default value for the report
1 hour	0.50 Bq/m³ · design value	nested window, always calculated
24 hours	25 mBq/m³ · design value	Monitoring limit

The cycle and the integration are independent. Each report also gives the nested windows of 10 minutes, 1 hour and 24 hours. Thus a short cycle decreases the response time and does not change the sensitivity.

The ranges for 2, 5 and 10 minutes come from the 1-hour value. The upper limit follows from 1/t, the lower limit from 1/√t. These ranges are an approximation for the counting window with a fully loaded filter. The relation with 1/t² and 1/t^1.5 in the overview applies when the collection time is equal to the counting time. Version G decreases each gamma limit by a factor of approximately 5.

The Environmental Solutions overview gives the calculation of the detection limit and its relation to the measurement time.

Measurement cabin

Measurement cabin and air conditioning

The measurement cabin is the housing of the measuring instrument.

A split unit on the roof and an electric reheater keep 5 to 35 °C inside at −30 to +50 °C outside. The heater at the intake head prevents ice. The sample line stays above the dew point to prevent condensation.

Version G needs an air temperature in the measurement cabin of less than 40 °C. The specification of the cooler is 40 °C ambient temperature. The specification of the electronics is 55 °C.

Outside −30 to +50 °C
Controlled inside 5 to 35 °C
Foundation Concrete slab

Access

Access and reports

The station monitors the door, the access and tamper attempts. It reports each event.

Area	Solution	Report
Door	Steel, three-point lock, mechanical key as fallback	Status in the header of each screen view
Access	RFID card and PIN at the door, based on roles	each access in the audit log
Door contact	Monitored reed contact with tamper line	DOOR OPEN in the message stream
Tamper attempt	Tamper contacts on the cabinet front and the roof hatch	Alarm, remote, in less than 1 minute
Climate control	An open door stops the air conditioning	Note when the door stays open for longer than the set time

Each door opening has a card identifier and a time stamp. A door opening outside an announced maintenance starts an alarm. The components are at the design stage. The selection of the components is not complete.

Operation

User interface

The user interface shows the station status, the measured values, the events since the last visit and the next tasks.

Spectrum

Fitted peaks and nuclide table with detection limit.

Limit values

Thresholds and responses.

Messages

Each event with a time stamp.

Magazine

Position, days left and change procedure in 4 steps.

System

Each transmission to EURDEP, IRIX and N42.42 with a time stamp, and the status of the data backfill after an interruption.

Screenshots from the shared operating software. Operating language English, example values, no measurements.

Programmes

P01 Continuous operation
P02 Campaign
P03 Single filter
P05 Background
P06 Magazine advance
P07 Cool-down, only version G
P08 Energy calibration
P10 Self-test

Maintenance

Maintenance schedule

Regular visit: 20 minutes each 60 days to replace the magazine. In addition, there are calibrations each year.

Task	Interval	Duration
Replace the filter magazine	each 60 days	20 minutes
Check source and energy calibration	automatic, each day	none
Flow rate calibration against a standard	each year	1 hour
Efficiency calibration at the installation site	each year	2 hours
Maintenance of the air conditioning	each year	1 hour

The daily check source measurement operates with no personnel. If the measurement drifts out of its window, the station reports this in the same message stream as the measured values. The message comes before the data become incorrect.

Technical data

Differences between the versions

The versions have a different gamma detector and different values that follow from the detector.

Parameter	Version S	Version G
Gamma detector	NaI(Tl) 3″ × 3″, PMT	HPGe, 50 % relative efficiency
Energy resolution	approximately 7 % at 662 keV	1.90 keV at 1.33 MeV
Cooling	none	electric cooler
Ready to measure	immediately	after a cool-down time of 5 to 8 h
Nuclide library	10 to 15 nuclides	more than 50 nuclides
Connected load	approximately 0.9 kVA	approximately 1.6 kVA
Mass ready for operation	approximately 2.6 t	approximately 2.6 t

Technical data

Common data

These values apply to the 2 versions.

Parameter	Value
Flow rate	6.0 m³/h nominal, controlled 3 to 12 m³/h
Alpha and beta	Silicon semiconductor detector 1 700 mm², 35 %, 55 keV alpha, 30 keV beta
Filter	Round filter 47 mm with NFC chip, magazine for 60 filters, 60 days
Weather station	Pressure, humidity, temperature, precipitation and wind, on the roof
Shielding	50 mm lead, on all sides, lining of copper and tin
Volume	referred to 0 °C and 1 013 hPa, collection efficiency 0.99
Power supply	230 V, 50 Hz, external UPS recommended
Ambient temperature	−30 to +50 °C outside, 5 to 35 °C controlled inside
Measurement cabin	ISO container 10′, 2 991 × 2 438 × 2 591 mm
Screen	1920 × 1080, touch-sensitive, control areas from 20 mm
Interface	Ethernet, router as an option, N42.42, EURDEP, IRIX, Modbus TCP
Data	Interval 2 minutes to several hours, 10 minutes recommended, ring buffer for a minimum of 3 years

The detector values come from the data sheets of the component manufacturers. All other data are design values. UPS: uninterruptible power supply.

Scope of delivery

Scope of delivery and options

The measurement cabin comes fully wired, with a factory calibration certificate.

Included

Measurement cabin with cabinet, fully wired
Intake head, mast and sample line
Air conditioning and heating
Weather station on the roof
Filter magazine with 60 filters
Factory calibration certificate
Efficiency calibration at the installation site
Interface description and test client

Options

Germanium detector, version G
Intake head for PM2.5
External uninterruptible power supply, recommended
Mobile network router
Spare filter magazines
Stack probe in accordance with ISO 2889

Validity

Development status

The measurement cabin is built. The measurement chain in the measurement cabin has no type test at this time.

Measurement cabins of this design are built. The photographs on this page show them. Each performance value on this page is a design value or a value from experience with comparable systems. The detector values come from the data sheets of the component manufacturers.

The design follows IEC 60761-1 and -2, ISO 2889 and ISO 11929. We write “tested in accordance with” only after a satisfactory type test. As an aerosol monitor, the station is in the scope of IEC 60761-2. The ENVIRO Station Iodine covers the iodine measurement in accordance with part 4. For the CE marking in accordance with EN 61326 and EN 61010, an external test house does the tests.

Enquiry

Enquiry and other measuring instruments

The ENVIRO Station Iodine measures gaseous iodine, with a prefilter, a cartridge changer and radon subtraction. The Station Aerosol measures the full particle chain with no additional module.

Measurement cabin · iodine ENVIRO Station Iodine
Mobile ENVIRO GO
Air and vehicle ENVIRO AIR
Under water ENVIRO NAUTA
Overview All measuring instruments

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