Detective and Detective-100
HPGe-Based Portable Nuclide Identifier

The "Gold Standard" Hand-Held Gamma-Ray Radioisotope Identifier!

Positive Identification of Gamma-Ray Emitting Radioactive Materials in a portable "expert" instrument. 

• Fast, Simple and ULTRA-Reliable Classification of NORM, Medical, Industrial, Nuclear and Natural Isotopes

• No more guesswork: definitive answers to the detection of illicit nuclear materials trafficking in seconds

• Search and Identify Modes including Dose Rate

• ~20 to 100 times better¹ than even the most advanced NaI and CZT instruments

• Faster still with Detective-100 version

• Battery operated instrument with high visibility touch pad display

• Instantly ready to use at all times, straight from docking station

As organizations trying to prevent illicit nuclear materials trafficking gain experience of real-world, in-situ nuclide identification, there is a continuing demand for ever more effective instrumentation in order improve detection abilities and reduce false determinations.

Portable instruments represent the detection front line. The ORTEC Detective family of Hand-held Radioisotope Identifiers ("HHRIDs") are based on high purity germanium (HPGe) gamma-ray detectors and represent the current technology state-of-art. Increasingly they are recognized as the "gold standard." This gold standard is now further enhanced by the addition of the Detective-100 model which, including a substantially larger gamma-ray detection element, has greatly increased sensitivity, and thus even shorter time to identify, with no loss in certainty of identification.

The Problem Described

The primary method for detection of illicit nuclear materials uses gamma-ray signatures. The problem is made complex because radioactive materials are very common in everyday life. Radioactive materials are commonly used in industry, in medicine and are found in nature. Material which can be used to make a nuclear weapon, (plutonium or uranium) is often termed "Fissile" material.

An ideal HHRID must overcome at least two major technical obstacles. One is SENSITIVITY, lack of which can give rise to failures to find any radioactivity at all. A second, and perhaps more important obstacle for a hand held instrument is SELECTIVITY, lack of which can lead to the innocent alarm or false positive situation, in which a benign radioactive signature is misinterpreted as being a threat. Moreover, lack of selectivity in a hand held instrument can result in the instrument being defeated by “masking” in which an innocent nuclide is intentionally used to “hide” the signature from the illicitly trafficked nuclear material. Innocent alarms lead to unnecessary disruption at check points such as a port or airport  whereas failure to detect illicit trafficking has potentially devastating consequences.

These are tough problems to deal with on the "front-line," especially with a portable instrument.

Examples of common substances, which can produce innocent alarms, are:

• Potassium nitrate fertilizers

• Granite or marble

• Vegetable produce

• Porcelain bathroom fixtures

• Camera lenses

• Ceramic tile

• Thoriated tungsten welding rods

• Kitty litter

• Lantern mantles

• Medical isotopes

Around 90% of innocent alarms at airports are due to medical isotopes in the bodies of travelers, while in cargo freight, the major problem is caused by common natural emitters.

The Detective Solution

Reliable detection and identification of radionuclides with a minimum of false negatives and false positives is a tough assignment for ANY instrument, not just portable instruments. Fortunately ORTEC has developed the Detective family of HHRIDs, which feature:

• Ruggedized HPGe gamma-ray detector cooled by proven miniature, high-reliability mechanical cooler

• Operates from internal battery, line power or 12 V DC

• Digital spectrometer electronics, performance enhanced by digital noise filter

• Proprietary nuclide identification software

ORTEC Detectives employ a unique class of gamma-ray detector, based upon High Purity Germanium (HPGe). ORTEC pioneered these detectors in the early 1970s and has been manufacturing them ever since, from "home grown" germanium, refined in its own facility. HPGe combines both sensitivity (the availability of large detector volume) and selectivity (the intrinsically high "energy resolution" of these detectors). Until recently, a major disadvantage of HPGe, especially for portable use, was the requirement that it operate at cryogenic temperatures. ORTEC has solved this problem by the use of miniature, ultra-reliable cryocoolers.

Other detector materials such as Sodium Iodide (NaI(Tl)) and Cadmium Zinc Telluride (CZT) are in common use in hand-held nuclide identifiers. While available in large sizes, the NaI detector has ~20 times inferior energy resolution as HPGe and is easily "fooled," especially by mixtures of radioisotopes. CZT is of intermediate energy resolution, but is only available in such small detector sizes as to make it impractical.

Independent testing has shown that room temperature gamma-ray detectors such as NaI or CZT are incapable of providing rapid, reliable and clear results.^3,4

The false negative issue is demonstrated by the spectra. The spectra show the energy range 220 to 480 keV. They show respectively, barium-133 (an innocent industrial isotope), in the upper part, and barium-133 mixed with weapons grade plutonium in the lower part. The left hand spectra are from an NaI detector and the right hand spectra were taken with an HPGe detector. The yellow arrows mark the positions of the Pu peaks. The mixtures were of equal dose rate from both Ba-133 and Pu. The NaI detector mixture spectrum (lower left) shows little or no evidence of the presence of the Pu, whereas in the HPGe spectrum (lower right) the Pu peaks are distinct. With a low-resolution NaI detector, it is possible to miss a nuclear material such as plutonium, because of the presence of an innocent nuclide which may be intentionally used as a "mask." Intermediate-resolution detectors such as CZT are not able to solve the problem because their small size and low efficiency make them impractical. The low efficiency gives unreasonably long measurement times to "clear" a suspect case. Moreover, their inferior resolution to HPGe means they are still more easily "fooled" than a HPGe detector.2

Detective Summary Benefits

The use of the Detective means:

• Fewer False Negatives

• Fewer False Positives

• "Expert Level" Determinations without an Expert

• Confirmation of SNM Material by High Resolution Gamma ID

The use of the Detective-100 means

• Even faster identification with no loss of certainty.

 In Widespread Use

The ORTEC Detective family is being deployed ever more widely in the battle against illicit nuclear trafficking. Currently instruments are being deployed world wide by:

• Departments of Homeland Security

• Emergency Management Teams

• Departments of Defense

• Civil Support Teams

• National Security Organizations

• Police Departments

• Bomb Disposal Teams

• Nuclear Safeguards organizations

• Emergency Response Teams

• Nuclear Fuel Manufacturers

• Customs and Border Control

• Nuclear Researchers

Operational Capabilities

Both model Detective Portable Nuclide Identifiers provide the following functions:

SEARCH: Scanning mode for location of gamma-ray-emitting radioactive sources, with audio alert using an external ear piece.

IDENTIFY: Proprietary scheme⁵ for identification and classification of gamma-emitting radionuclides such as:

            Industrial: Including ⁵⁷Co, ⁶⁰Co, ¹³³Ba, ¹³⁷Cs, ¹⁹²Ir, ²⁴¹Am, ⁷⁵Se
            Medical: Including ¹⁸F, ⁶⁷Ga, ^99mTc, ¹¹¹In, ¹²³I, ¹³¹I, ¹³³Xe, ²⁰¹Tl
            Natural (NORM): Including ⁴⁰K, ²²⁶Ra, ²³²Th, ²³⁸U
            Nuclear: Including ²³³U, ²³⁵U, ²³⁷Np, ²³⁹Pu, ²⁵²Cf

These classifications are based on an internal, fixed library according to ANSI N42.34. Customized libraries for specific applications can be supplied by special order.

GAMMA DOSE RATE: Gamma Dose Rate is monitored by the HPGe detector and by an internal compensated GM tube. The dose rate is displayed at all times. Dose rate units may be chosen as µSv/hr or mR/hr.

Gamma-Ray Identification Performance Data for Uranium and Plutonium

(Typical values based on data obtained from actual measurements by ORTEC personnel)

Single Sources
Unless otherwise stated, these data were taken at a standard dose rate from the source of 500 nSv/h measured with a calibrated dose rate meter at the instrument detector face according to ANSI N42.34.

When an absorber was present, the dose rate at the detector was measured THROUGH the absorber. Detective-100 performance is given in brackets, e.g., "Detective-100 <2 sec."

Unshielded and Shielded Uranium: DU, U-NAT, LEU, HEU
The time to identify as uranium, either unshielded or shielded by up to 5 mm steel, is <5 sec (Detective-100 <2.5 sec). For LEU and HEU samples, the type ("LEU" or "HEU") is also reported in <5 sec (Detective-100 <2.5 sec). LEU and HEU samples shielded by 1.6 mm lead are identified as uranium in <5 sec (Detective-100 <2.5 sec).

Unshielded and Shielded Plutonium: Weapons Grade (WG), Reactor Grade (RG)
(~60–93% Pu-239)
Time to identify as Pu, unshielded or shielded by up to 5 mm steel or 10 mm lead: <40 seconds for all types of Pu (with Cd filter if high Am content) (Detective-100 <13 sec). For WG Pu the type "WG Pu" is also reported in less than 100 sec (Detective-100 <35 sec).

Mixtures
In all cases, the mixture consists of 500 nSv/h of the "mask" nuclide, added to the specified quantity of uranium or plutonium. The "dose ratio threshold" is defined to be the standard 500 nSv/h dose rate from the mask in ratio to the smallest dose rate from U or Pu detectable in the time stated.

Uranium at 500 nSv/h in the presence of ¹³⁷Cs or ⁵⁷Co mask (unshielded)
Time to identify as uranium <5 sec (Detective-100 <2.5 sec). For LEU and HEU, the type ("LEU" or "HEU") is also reported in <5 sec (Detective-100 <2.5 sec).

Uranium Dose ratio threshold for 60 second measurement in the presence of ¹³⁷Cs or ⁵⁷Co mask (results apply to both Detective and Detective-100) (Dose from mask:Dose from uranium)
>7:1 for identification as uranium unshielded, >3:1 shielded 5 mm steel
>2:1 for reporting as LEU or HEU unshielded, >1.5:1 shielded 5 mm steel

Plutonium at 500 nSv/h in the presence of ¹³³Ba mask
Time to identify as Pu <60 sec (Detective-100 <20 sec), unshielded or shielded by 5 mm steel or 10 mm lead. Identified type as RG Pu or WG Pu in <300 sec (Detective-100 <100 sec).

Plutonium Dose ratio threshold for 5 minute measurement in the presence of ¹³³Ba mask (results apply to both Detective and Detective-100)
>6:1 for identification as Pu unshielded, >4:1 shielded by 5 mm steel or 10 mm lead
>1:1 for reporting as WG Pu or RG Pu unshielded or shielded by 5 mm steel or 10 mm steel (with Cd filter if high Am content)

Figure 2

Detective Models in Use

Figure 2 shows the operator keypad. Dedicated buttons are provided for simple search and identify operation.

Figure 3 shows the main operator screen. Gamma count rate and dose rate are

displayed continuously, numerically and in bar graph form. The battery life remaining is also displayed.

When the search button is pressed, the display in Figure 4 appears. This shows a scrolling "strip chart" display of total count rate versus time, for your search operations. Instantaneous count rate and dose rate are also displayed.

Figure 3.

Figure 4.

Figure 5.

When the Identify (ID) button is pressed, a screen like Figure 5 appears.

Unlike other identifiers in which the instrument counts for a pre-set number of seconds and then attempts an identification, Detective is a "real time" identifier. Immediately after the ID button is pressed, Detective begins to identify. While the current standards, such as ANSI 42.34 call for identification to take place in one or two minutes, Detective typically reports in a much shorter period, in some cases less than 1 second.

"Suspected" nuclides are indicated if the statistical accuracy is not adequate; with more time, this tentative identification will often change from "suspected" to "found". This dynamic process is halted at any time by pressing STOP.

In Figure 5, one industrial and one nuclear isotope (uranium) have been identified, a natural isotope is suspected, and with more time, other nuclides might be identified.

Help Messages may appear on the main screen to assist the operator, such as:

"consistent with background, keep counting"
"Count Rate consistent with background"
            "elevated radiation field"
            "possible beta emitter"
            "Possible nuclear material"
            "Medical - positron emitter"

The form of the primary ID messages is:

"Found CLASS(#)" or "Suspect CLASS(#)"
            where CLASS =
                                    Medical
                                    Industrial
                                    NORM
                                    Bremsstrahlung
                                    Other

And "#" is the number of nuclides of that class identified.

In compliance with the IAEA, nuclear materials and Th-bearing NORM get special treatment. Possible messages include:

            "Found nuclear uranium"
            "Found nuclear plutonium"
            "Found nuclear neptunium"
            "Found NORM-Th"

Figure 6.

Figure 7.

A single button push takes the operator from the identify screen of Figure 5 to the screen in Figure 6 where the identity of the found nuclides is listed. Again, nuclear materials receive special treatment.

If uranium has been detected, possible messages include:

            "Highly enriched uranium"
            "Depleted uranium"
            "Low enriched uranium"
            "Natural uranium"
            "Elevated uranium concentration"

Similarly, for plutonium, and depending on the nature of the sample, shielding and the counting statistics, the following may appear:

"Count for >5 minutes for Weapons/Reactor Grade"

Followed by:

            "Pu"
            "Reactor Grade Pu"

or alternatively

            "Pu"
            "Weapons Grade Pu"

You can also display the actual radionuclide spectrum, and manipulate the screen display (e.g., vertical scale, zoom) like a conventional multichannel analyzer. (Figure 7.)

Figure 8.

Figure 9.

Figure 10.

Calibration Check

The Detective is supplied pre-calibrated from the factory. The advanced digital electronics and detector are very stable giving a constant peak position. A very simple procedure is used to verify and update the factory calibration. A small ¹³⁷Cs source is used, which is installed in the docking station for use while recharging. The manual calibration check procedure is shown in Figures 8, 9, and 10.

When on the docking station, the detective continually recalibrates, meaning that when it says "READY", it is READY for you to use.

Detective Power Sources

Detective will go where you go. In addition to the internal battery, it can draw power from a variety of sources. For initial cool down from ambient temperature, the Detective is placed on the docking station, or attached to the compact AC/Power Adapter/Charger (PAC). The docking station provides small air movers to assist with initial cool down in conditions of high ambient temperature (>40şC). The PAC is a much more compact solution. The Detective is typically ready for use in less than 12 hours from starting to cool at room temperature. Once cold, sustaining the Detective requires only a few tens of watts.

The internal batteries provide an operating life of more than 3 hours before additional power support is needed. The optional battery belt can be used to extend the operating time without limit. An automobile adapter is supplied to provide charging through the docking station and support while in transit. For mains use, the docking station is supplied with a mains supply. 

Ordering Information

Note on Calibration Check Source
The calibration check source is internal to the docking station. It comprises a solid, sealed, ~0.25-µCi (9250-Bq) ¹³⁷Cs calibration source housed in the source holder on the front of the docking station. This source is exempt under U.S. and European regulations and is only supplied pre-installed by ORTEC (not separately). It is not recommended that it be removed, and ORTEC will not accept any responsibility for its removal. If this source is NOT required with the instrument because of local issues, this must be stated at time of order. THE SOURCE CANNOT BE SUPPLIED SEPARATE FROM THE DOCKING STATION.

Options
A separate data sheet covering Detective Options and accessories is available on request.

Software for Detective and Detective-100
Detective/Detective-100 is fully supported by the latest versions of the highly successful MAESTRO-32 MCA Emulator as well as the well-known ORTEC Gamma Spectroscopy Packages such as GammaVision-32 for generalized HPGe spectrum analysis, PC/FRAM and MGAHI for Pu and U isotopic ratio analysis and ISOPlus for in-situ waste assay analysis.

The integral USB connection in the instrument hardware provides full PC control, real-time live MCA display, fast data transfer of single and multiple spectra to the PC, and full ORTEC CONNECTIONS network support.

PLEASE NOTE: MAESTRO-32 (A65-B32) is supplied as part of packages containing "PKG" in the model number, or it can be purchased separately at a later date.