Atch_01,_Purchase_Description_Beta_Beam_Irradiator.pdf

PURCHASE DESCRIPTION

Beta-Beam Irradiator System Requirement

R. A. Hamilton, J. M. Rhodes, S. Zhu 09 July 2018

Radiation Standards Laboratory

U.S. Army Aviation and Missile Command

ASAM-TMD-SR

1. Scope

This purchase description covers a dosimetry-grade beta-beam irradiation system.

2. Components

The beta system shall include

2.1. Beta-beam irradiator

2.1.1. Source Shield

2.1.2. Radiation Sources

2.1.3. Flattening Filter

2.1.4. Safety Interlock System

2.1.5. Control System (with automated control system software)

2.2. Calibration Bench (and accessories)

2.2.1. Alignment Bench

2.2.2. Ancillary Equipment

2.2.2.1. Rotary axis

2.2.2.2. Instrument camera, NVR and monitor

2.2.2.3. Laser alignment

2.2.2.4. Temperature, pressure and humidity sensor

2.2.2.5. Instrument jig

2.3. Accessories

2.3.1. Bohm Extrapolation Chamber

3. Purpose

The system will be used in the U.S. Army Radiation Standards Laboratory (RSL) to calibrate Army RADIAC instrumentation used by first responders, calibrate Electronic Personal Dosimeters used in Army hospitals and medical activities worldwide, as well as irradiate Optically Stimulated Luminescent (OSL) dosimeters to meet NVLAP audit requirements for the US Amy Dosimetry Center.

4. Salient Characteristics of Components

The Beta system shall incorporate the following salient characteristics that have been identified as essential to the needs of the U.S. Government:

4.1. Beta-beam irradiator

The beta system shall be designed to provide a uniform beta radiation field for calibrating radiation detection instruments and exposing dosimetry. The system shall be capable of being loaded with up to four sources. The system shall consist of a controller, stand, 4-position source holder, filter holder wheel, and a servo-actuated shutter (with the necessary control components). It shall also include a radiation warning light for the room door and a safety interlock system for the door. All interconnecting wiring and cabling shall be provided.

4.1.1. Source Shield

The source wheel shall be mounted in a shielded box that reduces external exposure rates to safe levels. When shielded, maximum external exposure rates shall be less than 2 mR/hr at a distance of 30 cm. The source wheel shall be rotated by a servo motor and the shutter additionally shall be servo actuated. Teknic Clearpath® servo motors are recommended for this application and should be used. The commandable resolution of these motors is on the order of a few microns, featuring a 3-year warranty with a MTBF rating of 750,000 hours for the integrated drives.

4.1.2. Radiation Sources

The system shall be designed to accommodate two 90Sr and two 85Kr sources with combinations of activities 20 & 100 mCi and 50 & 200 mCi, respectively. A combination of four sources shall be provided and installed in the source wheel.

4.1.3. Flattening Filter

To ensure uniformity of dose rate over a broad area, a flattening filter shall be provided for each source. Filters shall be a polyethylene terephthalate disk of thickness and diameter appropriate for the source (ref. ISO 6980). The filters assembly shall be designed such that the sources are synced with their respective filters when used.

4.1.4. Safety Interlock System

A comprehensive safety system shall be provided with interlocks, warning lights, and “fail safe” design constraints in order to prevent the inadvertent exposure of radiation to operators or anyone else in the beta range. It shall—at minimum—include a door interlock, emergency shutoff switches (both inside the range and outside in the mezzanine), warning lights, and an audible warning siren to alert individuals of potentially being exposed to harmful radiation. The safety system shall meet all federal regulation requirements for this type radiation producing device.

4.1.5. Control System (with automated control system software)

A control console that enables complete remote operation of the beta-irradiator system and monitoring of its status shall be provided with an automated software control system.

The console shall include a keyed switch for turn-on and normal turn-off of the system. It shall include an EMERGENCY OFF control for emergency shutdown of the system. Other specific requirements for the control console follow.

1) The console shall include a control whereby the operator may select the filter to be used. The console shall include a display indicating filter in use.

2) The console shall include controls whereby the operator may position the exposure table. The console shall include a display indicating table position in all axes.

3) The console shall include controls for opening and closing the exposure shutter.

The console shall include an automatic reset, six digit exposure timer to count from 0 to 999.999 minutes in .001-min increments for control of the high-speed shutter. The timer shall be capable of preset or manual control of exposure time. The timer shall have a time-out feature that will enable an irradiation interrupted by closure of the shutter during either preset or manual operation to be resumed and completed upon reopening the shutter. The timer shall begin counting down from the indicated pre-set exposure duration when the shutter is in the fully-open position. When the timer reaches zero, beta exposure is terminated.

4) The software shall include an exposure-rate calculator to determine exposure rate based on initial distance, and vice versa.

5) The software shall include an automated irradiator characterization with the following capabilities:

• Irradiator characterized with NIST-traceable equipment,

• Multiple data points are measured and stored in database,

• Curves are generated based on the true, measured data,

• Software uses these decay-corrected curves to provide exposure rates (or distances).

6) Database to record results.

4.2. Calibration Bench (and accessories)

4.2.1. Alignment Bench

A remote-positioning exposure table shall be provided to securely translate and position— without deflection—the instrumentation, dosimeters, and a phantom (up to 80 kg). The table shall have three-axis (XYZ) motion provided by servo motors.

4.2.1.1. Servo motors

In order to maintain uniformity of motion-control capabilities with other linear motion systems being upgraded in the laboratory, Teknic Clearpath® Software Controlled (SC) servo motors shall be used. Teknic’s line of Clearpath® motors have an auto-tuning feature, greatly reducing the amount of time necessary for tuning the move profiles to less than 15 minutes (per axis). The determination of Clearpath® SC model series (e.g., SCSK or SCHP) and model is left to the design engineers, however, the selected Clearpath® SC motor(s) shall feature the Advanced Firmware Option, which includes the auto-tuning g-Stop™ anti-vibration move profiles. Integration with the designer’s choice of motion input command is easily achieved as the Clearpath®

SC series can easily be configured (via the included software) to accept simple step & direction (or quadrature A/B) inputs (e.g., from a PLC, indexer, or CNC controller), or alternatively can be fully controlled by software API using modern object-oriented programming for complex motion conditions and paths.

4.2.1.2. Hard-stop homing

The linear-motion system shall be designed to accommodate hard-stop homing for the most accurate and repeatable positioning, which is easily configured via the Clearpath® software. Teknic applications engineers are freely and readily available to accommodate design and integration needs.

4.2.1.3. Belt drive and pulley mounts

The linear-positioning system shall be belt driven with steel-reinforced belts. The belt mounting brackets shall include a belt tensioner for maintaining appropriate tension on the belts over time. The drive-pulley mount will be designed such that no radial or axial load will be induced on the motor shaft when the belt is being driven (i.e., double-ended bearings for mounting the pulley in a support block where the shaft is free of radial and axial forces).

4.2.1.4. Table design and positioning tolerances

Table distance from the face of the Beta source window shall range from 0 – 200 cm.

The table shall be height adjustable from the centerline of the radiation beam to at least 30 cm below the centerline and laterally adjustable to at least 25 cm either side of the beam centerline. Table positioning in all three axes (distance, height adjustment, lateral adjustment) shall be within 25 µm of selected position.

Dimensions of the table surface shall be at least 30 cm x 40 cm. Table positioning in all three axis shall be accomplished from the control console. Table shall have a temperature/pressure sensor that is easily removed to be submitted for calibration.

Articulating mounts for the instrument camera and monitor shall be provided. A spare electrical outlet (110 VAC, 1 A) shall be provided for powering equipment. RS- 232 and USB connectors shall be provided for connection to equipment and instruments. It is also desired that the table be capable of rotating to 40 and 60 degrees in either direction.

4.3. Accessories

4.3.1. Bohm Extrapolation Chamber

A Bohm Extrapolation Chamber for absorbed-dose measurements of beta radiation and low-energy x rays shall be provided. The chamber shall have a very-thin entrance window of 0.75 mg/cm2 and a collecting electrode of 30 mm in diameter that is surrounded by a guard ring of 15 mm. A built-in micrometer for moving the collecting electrode to adjust the depth of sensitive volume shall be incorporated in the design of the chamber.

5. General Requirements

5.1. The system shall comply with all applicable Federal Regulations, as well as the relevant standards of the IAEA, IEC, and ISO.

5.2. The contractor shall provide all cables and accessories required to enable proper operation of the beta system in accordance with these specifications. The control console will be located approximately 20 feet from the beta irradiator.

6. Warranty

The contractor shall provide a one-year warranty for on-site maintenance services. Optional extended two-year maintenance warranty shall be provided by the contractor at an additional cost that is deemed reasonable within the industry.