ESHQ Radiation Physics Engineering: Modernization and upgrades · 2018. 2. 19. · New Oxygen Safety System Project –Interlocks Team • Design a new hybrid system based on existing

Adam Olson

Engineer Retreat – Engineering within Fermilab

20 February 2018

ESHQ Radiation Physics Engineering:

New Safety System and Instruments

New Safety System and Instruments Presentation

• Topics for this presentation

– The design of a new PLC-based, rack-mounted, ODH safety

system

– The design of a new radioactivity classification instrument

– The design of a new interlocked radiation area monitor

instrument

2/20/2018Adam Olson | ESHQ RPE: New Safety System and Instruments2

New Oxygen Safety System Project – Interlocks Team

• Design a new hybrid system based on existing ODH systems

– Combines the advantages of the current rack-mounted ODH

system with beneficial features from the current PLC-based

ODH system

• Advantages of the existing rack-mount system:

– Simplified use, lower cost, smaller size and portability

• Advantages of the existing PLC system:

– More reliable oxygen sensor, industry-standard safety rated

components, and computer processing capability


New Oxygen Safety System – PureAire Sensor


• PureAire sensor chosen for the new system

– Zirconium oxide sensor not dependent on barometric pressure

– 10 year cell expiration

– 4-20mA current loop interface

New Oxygen Safety System – Helium Sensitivity Error

• PureAire sensor is sensitive to helium in the air

– Reads higher than normal oxygen in the presence of low levels

of helium – this is an unsafe condition

• Empirically derived look up table to compensate for an

assumed ever-presence of helium

– Piecewise linear curve with four inflection points across the

measurement range

– Thousands of data points can be programmed with a PLC


New Oxygen Safety System – Helium Compensated Data

• Application of the helium compensation curve to the raw data


New Oxygen Safety System – Block Diagram


New Oxygen Safety System – Prototype Internal


New Oxygen Safety System – Readout and Interface Panels


New Oxygen Safety System – Prototype Front Panel


New Oxygen Safety System – Benefits


• Benefits

– Reduces the number of false alarms under the current rack-

mounted system

– Reduces maintenance and calibration costs

– Cheaper to install than the full PLC ODH system

– More portable than the full PLC ODH system

– Uses a safety rated PLC

– Barometric pressure independent sensors

– Helium compensated measurement for unsafe condition

Wallflower 4 Project – Instrumentation Team

• The humble Geiger counter with some bells and whistles

• Replaces the original, 40+ years old wallflowers designed by

physicist Bob Shafer

• Fulfills instrumentation needs of radiological workers at

Fermilab


Wallflower 4 – Prototype Unit


Wallflower 4 – How it works


Wallflower 4 – Mechanical

• Housing modifications– Fit everything in a portable housing that can take abuse in the field

– Machining of the plastic housing

• 3D printed parts– 3D printer (MakerBot Replicator) custom parts

– Precise alignment of GM Tube, check source, and sonar transducers

• Custom overlay with integrated push button and transparent window


Wallflower 4 – 3D Printed Components


Wallflower 4 – Assembled Prototype Internals


Wallflower 4 – Prototype PCB


Wallflower 4 – Software

• Embedded system programmed in C– No operating system → creation of Wallflower Board Support Package (BSP):

– Modular C units sharing memory, data, interrupt time, and hardware resources

– No dynamic memory allocation allowed

• Embedded Rad Instrument – Abstraction of the radiation instrument to the application programmer

• Makes it easier to build up new instrument configurations without code restructuring

– USB communication and the instrument’s serial protocol

– Calibration/testing applications vs. the end user application


Wallflower 4 – Benefits

• ALARA-friendly goals:– Reduce user error in measurement and classification of items

– (Future) Reduce process duration with statistical analysis (standard error) to

complete measurements just-in-time.

• Directly measures a standard reference for the radiation

intensity with the sonar distance.

• Transformable, portable, modular BSP: – New graphics, fonts, peripherals, process pages, scales/units, USB

commands and more could be changed to make a completely new instrument

with the existing design.

– If the Fermilab Rad Worker procedure changes, the instrument could be

adapted in software.


New Area Monitor Project – Instrumentation Team


New Area Monitor – Design Committee


• It will replace the Chipmunk and Scarecrow radiation area

monitors all over the lab

• Fulfills the needs of RSOs to interlock radiation areas

• Created a committee for future radiological instruments with

stakeholders from ESHQ teams:

– Instrumentation

– Interlocks

– Radiation Safety Officers

– Radiation Physics Science team

New Area Monitor – Instrument Simplification

• Quality Factor-less

– Exact weighting factors will be determined by the RSO and

applied directly in the interlock’s trip setting without any need for

configuring the instrument hardware

• Uniform dose per pulse in units of 1 µrad to simplify math and

instrument configuration

– Inspired by the FOX x-ray area monitor with 1µR/pulse


New Area Monitor – Prototype


• Prototype made from a Chipmunk yellow box with new guts

New Area Monitor – Hardware

• Environmentally rugged specs

– -30 ° to +50 °C operating temperature

– 93% Relative Humidity at 30 °C

– EMI and ESD protection

• Surface mount digitizer board

– New Texas Instruments electrometer opAmp – LMP7721

– Active guard ring to minimize leakage

– Minimize parasitic effects on layout

– No floating components

– Sensitivity of 2pC/count working


New Area Monitor – Digitizer Prototype


• Electrometer with active guard ring around its input

• Case with gasket, grease seal, and desiccant plugs to keep

out moisture

New Area Monitor – Control Board Prototype


New Area Monitor – Benefits

• Flexible weighting factors

• Higher output sensitivity, uniform dose/pulse of 1 µrad

compared to Chipmunk.

• Lower power draw

• Reduces black magic required to build and fix digitizers

• Dual power, option to not need electrician work

• Smaller physical size

• Recycles the Chipmunk ion chambers

• Cheaper unit cost

• (Future) Expandable IO with the FPGA


The End

• Thank you for your time!


Documents

ESHQ Radiation Physics Engineering: Modernization and upgrades · 2018. 2. 19. · New Oxygen Safety System Project –Interlocks Team • Design a new hybrid system based on existing