# Presentation: 673701

## Radiation Litmus Paper

**Benjamin Warner, Deidre Johns,**
**Tony D’Alessio, Kimberly Sheafe**
**Chemistry Division**
**Los Alamos National Laboratory**
**Funding Provided by:**
**DOE Office of Nonproliferation and National Security,**
**Office of Research and Development (NA-22)**

## Project Goals:

**     ****1) Improve detection limits of chemical-based radiation   **
**         ****measurements**
**     ****2) Incorporate these reactions into a generally useable form**
**	****• ****Adjustable Sensitivity**
**	****• ****Lightweight and Portable - Similar to a TLD**
**	****• ****No Power/Cooling Requirements**
**	****• ****Require Little/No Training**
**	****• ****Inexpensive**
**	****• ****Extended Shelf-Life**

## Detect Radiation by a Color Change

**   ****Potential Uses:**
**        • “****First Responder” Badge**
**        • ****Personal Dosimetry**
**        • ****Form and Use Similar to **
**          ****Other Detection Equipment**

**Anachemia M256A1 Chemical Test Kit**

## Background Numbers: How Little Can You See ?

**A person can see a 2% change in color**
**Assume a good colorant (********=50,000), 1 cm path length, 1 cc volume**
**Log (I****o****/I) = ******** x path length x [colorant]**
**Log (100/98) = .009 = 50,000 x 1 x [colorant]**
**[colorant]  = 1.7x10****-7**** moles/liter**
**= 1.7x10****-10**** moles/mL **
**= 10****14**** molecules**

## Background Numbers: Chemical Reactions from Radiation

**Radiation produces ion or radical pairs**
**G = reactions / 100 eV**
**Commonly G=3 for gasses, liquids (G=30 for solids)**
**  **
**For a 100 keV h********: 10****5**** eV x 3 rxns/100 eV = 3,000 rxns/h******
**For a ****10****B(n,********) ****7****Li reaction: 2.4 MeV x 3 rxns/100 eV = 72,000 rxns/n**
**Radiation can produce ~10****3****-10****5**** reactions per interaction**
**	**

## Historical Problems with Colorimetric Detection:  Sensitivity

**     ****Radiation ionizes materials: ~10****3 ****(********) to 10****5**** (n****th****) molecules per event**
**     ****Common chain reactions give a 10-100-fold amplification**
**     ****A person can see ~10****14**** molecules of a colorant**
**          ****So need 10****7****-10****10**** captured events to see**
**Example: 100 keV ********: Assume a 1 mm thick hydrocarbon detector**
**	****= (10****14**** rxns) / (10****3**** rxns per ********) x (0.1% capture efficiency)**
**	****= 10****14**** h******** / cm****2**** to see = ~5,000 R**
**Example: Neutrons: Assume a 1 mm thick hydrocarbon detector, 10% ****10****B**
**	****= (10****14**** rxns) / (10****5**** rxns per n****th****) x (30% capture efficiency)**
**	****= 10****8 ****-10****9**** n****th**** / cm****2**** to see **
**	****however, thermal neutrons (n****th****) = 1% of initial flux (n****f****)**
**	****so to get 10****8**** n****th****, need initially 10****10**** n****f**** / cm****2**
***	******which is a initial dose of 300-400 rem***

## Historical Problems with Colorimetric Detection: Stability

**     ****Chain reactions can increase the chemical yield from captured  radiation**
**     ****Common chain reactions include decomposition of halogenated materials **
**     ****(RX), including CCl****4****, CHCl****3****, PVC**
**     ****RX decomposition can yield acid or oxidizers**
**     ****Can achieve chain lengths of 10-100 (realistically closer to 10)**
**     ****Problem: *****RX is usually unstable to light and heat ***

## Methods to Enhance Signal: Autocatalysis

**     ****Ionization Creates Catalyst**
**     ****Product of Catalyzed Reaction is Second Catalyst Molecule**
**     **
**    **
**Issues:**
**     ****Sensitivity vs Stability**
**     ****Stability to Environment (heat, light)**

## Need four atoms of Ag0 to activate grain

**Need *****four***** atoms of Ag****0**** to activate grain**
**Typical grains are .25-1 micron diameter = 10****8**** - 10****10**** atoms Ag/grain**

## General Schematic Drawing

**AgBr**

**Ind + Dev-H**

**IndH****+**** + Dev**

**opaque**

**transparent**

## Schematic:

**Fieldable form of Radiation Litmus Paper**

## Slide 12

## Prototype For Testing Chemistry:    

## Sensitivity vs Volume of Indicator Phase

**Volume of Indicator Phase (mL)**

**Dose (mR)**

## Sensitivity vs Detector Area

**Detector Area (cm****2****)**

**Dose (mR)**

## Sensitivity vs Chain Length

**Length of Chain Reaction**

**Dose (mR)**

## Features:

**Useful Lifetime of Material: Devices function for 8-36 hours**
**Material Form: Liquid and gel developers**
**Color Choice: Dark {blue, purple, red} to yellow, or red to blue**
**Multi-Component System Allows Tuning**
**Easy to Synthesize**
**Relatively Stable**
**Long Shelf Life    **

## Current Performance:

**	****• ****Adjustable Sensitivity - 17 to 2000 mR**
**	****• ****Easy to Make and Use**
**	****• ****Small - 17 mR Device ~ 2 cm****3**** **
**	****• ****Threshold or Continuous Dosimeter**
**	****• ****Inexpensive - Chemicals < $1**
**	****• ****Calibrated for ****137****Cs ********-Radiation**
**	****• ****Sensitive to ********, neutron**
**Future Work:**
**	****• ****Enhance Color Change Range**
**	****• ****Mass Produce for Field Test****	**