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Ultraviolet Disinfection of Radiological Instrumentation

Oct 13, 2020 12:31:44 PM

News Ultraviolet

This unsolicited report was prepared by Washington River Protection Solutions LLC for the U.S Department of Energy by E. B Wilkes. XtraLight extrapolated data from document RPP-RPT-62241 Rev. 01 to create this blog post.  See the press release here

E. B. Wilkes, Washington River Protection Solutions LLC

September, 2020

Download the original document here:

“Ultraviolet Germicidal Irradiation (UVGI) has a definite future in the control of contagious diseases, and if applied on a widespread basis, it may be the key to controlling epidemics and pandemics. No other current technology has the capability, the adaptability, and the favorable economics to make it viable for an extremely wide variety of disease control applications.” (Kowalski, 2009).


Ultraviolet Disinfection and Sanitation of Radiology Department In Hospital For UV-C High Power Ultraviolet Disinfection

(Figure 1. Radiology Department In Hospital For UV-C High Power Ultraviolet Disinfection)


Portable UV germicidal lamps have an excellent potential to disinfect Radiological Instrumentation Probes and Personnel Contamination Monitors

(PCMs), inactivating 99.999% of pathogens on solid, non-porous surfaces. The technology is proven against SARS and MERS Coronaviruses.


An XtraLight® UV-C Handheld Ultraviolet Disinfection System, model #UVCH240254WH, was purchased and tested August 26-27 and September

2-3, 2020. Tests were conducted to determine the feasibility of using this lamp to rapidly disinfect radiological instrumentation probes and

Personnel Contamination Monitors (PCMs). The irradiance readings, using a NIST-traceable radiometer, demonstrated that a sufficient fluence, or

radiant dose of Ultraviolet-C (UVC) to kill or inactivate 99.999% of many pathogens, would require the following times seen below on table 1.

(There was no response by the contamination monitoring instruments to the UVC, demonstrating that the instruments could be disinfected while

energized and immediately returned to service.)


Alpha and Alpha/Beta Scintillation Probes 10 Seconds
PCM Detector Panel 10 Seconds
Argos™ 5AB Whole Body Surface 1 Minute

Table 1. Disinfection Times for Radiological Equipment using a UV-C Handheld


Of the studies of germicidal effectiveness of UVC, the ambulance test is the most applicable. It was found that a dose of 52.6 mJ/cm2 was required

to inactivate at least 99.9% B. subtilis spores on a solid surface which would inactivate 99.999% of many pathogens on a solid surface. This value of

52.6 mJ/cm2 will be the standard disinfection dose to be required when evaluating any UVC lamp.


Find: Time of irradiation to achieve 52.6 mJ/cm2.

Since 1 Joule = 1 Watt-second, find time to reach 52.6 mW-sec/cm2.

(52.6 mW-sec/cm2)/(5.54 mW/cm2) = 9.5 sec


This chart displays the mW/cm2 (Ultraviolet-C Irradiance) per second when held 1.5" from calculation paper with the x and y values being inches from the dead center of the lamps.

  -12" -10" -8" -6" -4" -2" 0 2" 4" 6" 8" 10" 12"
+4" .366 2.11 3.36 4.02 4.24 4.31 3.90 4.52 4.34 4.60 3.59 2.24 .302
+2" 0.647 2.99 7.23 8.68 9.06 9.04 9.06 9.03 8.87 8.61 7.60 3.06 0.599
0 0.995 3.87 8.09 9.42 9.81 9.84 10.1 10.1 10.1 9.66 9.10 3.73 0.942
-2" 0.386 2.76 6.90 9.01 9.34 9.18 9.23 9.07 9.01 8.55 7.72 2.76 0.418
-4" 0.906 2.18 3.50 3.45 4.50 4.03 4.06 3.56 3.92 3.38 2.96 1.87 0.663

Table 1.1 Irradiance Map of Lamp with Paper Base. (Units: mW/cm2 Inches from dead center of lamp)


                    Terms and Fundamental Quantities:

Pathogens: “Pathogens are any microbes that cause infection in humans and animals, and these include viruses, bacteria, and fungi.” (Kowalski, Section 1.8)
Germicidal: “The term ‘germicidal’ implies that these UV systems destroy, kill, or inactivate microorganisms such as viruses, bacteria, and fungi. Technically, viruses are molecules, and so it is customary to refer to viruses as being inactivated rather than killed. In all cases, germicidal action means disinfection, and disinfection implies a reduction in the microbial population, whether in air, water, or on surfaces.” (Kowalski, Section 1.3)
Radiant Energy: The energy associated with and transmitted in the form of waves. Examples: light, heat, X-rays, and gamma rays. Symbol: Q. Unit: Joule. Note: 1 Joule = 1 Watt-second
Radiant Flux: The time rate of flow of radiant energy. Symbol: Φ. Unit: Watt. Mathematically: Φ=dQ/dt
Irradiance / Incident Radiant Flux Density: The radiant flux incident on a surface. Symbol: E. Unit: mW/cm2. Mathematically: E=dΦ/dA
Emitted Radiant Flux Density / Radiant Exitance: The radiant flux density emitted from a source, as a lamp. Symbol: M. Unit: mW/cm2.
Fluence / Radiant Dose: Radiant energy deposited; for a surface, deposited per unit area. Unit: mJ/cm2, or mW-sec/cm2.
SARS-CoV-2: Severe Acute Respiratory Syndrome-Coronavirus-2, or in early 2020, the “novel coronavirus.” The virus that causes Coronavirus Disease 2019 (COVID-19). (CDC 2020)
UVGI /  Ultraviolet Germicidal Irradiation: A disinfection method that uses UVC light to kill or inactivate microorganisms.

                                            Ultraviolet Radiation:

The full spectrum of ultraviolet radiation (UVR) can be classified into three

groups based on wavelength: ultraviolet A (UVA) (400-315 nm), ultraviolet B

(UVB) (315-280 nm), and ultraviolet C (UVC) (280-100 nm).” (Chang) UVA is

commonly known as black light and causes an immediate tanning effect to the

skin, UVB is the wavelength that causes suntan and sunburn, and UVC is the

wavelength that provides germicidal action.


(Figure 1.1 [when in] viruses, uracil takes the place of thymine. Inactivation of RNA viruses involves

cross-linking between the uracil nucleotides and the creation of uracil dimers.)


“UV wavelengths inactivate microorganisms by causing cross-link between

constituent nucleic acids. The absorption of UV can result in the formation of

dimers in DNA, which can lead to mutations or cell death. The primary dimers

formed in DNA by UV exposure are known as thymine dimers. The lethal effect

of UV radiation is primarily due to the structural defects caused when thymine

dimers form but secondary damage is also produced by cytosine dimers.”

(Kowalski, p. 21) See Figure 1.1 “In RNA …[when in] viruses, uracil takes the place

of thymine. Inactivation of RNA viruses involves cross-linking between the uracil

nucleotides and the creation of uracil dimers.” (Kowalski, p. 23)

“Worst Case” Threshold Limit Values (TLVs) for unprotected eyes and skin were

measured at 2, 4, 5, 6, 7, 8, 9, and 10 feet, with the unprotected worker staring

directly at the lamp output. TLVs were as follows:

     - 2 feet: 8 seconds

     - 4 feet: 27 seconds

     - 5 feet: 42 seconds

     - 6 feet: 1 minute

     - 7 feet: 1 minute, 19 seconds

     - 8 feet: 1 minute, 44 seconds

     - 9 feet: 2 minutes, 15 seconds

     - 10 feet: 2 minutes, 45 seconds



Title Name Date
Checker Lewis, Steven S 09/28/2020
Clearance Review Harrison, Sarah E 10/12/2020
Document Control Approval Alvarez, Efren 10/08/2020
Originator Wilkes, Ed B 09/21/2020
Other Approver Uliano, Tony 10/06/2020
Radiological Control Konzen, Kevin K 10/06/2020
Responsible Manager Konzen, Kevin K 10/07/2020



To see more information on XtraLight's UV-C products, please click here.

UV-C High Power Disinfection System HandHeld XtraLight LED SolutionsUV-C High Power Disinfection Mobile System XtraLight LED Solutions




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Cameron Dillehay

Cameron Dillehay

Cameron is a marketing specialist at XtraLight LED Solutions. He is affluent in UI/UX website design, Graphic Illustration, 3D Rendering/Animation, SEO optimization, Videography, and enjoys enlightening customers with innovative LED technology. "The best marketing doesn't feel like marketing." - Tom Fishburne