Material related questions Q: Stainless steel is the preferred material for conventional lighting in NPPs. Why do you promote aluminium housing? A: Because stainless steel has extremely poor thermal conductivity. Heat is number one killer (beside the radiation, of course) of any electronics and drastically reduces the lifetime of the product. Keeping operational temperature as low as possible has always been our main design goal. Q: What is thermal conductivity? A: Thermal conductivity is the ability of the material to conduct heat. It is measured in W/mK. Here are some thermal conductivities in W/mK: Air: 0.02 Wood: 0.04 Concrete: 0.8 Stainless steel: 16 Iron: 80 Aluminium: 200 Copper: 400 Diamond: 1000 From the table above it can be seen, that the stainless steel has poor ability to conduct heat. In fact, the ability of stainless steel to conduct heat is one of the worst in metals. This is the obvious reason, why we promote aluminium for LED Luminaires. Q: Did you try to make the same  Luminaire in stainless steel/aluminium/copper housing? A: Yes, we tried. We tested the same Luminaire housing made out of copper, aluminium and stainless steel. Stainless steel has by far the worst thermal performance. Q: You can compensate bad thermal performance of the stainless steel by adding more cooling fins, right? A: Wrong. You can add stainless steel cooling fins to infinity without results. The only effect is heavy, bulky product, without proper cooling. Q: What is emissivity of the material? A: Emissivity is the surface property of the material. It shows the ability of the material to exchange heat energy with the surrounding media. Any glossy finish of the heat sink material has bad emissivity and therefore slow exchange of the heat energy with the surrounding air. An aluminium foil (glossy finish) has emissivity coefficient of 0.04, while anodized aluminium has the emissivity of 0.8. In both cases the same material regarding thermal conductivity, but anodized one has 20 times better emissivity, i.e. exchange of the heat with the surrounding media. Q: Aluminium is not allowed in areas where hydrogen generation might be the problem. How do you solve this problem? A: For applications inside the RB we are offering Stainless Steel version of the Luminaires. Due to very poor thermal performance of the Stainless Steel, the maximum allowed ambient operating temperature is limited to 50 o C (Aluminium version 80 o C). The material of the housing however does not have any impact on LOCA compatibility.
Radiation related questions Q: Do you test your products with radiation source, or you just compile public documents describing radiation hardness of electronics? A: We always test our products and never assume anything. All our products have full nuclear qualification and tests, performed by third party certified laboratories. Q: Which part of your Luminaire is tested to radiation? A: Each and every part of our product is tested with gamma and neutrons. This includes all mechanical parts (housing, screws, optics, diffuser, sealings, coatings, connectors, wires etc.) and all electronic parts including LEDs and complete LED control gear (driver). Q: Where do you test your products and components? A: All our products are tested inside the core of General Atomics TRIGA Mk II nuclear research reactor in Jožef Stefan Institute, Reactor Infrastructure Centre in Ljubljana, Slovenia, EU. In case of gamma irradiation, the nuclear reactor is shut down, without presence of neutrons. In case of neutron irradiation the research reactor is operating normally. Q: Which part of LED Luminaire is the most problematic one regarding radiation? A: LED control gear (driver) is by far the most problematic part of any LED Luminaire. Q: Your electronics is not affected by gamma and neutron irradiation. Why? A: Every electronics is affected by the radiation, including ours. We achieved world’s best radiation hardness in LED lighting industry with careful selection of components and circuit topology, cancelling the effects of radiation damage. Q: Many producers of LED Luminaires are testing just LEDs to gamma. Is this correct? A: No. The LED itself is relative insensitive to radiation, opposed to power electronics which might be up to 1000 times (three magnitudes of order) more sensitive. Testing LEDs only and assuming the Luminaire has the same radiation hardness as LEDs, is false. Q: Do you irradiate your electronics biased? A: Of course. Our electronics (complete functional PCB) is irradiated biased, i.e. up and running at full power before, during and after the test. Irradiation of unpowered or unbiased electronics, or even components alone, not installed on PCB, gives wrong, misleading result - a magnitude better then biased. Q: Do you use Cobalt for gamma tests? A: No. For gamma and for neutron irradiations we use TRIGA Mk II Nuclear Research Reactor. Nuclear reactor has similar gamma spectrum to NPPs and better mimics real world situation inside the containment. Q: Is your LED driver sensitive to the dose rate? A: No. LED control gear is tested with the dose rates between 250 and 25.000 Gy/hour without any influence to operation of the Luminaire. Q: Your H series should have “World’s best radiation tolerance in LED lighting”. Is this correct? A: Yes, it is. We specify our products with radiation tolerance of up to 500 kGy. In fact we tested our electronic inside the core of the TRIGA MkII nuclear research reactor to more than 1 MGy (0.1 Grad). And the electronics is still functional. Q: Do you use shielding techniques? A: No, there are no radiation shields inside the Luminaire. Radiation hardness is achieved by design. Q: Are your radiation test reports available to the public? A: All test reports are available to qualified customers. More data are available here.  
H-50PLS Gen III Modular Rad-Hard underwater LED Luminaire
Modular underwater pool lighting system consist of any number of small, lightweight but powerful LED units, depending on lighting requirements. Each unit weight about 1 kg. One unit offers more than 7.000 lm. System is designed for continuous submersion. More…
H-50LBS Gen III Rad-Hard Low-Bay LED Luminaire
H-50LBS Gen III is very light and compact 50 W Low-Bay LED Luminaire, designed for simple one-to-one replacement of the existing 200 to 500 W tungsten or standard T8 based fluorescent Luminaires. The Luminaires are very light, easy to handle and replace. The weight of aluminium unit is just 0.8 kg. More…
Ultra robust design Designed for the unexpected
The radiation hardness of the product is just one - indeed the most important - property of the nuclear grade product. But for the the complete package other properties are equally important: ultra high temperatures survivability ultra robust design no browning of the optics high differences in ambient pressure water/chemical compatibility seismic shock compatibility 100% shatter proof design and very high reliability/lifetime Our H Gen III series fulfils all the requirements above.
H-100HBS Gen III Ultra Rad-Hard High-Bay LED Luminaire
H-100HBS Gen III is powerful, 100 W High-Bay LED Luminaire, yet very light, compact and easy to install. It is designed for simple one-to-one replacement of the existing 1 kW tungsten or 500 W HID based Luminaires. The Luminaire is available in Aluminium or Stainless Steel. Aluminium version is the preferred choice, except for application inside the RB (Reactor Building).  More…
H-100HBS Gen III Rad-Hard High-Bay LED Luminaire
100 W High-Bay LED LOCA compatible Survives 200 0 C for 24 h 16.000 lm @ 160 lm/W 5000 K @ CRI 80 IP 65 / IK 08 500 kGy (50 Mrad) gamma TID 5 × 10 14  neutrons/cm 2  1 MeV (Si) Read more.
H-50LBS Gen III Rad-Hard Low-Bay LED Luminaire
50 W Low-Bay LED LOCA compatible Survives 200 0 C for 24 h 8.000 lm @ 160 lm/W 5000 K @ CRI 80 IP 65 / IK 08 500 kGy (50 Mrad) gamma TID 5 × 10 14  neutrons/cm 2  1 MeV (Si) Read more.
L Gen III Series Affordable Rad-Hard LED Luminaires
50 or 100 W High/Low-Bay LED AC or DC operation same lumen output as H series aluminium housing 5000 K @ CRI 80 IP 65 50 kGy (5 Mrad) gamma 5 × 10 13  neutrons/cm 2  1 MeV (Si) Read More.
Industrial Gen III Series Heavy duty industrial LED Luminaires
A line of high performance, Heavy Duty LED lighting products. Designed for high temperature industrial environments. Based on our H series with the same mechanical and optical properties. The TID gamma is still 500 Gy (50 krad). Read more.
LED Pool Lighting Modular underwater lighting
Simple selection of illumination pattern, scalable illumination, simple upgrading, robustness and very easy replacement are main advantages of the modular approach. The Luminaire body is machined out of Aluminium. Holders are always custom made out of Stainless Steel, grouping any number of units together, if necessary. All the required electronics, i.e. LED control gear, is mounted inside the Luminaire housing. There are no need for any external units. The robust cable is directly plugged into the wall outlet.
Optics Browning free speciality optics
Complete Gen III series is equipped with the speciality optics. The lenses are 100 % shatter proof, chemically stable, suitable for the temperatures of up to 200 o C and full browning proof due to radiation. The optical transmissivity of the lenses is excellent and remains practically unchanged to the radiation doses of more than 500 kGy (50 Mrad). Two types of optics/lenses are available. The one with the middle and the one with the wide optical characteristic. The choice of optics covers most lighting scenarios.
LOCA compatibility H Gen III series of ultra Rad-Hard LED Luminaires is world’s first and world’s only LOCA (Loss Of Coolant Accident) compatible lighting system. H Gen III Luminaires are designed for typical DBA (Design Basis Accident), where beside ultra high radiation levels, very high temperature and very high pressure survivability are required. Our H Gen III series survives operational at ambient temperatures of 100 o C for the period of 350 hours, and ambient temperatures of over 200 o C non operational for 24 hours. World’s highest performance for any power electronics.
Photometrics Photometric properties of the Luminaires were measured in Europe leading photometric laboratories, using latest photo goniometer instruments. The results of measurements are overall Luminaire efficacy, polar light distribution, correlated colour temperature and colour rendering index. Optical .ldt  files for all our products are available on request.
Reliability and lifetime expectancy The reliability prediction was performed using A.L.D. Ltd. Software “RAM Commander”, in accordance with the MIL-HDBK-217F Notice 2, using Part Stress Analysis method. Environmental condition: GB (Ground Benign).  Mission profile 24/7/365 (continuous operation) at 50  o C ambient temperature. MTBF values versus temperature are shown in a graph. Lifetime expectancy at specified mission profile is more than 22 years. Calculation is based on 95 % confidence level.
About us DITO is fully privately held company founded in 1992 by Srecko Bizjak B.Sc. (CEO) and Rafael Kitak B.Sc. (R&D). Both are exclusive owners of the company to this day. In 1995 we developed world’s first multichannel, studio grade, PC based, digital audio recorder DAR-20. In the year 2000 we bring to the telecommunication market our DSP based multichannel, multifunctional, fully programmable, 2 Mbit/E1 digital voice announcement system. In 2007 we developed TNS++, railway copper wire transmission system. TNS++ is still worlds unique product for multichannel DSP based, fully programmable, very high performance tone communication, over standard railway copper wire cables. The system is used for communication between relay based safety related railway equipment worldwide.   In 2009 we started with LED Lighting development. First with the street and heavy duty industrial lighting products. In 2013 we jumped to nuclear LED Lighting business. Our goal is to bring to the nuclear market world’s best radiation hardness in the LED Lighting industry.
Postal DITO d.o.o. Gorica pri Slivnici 144 3263 Gorica pri Slivnici Slovenia, EU VAT: SI59718587 Sales terms and conditions
Photometry related questions Q: Are your photometric data simulated/calculated or measured? A: Our Luminaire photometric properties are measured in the Europe’s leading laboratories and not just calculated from LED vendor data sheets. Q: What is the output of the photometric measurements in the photometric lab? A: Beside standard test report, the output of the photometry are photometric files used in simulation software. Eulumdat .ldt and IESNA .ies files. Q: Do your Lumen/Watt specification represent LED efficacy? A: No, never. Our efficacy in lm/W is measured in the photometric lab and represent overall Luminaire efficacy - from the wall outlet to the luminous flux out of the product. Q: Your lm/W specification is relatively low in comparison to other LED Lighting vendors. Why? A: Correct. The numbers are lower then most others, because we are not specifying LED efficacy as Luminarie efficacy. There is big difference between this two numbers. LED efficacy is the number taken out of the LEDs manufacturer data sheet, measured in the ideal conditions. Luminaire efficacy takes into account also all optical and electrical losses, which lovers overall Luminaire efficacy. Optical losses are due to losses in optics, Luminaire housing, protective glass or diffuser. The best designs with optics or diffuser have at least 20% of losses. If we add at least 10% of losses in the LED driver, we can estimate overall losses to minimum 30%. In practice this value can be much higher. If Luminarie incorporates high performance LED with 200 lm/W and if we take into equation optical end electrical losses, then overall Luminaire efficacy is less than 140 lm/W. Q: Why should I check which efficacy is specified in the Luminaire data sheet - LED efficacy or Luminaire efficacy? A: Let me explain this with simple example. If we take high performance LED with data sheet efficacy of 200 lm/W and put this LED into the black box, then the overall efficacy of this “Luminaire” will be exactly 0 lm/W. Which specification for this “Luminaire” is now correct 200 lm/W or 0 lm/W? Q: How to avoid wrong and misleading figures in the Luminaire data sheets? A: Simple. Request photometric test report of the Luminaire. Q: Are your photometric test reports available to the public? A: All test reports are available to qualified customers. More data are available here.   
Reliability and lifetime related questions Q: What is MTBF? A: Mean Time Between Failures or MTBF represents the statistical approximation of how long a number of units should operate before a failure can be expected. It is expressed in hours and does not represent how long the unit will last. For instance. If we test 1.000 units for 1.000 hours and 1 failure occurs, the MTBF value would be 1 million hours. This does not mean, that the unit will operate for 1 million hours or 114 years. If 1 million units are operating with calculated MTBF of 1 million, a failure can be expected every hour. Q: Who performed MTBF calculation for you? A: We contracted our MTBF calculation with Israeli company A.L.D. , the leading consulting firm and software house in the field of Reliability Engineering and Analysis, Safety Analysis and Safety Management, Quality Engineering and Quality Assurance. Q: Which method do A.L.D. use for MTBF calculation? A: There are many methods and standards to choose from for MTBF calculation. We decide to perform MTBF calculation according to US military specification MIL-HDBK-217F Notice 2, one of the most frequently used and recognized standards in the industry. Q: What is the relation between MTBF and lifetime? A: The confusion between these two parameters is the most common confusion in the reliability theory. However, there is some mathematical way to use MTBF to roughly expect a lifetime. For our products the calculated lifetime with 95 % of confidence is about 22 years operating 24/7/365 - i.e. continuous operation. Due to exponential nature of mathematical formula, for 100 % of confidence the calculated lifetime is zero hours, or with 0 % confidence, the lifetime is indefinite. Q: 100.000 hours of lifetime is well known figure for LED lighting. Why are you complicating with calculations? A: 100.000 hours is the number you can find in any LED component data sheet. It is a pure theoretical figure and give us an idea how long a LED component (not a LED Luminarie) can last if it operates under ideal conditions. Conditions inside the LED Luminarie, where the LED component is operating, are far from ideal. The operating temperature (bad thermal design), current density (driving LED at maximum power), the technology and the quality of the LED component are all affecting real operating life, which can be much lower then 100.000 hours. Q: Does the LED Luminaire last as long as LEDs? A: Not at all. LED Luminaire has many other components too. The most problematic, and the most unreliable one, is LED control gear, sometimes called LED driver or ballast. By far the most unreliable components in any power electronics, are electrolytic capacitors and opto couplers. Our power supply does not use any of them. Just for comparison. The best electrolytic capacitors have lifetime expectancy of just few thousand hours at rated temperature. Should we expect, that the Luminaire itself will last for 100.000 hours? Probably not. Q: Finally, what is the lifetime of your Luminaire? A: A million dollar question. Statistically speaking, more than 22 years with the confidence level of 95 %. Also statistically, our Luminaire can fail in the first hour of operation or it can last forever. The probability of either is very low, but is possible. Q: Do you use third party LED driver? A: No. We are using only LED driver developed and produced in-house with all required nuclear qualifications.
L Gen III series Rad-Hard LED Luminaire
L Gen III is simplified version of our flagship H Gen III. The radiation hardness is tested and certified to 50 kGy (5 Mrad). The mechanical, electrical and optical properties of the L Gen III  are the same as the H Gen III. More…
Affordable LED Lighting For less demanding nuclear apps
L Gen III series is designed for less demanding nuclear applications. The series is not LOCA compatible and is available in Aluminium version only. L Gen III is cost effective alternative to our ultra performance H Gen III series for applications where lower doses of radiation can be expected Main applications are: spent fuel storage facilities fuel handling facilities medical facilities military facilities scientific facilities
DITO’s answer to unsolvable problem After three years of development and after more than hundred irradiation tests in the TRIGA Mk II nuclear research reactor, we find the solution for the unsolvable problem -  the high efficiency, extremely high radiation tolerant, LED Switch Mode Power Supply. DITO H series SMPSs are tested to: 500 kGy (50 Mrad) of gamma  5 × 10 14 neutron/cm 2  1 MeV (Si) equivalent fluence  Our H series of LED products is equipped with one of the variant of the same ultra high radiation tolerant LED control gear. The electrical efficiency of the electronics is more than 90 %.
Efficiency problem One of the main reasons, why select LED as the technology of choice, is energy efficiency. But LEDs require current source for proper operation. There are two options to drive LEDs. Linear based or SMPS (Switch Mode Power Supply) based electronics. Properly designed linear solutions have good radiation tolerance, but inherently bad efficiency. The only choice for the efficient LED lighting system is use of the SMPS technology. But commercial SMPSs have very low radiation tolerance and are practically unusable in any radiation environment. The problem looks unsolvable. One solution has good radiation tolerance, the other good efficiency. The challenge is to bring efficiency and radiation tolerance together in one product.
H-50PLS Gen III Rad-Hard underwater LED Luminaire
50 W underwater LED available as holder or pendel version AC or DC operation 7.000 lm at 140 lm/W 6000 K IP 68, continuous submersion 500 kGy (50 Mrad) gamma TID 5 × 10 14  neutrons/cm 2  1 MeV (Si)
Heavy duty industrial LED lighting High temperature, ultra performance LED Luminaire
Industrial-100HBS Gen III design is based on our ultra performance H-50LBS Gen III. The mechanical, electrical and optical properties are the same. It is designed for direct one-to-one replacement of the mature High Bay lighting technology typically found in the industry. More…
Harsh Environment High temperature applications
Industrial-100HBS Gen III has no nuclear qualifications. It is designed for the harshest industrial applications, especially where high ambient temperatures and aggressive atmosphere can be expected. Industrial-100HBS Gen III can continuously operate at ambient temperatures of 80 o C and up to 100 o C for limited period of time.
Custom solutions Full custom solutions/designs are available according to customer specification. Not just the mounting options, but the changes of the Luminaire outline are possible too. Our experts can offer to the customer complete lighting design, using latest lighting design/simulation software. This is the fastest, easiest, most cost effective and by far most accurate approach to lighting without any guessing. For the customers who wants to perform the calculations by themselves, the photometric files are available on request.
H series
L series
TID Gamma
500 kGy (50 Mrad)
50 kGy (5 Mrad)
Neutron fluence 1MeV (Si)
5 × 10 14  n/cm 2
5 × 10 13  n/cm 2
LOCA compatible
Housing material
SS / Aluminium
Ambient operational Al / Stainless Steel
80 o C / 50 o C
80 o C / NA
80 o C / NA
Ambient non operational 200 o C
24 h
Ingress protection
IP 65 / IK 08
IP 65 / IK 08
IP 65 / IK 08
Cable gland connection
In-line power connector
Ambient overpressure compatible
Comparison between versions H Gen III series is designed for most demanding nuclear applications, where very high doses of gamma radiation can be expected. L Gen III is designed for less demanding nuclear applications. Therefore much more cost effective and affordable. Industrial Gen III series has no nuclear qualifications. It is designed for demanding industrial applications, where high temperatures and aggressive atmosphere can be expected.
Comparison between generations The new Generation III of Rad-Hard LED Luminaires has major improvements over our previous generations. The differences are summarized in the table. Beside world’s highest radiation tolerance, Gen III offers world’s first and only LOCA (Loss Of Coolant Accident) compatibility. The Luminaires are also available in Stainless Steel for applications inside RB (Reactor Building), where use of Aluminium is not allowed. The new Gen III is in average three times lighter then the predecessors, simplifying installation and maintenance.
Gen II
LOCA compatible
Ambient temperature operational
50 o C
80 o C
Ambient over temperature
100 o C / 350 h
Seismic damper
Overall Luminaire efficacy
100 - 112 lm/W
150 - 160 lm/W
Weight (Aluminium version)
4.4 kg
1.5 kg
Weight (Copper / Stainless Steel version)
9.5 kg
2.5 kg
Customized solutions available
Housing material
Al or Cu
Al or Stainless Steel
Ambient temperature non operational
200 o C / 24 h
Ambient overpressure compatible
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Privacy policy related questions Q: By browsing your web site, do you track my activity? A: No, we do not track any of your activities. Q: Do you use cookies? A: No, we do not use cookies. Q: Do you use any of standard analytics - like Google Analytics or Yandex Metrica? A: No, we do not use any of them. Q: Do you respect my privacy? A: This is our first priority. We are always respecting your privacy, therefore we are not collecting any information about your activity on our web site.
H-100PLS Gen III Rad-Hard underwater LED Luminaire
100 W underwater  LED in-air operation possible continuous submersion up to 8 meters 16.000 lm @ 160 lm/W 6000 K @ CRI 70 IP 68 / IK 08 500 kGy (50 Mrad) gamma TID 5 × 10 14  neutrons/cm 2  1 MeV (Si) Read more.
LED control gear World’s highest radiation hardness
World’s best radiation hardness  in LED Lighting, of more than 500 kGy gamma and 5 × 10 14  neutrons/cm 2 1MeV (Si), is a result of careful selection of the components and the circuit topology. H series Gen III LED control gear is developed and produced by DITO Lighting.  Electronics is based on discrete components without integrated circuits, electrolytic capacitors and opto couplers. The photography above is symbolic.
H-100PLS Gen III Ultra Rad-Hard underwater LED Luminaire
H-100PLS Gen III is ultra performance, 100 W underwater LED Luminaire, yet very light, compact and easy to install, designed for simple one-to-one replacement of the existing mature technologies inside the reactor pool. The Luminaire is available Stainless Steel only. It is designed for continuous submersion in the water up to the depths of 8 meters. More…
Gamma and neutron hardness Gamma and neutron irradiation tests were performed in the General Dynamics / General Atomic TRIGA Mk II nuclear research reactor in Jožef Stefan Institute, Reactor Infrastructure Centre in Ljubljana, Slovenia. Gamma spectrum of the research reactor mimics real life situation in the NPP much closer then classic irradiation with the 60 Co gamma source. The only choice for neutron irradiation is nuclear research reactor, like TRIGA Mk II. In absence of nuclear standards for Luminaires, military and aerospace standards for irradiation of electronics were used where applicable: MIL-STD- 883, Method 1017 (neutrons) and Method 1019 (gamma) and European Space Agency ESCC No. 22900 for gamma. 
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World’s highest radiation hardness in LED Lighting World’s first and only LOCA compatible LED Lighting
Generation III Rad-Hard LED Luminaires