Marnie Surfaceblow: Marnie's Mailbag—Questions on Coal Ash and Tritium Lighting

Long-time POWER readers may remember Marmaduke Surfaceblow, a fictional character whose engineering escapades were brilliantly portrayed in hundreds of stories published within POWER magazine’s pages over more than 30 years beginning in 1948. Today, the fictional series continues through Marmy’s granddaughter, Marnie, who is an engineering wiz in her own right.

____

Marnie and Maya answer real questions from readers.

“Ma’am, don’t you think you should take a rest?” asked Maya Sharma, lead field engineer of Surfaceblow & Associates International.

“But how can I, Maya, when such a mass an’ mayhem o’ humanity need my help? Besides, it’s not like I’ll sleep in this Last Class aircraft seat. What are these, Soviet military surplus?” replied Maya’s boss, Marnie Surfaceblow.

Maya responded deadpan, “That would explain why the vodka was cheaper than your diet soda.” Craning her head to peer at Marnie’s laptop screen, Maya asked, “Are there any good questions?”

“Strewn amongst the spam asking me if I want to join certain religious cults or buy certain supplements on the dark web, yes. This, for example, ‘Dear Marnie, why do so many concrete companies say they can’t use any of our coal power plant fly ash now that we’re burning just 2% wood from old construction pallets? We used to get half a million dollars a year selling our fly ash and now it costs us that much to landfill it! What’s the big deal? Tom Beckhoff.’ ”

1. Marnie responds to questions via email. Source: POWER

Marnie began typing her reply (Figure 1). “What you’re thinking of are standards like ASTM C618-23, setting limits on the chemical composition, fineness, silica, lime, sulfur, moisture, unburned combustibles, etc. The goal is only allowing components with the best pozzolanic ability. While some biomass ash might meet the same specifications on paper, remember, ash isn’t a collection of mineral oxides—it’s scores and scores of minerals, and some coals don’t make the grade either. Until we get general agreement validating biomass ash’s suitability, consider other uses for your ash. Soil stabilization for berms and levees is possible, and depending on what all is in it, biomass ash can sometimes be a great fertilizer, especially if it’s high in phosphorous.”

Unable to resist, Maya added, “Kindly note that wood treatments and entrained metals may contaminate biomass from construction waste. Chromium, arsenic, lead, and zinc are common examples.”

“I was getting to that,” replied Marnie. “My innately incredible intellect is impeded by slow fingers.”

She finished the reply, scrolled through her inbox some more, then said, “This is interesting! ‘Dear Marnie, my manager installed tritium exit lights across our entire plant, even our engineering offices. He said some bean-counter report claimed it saved money replacing burnt-out signs. Our staff wonder how safe it is working around ironic radioactive safety signs? Libby Carmichael.’ ”

“Hm. It should be safe. Tritium releases only beta particles, easily stopped by minor barriers,” Maya commented.

“A-ha! I know something you don’t!” Marnie whooped with glee to the annoyance of their fellow Last Class passengers packed around them.

Regaining composure, Marnie typed her reply, “Well, Libby, I have bad news, and good news. Most folks think tritium only releases ionizing radiation as beta particles, easily stopped by minor barriers. Even in the unlikely event they impact your skin, tritium beta particles are low-energy, causing mostly minor damage. However,” Marnie paused, giving Maya a sly look, “when beta particles are stopped by shielding, the energy released from their deceleration can sometimes emit bremsstrahlung radiation—German for braking radiation—like the opposite of Fahrvergnügen.”

Raising an eyebrow, Maya said, “Fahrvergnügen? Ma’am! You made that up!”

Smiling smugly, Marnie replied, “Nope, it was a Volkswagen advertising gimmick. It probably inspired a post-grunge song featuring a 1986 Jetta by the musician Kaz.”

“Ma’am, with respect … why … do you know these things?” Maya said, shaking her head in wonder.

Marnie continued her response, “Bremsstrahlung radiation is detectable outside of the lights, but it’s just a low-energy X-ray and there’s not much tritium in these lights to begin with. The lights are typically ceiling-mounted, so the inverse-square law of radiation works for you. My Geiger counter squawks when next to a light, but if I move it six inches away, it barely makes a peep. Even if one breaks, remember—tritium is hydrogen; it quickly disperses. Just let your trained safety personnel dispose of the debris. Overall, the utility of a light source that can last 10 to 15 years or more greatly outweighs any risk.”

Maya watched Marnie send the e-mail on its way, then commented, “This explains the many tritium lights in your toolbox, but not the ones you carry in your purse.”

Glancing down to peer inside a softly green-glowing pocket of her battered Prada handbag, Marnie shrugged, “I like science, especially if it’s green.”

—Una Nowling, PE is an adjunct professor of mechanical engineering at the University of Missouri-Kansas City.