On April 15, two alleged terrorists in Boston killed three people, injured more than 170 others and terrified a nation — for about $100 it cost them to modify pressure cookers into bombs. We should be glad they didn’t come to Japan, where they may have been able to explode a ready-made nuclear dirty bomb, kill untold thousands, render huge swaths of the country uninhabitable — and get paid by Tokyo Electric Power Co. (Tepco) in the process.

I wish I were kidding. Japan has more than 50 gigantic nuclear “pressure cookers” ripe for exploitation by terrorists. And they wouldn’t even have to lay siege to the facilities. Instead, they could just walk into a nuclear plant and leave with enough weapons-grade plutonium for a small atomic device — which later could be detonated wherever they chose. How?

In Japan, getting access to a nuclear power plant is very simple: fill out a job application.

It is now more than two years since the start of the nuclear crisis following the Great East Japan Earthquake on March 11, 2011, and there are still no mandatory background checks for workers at its nuclear facilities.

After the three reactor meltdowns at the Fukushima No. 1 nuclear complex in March 2011, it became clear that Tepco, the plant’s operator, was allowing members of Japan’s organized crime groups, the yakuza, to staff the well-paid cleanup — just as they had been allowed into plants long before then.

Indeed, members and associates of the Sumiyoshi-kai (Kanto) and Kudo-kai (Kyushu) mobs have been arrested for their roles supplying labor to Tepco and its Kansai cousin, Kepco. So the dirty secret that yakuza-linked workers and companies have long sustained Japan’s nuclear industry — along with yakuza members themselves, ex-convicts, wanted criminals, and drug addicts working there — is now public knowledge.

Although many yakuza groups claim to have a protective role in society, most of their members are sociopathic felons who would commit theft, assault or murder to make a little money. And if you consider the black-market value of a little plutonium, you may feel a tad uneasy knowing such people have long had access to it — and can still get their hands on nuclear materials.

Don’t worry, though: Last month the Nuclear Regulation Authority (NRA) said a panel will be set up to discuss atomic energy security issues, and it will consider introducing a system to investigate the backgrounds of workers to avoid acts of terrorism at nuclear plants.

Specifically, it seems the panel will examine ways to check whether nuclear facility employees are drug addicts or have a criminal record, among other issues, in order to screen out anyone who could potentially get involved in terrorism.

The panel will comprise NRA Commissioner Kenzo Oshima and outside experts. However, one expert who will not be on the panel is Haruki Madarame, former chief of the now-dissolved Nuclear Safety Commission. He is currently being investigated by prosecutors for alleged criminal negligence.

But hey, let’s not dwell on the past. The good news is that the NRA is thinking about making nuclear plants safer in the future. They may even reach the same conclusions that the Nuclear Security Expert Commission of the Atomic Energy Commission announced … in September 2011. Of course, why take action when you can spend more time debating about taking action?

The AEC makes recommendations for nuclear energy policy. However, that 2011 report, titled “Basic Nuclear Security Assurance,” doesn’t give a positive view of Japan’s countermeasures.

There, the words “internal threats” appear five times in 14 pages of attached materials. And, in a section headed “Lessons of Fukushima,” it notes: “It is clear there were defects in the management of those leaving and entering the site from the start of the accident. … Licensed (nuclear facility) operators need to first strictly enforce measures to keep suspicious persons from sneaking into the facilities and strengthen countermeasures against threats from within.”

The report, without irony, also notes that criminal acts such as the theft of nuclear materials to build a dirty bomb, or the destruction of facilities, “should be detected, prevented, and stopped so as to cause as little negative impact as possible to life, physical health, property, society and the environment.”

It also recommends that law enforcement, regulators and the power plant operators share information to make sure that thieves, saboteurs or criminals do not have access to the plants or related facilities. But it stops short of mandating background checks.

The United States has long had a screening system in place, but Japan has delayed taking similar measures due to privacy concerns and “respect for human rights.” Meanwhile, Tepco is still unable to locate scores of workers who entered the disaster zone.

Maybe, though, we shouldn’t worry so about criminals gaining access to nuclear plants. After all, the National Diet of Japan’s Fukushima Nuclear Accident Independent Investigation Commission report in 2012 established Tepco’s responsibility for the triple meltdown. Then months later Tepco admitted it consciously ignored the threat of a tsunami-related disaster.

So perhaps the lesson to be learned is that the greatest threat of “nuclear terrorism” Japan faces is from criminally negligent power companies and a government that fails to punish them.

Come to think of it, maybe we shouldn’t worry at all about criminals gaining access to the nuclear power plants. As the Tokyo Prosecutor Office’s investigation into the top executives of Tepco for professional negligence resulting in injury and death grinds on, it seems more and more likely that criminals have been running the plants for a very long time — they just don’t all have tattoos.

When it comes to the nuclear security in Japan, the U.S. comics “swamp critter” Pogo Possum would tell you: “We have met the enemy, and he is us.” Let’s hope no other enemies decide to join the party — because if they do, Japan’s nuclear negligence may become the world’s problem as well.

Investigative journalist Jake Adelstein is the author of “Tokyo Vice,” a board member of Polaris Project Japan and a contributor to The Atlantic Wire and japansubculture.com. His email address is jakeadelstein@me.com.