[OPINION] What if there was a spent-fuel pool accident at the Bataan Nuclear Power Plant?

The following is the 25th in a series of excerpts from Kelvin Rodolfo’s ongoing book project “Tilting at the Monster of Morong: Forays Against the Bataan Nuclear Power Plant and Global Nuclear Energy.“

Spent-fuel pools of nuclear reactors are shockingly dangerous. Even more shocking is how little authorities seem to realize this, even though it has been documented for a long time. This took on added urgency after the 2011 Fukushima-Daiichi disaster.

We have seen that fuel rods of uranium ceramic pellets contained in zirconium-alloy tubes are bundled together with Boron control rods into fuel assemblies like the one on the left in this picture. After about six years in the reactor, the fuel rods are no longer radioactive enough to work, and have to be replaced. They are called “spent-fuel rods,” but are still powerfully radioactive. Standing a foot away from them would kill you in a few seconds. To contain their radiation and the heat they generate, they have to be kept deeply immersed in water, in spent-fuel pools, cubes 40 feet or 12 meters deep.

After operating for about ten years, a reactor like BNPP has accumulated much more radioactive material in spent-fuel pools than is in its reactor. About 40% of the radiation from spent fuel comes from Cesium 137, which poisoned the Chernobyl region so badly in 1986. Strontium 90, another lethal fission product, is also abundant.

Boron 10 is used in the pools to absorb neutrons, usually making harmless helium and lithium nuclei. Occasionally, however, the boron becomes two heliums and a radioactive tritium. Even in normal times, tritium dangerously pollutes reactor surroundings, as we will see.

One of the most shocking facts about spent-fuel pools is that only one of them typically holds 15 to 30 times more Cesium 137 than all that was released in 1986 by the Chernobyl accident.

Cesium 137 and Strontium 90

Chemically, cesium and strontium and their radioactive isotopes behave respectively like potassium and calcium, two of life’s basic stuffs. Their compounds dissolve easily in water, and so they permeate soils and water, partake freely in biological activity, and are easily incorporated into human tissue.

Cesium substitutes for potassium in nervous and digestive functions, and is distributed throughout the body in fluids and soft tissues. The half-life of Cesium 137 is about 30 years. Most of it decays by beta emission into Barium 137, which in turn has a half-life of about 153 seconds, emitting strong gamma rays to become stable. Both Cs 137 and Ba 137 are powerful carcinogens.

After the Fukushima disaster in 2011, the Japanese found Cs 137 in vegetables, tea leaves, milk, beef, and in fish caught 300 kilometers away. As Cs 137 moves up the food chain, the biologic processes accumulate and concentrate it in the heart, kidneys, small intestines, pancreas, spleen, and liver. Bioaccumulation is much faster in children because of their faster metabolisms.

Strontium is absorbed by teeth, bones, and marrow. Radioactive Sr 90 has a half-life of 29 years and decays by beta emission to Yttrium90, which has a half-life of 64 hours and also decays by beta and gamma emission to stable Zirconium 90.

Radiologists deliberately inject Yttrium 90 into blood vessels that feed cancerous tumors so that its gamma rays can enter and destroy them. But Y90 accidentally incorporated by a healthy body can cause cancer.

Spent-fuel pool accidents

Nuclear reactors are contained in air-tight, reinforced-concrete shells a meter or more thick to contain an explosion and its radioactive debris. But typical spent-fuel pools are housed outside, in buildings only strong enough to protect them from the weather. In the US, back-up generators to maintain the flow of cooling water are not required.

We have already seen (Foray 17) that uranium fuel rods are armored in zirconium-alloy tubes. If the pool loses its water, the zirconium armor of the newest spent-fuel assembly would ignite, and set assemblies near it on fire.

Once started, the fire would be virtually impossible to put out. Spraying water would only make things worse, because steam actually helps zirconium to burn. A fire and explosion in the spent-fuel pool would release huge volumes of radioactive gases to the atmosphere, including radioactive Cesium 137; much, much more than the Chernobyl accident did.

The US Nuclear Regulatory Commission says that such an accident would force 3.5 million Americans in an area of 30,000 square kilometers from their homes. Over time, the threat has worsened, because NPPs have increased the amount of U235 in fuel rods so they can be used longer. This weakens the zirconium-alloy tubes, and increases the pressure of hydrogen and other radioactive gases generated inside them, increasing the chance that they might explode.

During the Fukushima-Daichi accident in March 2011 a hydrogen explosion blew off the roof of Unit 4 reactor. It was feared that the hydrogen had come from its spent-fuel pool, and the Nuclear Regulatory Commission urged widening the evacuation zone beyond its 20-kilometer radius from the plant.

Fortunately, it turned out that the hydrogen had actually come from the melted reactor core of adjacent Unit 3. In fact, a freak accident had leaked water into the Unit 4 pool! Had this not happened, it was predicted that continued evaporation would have exposed the fuel assemblies in a couple of weeks, greatly enhancing the likelihood that their zirconium cladding would be set ablaze.

A BNPP spent-fuel pool accident

So how might BNPP’s spent-fuel pool lose its flow of cooling water? Not too difficult: A pump or valve failure. A pipe might rupture. A sleepy or inattentive technician…an electrical brownout or power surge…not much of a task for an even moderate earthquake, let alone an eruption.

Propagandists argue that neither the 1990 Luzon earthquake nor the 1991 Pinatubo eruption damaged BNPP. But in either case it was not running, and its spent-fuel pool was empty.

One propagandist comforts us, saying that eruptions can be predicted in time to shut the reactor down. But how to move the spent-fuel assemblies out of their pool and out of harm’s way to…where?

One effect of an eruption comes easily to mind. Huge quantities of frothy, low-density Pinatubo pumice fell on Zambales, Bataan, and Subic Bay in 1991. It floated on the ocean and took a long time to absorb enough water to sink. Had BNPP been active, pumice could easily have clogged its seawater intake.

Ironically, the very real threat of a BNPP accident might be why it may never be activated. The map on the left shows how widely Cesium 137 from the Chernobyl accident was dispersed. Here, an outline map of the Philippines, drawn to scale, is superimposed on it with BNPP centered on Chernobyl. The panel on the right is the geographic setting of the Philippines.

Of course, these maps are only meant to show how large an area a BNPP accident might affect. Where the fallout would go depends on the prevailing winds.

The Philippines cannot act alone to activate BNPP because a reactor or spent-fuel pool accident would gravely affect all of East Asia. The United Nation’s International Atomic Energy Agency, of which the Philippines is a member, would have to approve its activation, and BNPP would never pass the rigorous IAEA safety standards. Whew…

Next: Foray 26, on nuclear weapons and human health. – Rappler.com

Born in Manila and educated at UP Diliman and the University of Southern California, Dr. Kelvin Rodolfo taught geology and environmental science at the University of Illinois at Chicago since 1966. He specialized in Philippine natural hazards since the 1980s.

Keep posted on Rappler for the next installment of Rodolfo’s series.

[OPINION] What if there was a spent-fuel pool accident at the Bataan Nuclear Power Plant?

Cesium 137 and Strontium 90

Spent-fuel pool accidents

A BNPP spent-fuel pool accident

Previous pieces from Tilting at the Monster of Morong:

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