Those following issues related to nuclear power may be interested in a 'situation' that was recently reported by Dominion Virginia Power at the North Anna power station (2 PWR reactors) near Mineral. This is the power station that was nearest the epicenter of the 5.8 earthquake that occurred on August 23, 2011, just 5 months after the great Tohoku quake off northeastern Japan that led to the Daiichi disaster.
Event Number: 50457 [Update September 30]
FAILED FUEL ASSEMBLY IDENTIFIED DURING CORE OFF-LOAD
"With North Anna Unit 2 in Mode 6 during a scheduled refueling outage, discharged assembly 4Z9 was identified as a failed fuel assembly by In-Mast Sipping. The fuel assembly was located in core location B11. Initial inspection of the fuel assembly identified two (2) visibly split fuel pins of eight (8) to ten (10) inches long with visible damage to the top of the pins. The internals of the affected pins are visible and the springs from the top of each pellet stack are touching the top nozzle. The fuel assembly has been placed into its designated location in the Spent Fuel Pool. No abnormal increase was noted on any radiation monitor either after or during fuel assembly movement. This fuel assembly had been used during three (3) previous operating cycles and is not scheduled for reuse.
"On September 15, 2014, at 0900 [EDT], subsequent video inspection of the fuel assembly identified that the top springs of the two (2) fuel pins were dislodged. Video inspection of the reactor vessel identified debris that has the potential to be fragments of fuel pellets resting on the core plate. Additional investigations are in progress.
"Due to the fact that the failure exceeded expected conditions, this event is being reported per 10 CFR 50.72(b)(3)(ii)(A), as any event or condition that results in the condition of the nuclear plant, including its principle safety barriers, being seriously degraded."
Unit-2 at North Anna was shut down on September 7th for scheduled refueling outage, a time when a given plant may release the vast majority of its annual allotment of stray radionuclides to the environment and cause the vast majority of its allotted exposure to workers and the public. The NRC has long allowed nukes to average releases over a year so that it looks like no single release or period of release exceeds 'standards' the nuclear industry is obliged to adhere to, and also allows the utilities themselves to do all the monitoring and paperwork without oversight from the erstwhile regulators. This particular outage, however, uncovered a situation that could not be disguised in the records as just another outage high, but needed reporting directly.
On September 15th, eight days into the outage, Dominion "discovered" that fuel rods in a third rotation assembly [one that has been in the core for three refueling cycles - 4.5 years - thus to be replaced in this outage] displayed serious failure damage. Two of the ~10 foot long fuel rods in the assembly had failed, releasing crumbled [failed] fuel to the RCS [Reactor Coolant System]. Dominion reported the situation to the NRC on September 17th.
Damage to the two rods able to be seen on video inspection showed that the top springs of these rods were dislodged and the cladding welds displayed splits about 10 inches long which released about 15 highly radioactive fuel pellets apiece. They also reported that visual inspection of the reactor revealed "debris" that "has the potential to be fragments of fuel pellets" resting on the core plate.
Dominion of course claims that this irradiated fuel material 'loose' in the primary system does not represent any danger to the system, the workers or the public, and they fully expect that it'll eventually get filtered out by the demineralizers/polishers during normal operation when the outage is over. They only reported it, they say, because this amount of fuel and high level waste material lost in the system is more than 10 times the quantity specified in Appendix C of 10CFR74.11(a) "loss of special nuclear material." Well, duh.
They further claim that they know the 'cause' of the cladding failure. Which, we may presume (although it is not specified in the report), is lousy cladding welds that show up so inconveniently in too many fuel rods and which have led to certain manufacturers losing their license over the decades [cough... Kerr-McGee... cough]. This particular assembly at North Anna is likely an Areva construct due to its age, though North Anna has been moving to Westinghouse fuel. The "industry recognized" stressor that tends to aggravate weak welds in the cladding of fuel rods is known as baffle jetting, which occurs when a hole in the assembly structure itself squirts water over the rods, causing them to spin and vibrate. This occurs quite frequently, apparently. Which might make people begin to suspect that assembly manufacture is every bit as sloppy as is the manufacture of the rods themselves. The rods end up cracking off from the upper level supports and, if those welds are weak enough, excess heat from crumbled fuel pellets split them wide open to release the material to the RCS.
Okay, so much for the news on this incident. We now know what the problems are, and how they have been reported to the complacent, industry-toadying not-really regulators we call the NRC. Now I'd like to talk about what this actually means per possible 'danger' to the general public as well as to workers at the plant.
In the Richmond Times-Dispatch article linked above, NRC Atlanta spokesperson Roger Hanna said:
"It's a fairly low safety significance issue. [...] Even though the fuel is damaged, it's in a closed system, so you don't have the concern for an environmental release" of radioactivity.
This kind of deceptive claptrap is SOP for the industry and its pocketed regulators. They will always revert to the "In Theory" fallback position to protect themselves from the consequences of their many oopses. My problems with this cock and bull story are...
• There is no way that Dominion's operators were ignorant of either failed rods or failed fuel loose in the system at the time these failures occurred. Which could have been weeks, months or even a year or more prior to this scheduled outage.
(a) The "hot spot" in this fuel assembly would have registered on temperature monitoring sensors in the core, and
(b) The presence of fuel and gross fission products in the coolant water would have been detected as it occurred. The RCS does pick up quite a bit of dissolved gases (fission products loose and under pressure) from pinhole flaws in the cladding during operation, but if there's uranium in the RCS it's going to be very obvious and it's a serious issue.
• This kind of serious issue should have required shutdown of the reactor as soon as it became obvious, not ignored until the scheduled outage or "discovered" only after the offending assembly with its failed rods had been moved to the spent fuel pool.
• The depressurization of the RCS in preparation for defueling would have released the dissolved gases in the system from any number of pathways, not the least of which being removal of the reactor head so that defueling could commence. Even in the ridiculously unlikely event that the operators never knew they had failed fuel in the system before this outage, they sure as hell would have known when radioactivity levels in the containment atmosphere (and certain areas of the auxiliary building) shot up upon depressurization. Alarms would have sounded, I promise. Unless those had been disconnected, that is. Is THAT 'Standard Operating Procedure' at nukes these days? Where the hell is the NRC on that?
The isotopes in irradiated reactor fuel are very, very dangerous to humans and other life forms, ALWAYS present serious hazards to living things in the environment. The entire range of alpha-emitting actinides will be present (depending on how much fission is ongoing by the fuel isotopes released), as well as transuranics like plutonium. This described fuel "debris" is particulate - only some of its products are gaseous. At any rate, when some nuclear wig tells you...
"No abnormal increase was noted on any radiation monitor either after or during fuel assembly movement,"
...as the utility purportedly told the NRC, you can be sure they're spouting lies and the NRC knows all about them.
This technology proves yet again that it is far too dangerous to allow, and that its operational and regulatory power structures are hopelessly corrupt. North Anna's reactors needed to be put into immediate decommissioning status after the earthquake in 2011, but that didn't happen because the industry and its erstwhile watch-puppies were too worried about what Fukushima was going to do to their cash flow if people knew the truth. This current truth - and the self-serving lies being told about it by everyone involved - should be enough to cause heads to roll at NRC and serious fines for Dominion. Maybe even Congressional hearings about what these creeps are really up to. Unfortunately, none of that will happen. Again.
I'm sure the NRC will sign off on restart sometime in the next week or two, so everyone can go back to ignoring the dangers this technology continues to present to life on planet earth. So until the next nuclear oops nobody wants to know about, I bid you adieu.