A few days ago a community radio station out of Portland received a “hot tip” about a crack in a component of the Columbia reactor. It reported that “local residents who have become aware” are calling upon Energy Northwest to keep Columbia offline.
Enter the spokesperson for “local residents who have become aware,” an anti-nuclear activist who has likened Energy Northwest and its 1,100-plus workers (including many military veterans) to terrorists, and believes we shouldn’t have clean energy nuclear plants operating anywhere in the world.
The “local residents” spokesperson is joined by a nuclear “expert” who represents an organization that equates safe commercial nuclear energy to military nuclear bombs. The expert calls for a “thorough inspection” at a time when, ironically, Columbia begins a 42-day outage to thoroughly inspect the entire plant, to include opening up and inspecting the reactor vessel.
Our “local residents” spokesperson has now sent a news release to every agency on Energy Northwest’s news release list (our regrets to you all; we didn’t see that coming) hoping to make further news out of an indication of a potential tiny crack in a component called a jet pump riser.
So here are the facts.
A jet pump is not a pump as you might think of a pump. It has no moving parts but is simply a set of 19-foot tall pipes that help force water through the reactor core.
The talk about a “cracked jet pump” is a bit sloppy. The 1 ¼-inch crack indication – because there may be no crack – is in the inlet riser, which is part of the pump assembly. The actual pumps – Jet Pumps 17 and 18 (see graphic above) – have no issue. Further, it isn’t the size of the indication that matters, but the location.
We have evaluated the potential of the indication being a crack, and its location, and considered the possibility of crack growth at both tips under all conditions. There’s no doubt that the jet pumps and risers are capable of continuing to perform their intended function.
The jet pumps also do not control the power output of the reactor, as some anti-nuclear activists believe. The two reactor recirculation pumps handle that (and/or the control rods) and they are unaffected by the potential crack.
In the picture, you can see the indication for yourself. In reality, the indication is this long:
In April, Energy Northwest sent a letter to the Nuclear Regulatory Commission informing them of our assessment of potential crack growth rates on a single indication (the one in the photo above). The industry normally applies the same standard growth rate to both ends of a crack. The letter simply explains to the NRC that we are applying a slightly lower crack growth rate to one end of the potential crack and provided sound engineering support, including: the material condition at the potential crack tip; mitigation of cracking through effective hydrogen water chemistry; and, industry and plant experience which shows low crack growth rates for similar indications.
In fact this letter is similar to the 2011 letter to the NRC on the same issue. As stated in the 2011 letter to the NRC, the indication is more consistent with fatigue cracking, and “shows none of the characteristics associated with SCC (stress corrosion cracking).”
The common industry guidance is to assume a crack growth of approximately 0.44 inches per year on each end of a crack for any crack on a component inside the reactor. We are assuming that general growth rate at one end, but a slower growth rate at the other end; remember, our potential crack showed zero growth in the two years between 2011 and 2013, and we are inspecting it again during our current refueling outage.
Additionally, in 2005 we proactively installed slip joint clamps since these are designed to limit vibration and fatigue stresses.
The April letter to the NRC is a standard notification. It’s the second one we’ve sent since 2011. But it was new to the anti-nuclear activists so therefore an opportunity to push their agenda.
Energy Northwest is treating the indication as if it were a “through-wall” crack, and has been since it was first discovered. That is an appropriate and conservative approach. We will take another look at the indication this refueling outage and see if there is any noticeable growth. If so, we will take the appropriate actions. The bottom line is always the safe operation of the plant.
(Posted by John Dobken)