Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of nuclear services specialist EnergySolutions (NYSE: ES) plummeted more than 15% on Thursday after its quarterly results and full-year guidance failed to meet Wall Street expectations.

So what: According to the company, business activity was in line with expectations, but a change in accounting treatment for its Zion decommissioning project led to a fourth-quarter loss of $22 million, or $0.25 per share. Even when you exclude that one-time item, however, EnergySolutions' adjusted income of $10.5 million, or $0.12 per share, came in well below the average analyst estimate of $0.19 per share.

Now what: I'd look into this near-20% plunge as a possible long-term entry point. While EnergySolutions' full-year EBITDA guidance of $130 million to $140 million also disappointed Wall Street, the company seems to be building a solid foundation with the expected ramp-up of Zion, as well as a generally more focused growth strategy. The shares had been recovering nicely from its recent nuclear-fear-induced beating, but today's plunge might be giving investors yet another chance to pounce.

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