oksuz_ said:
Hi,
Can anyone give me a source from which I can obtain the radioactivity level in the coolant water circulating in the primary circuit?
Is one looking for activity limits, or actual activity values?
Radiochemistry in Nuclear Power Reactors is a good basic reference.
https://www.nap.edu/catalog/9263/radiochemistry-in-nuclear-power-reactors
Very little tritium comes from successive neutron capture in hydrogen. Most tritium comes from B in the coolant or burnable poison assemblies, and Li-6 in the LiOH buffer the coolant, even though LiOH is enriched in Li-7 and depleted in Li-6. In BWRs, boron is used in control blades, and some of the T produced in the control blades leaks into the coolant.
Corrosion products (metal ions) dissolved in the coolant may traverse the core, or may accumulate on the fuel (crud deposits), and become activated. Reactor coolant systems have resin filters to remove metal ions from the coolant.
Fission products can be released from failed (breached) fuel rods, but are also present as 'tramp' uranium.
Utilities are required to have programs in place to limit exposure to workers and keep coolant activity as low as reasonably achievable. There is also an economic incentive to maintain low coolant activity, since it is more costly to dispose of the waste products collected on the filters. Utilities have water chemistry programs to mitigate corrosion and prevent stress corrosion cracking of structural alloys.
The dose limits for iodine and noble gases were established during the AEC days and inherited by the NRC. I have seen very high coolant activities in some of the earliest operating plants in the 1970s that would be unacceptable today, and I know of two plants that were within hours of shutting down due to high iodine activity in the reactor coolant. In one case, it was a single high power fuel rod that had failed and degraded.
There were several BWR plants in the 1980s and 1990s that had to shutdown to remove failed fuel, before it became common practice to use power suppression testing (flux tilting) to identify the location of failed fuel by how the coolant activity responded when control blades where inserted in the core.