Document: NRC Regulatory Guide
Document ID: d0bc0d48-8edb-492d-b813-53be9418b4aa
Document Type: regulatory_guide
Title: Maintenance of Water Purity in Boiling Water Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740192.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.56
CFR Part: 
CFR Title: 

Content:
ve ionic impurities and to filter out suspended solids. Depending on the flow rate, type of resin, cleanli ness of resin of BWR full-flow demineralizer sys tems, and type of ions in the coolant, total capacity may not be available for ionic impurity removal in the condensate treatment system before decontamina tion factors become unacceptably low during con denser leakage. Demineralizer capacity reduction should be considered in the design so that there is adequate capacity margin available to permit orderly shutdown of the reactor in case of a serious con denser leak. There are no instruments that will directly measure the capacity of a demineralizer unit. The capacity may be determined indirectly, however, from the ini tial capacity of the unit and the calculated flows of ions through the unit. Subtraction of the total ion flow from the initial capacity gives the remaining capacity. Operation of a demineralizer unit after its ion exchange capacity has been depleted results in the di rect passthrough of ions into the reactor vessel. De pending on the nature of these ions, stress-corrosion cracking or other forms of corrosion might be accel erated, crud buildup on fuel and on other components might be promoted, and plant radiation levels might be increased. The conductivity of the inlet and outlet water of the demineralizer-should be measured to monitor de mineralizer performance. The monitoring instrument, which should be set to trigger alarms in the control room, should be capable of quickly detecting de mineralizer breakthrough and should have sufficient range to measure all conductivity levels up to and in cluding the limiting conditions of the plant technical specifications that require immediate shutdown of the reactor. Even with highly efficient condensate demineraliz ers, some contaminants, at very low concentrations, pass into the reactor vessel. Chloride ions and high or low pH conditions, which may promote stress corrosion cracking of austenitic stainless