Presented to: KEPRI & KHNP Presented by: Dr. Robert Litman RCS Action Levels and Recent Changes to the EPRI Guidelines

Recent Changes to the EPRI Guidelines Section 2 has been updated to reflect New research regarding PWSCC and primary water chemistry Low temperature crack propagation in hydrogen environments Benefits of high, constant pH to fuel deposits, radiation fields and CRUD management Benefits of zinc addition Silica intrusion into the RCS

Recent Changes to the EPRI Guidelines High, constant pH Industry experience in this area has shown that constant pH values of 7.1 to 7.3 have reduced general corrosion of Inconel alloys, reducing the production of 58 Co. These pH values have not affected the time to initiation of SCC. Hydrogen The crack initiation data for the hydrogen range of cc/Kg shows no significant effects. Emphasis is still on using excess hydrogen to overcome effects of low level oxygen intrusion during the fuel cycle.

Low Temperature Crack Propagation in Hydrogen Environments Recent research data suggests that at T < C (300 0 F) thick nickel based alloys and some weld materials may be susceptible to enhanced crack growth due to hydrogen diffusion into crack tips. A hydrogen management plan that limits H 2 below that temperature may be warranted.

Spent Fuel Pool and Silica In order to contain a larger number of spent fuel assemblies, the storage racks for spent fuel were made smaller. This required the addition of neutron absorbing material that had greater ability to reduce reactivity than the 2000 ppm boron in the SFP water. The material which was originally selected, boraflex, has boron carbide with a binding material that is made out of a polymeric silica compound. Over the course of the first cycle the polymeric silica binder began to break down, due to radiolytic effects, producing SiO Although silica in the SFP is not a big concern for spent fuel assembly integrity, it creates several secondary effects.

Spent Fuel Pool and Silica SFP Refueling canal Fuel Transfer Tube (fits one fuel element at a time) Reactor Cavity Reactor Vessel Cask Handling Area Fuel Racks

Silica Effects Migration to the RCS during refueling outages via the fuel transfer tube Saturates the SFP demineralizer with SiO 3 2-, taking up exchange sites which does not allow removal of Cl -, F - or SO Sulfate is particularly troublesome as it has as its source decomposition of the SFP resin (cation). High silica in the RCS raises a concern regarding increased potential for formation of fuel deposits, and fuel vendors place limits on allowed silica concentrations. This concern increases if zinc is to be added. Combined high silica and zinc addition may lead to need for additional fuel surveillance.

Recent Changes to the EPRI Guidelines (continued) All Appendices were revised significantly, four new appendices were added, AOA and Ultrasonic Fuel Cleaning Sampling Considerations for Monitoring RCS Corrosion Products Reactor Coolant Radionuclides Definition of High Duty Core One old appendix was deleted, on other old appendix was rewritten..

Recent Changes to the EPRI Guidelines Guidance was added in both Volumes 1 and 2 regarding pressurizer oxygen control during start up and shutdown Recommendations about administrative requirements to take after an Action Level has been entered.

Chemistry Control and Diagnostic Parameters as Defined in the EPRI Guidelines Control Parameters Parameters which require strict control due to material integrity considerations. This includes: Cl -, F -, SO 4 2-, Li +, H 2, O 2 Diagnostic Parameters Parameters which assist the chemistry staff in interpreting primary coolant chemistry variations or which may affect radiation field build up, corrosion performance of system materials or fuel integrity. These include: Conductivity, pH, B, suspended solids, silica, Zn

Action Levels An Action Level is a concentration of a particular contaminant when the reactor is >0% power, which if left unchanged will lead to increased corrosion. AL 1: If the concentration of a control parameter is greater than the AL 1 limit, efforts should be made to bring the parameter back below the limit within 7 days. Continued operation beyond 7 days requires a formal technical review.

Action Levels AL 2: If the concentration of a control parameter is greater than the AL 2 limit, efforts should be made to bring the parameter back below the limit within 24 hours. If the parameter is not below the AL 2 limit at 24 hours, an orderly plant shutdown shall begin to bring the RCS T avg to < F, as soon as all plant conditions permit. If the parameter returns to normal before a shutdown is initiated, power operation may continue. At any time during a power reduction if the control parameter returns to below the AL 2 or 3 limit, a technical review should be performed prior to power operation may be resumed After an AL 2 or an AL 3 condition has occurred, a technical review of the event, the effect on the plant system and methods to prevent reoccurrence needs to be performed.

Action Levels AL 3: If the concentration of a control parameter is greater than the AL 3 limit, an orderly unit shutdown should be initiated immediately. After an AL 2 or an AL 3 condition has occurred, a technical review of the event, the effect on the plant system and methods to prevent reoccurrence needs to be performed. At any time during a power reduction if the control parameter returns to below the AL 2 or 3 limit, a technical review should be performed prior to power operation may be resumed

Action Levels for the RCS Cl/F, ppb Sulfate 3 times per week (or per Technical Specifications) 1 time per week Plant specific Plant Specific  150 Plant Specific  1,500 Plant Specific Lithium3 times per week Plant specific Hydrogen, Cc/Kg 3 times per week 50 < 15 < 5 Dissolved Oxygen, ppb Based on plant Technical Specifications > > 100 Parameter Frequency AL 1 AL 2 AL 3

Notes to the Action Levels Cl/F Tech spec requirements may determine frequencies AL 1 limits should be based on historical plant data during normal operation Sulfate Principal source is resin ingress. Frequency should be increased when indications of resin leakage is noted. Hydrogen AL 1 limit of 25 may be exceeded if going into a plant shutdown within 24 hours AL 2 limit of 15 may be exceeded with no plant shutdown if immediate corrective action is taken Lithium The limits and frequencies for lithium will be based on a plant specific pH program.