Refueling Outage Activities

During the refueling and maintenance outages conducted every 12 to 24 months, the following activities occur in the containment:

Disassembly of the ventilation supplies to the reactor vessel head area (specifically, the Control Rod Drive Mechanisms-CRDMs) Removal and storage of the Pressurizer and Reactor Vessel Missile Shields Removal and storage of the Reactor Vessel Head Removal and storage of the Upper Internals of the reactor. Removal of spent fuel assemblies, addition of new fuel assemblies, and shuffle of selected fuel assemblies to optimize the power profile over the cycle.

The following describes some of the activities that occur during maintenance outages both inside and outside the containment.  Links (with photo size) are provided to photos that illustrate the operations:

If you want a good vertical perspective of the reactor, select the reactor graphic - 54K ). If you want a good perspective of the containment, upender, transfer tube, and spent fuel building, select the building graphic -- Courtesy SCE  -30K.

1. Reactor Vessel Head Movement

• The bolts that hold down the reactor vessel head to the reactor vessel have been removed. - 8K
• Lead Rigger connects load cell to measure the weight during the transfer and verifies lifting rig is connected properly to the reactor vessel head for the movement. Note the size of the hook.- 10K
• The lift of the 154,000 pound reactor vessel head starts. - 18K
• During the first part of the lift, supervisors check to make sure only the head is lifted and that all parts of the reactor stay in place. - 24K
• The reactor vessel head is lifted higher.  In this photo, all personnel monitoring the early part of the lift leave the refueling pool area. -    27K
• The head is lifted still higher until it will clear the top of the refueling pool -  15K -  24K  - 28K
• The underside of the head can be seen as it clears the top of the refueling pool. -  20K

2. Containment crane and ceiling

• The containment crane is a polar crane that can move in a radial direction and across the containment. It is used to lift the reactor vessel head (150,000+ lb.), reactor vessel missile shield (50,000+ lb.), and pressurizer missile shield (35,000+ lb.) In the upper part of the containment can be 4 spray headers used to spray down the containment during any accident in which pressure gets to about 1/2 of the design pressure. -  9K -  5K

3. Upper Internals Removal

• After the reactor vessel head has been removed, the upper internals are removed. A special 12,000 lb. rig is used to pull the upper internals (54,000 lb.) and transfer them to a special stand in the refueling pool. These photos show the internals being moved. -  26K - 13K
• The upper internals are stored on the upper internals storage stand as shown. - 26K

4. Fuel Handling

• During the refueling, new fuel assemblies are added, spent ones removed, and some fuel assemblies are placed in other places in the reactor to optimize the fuel consumption and power profile. In a PWR, the boric acid concentration may be 2000 to 3000 parts per million boron. In this photo, a nuclear engineer is monitoring the positioning of the fuel. - 2K
• This photo shows a closer view of the fuel. The large hole in the upper right of the reactor is the outlet where the hot water leaves the reactor. The manipulator crane that installs and removes the fuel is about 1/3 the way from the left. A fuel assembly can be seen being removed from the reactor. - 5K
• This photo gives the perspective of the refueling pool with the manipulator crane in the middle of the photo. The open reactor can be seen below. Reflections can be seen. In the foreground is the internals lifting rig which is used to lift the upper and lower internals of the reactor. - 12K
• Several photos show the fuel assembly being placed into the upender, which then transfers the fuel assembly between the containment and the spent fuel building.. Two TV shots show first the fuel assembly, then the gripper which hold the assembly at the top (just as it releases the fuel assembly) . The 3rd photo shows the manipulator crane as it approaches the upender for placing the fuel assembly.- 20K -  17K -  22K

5. Other Refueling Maintenance

• A 15,000 lb. circulating water pump being removed for scheduled preventive maintenance - 42K
• A 40,000 lb. circulating water pump motor being loaded onto a flatbed for shipment. - 32K
• A plant electrician performs testing on a motor operated valve in a containment. - 34K
• An electrician performing testing on relays and timing of a 480 Volt motor control center breaker. - 27K
• A technician performing relay testing for a high voltage electrical system. - 51K
• The reactor head studs being stored after cleaning and before reinstallation - 36K
• Views of low pressure turbines before stationary blading is installed. - 49K - 44K

6. Preparation for Operation

• The reactor head studs being stored after cleaning and before reinstallation - 36K
• The internals lifting rig being moved back to its storage stand after installing the upper internals in the reactor. - 32K
• Movement of the reactor vessel missile shield to its normal location above the reactor. - 29K - 31K
• Note the tight clearance as the reactor vessel missile shield is lowered into place. - 24K
• Movement of a 35,000 lb. pressurizer missile shield to its normal location above the pressurizer vault in a pressurized water reactor. - 23K
• The grooves in the reactor vessel head hold seal rings that provide a means of monitoring for any leakage from the flange of the reactor head - 26K
• Several steps in the replacement of the reactor head back onto the reactor - 31K - 43K - 45K - 48K
• The reactor head has been reinstalled and electrical and instrument systems are in the process of being installed. - 42K

7. A Final Inspection

• A model illustrating of typical vault arrangement containing steam generator, reactor coolant pump, and pressurizer in a PWR - 30K
• The annulus between the metal containment building and a concrete secondary containment, as used in some nuclear plants. 23K
• The reactor coolant pump motor viewed from above the vault. - 38K
• The reactor vessel missile shield viewed from the main refueling floor. - 32K
• A containment fan coil unit and the steam generator viewed from the main refueling floor. - 40K
• The bottom level of a plant containment. Note the electrical cable trays located at least 4 feet above the floor to ensure operability in case of any water (radioactive or non-radioactive) being released to the containment- 32K

8.  Operation

• The reactor operating at power - 34K
• The turbine generator set operating at power. - 74K

Copyright � 1996-2004.  Joseph Gonyeau. All rights reserved. Revised: March 15, 2001.