ML100550650

Developmental Revision B - Technical Requirements Manual Bases B 3.9 - Refueling Operations

ML100550650
Person / Time
Site:	Watts Bar
Issue date:	02/02/2010
From:	Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
References
Download: ML100550650 (9)

Text

Decay Time B 3.9.1 B 3.9 REFUELING OPERATIONS B 3.9.1 Decay Time BASES BACKGROUND Three analyses of a postulated fuel handling accident are performed:

1) a realistic analysis, 2) a conservative analysis, and 3) an analysis based on Regulatory Guide 1.25 (Ref. 1). Both the conservative analysis and the Regulatory Guide 1.25 analysis assume that the accident occurs 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> after plant shutdown. Radioactive decay of the fission product inventory during the interval between shutdown and placement of the first spent fuel assembly into the spent fuel pit is taken into account.

It is also necessary to consider a fuel handling accident occurring inside the primary containment. The assumption that the accident occurs 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> after plant shutdown is also applicable to this analysis (Ref. 2).

APPLICABLE The minimum requirement of 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of reactor subcriticality prior to SAFETY movement of irradiated fuel assemblies in the reactor vessel ensures that ANALYSES sufficient time has elapsed to allow the radioactive decay of the short-lived fission products. This decay time is an initial condition of a Postulated Fuel Handling Accident. Therefore, Reference 3 concludes that this requirement should be retained as a revised Technical Specification. However, in subsequent discussions with the NRC Staff, it was concluded that decay time was not strictly a process variable, and should be removed from the revised Technical Specifications.

TR TR 3.9.1 requires the reactor to be subcritical for at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

Implicit in this TR is the Applicability (during movement of irradiated fuel in the reactor vessel). This ensures that sufficient time has elapsed to allow the radioactive decay of the short-lived fission products, thus reducing the fission product inventory and reducing the effects of a fuel handling accident.

APPLICABILITY This TR is applicable only during movement of irradiated fuel in the reactor vessel. Therefore, it effectively prohibits movement of irradiated fuel in the reactor vessel during the first 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> following reactor shutdown.

(continued)

Watts Bar - Unit 2 B 3.9-1 Technical Requirements (developmental) A

Decay Time B 3.9.1 BASES (continued)

ACTIONS A.1 With the reactor subcritical less than 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, all movement of irradiated fuel in the reactor vessel must be suspended. As stated above, movement of irradiated fuel in the reactor vessel is prohibited during the first 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> following reactor shutdown.

TECHNICAL TSR 3.9.1.1 SURVEILLANCE REQUIREMENTS Since movement of irradiated fuel in the reactor vessel is prohibited during the first 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> following reactor shutdown, a verification of time subcritical must be made prior to movement of irradiated fuel in the reactor vessel. This is done by confirming the date and time of subcriticality and verifying that at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> have elapsed. The Frequency of "Prior to movement of irradiated fuel in the reactor vessel" ensures that the TR is met before irradiated fuel is moved in the reactor vessel.

REFERENCES 1. Regulatory Guide 1.25, "Assumptions Used for Evaluating the Potential Radiological Consequences of a Fuel Handling Accident in the Fuel Handling and Storage Facility for Boiling and Pressurized Water Reactors."

2. Watts Bar FSAR, Section 15.5.6, "Environmental Consequences of a Postulated Fuel Handling Accident."

3. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.9-2 Technical Requirements (developmental) A

Communications B 3.9.2 B 3.9 REFUELING OPERATIONS B 3.9.2 Communications BASES BACKGROUND During CORE ALTERATIONS communication ability must be retained between the control room and personnel on the refueling station. This is needed to allow the refueling personnel to be informed of any significant changes in the unit status or core reactivity conditions.

APPLICABLE This requirement helps assure direct communications between the control SAFETY room and refueling personnel during refueling, which would help to ANALYSES preclude inadvertent criticality. It also ensures that the refueling personnel are able to inform the control room if there are any problems or accidents during the refueling process. Refueling operations are not addressed in PRA studies and would not be important in accident sequences that are commonly found to dominate risk (Ref. 1).

TR TR 3.9.2 requires that direct communications be maintained between the control room and personnel at the refueling station. This ensures that information can be exchanged between the two groups if any unplanned events occur or if any significant changes occur in the unit status or core reactivity conditions.

APPLICABILITY TR 3.9.2 is only applicable during CORE ALTERATIONS (MODE 6). In all other MODES refueling procedures do not take place and are therefore not applicable.

(continued)

Watts Bar - Unit 2 B 3.9-3 Technical Requirements A

Communications B 3.9.2 BASES (continued)

ACTIONS A.1 If direct communications between the control room and the personnel at the refueling station cannot be maintained, all CORE ALTERATIONS must be suspended immediately. This is to ensure that the unit remains in a safe condition and that the workers are not placed in an unsafe situation.

Suspension of CORE ALTERATIONS shall not preclude completion of actions to establish a safe condition.

TECHNICAL TSR 3.9.2.1 SURVEILLANCE REQUIREMENTS TSR 3.9.2.1 requires that a demonstration be made to verify that direct communications between the control room and personnel at the refueling station are established. The Surveillance is to be performed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> prior to the start of the CORE ALTERATIONS and every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> during the CORE ALTERATIONS. The Frequency of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is based on engineering judgment and on the very small likelihood of the communication abilities being broken.

REFERENCES 1. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.9-4 Technical Requirements A

Refueling Machine B 3.9.3 B 3.9 REFUELING OPERATIONS B 3.9.3 Refueling Machine BASES BACKGROUND The refueling machine is used during CORE ALTERATIONS to either move fuel assemblies to new positions in the core, load new fuel assemblies, or unload spent fuel assemblies. The refueling machine consists of a rectilinear bridge and trolley crane with a vertical mast extending down into the refueling water. The bridge and trolley motions are used to position the vertical mast over a fuel assembly in the core.

A long tube with a pneumatic gripper on the end is lowered down out of the mast to grip the fuel assembly and manipulate it so that it can be transported to its new position.

The refueling machine has two auxiliary monorail hoists which are located on each side of the bridge. The auxiliary hoists are used for the movement of control rod drive shafts in order to facilitate the refueling process. Before using the hoist, the drive shafts must be disconnected from their respective control rods and, with the upper internals, removed from the vessel (Ref. 1).

APPLICABLE This requirement ensures that the refueling machine and auxiliary hoists SAFETY have sufficient load capacity to lift a fuel assembly or a drive shaft, ANALYSES respectively. This is to prevent a load from being accidentally dropped during the refueling process. The requirement also ensures that load limiting devices are available to prevent damage to a fuel assembly during fuel movement. These requirements have not been identified as a significant risk contributor (Ref. 2).

TR TR 3.9.3 requires that the refueling machine and auxiliary hoist shall be used for the movement of fuel assemblies or drive shafts and that they shall be OPERABLE with certain requirements as discussed below. The refueling machine shall have a capacity of at least 3150 pounds, with two electrical overload cutoff limits of 2650 pounds, and 2800 pounds, respectively.

(continued)

Watts Bar - Unit 2 B 3.9-5 Technical Requirements (developmental) A

Refueling Machine B 3.9.3 BASES TR (Although the manufacturer's dynamic capacity rating of the refueling (continued) machine is 4000 pounds, only a capacity of 3150 pounds is required for movement of fuel assemblies or drive shafts). The auxiliary hoist shall have a capacity of at least 1200 pounds and a load indicator which shall be used to prevent the lifting of loads which are greater than 1190 pounds. These load requirements are specified in order to ensure that the equipment can handle the nominal weights of the components it must manipulate, while assuring that core components are not damaged from excessive lifting forces.

APPLICABILITY TR 3.9.3 is applicable only during the movement of fuel assemblies or drive shafts within the reactor pressure vessel. The refueling machine's and auxiliary hoist's maximum loads and limitations are required when used for these purposes only, so the requirements are not applicable at any other times.

ACTIONS A.1 If the refueling machine does not meet the requirements above, it is considered inoperable. Therefore, its use involving the movement of fuel assemblies within the reactor pressure vessel must be suspended immediately.

Suspension of the refueling operations shall not preclude completion of actions to establish a safe condition.

B.1 If the auxiliary hoist does not meet the requirements above, it is considered inoperable. Therefore, its use involving the movement of drive shafts within the reactor pressure vessel must be suspended immediately.

Suspension of the refueling operations shall not preclude completion of actions to establish a safe condition.

(continued)

Watts Bar - Unit 2 B 3.9-6 Technical Requirements (developmental) A

Refueling Machine B 3.9.3 BASES (continued)

TECHNICAL TSR 3.9.3.1 SURVEILLANCE REQUIREMENTS TSR 3.9.3.1 requires the performance of three tests on the refueling machine. A load test of 3150 pounds must be performed on the refueling machine to verify its capacity. A test must be performed to demonstrate an automatic electrical load cutoff before the crane load is greater than 2650 pounds. A test must also be performed to demonstrate a second automatic electrical load cutoff before the crane load is greater than 2800 pounds. These tests verify that the capacity and the load limits are still within the Technical Requirements. The Surveillance Frequency of 18 months is based upon engineering judgment, manufacturer recommendation, the fact that the refueling machine is an infrequently used and highly reliable piece of equipment, and consistency with the typical industry refueling cycle.

TSR 3.9.3.2 TSR 3.9.3.2 requires a load test of at least 1200 pounds be performed on each required auxiliary hoist and its associated load indicator. This test verifies that the capacity is within the Technical Requirement and that the load indicator is functional. This surveillance is to be performed within 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> prior to starting the movement of the drive shafts within the reactor pressure vessel. The surveillance frequency is based on engineering judgment and the fact that the auxiliary hoist is an infrequently used and reliable piece of equipment.

REFERENCES 1. Watts Bar FSAR, Section 9.1.4, "Fuel Handling System."

2. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.9-7 Technical Requirements (developmental) A

Crane Travel - Spent Fuel Storage Pool Building B 3.9.4 B 3.9 REFUELING OPERATIONS B 3.9.4 Crane Travel - Spent Fuel Storage Pool Building BASES BACKGROUND The spent fuel pool is a reinforced concrete structure with a stainless steel liner for leak tightness. The spent fuel storage racks consist of stainless steel structures with receptacles for nuclear fuel assemblies as they are used in a reactor, receptacles for neutron poison assemblies, and a supporting structure. Design of these storage racks is in accordance with Reference 1.

The racks can withstand the drop of a fuel assembly from its maximum supported height and the drop of tools used in the pool. Crane travel in the spent fuel storage pool building is limited through electrical and mechanical stops which prevent the movement of heavy objects, including shipping casks, over the spent fuel pool. The movement of casks is restricted to the cask loading area and areas away from the pool (Ref. 2).

APPLICABLE The release of radioactive material from fuel may occur during the SAFETY refueling process, and at other times, as a result of fuel-cladding failures ANALYSES or mechanical damage caused by the dropping of fuel elements or the dropping of objects onto fuel elements (Ref. 1). The restriction on the movement of loads in excess of the nominal weight of a fuel and control rod assembly and the associated handling tool over other fuel assemblies in the storage pool areas ensures that, in the event this load is dropped, the activity release will be limited to that contained in a single fuel assembly, and that any possible distortion of fuel in the storage racks will not result in a critical array. These are design basis type accidents that have not been significant to risk when analyzed in environmental reports (Ref. 3).

TR TR 3.9.4 requires that loads greater than 2059 pounds shall be prohibited from travel over fuel assemblies in the spent fuel pool. This ensures that objects traversing the pool are within the design basis and will not cause an unsafe condition if accidentally dropped.

(continued)

Watts Bar - Unit 2 B 3.9-8 Technical Requirements (developmental) A

Crane Travel - Spent Fuel Storage Pool Building B 3.9.4 BASES (continued)

APPLICABILITY TR 3.9.4 is applicable only when fuel assemblies are in the spent fuel pool. If there are no fuel assemblies in the pool, there is no danger of damaging a fuel assembly with a dropped load, therefore, the TR does not apply. The Applicability has been modified by a Note stating that the provisions of TR 3.0.3 do not apply.

ACTIONS A.1 If a load in excess of 2059 pounds is allowed to traverse fuel assemblies in the spent fuel pool, the load must immediately be placed in a safe condition. This entails moving the load to a position which is not over the spent fuel pool.

TECHNICAL TSR 3.9.4.1 SURVEILLANCE REQUIREMENTS TSR 3.9.4.1 requires that the crane interlocks and physical stops, which prevent crane travel over fuel assemblies, are demonstrated to be OPERABLE. This surveillance must be performed within 7 days prior to using the crane and at least once per 7 days thereafter during crane operation. The 7 day Frequency corresponds to ANSI B30.2, "Frequent Inspection for Heavy to Severe Service."

REFERENCES 1. Regulatory Guide 1.13, "Spent Fuel Storage Facility Design Basis."

2. Watts Bar FSAR, Section 9.1.2, "Spent Fuel Storage."

3. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.9-9 Technical Requirements (developmental) A