Development of Process Equipment for the Lepse Shelter
In the few last years, Sosny R&D Company has been taking an active part in implementation of the project on decommissioning the Floating Maintenance Base Lepse currently located at the Nerpa shipyard near Murmansk in northern Russia.
The Shelter facility was built at the Nerpa shipyard in order to create safe conditions to retrieve the spent nuclear fuel from the Lepse storage tanks.
In 2015‑2018 under the contract with the Kurchatov Institute, the specialists of Sosny R&D Company designed, fabricated, delivered and pre-commissioned the following process equipment and systems:
- 16T Trolley,
- Knuckle Boom Crane,
- Criticality Alarm System,
- Process CCTV System, and
- Guiding Device Remote Control System.
16T Trolley is intended to transport the Type KB-650B Cask filled with the spent nuclear fuel, the metal and reinforced concrete casks with solid radioactive waste, and the drums with the liquid radioactive waste from the Shelter. The configuration of the trolley depends on the object to be transported. The lower platform has some place for interim storing of the components which are not needed for the specific activities.
16T Trolley consists of two platforms arranged one above another. The trolley is power driven along the standard rail track. The electric motor has two speeds (high and low).
The power to the trolley is fed through a flexible cable connected to the power cabinet. The cable drum located on the trolley is used to wind up (out) the cable.
The trolley has two metal plates secured to its front and rear parts. Each plate functions as a position limit sensor which automatically stops the trolley whenever it comes in contact with an obstacle.
16T Trolley can be operated using either a fixed control panel or a pendant control station. The trolley travel logic depends on its current location, the actual position of the Shelter entry gates and the temperature of the trolley main components. The trolley is designed for operations at the ambient temperature below zero.
In case of the power failure the moving trolley can be controlled manually. The trolley has a coupler at its front (rear) part needed to attach the trolley to the truck for further towing if its electric motor fails.
Knuckle Boom Crane is an auxiliary equipment for safe retrieval of the spent nuclear fuel from the Lepse Large Storage Package (LSP) in the Shelter. Its main component is the INMAN commercial loader crane.
Outreach 14.66 m.
Capacity 500 kg.
The crane can be operated both remotely and manually. The remote control of Knuckle Boom Crane can be done via a fixed control panel located in the control room or a mobile control panel intended for radio remote control of the crane from the Lepse LSP at the distance not more than 30 m.
The loader crane is a lifting machine with a hydraulic drive and a knuckle boom. The functional enhancement was done to the standard control system of the loader crane. Then an ungraded control system was integrated to Knuckle Boom Crane.
The standard crane hook is replaced by a grapple designed by Sosny R&D Company for secure gripping and holding an object being handled. The force applied for moving the grapple up and down can be automatically controlled via interlocks. The design prevents inadvertent grapple opening in all cases, including the power loss. Moreover, the grapple jaws can be opened manually. A guide tube shall be attached to the grapple in order to align the grapple and the SNF retrieval equipment.
Knuckle Boom Crane is equipped with a support plate designed for secure fastening and uniform distribution of loads induced by the crane on the Lepse LSP. Also, this plate is intended to collect oil leaks caused by failed hydraulic system.
A hydraulic station creates and maintains necessary pressure of the operating fluid in the hydraulic system.
Knuckle Boom Crane has a remote-control system intended to perform the following functions:
- Rotate the crane and control the knuckle boom movements,
- Control the grapple movements and monitor the loads,
- Lock the boom movement up (down) if it is indicated that the limit load is exceeded, and
- Monitor the state of the knuckle boom crane equipment.
To perform remote control of the process operations, a TV camera which is a component of Process CCTV System shall be mounted on the knuckle boom on a bracket.
Criticality Alarm System is intended for criticality detection and evacuation signals during SNF unloading operations in the Lepse SNF storage tanks. This Criticality Alarm System is based on SRKS-01D Criticality Accident Alarm System made by DOZA Scientific&Production Company, Russia. The SRKS-01D system hardware has a certificate approving its compliance with standards and codes issued by the Department for Nuclear and Radiation Safety and the Organization of Licensing and Approval Activities, part of ROSATOM State Atomic Energy Corporation.
Sosny R&D Company developed the technical design of Criticality Alarm System and obtained the positive expert assessment on its nuclear safety from the IPPE Nuclear Safety Department. The technical design documentation justified locations of the criticality accident detector units at two monitoring points, identified the alarm setpoints, boundaries of the nuclear hazardous area and adequate (inadequate) radiation shielding.
Each monitoring point has two backup criticality accident detecting units that are enclosed in lead shielded casings to minimize the background gamma radiation effect and the nuisance alarm probability.
Audible alarm units BZS-01D and visual alarm units BSS-01D generate emergency signals in the nuclear hazardous area. Each entry to the nuclear hazardous area has a warning sign DO NOT ENTER! at illuminated information panel and a visual alarm unit BSS-01D. The alarm units are connected to the control unit through establishing ring coupling, thus enhancing reliability.
Process CCTV System is designed for visual monitoring of SNF retrieval process in the Lepse Shelter from the control room in the Sanitary Pass and the shielded room on the Lepse LSP.
This system has a distributed structure. It is intended to perform the following functions:
- Remote visual monitoring of radiation hazardous process operations related to the SNF retrieval from the Lepse storage tanks, SNF loading into canisters and try-out of the process operations on the mock-up facility,
- Display video streams from the cameras of the CCTV system on monitors located in the control room in the Sanitary Pass and the shielded room on the Lepse LSP,
- Remote visual monitoring of proper positioning the right (left) guiding device rotating plate located on the top of the right (left) SNF storage tank,
- Check video recording and playback.
The equipment of Process CCTV System includes TV cameras, video recorders, switchboard cabinets and monitors. The camera video streams are transferred to the IP video recorders through the communication cabinets and switchboard cabinets using the Ethernet local network. Then IP video recorders transfer these video streams to the monitors located in the control room in the Sanitary Pass and the shielded room on the Lepse LSP.
In process of aligning with a cell of the SNF storage tank, the TV cameras are used to monitor position of the guiding device rotating plate. These cameras are installed to replace position switches with the expired service life which have been removed before. A special lead shielded casing has been developed for shielding the TV camera from external gamma radiation.
Guiding Device Remote Control System is designed for remote control of the guiding device actuators installed on the rotating plates covering the right and left SNF storage tanks from the control room. Process CCTV System is used to monitor proper positioning of the rotating plates.
Guiding Device Remote Control System includes the control cabinet with connected electric motors of the guiding device actuators. The need to replace electric motors of the guiding device actuators resulted from significant wear and impossibility of any further operation. Such a need was revealed at the pre-design studies stage while examing the guiding device rotating plates. The new electric motors are mounted on the special support plates designed for easy arrangement, positioning and coupling of the motor with standard reducer.
The operator can remotely change the system control mode, and the rotation speed and direction of each guiding device rotating plate. The emergency stop of the electric motors prevents any emergency. A special interlock prevents simultaneous rotation of two plates.
In late 2018 the Lepse LSP was placed inside the Shelter. In early 2019 under the contract with the FCNRS, all installation and pre-commissioning activities were successfully completed and followed by the site acceptance tests which confirmed the readiness of the equipment and systems for commissioning and operating within the project on SNF retrieval from the Lepse storage tanks.
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