Reactor compartment

All SNF and the core barrel from the N2 reactor were removed from the three RPVs. Before disposal, the primary circuit loops and equipment were washed, dried, and sealed and the ceiling of the RC was equipped with special pressure relief valves. 

The icebreaker, with the RC aboard, was towed from Murmansk to Tsivolka Fjord for the disposal operations. On September 19, 1967, the RC with three RPVs was dumped in the shallow water of Tsivolka Fjord at an estimated depth of 60 m directly from the icebreaker through the bottom of the hull. The disposal site was approximately one kilometer from the site that was used for the damaged SNF and core barrel from the N2 reactor. 

Like the icebreaker, the pontoon was towed from Murmansk to Tsivolka Fjord for disposal. During transit, a storm occurred in the region of the Kara Gate and the pontoon was temporarily lost due to rupture of the towing cable. The pontoon was subsequently found, secured to the towing vessel Lepse, and towed to Tsivolka Fjord. On September 18, 1967, e pontoon was dumped within one kilometer of the site that would be used for the RC. 

Schematic cross-section of the technical fuel channels and core barrel from the icebreaker N2 pressurized water reactor [4J. 

In order for the lASAP to provide an assessment of the radiological impact of the dumped marine reactors, source terms were required for the following release scenarios  

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The reactor operates with the effluent at about 166 C and 62% conversion. Temperature control is effected primarily by reflux cooling as indicated in Fig. 20 with the condensed vapors being returned to the upstream reactor compartment. 

Figure 7.11 Superstructure for two-phase reactions with three reactor compartments in each phase. Mass transfer is only allowed with the corresponding shadow compartment.

If a model is available for the reaction chemistry and kinetics, then a temporal superstructure can be developed to represent a batch reactor in the time dimension with a series of reactor compartments that connect to each other sequentially in the time dimension3. This temporal superstructure network, representing a batch reactor, is created... 

A simulation model needs to be developed for each reactor compartment within each time interval. An ideal-batch reactor has neither inflow nor outflow of reactants or products while the reaction is carried out. Assuming the reaction mixture is perfectly mixed within each reactor compartment, there is no variation in the rate of reaction throughout the reactor volume. The design equation for a batch reactor in differential form is from Chapter 5 ... 

For the first time interval, the input to the reactor compartment are the reactants charged to the vessel... 

Figure 14.3 shows a temporal superstructure for a multiphase batch reactor3. As with the continuous steady state reactors discussed in Chapter 7, mass transfer is only allowed between adjacent reactor compartments. 

In SSP, the boundaries for the mass balances are defined by the particle instead of the reactor or the reactor compartment dimensions and the process conditions are accounted for by a boundary condition. The mass transfer at the particle/gas interface is mostly described according to the film theory by using a mass-transfer coefficient. 

Equations (32) to (37) are related to the reaction mechanism considered. In the models developed in this work, several mechanisms were considered, and they are detailed in the following subsections. Initial conditions for equations (32) to (37) are defined by the concentrations of the substrates, products, and enzymes in the reactor compartments at the onset of operation (at time t = 0), for 1 < / 5 n, according to... 

The building block of the superstructure representation is the generic reactor unit, which follows the shadow reactor concept (32). This generic unit is illustrated in Figure 4. Each generic unit consists of reactor compartments in each phase of the system, and each processes the reaction. The shadow reactor compartment assumes a state from the set of homogeneous reactors. The default units in the set include CSTRs and PFRs with side streams. The interface between a given pair of... 

Nonisothermal systems are accounted for by the introduction of temperature-control units into the generic reactor unit representation. These units consist of elements associated with the manipulation of temperature changes and constitute temperature profiles (profile-based approach) and heaters/coolers (unit-based approach). The assumption of thermal equilibrium between the contacting phases reduces the need for a single temperature per shadow reactor compartment. The profile-based system (PBS) finds the optimum profiles without considering the details of heat transfer mechanisms. Because the profiles are imposed rather than... 

Figure 3.27 Schematic of the flow diffuser and the reactor (only half of both designs is shown for reasons of symmetry). The two parameters a and b taken for a design study to reflect the relationship between structural details of the diffuser and reactor compartments and the flow distribution are indicated [55] (by courtesy of ACS).

Figure 3.28 Flow distributions in the reactor compartments as a function of the ratio of the structural parameters b/a (a). Mean-square deviation from the average value at various b/a ratios and various flow velocities (b) [55] (by courtesy of ACS).

To achieve level 2, the reactor compartment is separated from the rest of the ship, sealed and stored on a ground facility located inside Cherbourg Naval Dockyard. The rest of the ship is decontaminated, controlled and sent for scrap like any conventional submarine. The reactor compartment will stay in this intermediate storage facility for roughly 15 years a duration calculated to allow enough time for short lives corrosion products to disappear, and hence reduce the radioactive dose to workers during the next phase. 

After the 15 years period, work will be resumed on the reactor compartment in order to achieve level 3. At this time, all remaining pipes, structures, equipments will be cut into pieces, conditioned and sent to ANDRA for definitive storage. 

Today, 4 SSBN are decommissioned, the first one Le Redoutable in complete level 2 dismantling two other ready for the ultim operation of level 2, the cutting of reactor compartment. 

SRW was removed from the NIB s storage and transferred to Atomflof for processing and disposal. To improve the radiation situation at the icebreaker, all reactor compartment rooms were decontaminated. 

The very first NS with LMC (design 645) was equipped with two-reactor Power Reactor Installation (PRI). After the port-side-reactor accident during the second fuel lifetime (1968), the NS was kept afloat for some period. Then, after filling of free reactor cavities and the whole Reactor Compartment (RC) with preservative agents, the NS was dumped in the Kara Sea close to the Novaya Zemlia (New Land) archipelago at 50-m depth (1981). Some characteristics of NS, design 645, are given in Table 2. 

Under accident-free haulage of NSs, Nuclear-Powered Surface Ships (NPSSs), Reactor Compartment (RC) units, nuclear Maintenance Vessels (MVs) and Radioactive Waste (RW) as well as during defueling operations the radiation impact on population is virtually lacking, and the radiation risk does not exceed an unconditionally acceptable level of 110 [1]. However in a case of emergency the radiation risk would increase potentially reaching 6010 - 7000 10 that would be unacceptable for population (acceptable risk < 50T0 [1]) (Table. 2). 

The issue of radionuclide migrations from nuclear power installation to reactor compartment and adjacent compartments is still unclear that could result in seawater contamination when salvaging and towing the submarine to shipyard. 

In the Kamchatka region the retired Nuclear Submarines (NSs) pending/under dismantlement along with made up Reactor Compartment (RC) imits are stored afloat at the Federal State Unitary Enterprise (FSUE) North-Eastern Regional Center (NERC) and at the former naval base in Krasheninnikov Bay. 

A LONG-TERM MOTHBALLING TECHNOLOGY FOR REACTOR COMPARTMENTS WITH DAMAGED CORES... 

Gorigledzhan, E.A. (2001) Methods and procedures of ensuring environmental safety when dismantling nuclear submarines with damaged reactor compartments, in Proceedings of international conference Environmental Problems of Complex Decommissioning of Nuclear Submarines", Severodvinsk, pp. 71-75 (in Russian). 

RADIATION RISK DURING WATERBORNE STORAGE OF NON-DEFUELED REACTOR COMPARTMENT UNITS... 

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