Primary sodium system

The primary circuit consists of 2 pumps and 4 IHXs with one IHX on either side of each pump. The two IHXs on either side of a pump are linked to one secondary sodium loop. The primary sodium from the hot pool flows on the shell side while secondary sodium flows on the tube side of the IHX. The IHXs discharge primary sodium to the cold pool, from where it is pumped to the grid plate through a pump-grid plate pipe connection. 

Intermediate heat exchanger (IHIQ This is a vertical shell and tube counter-flow heat exchanger with no free sodium level. The tubes are straight with no expansion bends and the tube-to-tubesheet joint is rolled and welded. Thermal shields are provided to protect the bottom tubesheet from thermal transients. Antivibration belts surround the tube bundle to prevent vibration. A sleeve-type valve is used to isolate the IHX primary side when it is non-operational. 

Primary sodium purification Purification of the primary sodium is accomplished by two cold traps located outside the main vessel. Organic cooling with a NaK jacket is provided. 

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Figure 11. Primary sodium system EBR-ll working model...

Sodium is a chemical that has been used extensively and has an established record of safe handling on a large scale. The PRISM reactor has been designed with the potential for sodium-water reaction in mind. The primary sodium system is entirely encompassed within the reactor vessel and surroxmded by the containment vessel, to eliminate the potential for loss of primary coolant and to reduce the potential for sodium-water reaction. The IHTS transports heat from the primary system to the SG where the heat is transferred to the cooling water. The sodium-water interaction is mitigated in the SG with the pressure cap inert gas and the SGIS as described in Section 6.4.5.I. 

The 4S is sodium-cooled reactor therefore, an intermediate heat transport system is employed to avoid a reaction between the primary (radioactive) sodium and water/steam of the power circuit. The 4S has three heat transport systems the primary sodium system located inside the RV, the secondary sodium system in which sodium is sufficiently non-radioactive to define it as an uncontrolled area , and the water/steam turbine system. 

Reactor core. The reactor block is of an integrated design (pool) except for a few auxiliary circuits. The entire primary sodium system, containing 800 tons of radioactive sodium, is enclosed in the main reactor vessel, which is 11.8 m in diameter (Fig. 2.10). 

Reactor maintainability. The reactor plant operating experience has demonstrated quite acceptable maintainability of the integral LMFR. There have been no additional difficulties in repairing primary system components on BN-600 compared with BN-350. Repairs of the reactor equipment items and sodium systems, including such complicated operations as replacement of the reactor coolant pumps and SG modules, re-arrangement and jacketing of primary sodium systems, extraction of distorted items from the reactor core, etc. had virtually no influence on the duration of planned outages, which were defined, as a rule, by inspections and preventive maintenance of the steam-water system components. 

Sodium is used as a heat-transfer medium in primary and secondary cooling loops of Hquid-metal fast-breeder power reactors (5,155—157). Low neutron cross section, short half-life of the radioisotopes produced, low corrosiveness, low density, low viscosity, low melting point, high boiling point, high thermal conductivity, and low pressure make sodium systems attractive for this appHcation (40). 

Blood has several buffer systems that work together to maintain a narrow pH range between 7.35 and 7.45. A pH value above or below these levels can be lethal, primarily because cellular proteins become denatured, which is what happens to milk when vinegar is added to it. The primary buffer system of the blood is a combination of carbonic acid and its salt, sodium bicarbonate, shown in Figure 10.21. Any acid that builds up in the bloodstream is neutralized by the basic action of sodium bicarbonate, and any base that builds up is neutralized by the carbonic acid. 

Liver disease is often associated with edema and ascites in conjunction with elevated portal hydrostatic pressures and reduced plasma oncotic pressures. The mechanisms for retention of sodium by the kidney are complex. They probably involve a combination of factors, including diminished renal perfusion resulting from systemic vascular alterations, diminished plasma volume as the result of ascites formation, and diminished oncotic pressure from hypoalbuminemia. In addition, there may be primary sodium retention by the kidney. Plasma aldosterone levels are usually high in response to the reduction in effective circulating volume. 

These terms are also used to name salts of ortho-phosphoric acid (H3P04) in which one, two, or three of the hydrogen atoms have been replaced by metal or radicals NaH2P04 is primary sodium phosphate, Na2HPC)4is secondary sodium phosphate. The same system of names is used for salts of other acids containing three replaceable hydrogen atoms. 

A partial tear of a compressor membrane in a cover gas activity measurement line resulted in the admission of an argon and air mixture into the reactor, which was at nominal power. The total pollution was estimated at between 300 and 350kg of sodium oxides. There was no system to measure the purity of the reactor sodium argon cover gas to provide an alarm for the operator in case of pollution, and the reactor operated outside the operation specification range for three days before shutdown. An unplanned reactor outage of over 10 months was needed to remove the impurities from the primary sodium. 

The PFR primary sodium circulation system is shown in Figures 9.1 and 9.2, and Figure 9.3 shows details of a primary sodium pump (PSP). The sodium from each PSP flows through filters and a stop valve to the diagrid, and thence to the fuel subassemblies. Each subassembly has a filter at its inlet. Figure 9.4 shows the relationship between the pump and subassembly filters. 

Reactor vessel height / diameter Primary coolant systems Primary coolant sodium mass Inlet / outlet reactor temperature Primary coolant flow rate Primary coolant flow velocity Secondary coolant systems Secondary coolant sodium mass Inlet / outlet IHX temperature Secondary coolant flow rate Secondary coolant flow velocity Water - steam systems Feed water flow rate Steam temperature (turbine inlet) Steam pressure (turbine inlet) Type of steam generator Refueling system... 

The principle of this project review was to identify the causes of the anomalies and the dysfunctions which could affect the intermediate containment barrier and the primary sodium inert gas cover" functions of the primary argon systems. They led to additional studies, corrective actions, counter-measures and modifications being defined and progressively implemented. 

Besides it was required to develop and modify core components (fuel sub-assemblies, control rod guide tubes and control rods), to explore and modify electrical drives of sodium pumps, to modify a reactor refuelling system, to construct advanced failed fuel detection systems, to design and construct advanced reactor vessel integrity inspection systems, reactor vessel and auxiliary primary sodium pipeline displacement measurement systems, to remarkably improve water-sodium reaction detection systems of the water-sodium steam... 

Primary Sodium and Irradiated Fuel Storage Drum Sodium Purification Systems... 

The most serious leak occured in the primary sodium purification system pipeline on October 7, 1993. The volume of the spilled sodium was about 1000 litres but owing to sufficiently effective performanceof the leak suppression system the release of radioactivity outside the plantwas only 10 Ci. The increased exposure of the plant and public did not occur. 

Four leaks occurred because of poor-quality manufacture of sodium system units. So, at the BR-5/10 immediately after mounting of the primary circuit impurity cold trap a leak occurred at the trap nozzle through a microcrack in the joint weld at sodium heating up in the pipe. The cause of the leak was poor quality inspection of joint welds after completion of assembling. Similar situations took place at the BN-600 as well. Such leaks were detected immediately after putting into operation of a failed section of the system. 

Primary sodium purification system Electric heaters, radioactive aerosol monitoring Insufficient selfcompensation of pipelines 1000 kg... 

FIG. 3. Scheme of primary sodium room ventilation system... 

Experience with sodium leaks at our domestic reactors indicates that all leaks without exception, were timely detected. All leaks that occurred on the electrically heated sodium system sections were registered by heaters control systems. In addition, primary sodium leaks were sensed by the radioactive sodium aerosol detection systems. Calculation and experimental analysis of the radioactive sodium aerosol detection system has revealed its high sensitivity and fast response. 

In order to make measurements of caesium-137 activity, special device containing graphite pellet was installed in the loop connected in parallel to the primary sodium purification system. Just after the event of January 21, 1987, some decrease of the system indications was observed. Further, indications of the system came back to the previous level, however, some feature in caesium behaviour was noticed. While in the period preceding described events the decrease of the system indications in case of the reactor shutdown and sodium temperature reduction down to 250°C was 30-40%, later this decrease became as large as 10-12 times. After full power of the reactor had been reached, sodium temperature being as high as 530-540T, indications of caesium activity measurement system returned to the rated level. 

Primary and Secondary sodium systems are in service for the past 14 years at a maximum temperature of 485°C at the outlet of core and 420 C in sodium circuits and tibe performance of the sodium circuit components has been satisfactory/ The sodium purity has been well maintained and there has been no incident of any radioactive sodium leak from the primary circuit. Once-through steam generator (SG) has been in service for about 6600 h and there is no incident of steam generator tube leak. 

Sodium ingress in gas-type pressurizer through pipeline of primary sodium cleanup system and blow-down pipeline of failed MCP-2 while primary sodium cleanup system was being connected to the primary circuit, 17.08.1976. 

The second occurrence in this group is Sodium ingress in gas-type pressurizer through pipeline of primary sodium cleanup system and blow-down pipeline of failed MCP-2 while primary sodium cleanup system was being connected to the primary circuit (FIG.4). The primary sodium cleanup system, connected with pipelines with pipelines of loops-2 and 3, is general for all sodium coolant of primary circuit. Loop-2 was on maintenance and separated from primary circuit with isolation gate valves N 1,2. When personal began to put into operational primary sodimn cleanup system, it was fed from pressure pipeline of MCP-3... 

The top shield includes roof slab and two rotatable plugs. Warm roof concept is adopted for top shield to minimise sodium deposition in the annular gaps. The roof slab is a box type structure filled with concrete as the shielding material. It supports the main vessel, primary sodium pumps, IHX, and direct reactor heat exchangers (DHX) of the decay heat removal system. Use of liquid metal seals has been avoided in order to reduce the rotatable support... 

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