BS IEC IEEE 63113:2021 pdf free download – Nuclear facilities – Instrumentation importantto safety – Spent fuel pool instrumentation
This annex describes the spent fuel pool conditions of interest to be monitored by spent fuelpool monitoring instrumentation.These conditions are:
a) Thermodynamic conditions in the pool.Pool thermodynamic conditions may be determined
by measurement of pool temperature.Higher than normal temperatures may indicate anabnormally high rate of pool water evaporation. Normal temperatures in combination withunexpected loss of inventory may indicate that the pool is leaking.
Spent fuel pool monitoring instrumentation functions provided to detect these conditions areintended to support operators during plant operational states and design extensionconditions. In operational states pool temperature is a direct indication of loss of heatremoval.During design extension conditions temperature measurement provides an earlyindication of the possible loss of pool inventory, provides information that operators need tounderstand the thermodynamic conditions in the pool, and provides a means for determiningif reduction in pool level results from evaporation or leakage.
b) Maximum water level.Pool inventory has approached the point where there is a risk of water overflowing the top of the pool. This condition will normally be detected by water levelmonitoring instrumentation.Control of water level at or below this point prevents damagethat may be caused by flooding in the structure that houses the spent fuel pool.
Spent fuel pool monitoring instrumentation functions provided to detect this condition areintended to support operators during plant operational states.This condition is normally apoint high enough to ensure sufficient water inventory in the pool and low enough to preventwater from sloshing or overflowing out of the pool during operational states or as a result ofexternal events that are included in the plant’s design basis.
c)Minimum water level for moving fuel. Pool inventory has approached the point where compliance with accident analysis assumptions of iodine decontamination factors followinga fuel handling accident are not met. This condition will normally be detected by water levelmonitoring instrumentation.Control of water level above this point is intended to enable fuelmovement consistent with safety analysis assumptions. Below this point movement of fuelassemblies in the spent fuel pool shall be immediately suspended and placed in a safeposition.Failure to take such action may result in violation of plant operational limits andconditions.
Spent fuel pool monitoring instrumentation functions provided to detect this condition areintended to support operators during operational states.This level will normally be specifiedin the plant’s safety analysis and included in the operational limits and conditions. Somepool segments might not need this measurement.
d) Minimum active cooling water level.Pool inventory has approached the point where there is a risk that operation of the normal fuel pool cooling system cannot be supported.Thiscondition will normally be detected by water level monitoring instrumentation.Control ofwater level at or above this point is necessary to ensure continued availability of forcedcooling for fuel in the spent fuel pool.
Spent fuel pool monitoring instrumentation functions provided to detect this condition areintended to support operators in preventing fuel damage as a result of design extensionconditions.This level may be the higher of the following two points: the level at which thesuction line for the spent fuel cooling system becomes uncovered; or the level at which thereis insufficient water above the suction line to provide the required net positive suction headfor the coolant system pump that draws water from the pool. The determination of this levelaccounts for hydrodynamic effects (e.g.，vortex formation near the suction pipe) andthermodynamic effects (e.g., voiding in the suction line due to steaming in the pool).
e)Minimum shielding water level.Pool inventory has approached the point where the coolant
cannot provide substantial shielding for a person standing on the spent fuel pool operatingdeck.This condition will normally be detected by water level monitoring instrumentation.Control of water level above this point is important to enable operator access to the spentfuel pool operating deck.