transient accident analysis

what are the safety limits in regards to DNBR, LPD, Fuel peak centerline temp, and Pzr pressure

DNBR greater than or equal to 1.34

peak fuel centerline temp less than 5080 F

LPD less than 21 kW/ft

Pressurizer pressure less than 2750 psia

describe a limiting event

worst case potential set of conditions in a particular event category

Events that would require LCO’s, procedures, plant designs ect that minimize release to the public

what is a single failure criteria?

an occurrence which results in a loss of capability of a component to perform its intended safety function

under limiting faults describe the moderate frequency

condition 2 incidents are any incident which may occur during a Calander year

define and infrequent event?

condition 3 incident that may occur over the lifetime of the plant

describe a limiting fault

faults that are not expected but planned for anyways

how is an uncontrolled CEA withdraw protected from during subcritical vs at power operation

Hi log trip when subcritical

CPC VOPT or High PZR trip at power

describe a limiting case for a single full strength CEA drop?

limiting case is the CEA drop which does not cause a trip to occur but results in an approach to the DNBR SAFDL

during an inadvertent dilution, what mode results in the least time available for termination of the event?

mode 5 (cold shutdown) with RCS drained results in the least time available for detection and termination of an ID event

what results from an instantaneous circumferential rupture of the CEDM housing or CEDM nozzle?

results in a CEA ejection

what are CEDM housing capable of withstanding? how is housing failure classified

capable of withstanding all normal operating loads including the steady state and transient operating conditions specified for the reactor vessel, failure is considered to be incredible and is therefore classified as a limiting event fault

what kind of trip does a CEA ejection cause?

causes a high power trip and power begins to drop as the CEAs enter the core

what percentage of fuel is assumed to suffer clad failure? and why?

19% of the fuel rods are assumed to suffer clad failure (provides a conservative assessment of radiological consequences)

why is a single RCP shaft break the most limiting Loss of flow event?

most limiting because of the longer RPS trip response time, most core damage and higher radiological dose

what does an RCP shaft break allow as the impeller spins to a stop

allows for a flow coastdown

how does a single RCP shaft break affect the plant?

will cause some core damage , DNB is the parameter of concern

what would occur if an ADV failed to close during a sheared shaft RCP event?

stuck open ADV causes eventual dry out of the affected SG w

what trips does a locked RCP rotor have, what trips does a RCP sheared shaft have?

locked rotor; CPC trip on Lo DNBR when RCP speed less than 95%

Sheared shaft; low S/G DP RPS trip