Optimization of the number of spacers in a nuclear fuel bundle with respect to flow-induced vibration

Meher, K.K.; Rao, A. Rama

doi:10.1016/j.nucengdes.2006.02.015

Cited by 7 publications

(2 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fretting wear, if significant, can bring down the operational life of the feeders drastically [7]. Study was carried out to assess critical life limiting parameters by simulating fret ( [8], [9], [10], [11]). …”

Section: Introductionmentioning

confidence: 99%

Simulation of Fret for Life Assessment of Feeder Pipes of PHWR

Meher

Pandey

Sinha

et al. 2014

Procedia Engineering

Self Cite

View full text Add to dashboard Cite

In case of KAPS and KGS, different ingots were used for manufacturing the coolant channels. Due to difference in the creep related material properties of different ingots, the coolant channels in these reactors experienced different creep rate. Due to the differential creep rates, especially in the neighboring channels, the coolant channels came into contact with each other. This is a serious deviation from as installed conditions wherein the gaps and spacing between closely assembled coolant channel components are decided based on accurate assessment of known loads and forces. Differential creep results in closing of gaps between neighboring feeder pipes or between feeder pipe and gray-loc clamp. Depending on the orientation of the clamp and direction of the feeder pipe at that location, worst contact could be between the first elbow of feeder pipe and the sharp edge of the crown nut on clamp. Several such contacts have been detected in KAPS and KGS. Seriousness of the contact emerges from the fact that the coolant channel and the feeder pipes vibrate due to coolant flow with high velocity. With time the contact conditions like the contact force and location(s) of contact change and this has significant influence on the life and performance of the coolant channel as a whole. Since feeder pipes are constantly vibrating, the contacting locations are likely to be dented or damaged. Whenever and wherever possible, NPCIL has tried to remove the contact locally. Since the process of creep is ongoing, more and more feeder pipes are likely to come in contact and those in which the local corrections for removing the contact are made could also need correction as the time progresses. In order to assess the severity of damage, a full scale setup was erected. Contact was established between feeder pipe and the hard locking nut of gray-loc clamp. Based on previous vibration data collected from feeder pipes and end fittings, and the ASME`s O&M guidelines on acceptable level of piping vibration in nuclear piping, vibration was induced in the contacting feeder pipes. The test was continued for more than 10 07 cycles. On the basis of damage seen on the feeder pipe due to contact, R6 method has been employed to determine the critical crack size in the feeder pipe with a postulated axial part-through semi-elliptical crack. The failure assessment diagram was constructed in the K-L plane. The lowest critical crack depth was calculated as 4.67 mm as against observed depth of dent of 1.1 mm. The paper deals with the critical assessment of contact between neighboring coolant channels caused by differential creep and assessment of safety margin available before corrective action need to be initiated.

show abstract

Section: Introductionmentioning

confidence: 99%

Simulation of Fret for Life Assessment of Feeder Pipes of PHWR

Meher

Pandey

Sinha

et al. 2014

Procedia Engineering

Self Cite

View full text Add to dashboard Cite

show abstract

“…Though there are many standard procedure and facilities available to cater for small size component testing [5], one has to tailor the procedure to fit the design requirement especially when the components are very big and cannot be tested by the available conventional facilities. There are many references in this area [6][7][8][9] which address specific problems related to structural dynamics. A Bertram [9] suggests a method for dynamic qualification of large structure.…”

Section: Introductionmentioning

confidence: 99%

Qualification of Large Structures for Shock Loads

Meher

Rao

2014

Mechanisms and Machine Science

View full text Add to dashboard Cite

Many critical equipments and components have to withstand shock and vibration during its life time. In defence, space and nuclear industries in particular, it is mandatory to test and analyze such components before acceptance. Analytical and experimental qualification of these components is an important exercise to be fulfilled as per the applicable codes and practices. Test for shock qualification is particularly important for components designed for defence and space applications. When the structure is large, generally an analytical approach is followed and a small scale model is experimentally validated for such qualification and the result is extended to the prototype. This approach may or may not be true always. The paper discusses about the phases of qualifying a large component for a certain level of shock. Achieving the required shock level and the pulse duration experimentally with repeatability is a challenging task. Besides, when the size and shape of the structure is odd, the qualification procedure becomes more complicated and at times difficult to achieve the desired objective. The objective was to achieve the required shock pulse by dropping the test structure from a predetermined height on a target made of commercially available rubber material. The test object is a long stainless steel vessel weighing 805 kg and 2.8 m long. The vessel is housed in a rigid cage with arrangement to lift with a magnetic clutch for instantaneous release for dropping. It was required to subject the vessel to both vertical and horizontal shock of 25 g of 35 ms duration. For dropping the vessel horizontally, the housing cage was dropped on more than one target from a predetermined height. The procedure followed in arriving at the drop height, actual drop height and the achieved shock levels are discussed in the paper.

show abstract