Absorber pins

Plant Safety rods Group 1 rods Group 2 rods 

Plant Outer diameter of absorber pin safety (mm) Group 1 Group 2 

JOYO (Japan) none(BC90inMK-l) BC90 none 

BOR-60 (Russian Federation) BC80 BC80 or EU2O3 BC80 

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Polydioxanone was the first polymer used commercially as monofilament for biomedical applications under the trade name PDS . As a monofilament, it has a smaller risk of infection with use and causes less friction when penetrating tissues [153], Also, the material has been used by companies like Johnson Johnson Orthopedics as an absorbable pin for fracture fixation composed of poly(dioxanone) [178],... 

PDS demonstrated no acute or toxic effects on implantation, and thus has been used in a number of clinical applications ranging from suture materials to bone fixation devices. Johnson and Johnson Orthopedics provides an absorbable pin for fracture fixation, and bone pins have been introduced into the market under the names OrthoSorb and Ethipin, respectively, in the USA and Europe. In craniofacial applications, the structure of PDS has been examined clinically in cranial vault procedures with promising results. Advantages include the absence of observed intracranial translocation, acceptable aesthetic outcomes and low complication rates. Nevertheless,... 

Pihlajniaki, H., Bostman, O., Hirvensalo, E., Tormala, P., Rokkanen, P. (1992) Absorbable pins for self-reinforced poly-l-lactic acid for fixation of fracture and osteotomies,./ Bone and Joint Surg. [Br], 74-B, 853-857. 

Pihlajamaki H, B5stman 0, Hirvensalo E, T5rmala P and Rokannen P (1992) Absorbable pins of self-reinforced poly-L-lactic acid for fixation of fractures and osteotomies, J Bone Joint Surg 6 853-857. 

CONTROL RODS AND DRIVE MECHANISMS (cont.) 5.5. Absorber pins... 

Failed absorber rod behaviour. Although limited, some experience with absorber pin failures has been gained particularly in PHENIX, PFR, EBR-II and BOR 60. Most of these defects were explained by pellet-clad mechanical interaction with clad-strains greater than 2% or local deformation due to B4C fragment relocation. For all the observed ilures, there was no evidence of material loss from any pin. 

FIG. 7.29. Pellet cladding interaction in a FFTF test absorber pin. 

FIG. 7.30. PHENIX PRECURSAB A1 experimental absorber pin - Relocation of pellet fragments in pellet-clad gap and consequent clad failure. 

Figure 15.10 Postittadiation observation of absorber pins [38]. (a) Low-density (70%), natural B4C pellet in tbermal neutron reactor (French Osiris reactor), (b) High-density (95%), B-enriched (48%) B4C pellet in SFR (French Phenix reactor). In both cases, the maximum biunup is about 5. lO Vcm. The primary damage in Osiris comes from strong radial capmre gradients, whilst in Phenix it comes from high-temperature gradients.

As a result of these difficulties, modifications of the absorber pins have been performed [2,12,31] ... 

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