RADIATION HAZARDS FROM CRITICALITY ACCIDENT IN OPEN POOL TYPE REACTOR.

In this study, a hypothetical nuclear criticality accident has occurred in open pool type reactor due to ejection of the control rod during loss of coolant accident. Dose rate distribution was determined for prompt neutrons and gamma rays resulting from first radiation pulse of the criticality accident. MCNP code has been used to determine the dose rate in different positions that the worker may locate inside the reactor during the accident. The results show that the maximum radiation dose is 2.52 Sv which located at the center of the top of the main pool. The worker located in the control room, the first floor and the ground floor will receive a dose of 68.2, 11.6 and 0.85 mSv, respectively. The worker located in the underground floor will receive a dose of 35 µSv. SKYDOSE and SKYNEUT codes were used to determine the dose distribution outside the reactor building resulting from skyshine effect where the shielding around the reactor core is sufficient to attenuate the radiation in the radial direction. MCNP code was used to verify the SKYDOSE and SKYNEUT results along the distance of 1200 m from the reactor. The results show that the person around the reactor would receive an accumulated dose ranged between 1776.7 and 0.02 µSv along the distance between 20 and 1200 m.

Radiation dose level inside the control room of open pool type reactor during emergency situation.

The objective of this paper is to estimate radiation dose level in the control room due to air contamination in the containment of open pool type reactor during emergency situation. A postulated core degradation accident, due to fuel element blockage, causes fission products to release to the reactor containment and then, the ventilation system would convert automatically from the normal situation to the emergency situation to purify the contaminated air by forcing it to pass through a group of filters. The study computed the dose rate in the control room, adjacent to the containment, during the emergency situation. The dose rate level in the control room depends on the degree of the core degradation and so, the maximum dose rate is corresponding to the complete degradation of the core and the minimum dose rate is corresponding to the degradation of one fuel plate. The dose rate in the control room was calculated using MCNP5 code and it ranged from 1.12 to 2.03E-3 Sv/h. The results also show that the dose rate level in the control room would continue having values more than the permissible limit for a long time and so, a suggestion of venting the radioactive isotopes from the containment into the environment was studied to decrease the dose rate level in the control room. The suggestion was possible because the maximum dose, resulting from the contaminated air venting, would fortunately locate in a free-inhabitant area.

Radiation dose distributions due to sudden ejection of cobalt device.

The evaluation of the radiation dose during accident in a nuclear reactor is of great concern from the viewpoint of safety. One of important accident must be analyzed and may be occurred in open pool type reactor is the rejection of cobalt device. The study is evaluating the dose rate levels resulting from upset withdrawal of co device especially the radiation dose received by the operator in the control room. Study of indirect radiation exposure to the environment due to skyshine effect is also taken into consideration in order to evaluate the radiation dose levels around the reactor during the ejection trip. Microshield, SHLDUTIL, and MCSky codes were used in this study to calculate the radiation dose profiles during cobalt device ejection trip inside and outside the reactor building.

Anatomic physeal-sparing technique for medial patellofemoral ligament reconstruction in skeletally immature patients with ligamentous laxity.

PURPOSE: To evaluate the clinical outcome of this modified physeal-sparing technique for MPFL reconstruction in skeletally immature patients with ligament laxity. PATIENTS AND METHODS: This study was conducted on 16 patients (11 females and 5 males) with an average age of 11.5 years (8-15). They all had recurrent patellar dislocation with generalized ligament laxity (mean Beighton's score of 7) and no patellar tilt on X-ray. We modified the Frank Noyes' non-anatomic technique for MPFL reconstruction to become anatomic without hardware fixation for the graft. RESULTS: The mean follow-up period was 29.25 months (SD 4.3) ranged from 24 to 34 months. Preoperative Kujala score had ranged from 49 to 61 points (mean of 56, SD 4.72), improved to be ranged from 90 to 99 points (mean 94, SD 2.73), which is considered highly significant (p value < 0.005). Till the latest follow-up, there were no definite re-dislocation episodes in any of our patients. CONCLUSION: The described technique allows reconstruction of the MPFL in skeletally immature patients with ligament laxity avoiding any potential risks of growth disturbances or chondral damage as compared to other techniques. The modification of two-point femoral fixation allows both a more anatomic and more secure form of reconstruction and is cost-effective without the need for hardware.

Latarjet procedure in patients with multiple recurrent anterior shoulder dislocation and generalized ligamentous laxity.

PURPOSE: Patients with generalized hyperlaxity with frank recurrent anterior shoulder dislocation had high failure rate after conservative and soft tissue stabilization procedures. Our hypothesis is that a Latarjet procedure can provide an alternative successful approach to manage such cases. METHODS: This prospective study was conducted on 13 patients with multiple recurrences of anterior shoulder dislocation. The mean age was 24.4 years. They all had generalized ligamentous laxity according to Beighton's scale with a mean score of six points. Hill-Sach's lesion was <20 % of the head diameter with no glenoid defect; otherwise, the case was not included in the study. The modification of Burkhart and de Beer "congruent-arc Latarjet procedure" was performed for all patients through a limited deltopectoral approach. RESULTS: Re-dislocation occurred in one case only over the follow-up period. It occurred once after a violent act. Their preoperative mean Rowe score was 47.5 points preoperatively and increased to 91.07 postoperatively. This improvement was statistically highly significant (p value <0.001). The mean range of postoperative external rotation was 69.29°. CONCLUSION: Latarjet procedure provides a higher success rate in such patients with multiple recurrences regarding both shoulder stability and function compared to capsulolabral repair procedures. LEVEL OF EVIDENCE: IV.

Timing of shoulder arthroplasty in comminuted proximal humerus fracture, how much does it matter?

Shoulder hemiarthroplasty is a salvage treatment for comminuted fracture of the humerus especially in elderly patients. Several factors contribute to the final outcome like bone quality and tuberosity reposition. Timing of the surgery is considered one of these factors. This study was done to assess the effect of delaying the surgery up to 2 weeks on the final outcome. This retrospective study was done on 33 patients with four-part fracture of the humerus, divided into two groups, group 1 (17 patients) who had surgery within the first 3 days after trauma, and group 2 (16 patients) who had surgery within the second week after injury. Operations were done by the same surgeon, same technique, and same implant. Constant score was used to assess the final follow-up, and there was a significant better result for group one especially in the items of range of movements and power.

Neglected anterior shoulder dislocation: open remplissage of the Hill-Sachs lesion with the infraspinatus tendon.

Neglected anterior shoulder dislocation is a rare condition; reduction usually requires an open procedure. There is usually a concurrent Hill-Sachs lesion, with the humeral head impaled over the anterior rim of the glenoid. Large, engaging Hill-Sachs lesions can contribute to continued shoulder instability, and therefore require a specific action. Reconstruction of the humeral head with an osteochondral allograft has been advocated, but allografts are not easily available in some countries, such as Egypt. For this reason, I switched to the open infraspinatus remplissage technique. I report the results with this technique, in four young adult patients who presented with a locked anterior shoulder dislocation, which had been left unreduced for 10 to 20 weeks. The infraspinatus tendon was pulled into the humeral defect with a four limbs suture anchor; as a result, the lesion became extra-articular. A Putti-Platt procedure was added to obtain anterior stability, except in one patient with a concurrent glenoid defect which required a Latarjet procedure. The mean follow-up period was 32 months, without recurrence or other complications. The mean postoperative Constant score was 74, and the range of motion was satisfactory, with a functional range of external rotation.

Resection arthrodesis for the management of aggressive giant cell tumor of the distal femur.

BACKGROUND: Giant cell tumors (GCTs) of bone are aggressive benign tumors. Wide resection is reserved for a small subset of patients with biologically more aggressive, recurrent, and extensive tumors. Wide resection and mobile joint reconstruction are preferable for treating tumors around the knee. In certain situations, resection arthrodesis or an amputation is suggested. In this prospective study we report the outcome of 8 patients of aggressive GCT of lower end of femur treated with resection arthrodesis. MATERIALS AND METHODS: Eight patients with mean age of 37.25 years (range 30-45 years) with Campanacci Grade III (Enneking stage III) giant cell tumors at the distal femur were treated with wide resection and arthrodesis using dual free fibular graft and locked intramedullary nail from January 2003 to January 2008. There were four males and four females patients. The mean follow-up was 48.75 months (range 30-60 months). The functional evaluation was done using the standard system of musculoskeletal tumor society with its modification developed by Enneking et al. RESULTS: At the final follow up the functional score ranged from 20 to 27 out of total score of 30. Graft union was achieved in all cases in a duration mean of 14.5 months (range 12-20 months).One case required secondary bone graft due to delayed union, and one case had superficial wound infection which healed on systemic antibiotics. At final followup, all the patients were disease free. CONCLUSION: Wide resection and arthrodesis in aggressive GCTs of the distal femur with involvement of all muscle compartments is a good treatment option. Resection arthrodesis offers a biological reconstruction alternative to amputation in a special group of patients when extensive resection precludes mobile joint reconstruction.