1. Does your plant use all seven compartments per Regulatory Guide 8.40, Table 1 when using EDEX (i.e. every multipack has seven dosimeters)? We calculate dose for all compartments, but may combine compartments.
2. If "No" to #1 and your site combines compartments, what locations do you group together? Each job is a specific evaluation where the placement of dosimeters within a compartment or the combination of compartments is determined. Have also put more than one dosimeter in a compartment before and took the max reading of the dosimeters in that compartment. Watch out for changing fields as well. As an example a BWR under-vessel area has a top-down gradient before people start removing control rod drives. That changing gradient and the inability to predict whether the knee or head dosimeter will have the highest dose has me monitor multiple compartments instead of assuming a single relocation to the head. My data shows I cannot consistently predict the location of highest dose, which means I'll keep doing multiple dosimeters for CRD exchange. BWR nozzle workers are another group that is in every conceivable geometry. I'll have a dosimeter at the lower thigh and lower abdomen and use the higher of the two responses for the thigh. For the torso, I put one at the top of the thorax, one at the thorax/abdomen boundary and one at the bottom of the abdomen. I use the higher of the two for the thorax dose and the higher of the two for the abdomen dose. I try to make the multiple dosimeter logic reflective of the fact that I cannot control the changing worker geometry. If the field is top-down, you'd want to monitor at the top of the thorax and top of the abdomen. In this case your dosimeters are in the highest dose portion of the compartment and the weighting factor of the abdomen compartment will likely reduce the over-response if you used one dosimeter at the top of the thorax for a combined thorax/abdomen compartment. We use a fish net vest and fit each person in about 3 minutes so we know we're good for location. We tie wrap the dosimeters to the vest and they return the vest to the dosimetry office after every jump. We avoid placement in the field or by personnel who may not understand the significance of placement... 3. Has your site performed any calculations to determine the delta in total EDEX dose using all seven dosimeters versus the overall dose using combined compartments? If "Yes", would you be willing to share your results with me at [email protected]? I typically calculate my differences by dividing the final EDE dose value by the highest single dosimeter. I've seen a 20% savings on Rx Cavity decon. Got 6% on nozzle work with the nozzle pipe about waste high the abdomen and thorax compartments got the highest exposure and have the highest weighting factors. Got 8% for CRD exchange. The pic below shows the ave dose from all of the workers at each body location. As stated earlier, while the job starts with a top-down gradient, I cannot expect that to remain the same once work begins. Glen Vickers Exelon Corp RP Technical Lead, CHP 815-216-2723 (work/cell) From: [email protected] [mailto:[email protected]] On Behalf Of Chlebowy, Corrin N Sent: Wednesday, September 18, 2013 3:11 PM To: [email protected] Subject: Powernet: EDEX Compartment Usage Inquiry Nine Mile Point is conducting a dosimetry focus self assessment. Any and all information you can provide on the following effective dose equivalent external questions would be greatly appreciated. 4. Does your plant use all seven compartments per Regulatory Guide 8.40, Table 1 when using EDEX (i.e. every multipack has seven dosimeters)? 5. If "No" to #1 and your site combines compartments, what locations do you group together? 6. Has your site performed any calculations to determine the delta in total EDEX dose using all seven dosimeters versus the overall dose using combined compartments? If "Yes", would you be willing to share your results with me at [email protected]? Thank y'all for your time. Have a wonderful day. Corrin Chlebowy [email protected] Associate Plant Health Physicist Nine Mile Point Nuclear Station This e-mail and any attachments are confidential, may contain legal, professional or other privileged information, and are intended solely for the addressee. If you are not the intended recipient, do not use the information in this e-mail in any way, delete this e-mail and notify the sender. -EXCIP
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