We had a situation recently where the containment tritium levels spiked after we stopped a source of secondary side containment leakage. It was determined that the secondary side leakage was enhancing removal of tritium from the containment atmosphere (such as through more frequent sump pump downs and containment depressurizations). If you can't find a tritium source, perhaps something has changed to decrease the removal of tritium from the atmosphere.
Our tritium never reached the action levels to require bioassay so I don't have any direct experience to share with you on that aspect. Perhaps you could estimate CEDE based on air sampling and then assign dose based on the urinalysis. This is how we handle differences between the electronic dosimeter dose and the OSL/TLD dose. We communicate that the ED dose is just an estimate, and we report the actual dose after the dosimetry is processed. My feeling is that the urine results will give you a better/more defensible estimate of CEDE than the air sampling. Hopefully, the air sample results and urine sampling results will agree pretty well. If you can do the urinalysis in-house, it shouldn't take too long to get the final CEDE numbers. With air samples, there is always the question of how well the air sample represents the actual intake activity. If you know anybody who works at a CANDU reactor, they do extensive tritium sampling and should be able to give you good advice. I have a couple of contacts which I can share with you if you need them. -Steve Stephen J Holmes, CHP, PE Sr. Plant Health Physicist, CENG-RE Ginna NPP [email protected] 585-771-3577 From: [email protected] [mailto:[email protected]] On Behalf Of Rolph, James Thomas Jr Sent: Monday, June 03, 2013 4:25 PM To: [email protected] Subject: Powernet: Tritium Bioassay Practices We have encountered an unusual situation for us here at Sequoyah. We are having some ice condenser issues inside containment requiring frequent containment entries where we typically entered containment once or twice a month while online. We are experiencing increased temperatures and humidity levels inside containment, and along with this increased tritium levels. Our containment tritium airborne activity has been 35% to 105% of a DAC, whereas we typically are < 5% of a DAC. As a result, we realize that we may reach the 10 mrem CEDE threshold on many of the individuals involved in the work being conducting inside containment and that we need to assess the workers internal dose as a result. We are requesting and obtaining urine samples for bioassay analysis, typically 24 hours after an entry so we will have the data available. Acute intake situations are what we typically experience from airborne not continuous exposures. Besides Regulatory Guide 8.9 (based on NUREG CR-4884) do you have any other suggestions, guidance, or recommendations on using DAC-hrs and time versus urinalysis data for dose assessment based on your experience? If you monitor and report CEDE, what CEDE do you use the one based on air sample results, or wait until you have the bioassay results, or replace the air sample one with the bioassay one after you have the results? We are concerned that if we report the one based on air sampling and then adjust that number after we complete the dose assessment based on urinalysis that this will look funky to individuals who look at trending results. Any tips or suggestions on addressing this situation would be appreciated. Thoughts on possible sources of increased tritium levels without a noticeable increase of RCS leakage may also be of interest. Best regards, Jim Rolph, CHP RP Technical Support Superintendent Tennessee Valley Authority Sequoyah Nuclear Power Plant SB2A PO Box 2000 Soddy Daisy, TN 37384-2000 (423) 843-8115 - Work (423) 593-0247 - Cell Notice: This electronic message transmission contains information which may be TVA SENSITIVE, TVA RESTRICTED or TVA CONFIDENTIAL. Any misuse or unauthorized disclosure can result in both civil and criminal penalties. If you are not the intended recipient,n be aware that any disclosure, copying, distribution or use of the content of this information is prohibited. If you have received this communication in error, please notify me immediately by email and delete the original message 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
