64 C.J. W
Chemical decontamination technology ~55 7.4.1 Costs The vendor costs assumed are much higher than for the BNR case, because it is assumed that nozzle dam supply and Installation will be the responsibility of the decontamination vendor. The utility In-house costs and critical path time are also significantly greater than with the BNR reclrculation piping example, reflecting the complexity of equipment connections and level control involved in decontaminating four channel heads (two steam generators) simultaneously, then repeating the exercise on the other two steam generators. The total cost estimates (minimum, best estimate, and maximum) are $6.4M, $8.2M, and $II.I~ for LOMI and $6.9M, $9.3M, and $12.2H for CAN-DECON (see Reference 57). The major difference between the processes is the extra critical path time assumed for CAN-DECON. Wlth a relatively small volume compared with a full system decontamination, the advantage of lower chemical cost and less waste produced for CAN-DECON is not significant in the overall total. 7.4.2 Benefits The decontaminatlon is assumed to be coincident with major steam generator inspection and repairs, so that 300 Ram are saved by the decontamination in the best estimate case (exposure without the decontamination assumed to be around 400 Rem or more). The maximum immediate benefit is 500 Ram saved, and the minimum 150 Ram saved. For the second year (or next outage), additional savings of 200 Ram (max.), 120 Rem (best estimate), and 60 Ram (mln.) are assumed. Savings in critlcal path time for the work to be done after the decontamination are assumed to be 12 days (max.), 6 days (best estimate), and 4-I/2 days (mln.). In the subsequent outage, savings of 4 days (max.), 2-I/2 days (best estimate), and i-I/2 days (min.) are assumed. 7.5 Discussion The decontamination shows a net benefit in the best estimate and maximum benefit cases, with the cost to save a Rem being significantly less than $10,000. In the minimum benefit case, the decontamination is not cost beneficial, and it would cost more than $30,000 to save one Ram. This could only be Justified if crucial work has to be done which could not be done in the existing fields. 8. FULL SYSTEM DECONTAMINATION 8.1 Introduction Compared with the current practice of part-system decontamination, full-system decontamination offers a number of advantages (57): Lower rate of recontamlnatlon, thereby avoiding additional exposure in subsequent years of plant operation and maintenance. Extended interval between subsequent decontaminations, because of lower rate of recontamination. Easier and quicker to apply than major subsystem decontamination, with consequent additional savings in critical path time. General reduction in fields all around the plant, with consequent savings in exposure of all the work force not Just those involved with a particular system maintenance. Increased reactor availability, because the preventative maintenance which is possible following a full system decontamination should reduce the frequency of outages due to equipment malfunction. The additional maintenance, repair, replacement, end general equipment overhaul made posslble by reduced radiation flelds will contribute to the improved performance of crltlcal items and increased plant 1lie (PLEX, plant 1lie extension).