The need for a removable-tank HEPA vacuum was first brought to the attention of Goodway Technologies Corp., Stamford, CT, by maintenance management at Bartlett Nuclear Inc., Plymouth, MA, a prominent cleaning contractor for nuclear energy power plants, who then assisted with product development. The following information was gathered during interviews with Mr. Alphonse Pavone, Jr., and Mr. Ralph Torres, of Bartlett Nuclear.
Cleaning and maintenance at nuclear power plants are very important and dedicated procedures. There are usually two or more major buildings comprising a typical plant, each with scheduled shutdowns for cleaning. To give an idea of the enormity of the HEPA vacuum cleanup required, the vapor containment (VC) areas alone can each average four levels totaling about 120,000 square feet of floor space for wet and dry pickup. HEPA vacuums are also used to clean the reactor cavity, running some thirty feet deep, the integrated crane, and even the debris inside extensive configurations of pipes in a plant.
Since painting is an ongoing maintenance procedure at these plants, HEPA vacuums are used to remove paint chips and swarf after scraping prior to new paint application. In this instance, HEPA is important to contain any lead that may be in the old paint, as well as ambient radioactivity.
While radioactivity during routine maintenance can be one to five rad per hour, it can reach up to fifteen to twenty rad per hour in “hot spots” and during quick response spill cleanups. Cleanup crew members are completely protected by special clothing and gear, while the environment is protected by the sealed HEPA containment tanks.
At one of Bartlett Nuclear’s contracted plants, about thirty standard HEPA vacuums were needed to do the job. During major building cleanups, all sealed vacuums could be quickly filled, with workers experiencing downtime while waiting for replacement or additional HEPA vacuums to complete the job. The reason? When a standard HEPA vacuum’s tank is filled, the monitor unit (head) and the entire bottom unit, which includes the tank, are transported to an appropriate waste disposal site and emptied. The head and bottom unit then undergo a thorough cleaning and are tested according to strict decontamination regulations before being returned for re-use. Downtime for these procedures is extremely costly.
When a reactor is out of service for cleaning maintenance, lost revenue at some plants amounts to tens of thousands of dollars an hour. Having on hand several HEPA vacuum motor and filter lid assemblies and multiples of tank units helps, but the crew must still perform time consuming switch-overs and sometimes wait when the vacuums are out being emptied and decontaminated. The ideal scenario is to have the necessary equipment to allow vacuuming, virtually non-stop, until the job is completed and the reactor returned to service.
The answer to this and similar problems in other industries where sensitive materials are involved has proven to be the newly designed Goodway VAC- 2.1 - HEPA Vacuum. A key factor to increased productivity delivered by the VAC -2.1 has been the taking of the motors (two motors, each 1 1/3 hp) and filtration assembly, which traditionally sit on top of the tank, and repositioning them into the base of the unit. The removable stainless steel containment tank now sits on top. The operator simply disconnects the hose, caps off
the intake, lifts the sealed tank off the power unit, locks a new tank in place, connects the hose and continues vacuuming. The procedure is very quick, and extremely easy, simply a matter of seconds. Downtime is virtually eliminated.
Sealed tanks can be easily and safely stored. And, at convenient intervals, emptied, cleaned, tested for decontamination and returned for repeated use. The required number of “clean” tanks can be kept on hand for each unit to assure non-stop vacuuming and operators no longer have to wait for their return.
According to Mr. Torres, this “wait” sometimes amounted to a full day while the standard HEPA vacuums were being emptied and decontaminated. And, if a seal broke during use, that vacuum was “out of service”. That procedure required a lot of vacuums and some frustrating downtime. The introduction of the Goodway productivity-designed HEPA vacuums with separate containment tanks has saved time and money while maintaining required safety standards. Only a dozen Goodway HEPA vacuums with an extra supply of containment tanks are now needed, says Mr. Torres, compared to the thirty standard HEPA vacuums previously required.
Another benefit of the tank-on-top design is the unit’s very low center of gravity which reduces the chance of tip-overs and spills. Further, wide wheels and casters were included in the design to permit easy rolling over uneven floors or large grates such as are common in power plants. Also, since ladders, instead of elevators and stairways, are commonly used in many buildings to reach the various levels, a hoisting sling was incorporated. Supporting the
vacuum from its base, rather than from top-hooks or handles, permits safe lifting and lowering between levels.
A unique feature of the VAC-2.1 HEPA Vacuum is its AutoOff or bulk capacity of 10 gallons. When wet capacity is reached and air flow is interrupted for 50 seconds, a monitoring sensor automatically shuts the motors off. This prevents the possibility of waste being drawn into the motors, evacuated through the exhaust and contaminating the surrounding area. With AutoOff, such accidental discharge is prevented, further reducing downtime while maintaining the integrity of the vacuuming operation. The HEPA filter is certified 99.97% efficient at 0.3 microns and 150 CFM.
While developed for nuclear power plants, benefits of the VAC-2.1- HEPA Vacuum can be seen reaching into other industries such as chemicals and pharmaceuticals, and for applications involving fast recovery of accidentally released asbestos and other hazardous materials.
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