Nuclear power stations do vent gases

In your reply to Rory Shannon’s letter on nuclear power (Mailbag, February 2006), you stated that "nuclear power stations do not routinely vent radioactive gases".

This is not correct. The dominant design in the US, Babcock and Wilcox pressurised boiling water reactors (PWR), such as Three Mile Island, do exactly that. Short-lived daughters are formed in the primary loop and routinely vented in normal operation, for which they are licensed.

This has all been very well documented, not least by the US Nuclear Regulatory Commission in their ‘WASH’ incident reports. "Sniffing" the composition of reactor emissions is a stock tool of spying (eg, the US and North Korea).

Nuclear power stations do not operate in isolation but as part of a system; mining, fuel fabrication, operation, fuel waste treatment and reprocessing, intractable waste disposal and decommissioning.

Diversion of material for weapons, either nuclear or terrorist dirty bombs, is a real and very obvious concern (eg, Iran, North Korea, India, Pakistan, Israel and China). At least coal-fired power stations don’t produce a highly toxic explosive as waste.

No power system, nuclear, hydro, geothermal, solar, wind, tidal, even fusion, can meet an endless and ever-growing demand.

The real question is how we maintain a genuine quality of life with far less energy use. The current winners, Big Energy Money, represented by the AP6 have no interest in fostering debate on this vital question.

Coupling our future well-being to ever growing energy use is junkie logic.

Roly Roper,
Ivanhoe, Vic.

Telephone ring cadence correction

In current March 2006 issue there is an article by Jim Rowe on a telephone/fax indicator circuit. He states that the cadence of ring current in Australia is 200 millisecond pulses of ring. In fact they are twice this and the cadence is 0.4 on, 0.2 off, 0.4 on, then two seconds off then repeat.

It is a small point but worth correcting.

Alec Slamin,
via email.

Salvage possibilities for washing machines

As a ruthless ratter/hoarder/tinkerer, I very much enjoy the "Salvage It!" article each month – so much so that I now look back a bit forlornly at those old washing machines that got away.

Would there be room for a stripper’s list – the stuff that is worth extracting from some different kinds of ancient, wheezy or just busted appliances before chucking the stripped corpse?

And how about a "Salvage It!" online forum on what we have got and what we are after? Transport and handling can be a cost in all this, I know, but it seems a pity to limit your scrounging to just one pair of eyes and one "junk" box. Some of the online forums get a lot of use and could alert other dedicated salvagers to potential treasure troves.

Peter Brownlee,
Katoomba, NSW.

Comment: we’ve probably covered this topic in the past. However, if you are ratting washing machines, dishwashers or clothes dryers, you should certainly look at saving motors, motor/pumps, water solenoids or anything controlled by solenoids, water level and temperature sensors, timers and microswitches. You might also want to save drive belts and parts of the wiring harness with quick-connects. Of course, if you go overboard you will eventually find yourself with too much stuff that you can never use.

The pumps in washing machines and dishwashers could be useful in water reticulation, fish ponds, hydroponics and so on. Mind you, most of these items are not rated for continuous use and may not have a long life in these applications. If they are free though, that probably does not matter.

One other point should be considered. All motors used in appliances such as washing machines and dishwashers are usually of open-frame construction and have exposed windings and connections. Hence, if they are recycled, they should be housed in an earthed metal enclosure so that there is no possibility of accidental contact with them.

Too much bass could have been more

I was very impressed by Phil Prosser’s letter (Mailbag, April 2006) showing his couch subwoofer. Like Mr Prosser, I am a devotee of the philosophy "you can never have too much bass".

My question to Mr Prosser is this: what’s wrong with the back side of the couch? You could have fitted another four of the CS2345 subbys and looking at the picture of the couch, you could probably have fitted one at each end as well! Even more fun! Even more bass!

Gary Johnston,

Managing Director,
Jaycar Electronics.

Comment: Jaycar might sell a few more subwoofers as well, eh?

Question on PIC-based PLL

I have a possibly naive question about phase locked loops with which readers might be able to help. Is it easy or difficult to write a program for a PIC that will implement a phase locked loop that will recover the zero crossing from a 50Hz or 60Hz input that is badly mangled near the zero crossing but a clean sinewave elsewhere?

I’ve done quite a lot of the obvious homework, checking the Microchip website, buying a book about phase locked loops, surfing the web, testing ideas using Excel, etc.

I’ve also tried some hardware approaches using a 4046 but this was disappointing. It is mostly a "digital" phase locked loop and preserves rather than removes errors near the zero crossing. I also discovered that when I use a long time-constant for the loop filter, I needed to adjust the centre frequency accurately.

The XOR phase detector worked moderately well but finds the peak and I need extra circuits, such as at least one flipflop, to find the zero crossing. The PFD phase detector is very sensitive to the noise associated with the mangled zero crossing.

Naively, I assumed that it should be easy to write a PLL program for a PIC and that I’d find several programs on the Microchip website. None! I now think that a phase locked loop program might be too difficult for the 16F PICs and only just within the capabilities of the larger 18F PICs. Even as I type this, I also think, "that can’t be right".

I’d be grateful for help from anyone able to answer the question.

Keith Anderson,

PO Box 58,

Kingston, Tas. 7051.

C-Tick sticker is no guarantee The Mailbag pages for March 2006 featured a letter from Mike Abrams who was attempting to allay the fears of Graham Lill in relation to PC board track spacing in a compact fluoro. He suggests that we should purchase only products tested to Australian Standards and the C-Tick (EMC compliance) sticker is a good indication that the product complies. I cannot comment on the fluoros he was referring to and their track spacing but would like to make the following comments: I dismantled a failed dimmer many years ago from an Australian manufacturer/supplier and it was an approved type. Its track spacing did not seem to meet the standards for track spacing for 240VAC as required by a Telstra guideline. I have recently returned a non-Australian made 2HP electric motor supplied as part of wood-working machinery and its grommetting of the 240VAC wires entering the case would have not met the standards of "the Irresponsible Cowboys Corporation" let alone any local standards. I have a standard lamp of recent years made in Asia and approved for sale in Australia. It has figure-8 wiring which is cracking, exposing copper at the entry to the metal base and the grommet would not withstand the attack of a lethargic cockroach. I can say absolutely that C-Tick compliance is NO GUARANTEE of anything, except perhaps that funds will be transferred to testing organisations. I went through the C-Tick compliance testing process when operating a quite small business making single and multi-zone fire warning systems for the fire protection industry. We did get certification. As a process, the testing was logical but in our case I had to supply much of the test gear (large PSUs, etc). From an ongoing perspective, it was logical nonsense and a technical farce. I could detail why but it would take several pages. I am advised that the C-Tick stickers can be purchased in newsagents and stationers in Germany. I have a manual (ie, non-electric) steak knife made overseas and it has a C-Tick sticker on its cardboard box! A 2-way radio gear supplier in Melbourne told me that he had test equipment from overseas that generated lots of EMI radiation but it had C-Tick stickers. Sorry Mike. The real world submits reasonable things for test and then builds lower cost rubbish for sale – I have had many examples of it. Ranald Grant, via email.