Which is more radioactive, Potassium-40 or Thorium-232?

Recently one professor and one nuclear scientist claimed that potassium-40 is far LESS radioactive than Thorium-232 and they cited the EPA (environment protection agency of American) and the WHO UNSCEAR as proof of their statements!

One of my friends who stated that K-40 is about 62 times more radioactive than Thorium-232 was rubbished by the nuclear scientist!

Well, that depends on what we are talking about.

Quote ” It was written somewhere above that potassium-40 is 62 times more radioactive than thorium. That is, I am sorry to note, a complete and utter rubbish:”
Unquote.

1. I think what my friend was thinking about is radioactivity in terms of Bq i.e. activity rather than biological effect (Sv) when he said potassium-40 is 62 times more radioactive than Thorium-232.

Pure Potassium-40 = 254,000 Bq/gram
Pure Thorium-232 = 4,080 Bq/gram

Therefore potassium-40 has about 62X more Bq than Thorium-232

Even in terms of biological effect, 1 gram of pure potassium-40 will still have a greater biological effect when compared with 1 gram of pure Thorium-232.

****************
Pure Potassium-40 = 254,000 Bq/gram

Quote from nuclear scientist: 1 Becquerel per gram of K-40 in the soil (should actually be 1 Bq of K-40 per gram of soil) results in an increase in gamma-levels by ~0.042 microSieverts per hour (WHO UNSCEAR). Unquote

Therefore 254,000 Bq = 10,668 microSieverts/hour
(from 1 gram of pure potassium-40 i.e. not mixed with K-39 and K-41)

****************
Pure Thorium-232 = 4,080 Bq/gram

Quote from nuclear scientist: Each becquerel per gram of Th-232 (should actually be 1 Bq of K-40 per gram of soil) increases this level by ~0.604 microSv/hour.

Therefore 4,080 Bq = 2,464 microSieverts/hour

*************************

10,668 microSv/hr divided by 2,464 microSv/hr = 4.33

or the biological effect of radiation from pure Potassium-40 is actually 4.33 times more than that of pure Thorium-232.

2. If we are talking about 1 gram of naturally occurring Potassium which contains only 0.0118% of K-40, then it is perfectly correct to say that Thorium-232 is more radioactive biologically than Potassium as the naturally occurring potassium has only 32 Bq per gram as compared to K-40 which has 254,000 Bq per gram.

So 32 Bq of K = 1.344 microSieverts/hr while 4080 Bq of Thorium-232 = 2,464 microSieverts/hr which is far more biologically radioactive than Potassium.

3. If we compare radioactivity in terms of becquerel (number of atoms decaying per second), 1 Bq of course is equal to 1 Bq in terms of activity.

But in terms of PER Bq (radioactivity from only one nuclear decay) the biological effect, according to UNSCEAR, Potassium-40 and natural potassium is less radioactive biologically than Thorium-232 (but remember that 1 gm potassium-40 has 254,000 atomic decay per sec while 1 gm of Thorium-232 has only 4.080 atomic decay per second ).

SO, BEFORE YOU RUBBISH ANYONE FOR SAYING THAT POTASSIUM-4O IS MORE RADIOACTIVE THAN THORIUM-232 OR VICE VERSA, MAKE SURE YOU KNOW WHAT YOU ARE TALKING ABOUT.

It all depends on whether you are comparing activity (Bq) or biological effect (Sv), whether you are taking about pure potassium-40 or natural potassium which is composed of only 0.0118% highly radioactive K-40 and whether you are comparing Bq per gram of potassium-40 or Bq per gram of soil.

Moreover, we have to state that the Thorium-232 is not that of pure Thorium-232 as freshly isolated pure Thorium-232 do not produce any gamma rays and as such has practically no external biological effect (the 0.09 MeV of gamma rays in freshly isolated Thorium-232 actually comes from Radium-228).

The same arguments apply to the comparison of the cancer coefficients of potassium-40 and Thorium-232.

In fact the nuclear scientist had to apologise and agree that it all depends on what we are trying to compare with.

Dato’ Dr Looi

Recently one professor and one nuclear scientist claimed that potassium-40 is far more radioactive than Thorium-232 and they cited the EPA (environment protection agency of American) and the WHO UNSCEAR as proof of their statements!

One of my friends who stated that K-40 is about 62 times more radioactive than Thorium-232 was rubbished by the nuclear scientist!

Well, that depends on what we are talking about.

Quote ” It was written somewhere above that potassium-40 is 62 times more radioactive than thorium. That is, I am sorry to note, a complete and utter rubbish:”
Unquote.

1. I think what my friend was thinking about is radioactivity in terms of Bq i.e. activity rather than biological effect (Sv) when he said potassium-40 is 62 times more radioactive than Thorium-232.

Pure Potassium-40 = 254,000 Bq/gram
Pure Thorium-232 = 4,080 Bq/gram

Therefore potassium-40 has about 62X more Bq than Thorium-232

Even in terms of biological effect, 1 gram of pure potassium-40 will still have a greater biological effect when compared with 1 gram of pure Thorium-232.

****************
Pure Potassium-40 = 254,000 Bq/gram

Quote from nuclear scientist: 1 Becquerel per gram of K-40 in the soil (should actually be 1 Bq of K-40 per gram of soil) results in an increase in gamma-levels by ~0.042 microSieverts per hour (WHO UNSCEAR). Unquote

Therefore 254,000 Bq = 10,668 microSieverts/hour
(from 1 gram of pure potassium-40 i.e. not mixed with K-39 and K-41)

****************
Pure Thorium-232 = 4,080 Bq/gram

Quote from nuclear scientist: Each becquerel per gram of Th-232 (should actually be 1 Bq of K-40 per gram of soil) increases this level by ~0.604 microSv/hour.

Therefore 4,080 Bq = 2,464 microSieverts/hour

*************************

10,668 microSv/hr divided by 2,464 microSv/hr = 4.33

or the biological effect of radiation from pure Potassium-40 is actually 4.33 times more than that of pure Thorium-232.

2. If we are talking about 1 gram of naturally occurring Potassium which contains only 0.0118% of K-40, then it is perfectly correct to say that Thorium-232 is more radioactive biologically than Potassium as the naturally occurring potassium has only 32 Bq per gram as compared to K-40 which has 254,000 Bq per gram.

So 32 Bq of K = 1.344 microSieverts/hr while 4080 Bq of Thorium-232 = 2,464 microSieverts/hr which is far more biologically radioactive than Potassium.

3. If we compare radioactivity in terms of becquerel (number of atoms decaying per second), 1 Bq of course is equal to 1 Bq in terms of activity.

But in terms of PER Bq (radioactivity from only one nuclear decay) the biological effect, according to UNSCEAR, Potassium-40 and natural potassium is less radioactive biologically than Thorium-232 (but remember that 1 gm potassium-40 has 254,000 atomic decay per sec while 1 gm of Thorium-232 has only 4.080 atomic decay per second ).

SO, BEFORE YOU RUBBISH ANYONE FOR SAYING THAT POTASSIUM-4O IS MORE RADIOACTIVE THAN THORIUM-232 OR VICE VERSA, MAKE SURE YOU KNOW WHAT YOU ARE TALKING ABOUT.

It all depends on whether you are comparing activity (Bq) or biological effect (Sv), whether you are taking about pure potassium-40 or natural potassium which is composed of only 0.0118% highly radioactive K-40 and whether you are comparing Bq per gram of potassium-40 or Bq per gram of soil.

Moreover, we have to state that the Thorium-232 is not that of pure Thorium-232 as freshly isolated pure Thorium-232 do not produce any gamma rays and as such has practically no external biological effect (the 0.09 MeV of gamma rays in freshly isolated Thorium-232 actually comes from Radium-228).

The same arguments apply to the comparison of the cancer coefficients of potassium-40 and Thorium-232.

In fact the nuclear scientist had to apologise and agree that it all depends on what we are trying to compare with.

Dato’ Dr Looi Hoong Wah

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Quote Optiplex330:

“Giving tax break is very common to entice people to set up business. If you are a Indian or Chinese your forebear coming from India or China know that very well. They were entice to come to Malaysia to open up the country and land were practically given free. Old people told me their land rental is a single pepper corn. Those who don’t know about tax break know zero about businesses. Having said that, I think the maximum is 10 yrs so Lynas is unusual to be given 12 years.

A classic example: Business has to give Bumi 30% share but when Intel came to Penang, they were allowed SPECIAL treatment and don’t have to give a single share to Bumi (may be this explain the extra 2 yrs tax break?). Why? This is because the government badly wanted Intel because when they come, they will bring along an entire electronic industry to Malaysia. So while government do not directly benefited from Intel, the follow on industry created by Intel greatly benefited Malaysia. And for this reason, all responsible Malaysian should go read this document.

And also for this reason, those who think Lynas is a only about 300 jobs and no tax revenue for Malaysia are just being short sighted. They don’t know that because of Lynas, a Green Technology industry could be born and Siemens is the 1st to annouce coming precisely because of Lynas. But because of Anti-Lynas, Siemens may pull out so there go more jobs and tax revenue for Malaysia.”

In Other Words,The Plant WILL Boost Local and Country’s Economy.
The Lynas plant WILL provide substantial economic benefits during the decades of operation. The jobs, employee’s taxes, and direct and secondary spending WILL strengthen the economy.

SO DO NOT ASK THE NON-PHYSICAL and RATHER CHILDISH QUESTION OF WHAT BENEFIT DO MALAYSIA GET FROM THE LYNAS PLANT!

Dato’ Dr Looi Hoong Wah
FAMM, MB.,ChB(Manchester), MRCS(England), MRCP(UK) MRCP(London)