Nuclear Safety - Science topic

Dear Dr Shah,

I have seen in the thermal-hydraulics modeling of SBOs, this modification (injection of some numbersof accumulators into the SGs instead of primary circuit) will result in increase of coping time, but I think the answer to your question is very dependent to the NPP design and also consideration of other accidents. In other words it should be assessed case by case.

First, I consider an under operation PWR. This Plant is designed with specific numbers and configuration of accumulators, HPIS, LPIS and the associated accident analysis including (LOCA, SBO, MSLB, and ...) is performed considering these safety injections. Modification of Accumulators injection lines needs Re-assessment of all theses accidents and performance analysis of other injection systems, as the modification may be useful for SBO stand alone, but it may deteriorate the situation for some break sizes of LOCA or other accidents. Furthurmore, backfitting of the NPP should be assessed from the structural-civil work aspects and also some new setpoints, as this kind of modifications may need closing/ opening new penetration in the SG's piping, compartments of the containment and etc. but it doesn't mean that it's not applicable, this modification is more practical for NNP designs with larger number of accumulators or other sources of water that is capable of injecting water into SGs. You can find some studies that the SG shell side can be refilled by use of fire fighting hoses that are fed from outside of the containment.

For newer designs of NPPs and under construction NPPs, I have done some literature search and what I found is that the designers are more tended to use passive heat removal systems for condensing steam from SGs and send it back to them. these kind of systems can extend the coping time much more in comparison to accumulators injection into SGs.

Best Regards.

Alireza

ICT on Radio active waste management? From my experience, the sweden government use SKB ()Sweden waste management facility) to dispose wastes under bedrock. they dig a whole which is 500 m deep under the bed rock and buried it there. But so far, ICT's are not implemented on radio active waste management.

I am interested on this topic too, but how can we use tele-coms on radio active waste?

i was thinking to buried a high frequency chips around the whole to control the status of the waste, because radio active wastes can be proactive around 1,000, 000 years. this needs thou, a detail scientific experiment and analysis.

A good introduction to the nuclear law is the book: Handbook on nuclear law by Carlton Stoiber, Alec Baer, Norbert Pelzer, Wolfram Tonhauser — Vienna : International Atomic Energy Agency, 2003, https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1160_web.pdf

Hi Erol, I guess that you are looking for Analysis of Desing Basis accidents, in that case check out publlications from the UPM safety group.

In case you are looking for Severe accidents with Hydrogen, there is an excellent researcher that works with GOTHIC: Michelle Andreani from PSI, that has contributed the most to hydrogen distribution in large enclosures.

Contact me for more info.

In the USA, Regulatory Guides (RGs) 1.79 and 1.79.1 relate to the preoperational and startup testing of emergency core cooling systems (ECCS) for Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs). These regulatory guides identify the ECCS functions that are to be tested as those necessary to ensure the specified design functions of the ECCS are met during conditions of normal operation, anticipated operating occurrences and postulated accident conditions.

In Japan, METI (Ministry of Economy, Trade and Industry) periodic inspections are conducted every 13 months in accordance with the EUIL (Electric Utility Industry Law) for light water reactors. These inspections include ISI (in-service inspection), system performance tests, containment leakage rate tests, and overhauls of mechanical equipment. In addition, many voluntary maintenance activities, most of which are periodic overhauls for mechanical equipment, are planned and conducted by electric utilities during the plant refueling outages.

OK, I got your situation.

The electron range get shorter when the electron energy get lower.

You can check the homepage below.

Then the stopping range of 300-eV electron is much shorter than 10-keV electron (0.5 micro-m in copper).

Hi,

Such statement cannot be assumed for all sistuations and its relevence depends of the goal of your study. Just in the case of a cloudy day, the impact of a cloud passage is very local (depending of the sun location and the cloud size) and the DNI in the shadowed zone will be highly impacted. The assumptions of your work very depends of the aim of your data. Without more knowledge of your study, it is a bit hard to answer. But to keep it general, no, you cannot say that the solar irradiance/temperature is the same everywhere within a km range area.

Best regards,

Rémi

The agreement, on one side, is very good for India and for the nuclear sector of this country. It is important for the international community that nuclear power plants in India operates under strict safety regime in order to avoid a new nuclear accident. On the other hand, the position of the USA in favor of the agreement is against the principles of the NPT, because India is a nuclear weapon state outside this treaty. According to the NPT, states parties should not in any way assist non state party in the development of their nuclear sector. To take care of this issue, the USA is providing nuclear technology to India, if this technology is under the IAEA control, but this depend of the India political position.

This is a clear example how the nuclear weapon states parties to the NPT ignore the principles associated to this treaty, when their political interests are involved.

Hi Karnal,

You may have the answer to your questions by interogating researchgate: 

Success!

F. Glodeanu

Thank you sir,

In recent years gamma-H2AX assay gaining importance in triage application, how it is useful ?

Dear Florian,

unfortunately I have only now seen your question. As far as I know, there in Romania still exist no repository and Romania also relies on a national solution and summarizes long-term safekeeping of HAW on as a national task? If this is so, and one has determined one location, then it is also a national responsibility, the "host municipality" to compensate the fulfillment of this national burden reasonable. This should be previously laid down by law, so there is a claim and no mercy. In Germany, this discussion is also running. I have you delivered my opinion, the opinion which I spread here also.

Best regards

Michael Lersow

The European Council of 24/25 March, 2011, requested that the safety of all EU nuclear plants should be reviewed, on the basis of a comprehensive and transparent risk and safety assessment ("stress tests"). These “stress tests” are defined as targeted reassessments of the safety margins of nuclear power plants, developed by ENSREG, including the European Commission:

All nuclear power plants in the EU underwent stress tests and peer reviews in 2011 and 2012. Many other countries and territories also conducted comprehensive nuclear risk and safety assessments, based on the EU stress-test model. These include Switzerland and Ukraine (both of which fully participated in the EU stress tests), Armenia, Turkey, Russia, Taiwan, Japan, South Korea, South Africa and Brazil:

Follow-up of the peer review of the stress tests performed on European nuclear power plants - see:  http://www.ensreg.eu/EU-Stress-Tests/Follow-up

The March 2011 accident at the Fukushima Dai-ichi plant resulted in a new effort on the part of the nuclear industry to ensure that the existing SAMGs were as effective as possible. EPRI Report „Severe Accident Management Guidance Technical Basis Report Volume 1: Candidate High-Level Actions and Their Effects“, Final Report, October 2012, updates the original technical bases for SAMGs to reflect the lessons learned to date from the Fukushima Dai-ichi accident:

This update also incorporates insights gained from a substantial body of severe-accident research and analysis conducted since the original development.

This document of IAEA is useful source

Heat transfer behaviour and thermohydraulics code testing for supercritical water cooled reactors (scwrs) iaea-tecdoc-1746, IAEA 2014.

Sorry, but the definition of "Flux" posted by Sathian is incorrect.

Flux has units of particles/unit area/unit time, and is usually written as particles/cm^2/second, or particles/m^2/sec. It measures the flow of "particles" crossing a unit surface per unit time in any direction. In some fields, you can replace "particles" with "energy". It is not defined with reference to "emission", although emission can be measured in flux units if you are so inclined.

Thanks Lung-Kwang Pan for your views, but the facilities which really use only GM for practical applications, it may not be appropriate to use data of other monitors/detectors.

you can use the URAN Stochastic Geometry Card . I don't know how but I think  It may be useful to do that.

The latest new on this important issue:

Final push in historic Iran nuclear talks

Vienna (AFP) July 02, 2014 - The United States and Iran traded barbs on Wednesday as negotiators arrived in Vienna for a marathon final round of nuclear talks aimed at securing a historic deal by a July 20 deadline..

A sixth and final round of talks starts officially on Thursday and could potentially last until July 20 when an interim deal struck in November expires, although in theory this can be extended for six months.

US Secretary of State John Kerry, writing in the Washington Post, said that the negotiations constituted "a choice for Iran's leaders". "They can agree to the steps necessary to assure the world that their country's nuclear program will be exclusively peaceful and not be used to build a weapon", Kerry wrote. Or "they can squander a historic opportunity to end Iran's economic and diplomatic isolation and improve the lives of their people." The P5+1 powers  have proposed a "series of reasonable, verifiable and easily achievable measures that would ensure Iran cannot obtain a nuclear weapon and that its program is limited to peaceful purpose," he said.

But Iranian Foreign Minister Mohammad Javad Zarif, writing in French daily Le Monde, said that some among the P5+1 were suffering from "illusions" about Iran's nuclear programme. He said that contrary to fears in the West, Iran -- even if it wanted to -- is "several years, not a few months" away from being able to build an atomic bomb. Iran "will not abandon or give up its technological or scientific advances. In addition it would not be prudent ... to expect us to do otherwise," Zarif said in remarks printed in French. "I appeal for these illusions not to derail a process that could put an end to a pointless crisis," he said.

Iranian nuclear negotiator Majid Takhte Ravanchi went further, telling the ISNA news agency that Iran has set out clear "red lines" in the talks. "The other side knows that these red lines cannot be crossed. If we reach a deal it will be one respecting these red lines. If not there will be no accord," he said. "The outcome depends on the other side. If they have a maximalist position, or if they want to address issues that have nothing to do with the talks, if they are far from reality or if they have illusions, there will be no deal," he said. "We will not accept definitive restrictions" on our nuclear programme, he said.

But Kelsey Davenport, Arms Control Association analyst, was upbeat about prospects for a deal, saying there is "considerable political will" and that an accord is in the interests of both sides. "There is a lot of time left for diplomacy and a good comprehensive nuclear agreement is within reach, despite significant gaps between the two sides on core issues," she told AFP.

Iran nuclear talks enter the decisive, dangerous endgame Thursday with a marathon final round of hardball negotiations potentially going all the way to the July 20 finish line.

The deal being sought by Iran and the five permanent members of the UN Security Council plus Germany would finally ease fears of Tehran getting nuclear weapons -- and silence talk of war for good.

"In the next three weeks, we have a unique opportunity to make history," Iranian Foreign Minister Mohammad Javad Zarif said in a video message released ahead of the talks. "To forge a comprehensive agreement over Iran's nuclear energy programme and to end an unnecessary crisis that has distracted us from addressing together our common challenges, such as the horrifying events of the past few weeks in Iraq."

After five rounds of talks in Vienna seeking to secure a deal by July 20 -- when an interim deal struck in November expires -- the differences appear considerable, however. The last meeting from June 16-20 saw both sides begin drafting the accord, but haggling over language concerning the thorniest problems was put off until later. The United States, Russia, China, Britain, France and Germany want Iran to reduce drastically in scope its nuclear activities in order to render any Iranian drive to assemble a weapon all but impossible.

This would include in particular Iran slashing its capacities to enrich uranium, a process producing nuclear fuel but also at high purities the core of a nuclear weapon. French Foreign Minister Laurent Fabius said last month Iran has to slash the number of centrifuge enrichment machines to several hundred from almost 20,000 at present. But Iran rejects this, saying it even needs to expand the number of centrifuges to fuel a fleet of nuclear power plants -- facilities that it is however years if not decades away from having.

Demands that Iran's programme be "radically curbed" rest on a "gross misrepresentation of the steps, time and dangers of a dash for the bomb", Zarif said. Writing in French daily Le Monde, Zarif said Iran "will not abandon or make a mockery of our technological advances or our scientists."

In theory, the July 20 deadline could be extended by up to six months, and many analysts believe that such a move is already being discussed. But US President Barack Obama, facing midterm elections in November and Republican accusations of weakness, is wary of doing anything that could be construed as simply giving Iran more time to get closer to having the bomb. This is the long-standing accusation of Israel, the Middle East's sole if undeclared nuclear-armed state. But Kelsey Davenport from the Arms Control Association believes that Washington should not shy away from pushing back the deadline if necessary and if Iran is "negotiating in good faith". "The alternative to no deal is far worse for the international community -- a constrained, unlimited Iranian nuclear programme," she told AFP.

 Iran's foreign minister said Wednesday his country and world powers have a "unique opportunity to make history" by agreeing on a nuclear deal, as talks enter a crucial final round. Mohammad Javad Zarif was speaking as the five permanent members of the United Nations, plus Germany, prepare to sit down with Iran in Vienna Thursday in a bid to reach a historic deal by a July 20 deadline. The world powers want Iran to scale down its nuclear activities in order to ease long-held fears that Tehran might develop atomic weapons.

Iran, subject to damaging UN and Western sanctions, insists its nuclear programme is purely peaceful and even wants to expand key parts of it. Zarif said forging a deal would "end an unnecessary crisis that has distracted us from addressing together our common challenges, such as the horrifying events of past few weeks in Iraq." He claimed an agreement could have been reached in 2005 when he had been nuclear negotiator, but that the administration of then US president George W. Bush "torpedoed the deal". They then opted for pressure and sanctions. For eight years." But he said sanctions "didn't bring the Iranian people to kneel in submission. And it will not now nor in the future." "We are trying to reach a deal," he added. "Not a good deal or a bad deal, but a doable and lasting deal."

Without elaborating, Zarif said "we are willing to take concrete measures to guarantee that our nuclear programme will always remain peaceful. "We still have time to put an end to the myth that Iran is seeking to build a bomb."

For PARET code, the Core-Average Thermal Flux means the average value considering only fuel elements.

You do not "control" reactions in a reactor. They are governed by the reaction cross sections, which are a physical property of individual nuclei. In the presence of neutrons these reactions will take place. The cross sections are energy-dependent. Therefore, cou cannot "control" the reactions, but you can influence them by the design - i.e. by the presence or absence of a particular meterial, or by influencing the neutron energy distribution (the neutron spectrum). For a more detailed answer you will have to provide amore detailed description of what you actually want to do.

Hello Thiago! Welcome to the reactor simulation world! Now I have a better picture of what you are asking. Well, core simulators that rely on diffusion theory are indeed used nowadays in the fuel loading design of thermal reactors. Your are right in the sense that Monte Carlo is a very powerful technique (quite clever from the guys who deigned it). However, a full core calculation of a commercial thermal reactor is very computational expensive. Deterministic modelling of reactor cores rely on a two-step approach, where first you create the homogenized and energy-collapsed macroscopic cross-sections with a so-called lattice code. Basically, the lattice code creates the input data for core simulators. Mostly the validation against Monte Carlo has been done at the lattice stage rather than at the core stage. Nevertheless, nowadays, with the increase of computational power, Monte Carlo can be used in burnup core calculations of not so big cores like for example, research reactors (especially because it might be that in this type of reactors, diffusion theory could not work so well). Anyhow, for LWRs, deterministic diffusion codes are coupled with fuel performance and thermal-hydraulic codes in order to design fuel cycles. In practice, such core simulators are validated with diverse experimental data and in-core detectors information. You have to keep in mind that diffusion theory is a way to treat the angle dependence of the flux. Therefore, it is equivalent to P1 theory by assuming certain considerations (i.e. time independence, no anisotropic neutron source, incoming and outgoing energy integration of the scattering term should be the same). The thing is that in transport theory the boundary condition is well defined, while in diffusion theory is not!! I hope this is kind of useful for you. If you like to keep on chatting about this in more detail, we can e-mail (auhs@kth.se).