Oskarshamn nuclear power plants units 1, 2 and 3 on Sweden’s southeast Baltic Sea coast. Oskarshamn 3 is in the distance behind units 1 and 2 Source: OKG
Ingemar Engkvist, E.ON Karnkraft Sverige, Sweden
Sweden is at the forefront of the European renaissance in nuclear power. Having held a referendum in 1980 to phase-out nuclear power by 2010, public opinion has shifted to a more positive view of atomic energy.
On 1 June, 2010, the Swedish parliament voted to end the phase-out while also allowing new nuclear power plants to be built at existing sites. This year will see the consultation on a new nuclear waste depository, with the municipalities of Forsmark and Oskarshamn battling it out to host the new facility. Sweden is also in the middle of a €3 billion ($4.1 billion) investment programme (2005–2012) to upgrade existing nuclear power plants. There are three reasons behind the programme.
First of all there is a government initiative from the regulator, the Swedish Radiation Safety Authority, to increase nuclear safety to fulfil new requirements. The new safety requirements were implemented with a transition plan that nuclear operators have to comply with by the end of 2012. The programme also consists of measures to extend the lifetime of Swedish nuclear plants from 40 years to 60 years. The third component is power uprates and enhanced power efficiency with replacements of key components like steam turbines and generators.
Project PULS at Oskarshamn 3
E.ON Sverige operates the three-unit Oskarshamn nuclear power plant on Sweden’s southeast Baltic Sea coast. A power uprate for Oskarshamn 3 was considered sufficiently profitable despite the unit’s recent commissioning in 1985. This project is known as Project PULS (Power Uprate and Licensed Safety) and its objectives were:
- Safety upgrades according to new regulatory requirements;
- The upgrade of all critical parts of the power station in order to extend the expected technical lifetime to 60 years;
- Uprate the thermal power of Oskarshamn 3 to 3900 MWt and the electrical output to at least 1450 MWe (gross);
- Secure the average yearly availability of the power station to at least 94 per cent
- Cost-effectively power uprate Unit 3 with more than 92 per cent availability between 2006–2008.
Preparations for the uprate began in 2003, with pre-study investigations and the decision to invest in the upgrade was made by E.ON Sverige in 2005. The implementation was made in 2009.
SCOPE of Turbine Island work
For Oskarshamn 3, Alstom conducted work on the steam turbine island. The scope of this work included:
- HP turbine and LP turbines;
- Separate electro-hydraulic converters for the four main inlet/stop valves;
- Reheater upgrades;
- Main sea water cooling pumps;
- Feedwater pumps (11 MWe each => 13.5 MWe each);
- Generwator (20.5 kV => 25 kV);
- Plant transformer and station transformers;
- Modifications in the electrical power systems auxiliary power increases from 41 MWe to approx 48 MWe;
- Comprehensive analyzes and simulations.
Scope of Reactor Island work
Westinghouse worked on the reactor island, including the protection system and other works in preparation for a higher thermal power output. Westinghouse was tasked with increasing the diversity and redundancy of the nuclear unit, as Swedish safety regulations are now significantly stricter than those when the plant was commissioned in 1985.
|The reactor hall at Oskarshamn 3 Source: OKG|
The scope of the reactor island work included:
- Updated and modernized SAR/Tech Spec;
- Uprating of safety systems such as reactivity control, core cooling, residual heat removal and pressure relief;
- Requalification of all safety systems, structural and functional; improved capacity of the internal recirculation pumps;
- Frequency converters for recirculation pumps including energy storage;
- Core shroud cover, steam separators and steam dryer;
- New MSIVs (main steam isolation valves) to minimize pressure drop;
- Cyclones (debris catchers, 4 + 1).
The control room was also updated and a new full-scale simulator set up, although the main operation principles were maintained and the I&C systems and building structures remain essentially unchanged. We have now increased the lifetime to 60 years, to about 2045. The modernization will raise Oskarshamn 3’s net capacity from 1150 MWe up to1410 MWe, which will make it the largest boiling water reactor unit in the world. But this power uprate project has been far from straightforward; delays have pushed the project back at least six months.
The turbine hall at Oskarshamn 3 Source: OKG
Paperwork, paperwork and yet more paperwork
To perform safety upgrades, a lifetime extension and a power uprate simultaneously is extremely labour intensive. For Oskarshamn 3 over one million components were either replaced or upgraded. Around 2000 people were involved with the modernization programme, and 400–500 safety documents were reviewed, on average, every week.
In total, 80 000 documents were produced. Of these, 60 000 documents were sent to the contractors, while 20 000 documents were sent to OKG, the subsidiary of E.ON Sverige that operates Oskarshamn 1, 2 and 3. In my experience, having gone through a similar upgrade process at Ringhals 3 where I was site manager, the documentation process is usually the bottleneck that delays proceedings.
We tried to streamline the process and have the resources available, but document delays happened all the time, either by the supplier or by the general project organization. The scheduling for reviewing the documents is very difficult, but this is the case for every major project.
Delays, costs, overruns
The installation was planned for August 2008. However, by spring 2008 so much of the documentation was late that we decided to postpone operations until the following October. Subsequently a particularly bad winter further delayed start-up until early 2009.
Unfortunately, we severely underestimated the installation time for the upgrades. The deal was 92 days, but the project overran by around 50–60 days. It was a little complicated to get an exact number of days required as problems with the control rods arose during those 92 days.
These fatigue cracks in the control rods were not the responsibility of either Alstom or Westinghouse, but they had a knock-on delay for the execution time. It was difficult to ascertain who was ready and when and to what extent each party was delayed.
The two contracts for Oskarshamn 3 with Westinghouse Electric Sweden and Alstom Power Service Sweden were signed in January 2006 on a turnkey, fixed price basis, which was a mistake. In retrospect, all parties concerned were naïve in signing these contracts.
The deal was good for E.ON but due to the overruns perhaps not so good for Westinghouse and Alstom. The complexity of this project was severely underestimated. Increasing the physical separation and diversity of nuclear units in an existing plant is very difficult to achieve.
The project was too big to complete in too limited a timescale. The national modernization programme means there are many such projects running in parallel in Sweden and, while in many ways Project PULS was an engineer’s dream, it merely exacerbated the tightness in nuclear capacity.
I have no axe to grind with the vendors for Oskarshamn 3, but there have been so few major nuclear projects in recent years that the capacity and competence of many nuclear technology companies are limited. This leads project managers to underestimate the risks with major projects like Project PULS.
The overall success of a major project like Oskarshamn 3 requires more of a win-win situation. If you go into turnkey, fixed-price contracts as we did you really have to be certain the suppliers are very familiar with the technical status of the unit and the documentation before the contract is signed. Otherwise the weaknesses will be in the scope of the contract, and these weaknesses will become fixed.
We should have been better prepared by knowing the status of our own unit. One must never outsource these weaknesses to a supplier as they have less experience of the problems in question. If we were to do the project again, we would have spent more time in preparation. We would have worked on forming teams to focus on the final outcome of the PULS project rather than focusing on the responsibilities of each party in the contract. We would have spent more time with the suppliers to ascertain the technical status of Oskarshamn 3 before commencing the implementation of the project. This would have flagged potential problems and resolved more quickly the deadlocks arising from the additional costs not accounted for in the original calculations.
In summary, these are the lessons learned from Project PULS:
- Investments decisions need good pre-studies and thorough risk assessment;
- Despite the large investment needs, the scope should be split into smaller, more manageable parts;
- Start re-investing in the plant early in order to get a reasonable and manageable scheme. In the life-time perspective, limit the number of outage days;
- Ensure good communication between customer and vendor;
- Ensure enough steering capacity;
- Create a mechanism to resolve technical disputes and ensure regular top management meetings;
- The plant should always be steering. Do not rely on a ‘good contract’. Customer and vendor always have different targets. The plant is responsible for the generation risk.
Oskarshamn 2 plant upgrade
Oskarshamn 3 is currently operating at 1050 MW, which is the pre-modernization capacity. We had to delay the testing for Oskarshamn 3 because of recurring operational disturbances, such as problems with bearings in the new turbine equipment. We hope to resume trial operations, which is required before the unit can formally be run at its new capacity, on 1 March this year, around six months later than planned.
The next stage is to modernize the 638 MW Oskarshamn 2, which was originally commissioned in 1974. The completion date for the upgrade of Oskarshamn 2 is 2013. The low-pressure steam turbine was changed in 2009 and the work was due to be completed in 2011. However, this date has been postponed until 2013 because of the lessons learned from unit 3, that is to say the need for better preparation.
For Oskarshamn 2, Siemens and Areva are conducting the upgrading programme. Siemens will be working on the steam turbine island, while the reactor island programme will be installed by Areva. We conducted a full assessment of the bids, evaluating engineering capacity, track record, price, quality, etc.
Sweden’s Ringhals plant and Forsmark plant – in which E.ON holds, respectively, a 30 per cent and 10 per cent stake – are also seeing uprates. Unit 3 of Ringhals has already been upgraded, while Unit 4 will undergo a major technical modification this summer, with the replacement of steam turbine generators and pressurizers.
The upgrade of Forsmark 1 has been delayed because of the lessons learned elsewhere, while Vattenfall, which operates the plant, has put back the installation of the Forsmark 2 upgrade from 2014 to 2016.
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