DIFFICULTIES FACED IN FOLLOWING THE CURRENT LICENSING REGIME

In spite of their almost universal acceptance as reference safety standards, the IAEA’s new safety standards have never been applied to the entire licensing process of a nuclear power plant, and very little experience exists in the nuclear industry on fully complying with these standards.

PAEC thinks that PNRA has taken a big stride in adopting the IAEA’s NS-R-1 [4]. At the moment, hardly any nuclear steam supply system (NSSS) vendor is supplying a nuclear power plant that would systematically comply with NS-R-1.

Further, neither the IAEA standards nor the PNRA regulations are fully supported by regulatory guides. The same is the case with NNSA, which has also adopted the new IAEA standards. However, both NNSA and PNRA allow that, where regulatory guides for the new regulations do not exist, the designer and the utility are free to select a set of guides and obtain approval from the regulator to follow these guides.

The above approach helps to get around the regulator’s problem of detailing the regulatory requirement, but leads to a difficult situation for the designer because most of the guides available were originally written before NS-R-1. The designer is never certain as to what exact requirements are to be met and whether it would be sufficient to follow the existing regulatory guides.

The situation becomes even more complex if one has to settle the terms of a commercial contract in that situation.

In the buyer’s country, PNRA maintains that it would lay emphasis on verifying the new licensing requirements. For instance, in addition to meeting the quantitative goals, PNRA is expected to emphasize such areas, as design management, management of safety, complementing a deterministic approach by the PSA, verifying defence in depth analysis philosophy, ageing management, human factors engineering, severe accident management or decommissioning. But it may take considerable effort to define the exact requirements based on these principles. At least on paper, PNRA makes no additional concessions for the duplicates of the existing nuclear power plants.

In the vendor country, NNSA has also adopted the new IAEA standards and is involved in the process of making a gradual transformation. NNSA first issued a ‘safety policy’ and kept it open for about two years for discussion with

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their vendors and designers. It is to their advantage that China now has a well established and fast growing nuclear industry, and quite a few indigenous design authorities which offer NNSA a chance to discuss and negotiate. While issuing the regulation for the next generation of nuclear power plants, NNSA has reportedly been careful about applying the regulations fully to the already planned ‘duplicates’ of the existing plants. NNSA may require incorporation of certain additional safety measures to make such plants licensable in China.

From the perspective of PAEC, and in view of the current national licensing requirements, the following problems are foreseen during the licensing of C-2:

(1) Because of the not-so-complete guidance from PNRA, the designer and the vendor may face problems in fully understanding and meeting the licensing requirements.

(2) The IAEA has developed a standard format and content of safety reports to which PNRA will refer. But no reference SAR has been prepared as was done in the 1970s by leading NSSS vendors, such as Westinghouse and General Electric, which published RESAR and GESAR, respec-tively. These reference reports were ‘role modelled’, as quite a few safety reports were based on them. So the preparation of the safety report based on the new standards may be difficult, e.g. incorporation of severe accident analysis and PSA can be done in several ways, and with a different level of detail.

(3) The regulators or the IAEA are yet to develop a generic safety review document on lines similar to the NRC Standard Review Plan (SRP) [2] to cause an effective review. The NRC was able to develop such a document after the practical experience of application of regulations to a large number of nuclear power plants.

(4) For the two-loop PWR design on which C-2 is based, it may be difficult to meet the quantitative targets set by the PNRA, e.g. a CDF of less than 10^–5 per reactor-year.

(5) There may also be technological limitations because not many nuclear power plants have been built in Pakistan and the vendor country also has no practical experience of designing the plants in accordance with the new safety standards.

Because of the above considerations, the application of national regulation based on the new IAEA standards is going to be a very challenging task for all three — the regulator, the supplier and the utility.

TOPICAL ISSUE 1

65 4. APPROACH TO FOLLOW THE NEW

NATIONAL LICENSING REGULATIONS

Pakistan is not a vendor country nor does it have much experience with the design of nuclear power plants. Besides C-1, which has been operating for about four years, PAEC’s experience in the field of managing nuclear power plants over the last 30 years has been limited to essentially one nuclear power plant which is basically a first generation PHWR — KANUPP. When this plant was designed and built 40 years ago, there were very few regulations at the national level and the licensing requirements at the international level had also not been developed so well.

For the C-2 project, the main difficulty for PAEC and CNNC lay in establishing a design basis for which a price could be finalized and a contract could be developed because a commercial commitment could not have uncer-tainties in it. Otherwise, the cost of the project and the time required to complete it would be too large to prove economical. Ultimately, it was decided by PAEC and CNNC that the C-2 design would be based on the proven C-1 design with the following additional features:

(1) C-2 would meet all the NNSA licensing requirements as of 12 October 2003, the date when the decision was taken (by that time NNSA had not adopted the new regulation but was essentially following the IAEA’s Safety Series No. 50-C-D (Rev. 1) [3]);

(2) Modifications based on feedbacks from C-1 would be incorporated;

(3) Advantage would be taken of the technological developments and improvements since the time of C-1;

(4) A series of measures would be introduced in the design, and the execution of the project would aim at meeting the national licensing requirements of Pakistan.

Considering the fact that, in spite of its recent phenomenal technical development and economic growth, China is still a developing country, and neither of the two countries nor the regulators of either country have any experience of the latest IAEA safety standards, this was a very practical approach. It also reflected the desire on the part of Pakistan to make progress towards a better safety regime without rendering its nuclear power programme a ‘wait and see’ policy.

Based on the above premise, PAEC and CNNC finalized the base price and signed agreements subject to the approval of their respective Govern-ments. When such approval had been obtained, PAEC and CNNC formally

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signed the contract for the construction of the second unit (C-2) at a rated capacity of 325 MW(e) (gross) at Chashma, Pakistan.

The contract is now in effect and the licensing process has already been initiated with the submission of the Site Evaluation Report (SER) to PNRA. It is an 81 month project but the successful and timely completion of the project depends critically on meeting the licensing milestones, particularly the approval of the PSAR by October 2005, the time set in the project schedule for the first concrete pour.

The approach adopted by CNNC and PAEC was to take C-1 as a reference plant, review the design and make modifications based on the new requirements. As a result of a two year effort, it was agreed between the two parties that the C-2 design would include the following:

(1) Incorporation of more than 170 design changes on the basis of feedback from Qinshan-1 and C-1;

(2) Installation of the loose part monitoring system in the primary circuit;

(3) Use of probabilistic safety analysis to check and balance the plant design with respect to safety;

(4) Severe accident analysis leading to the design of preventive and mitigation measures and preparation of severe accident management guidelines (SAMGs);

(5) Specific measures for the prevention and mitigation of a selected set of severe accident sequences based on international experience, engineering judgement and the result of the above analysis. Typically, the list would include the following:

●Large break loss of coolant accident (LOCA) with high pressure injection/low pressure injection failure (during the safety injection phase);

●Large break LOCA with high pressure injection/low pressure injection failure (during the safety injection recirculation phase);

●Small break LOCA with high pressure injection/low pressure injection failure (during the safety injection phase);

●Small break LOCA with high pressure injection/low pressure injection failure (during the safety injection recirculation phase);

●Loss of off-site power with auxiliary feedwater failure;

●Steam generator tube rupture with high pressure injection and feedwater failure;

(6) Upgrading of the control room to meet the requirements of human factor engineering;

(7) Safety system bypass and inoperable status indication system in the control room;

TOPICAL ISSUE 1

67 (8) Commitment of the designer to follow the principles of defence in depth

and ALARA in the design.

Both the regulator and the operator are aware of the difficulties involved in the process. Effective communication must exist not only between the designer and the utility but also between the utility and the regulator. This dialogue will focus on the approach to meet the licensing requirements. For example, as a prelude to the submission of the design report and the PSAR of the plant, two documents related to the design were prepared and submitted to PNRA. The first one gave a topic-wise résumé on how and to what extent the regulatory requirements for the design would be met by C-2. The second document provided a clause-by-clause response to PAK/911 — the safety regulation related to nuclear power plant design. PNRA reviewed these documents and has provided an informal response which has been helpful during the contract technical negotiations.

The SER submitted by C-2 is the first formal document submitted to PNRA. It is based on Chapter 2 of the PSAR according to the NRC’s Regulation 1.70 (Rev. 3) [1]. PNRA has notified that the SER will be reviewed according to NUREG-0800 [2]. The PSAR to be submitted in 2005 is also likely to be reviewed by using the same NRC document. This NRC does not take into account the IAEA’s latest safety standards or the PNRA regulations.

Therefore, difficulties are anticipated.

The project schedule of C-2 provides six months for review of the PSAR after its submission to PNRA. To ease the review process, PAEC has made the vendor contractually obliged to provide international equivalence for all safety related Chinese codes that will be used in the design of C-2. To save time, PAEC has requested PNRA to accommodate an on-line informal review of the PSAR before its formal submission.

5. RELATIVE ASSESSMENT OF THE DESIGN SAFETY OF C-2