A new computational method, by incorporating wavelets in the improved quasi static (IQS) scheme, is developed and presented here for the analysis of CANDU PHWR and TWIGL reactor transients. According to this method the time dependent neutron diffusion equation is split into amplitude function and shape function. The amplitude function is solved using the Haar wavelet and its solution is used in the estimation of shape function. The advantage of this computational method is that the concept of micro time step and macro time step, adopted in the IQS scheme, does not arise here at all and the transient can be estimated with only one time step, i.e. single time step. In this method, the transient estimation methodology is different from the improved quasi static scheme. This computational method is applied to estimate the transients in CANDU 3D-PHWR benchmark, CANDU-2D and TWIGL reactors. In TWIGL reactor, a Doppler temperature feedback in introduced and the transient is estimated with feedback. The estimated transients are compared with the reference. From the comparison of results, it is observed that this method is capable of estimating the reactivity initiated transients in heterogeneous reactors to a good accuracy, by adopting only one time step. This computational method is first of its kind in the estimation of reactor transients. It is also shown that as the order of resolution of wavelet is increased, the error in the estimation of transient is reduced.

通过在改进的准静态 (IQS) 方案中加入小波，开发并介绍了一种新的计算方法，用于分析 CANDU PHWR 和 TWIGL 反应堆瞬态。根据这种方法，时间相关的中子扩散方程被分解为振幅函数和形状函数。幅度函数使用 Haar 小波求解，其解用于形状函数的估计。这种计算方法的优点是IQS方案中采用的微时间步长和宏时间步长的概念在这里完全没有出现，瞬态可以只用一个时间步长，即单个时间步长来估计。在该方法中，瞬态估计方法不同于改进的准静态方案。该计算方法用于估计 CANDU 3D-PHWR 基准、CANDU-2D 和 TWIGL 反应器中的瞬态。在 TWIGL 反应堆中，引入了多普勒温度反馈，并通过反馈估计瞬态。将估计的瞬变与参考进行比较。从结果的比较中可以看出，该方法仅采用一个时间步长就能够以良好的精度估计多相反应器中反应性引发的瞬变。这种计算方法在估计反应堆瞬态方面是同类中的首创。还表明，随着小波分辨率阶数的增加，瞬态估计的误差减小。将估计的瞬变与参考进行比较。从结果的比较中可以看出，该方法仅采用一个时间步长就能够以良好的精度估计多相反应器中反应性引发的瞬变。这种计算方法在估计反应堆瞬态方面是同类中的首创。还表明，随着小波分辨率阶数的增加，瞬态估计的误差减小。将估计的瞬变与参考进行比较。从结果的比较中可以看出，该方法仅采用一个时间步长就能够以良好的精度估计多相反应器中反应性引发的瞬变。这种计算方法在估计反应堆瞬态方面是同类中的首创。还表明，随着小波分辨率阶数的增加，瞬态估计的误差减小。